EP0485705B1 - Telemetric device for measuring the duration of a period - Google Patents

Abstract

In a telemetry method for measuring the duration of a period, an increased measurement resolution is achieved by the fact that firstly clock pulses are counted over the duration of one period of the signal to be measured for determining an approximate duration of the period, that then a table containing this period duration count is read out in order to obtain a number of measurement periods which is allocated to a period duration range, the number of measurement periods being selected in such a manner that counting of the clock pulses by means of the counter does not quite lead to a counter overflow even with the longest duration of a period in this range of period durations, and that then clock pulses are counted over the number of period durations of periods of the measurement signal so that finally the count obtained, together with a coding of the number of measurement periods, can be transmitted to a telemetry receiver. <IMAGE>

Description

The present invention relates to a telemetry period measurement method according to the preamble of claim 1.

In general, the invention relates to a telemetry measuring method for a telemetry system, which among other things determines the period of a signal generated by a sensor and transmits it to a telemetry receiver.

A period duration measuring method for a telemetry system is already known, in which a period duration of a signal to be measured is measured by means of a microprocessor in that a counter is counted up by means of a clock signal between two edges of the same direction of the signal to be measured. The counter reading, which corresponds to the period, is then transferred. It is also known in such a system to count the clocks in the case of relatively high-frequency signals to be measured, which are supplied to the counter during a fixed number of periods of the signal to be measured. The number of measured period durations of the signal to be measured is determined in this system in such a way that the maximum counter reading of the counter is just reached during the number of measuring periods at the lowest frequency to be measured. As the frequency of the signal to be measured increases, the measurement time decreases, so that the achievable resolution is also necessary decreases with increasing frequency.

In the case of period duration measuring devices or frequency measuring devices for the laboratory area, it is known to bring about an automatic frequency measuring range setting of the microprocessor-controlled measuring device by first carrying out the period duration measurement on the basis of a number of measuring periods which correspond to the measuring signal with the lowest measurable frequency. If a counter overflow occurs, the number of measuring periods is reduced by a factor of 1000, whereupon the counter is incremented again. Should an overflow occur again, the number of measuring periods is reduced again by a factor of 1000 until a very high-frequency signal can also be measured with regard to its period duration without counter overflow.

It is also known in the case of such multiple measuring devices to switch over from a period measurement to a frequency measurement of the signal to be measured in the event of a counter overflow. However, such a measuring method requires a basic setting time for the measuring device, which depends on the frequency of the signal to be measured. Since within a telemetry measuring method only a certain, unchangeable time window is available for measuring and transmitting measuring data for one sensor at a time, the measuring method just described, used in the case of multiple measuring devices in the laboratory, does not come into play for the field of telemetry measuring technology Consideration.

EP-A-204310 discloses a frequency measurement method in which the number of measurement cycles over which the frequency of the signal of interest is to be measured is set during an initial test interval in which the signal is first converted into a digital number to be used for rough estimation The frequency range within which the signal lies is derived therefrom, the frequency being determined in a frequency measuring mode of operation if the initial examination shows that the experimentally measured frequency value is above a threshold, otherwise a period duration measuring type is selected. If the period duration measurement is selected, the number of cycles during which a measurement is carried out is progressively reduced.

From the patent abstract Patent Abstracts of Japan, Volume 7, No. 130 (P-202) (1275), June 7, 1983, a counter device is known in which a count value is derived as an address from a signal to be measured with regard to its frequency, with which a division ratio is derived from a table by which the signal to be measured in terms of frequency is divided in terms of frequency. In this way, the desired resolution can be set.

Based on the above-mentioned prior art, the present invention has for its object to develop a telemetry period measurement method of the type mentioned so that without increasing the circuitry for the telemetry measuring system with which the measuring method can be carried out, an increased Measurement resolution is reached.

This object is achieved by a telemetry period measurement method according to claim 1.

In the telemetry period measurement method according to the first aspect of the invention, the counter is stopped after measuring the duration of the first period, which follows the synchronization on the first edge of the measurement signal. This value is used to read out a table to determine the approximate number of periods. Only then will the counter be restarted. Between the stopping and the restarting of the counter, a time period that corresponds to at least one period remains unused for the measurement. Since the total measuring time in the telemetry period measurement method is limited, the interim stopping of the counter leads to a loss of accuracy, particularly when measuring the period at low frequencies.

In contrast to the telemetry period measurement method according to the first aspect of the invention, the counter according to the second aspect of the invention as set out in claim 8 is not stopped after the first period, but only the counter value is stored. The counter thus continues to run during the following method steps, which include access to the table, and thus also registers at least a second period.

According to a further aspect of the invention, a counter with a word length of 16 bits can be used. A 16-bit "move" command would normally be required to store the counter reading of such a 16-bit counter when the counter is running. However, the invention according to the further aspect of the invention also enables the counter reading to be stored by means of processors in which only 8-bit instructions are available. This is the case with most processors and applies in particular to the usual processors of the 8051 processor family.

According to the invention, the counter reading is stored in succession for a higher and a lower bit group of the counter. If this were done with a running counter, an incorrect 16-bit counter reading could be saved, since a transfer from the 8th bit to the 9th bit of the counter can occur between the storage of the higher-order bit group and the storage of the lower-order bit group. For this reason, the counter is briefly stopped and then started again shortly afterwards.

According to a supplementary aspect of the invention, the duration of the interruption of the counting process is taken into account in that the current counter reading is increased by a corresponding number of counter readings which correspond to the elapsed time of the interruption.

In the subject of the first aspect of the invention, the clock pulses are counted over a period of the measuring signal in order to determine the approximate period of the measuring signal. A table access is carried out with this count value, whereby the number of measuring periods is determined. The counter with the clock pulses is then counted up using the number of measuring periods read from the table. However, if the measurement signal has a rapidly falling signal frequency, the initial period measurement for determining the number of measurement periods for the signal to be measured then no longer applies, so that the measurement time could be exceeded. In the case of a telemetry period duration measurement method, however, it must be ensured that the determination of the signal frequency, for example of a sensor, has been completed with certainty during the measurement time provided for this.

In deviation from the telemetry period measurement method according to the first aspect of the invention, the subject of the third aspect of the invention defined in claim 10 not only reads the number of measurement periods from the table, but also an overflow counter status and the current one Meter reading added. If a counter overflow occurs during the counting of the clock pulses over the number of measuring periods read from the table, the measurement is terminated. If, however, the counting of the clock pulses can be completed via the number of measuring periods read from the table, the overflow counter status is subtracted from the counter status determined in this way before the step of transferring the counter status is carried out.

The overflow counter reading is dimensioned such that the counter overflows after the maximum measuring time, so that the counter overflow can be used to end the measurement. If a measurement signal is now measured with a signal frequency that falls too sharply, the predetermined number of periods would lead to the measurement time being exceeded. However, taking the overflow counter into account results in a counter overflow that ends the measurement in this case. After completion of the measurement, the overflow counter is subtracted from the current counter before the counter is transmitted to the telemetry receiver.

In the subject of the first aspect of the invention, an initial counting of the clock pulses over a period takes place for the determination of the number of measuring periods before the table is accessed. If the measurement signal is a high-frequency measurement signal, the counter only reaches a low count during the measurement over a single period, which is therefore also an inaccurate reproduction of the measurement period. If the table for reading out the number of measuring periods is now accessed on the basis of this initially determined counter reading, it may result in reading out a number of measuring periods which is only applicable to measuring signals which lie in a different period duration range. In order to prevent invalid measurements caused by this, the assignment of the initial period duration readings to the various measurement period numbers in the table must have sufficient scope for prevention Take invalid measurements into account, however, this means that the best possible utilization of the meter capacity and thus the maximum possible measurement accuracy is dispensed with.

The inventive telemetry period measurement method according to the third aspect of the invention provides that after reading out the first table, a check is made based on the period duration count, for example, for a period duration, to determine whether the measurement period number read from the first table exceeds a limit value. If this is not the case, the method according to the invention continues with the counting of the clock pulses over the number of measuring periods, whereupon the meter reading determined in this way is transmitted to the telemetry receiver. However, if the result of the test is positive and the measurement signal is classified as high-frequency, after reading out the first table, clock pulses are counted over a plurality of period durations of the measurement signal, before counting to a second value determined over a plurality of period durations Table for reading out the exact number of measuring periods is accessed. After reading out the second table, the counter with the clock pulses is counted up over the number of measuring periods read from this second table before the count value is transmitted to the teleletry receiver.

In the telemetry period measurement method according to the first aspect of the invention, the upper limit frequency for the detectable measurement signals is predetermined by the speed of the processor used, since one interrupt has to be processed per edge of the measurement signal. The period of the measurement signal must not be less than this processing time, since otherwise the individual edges of the measurement signal cannot be registered.

The invention is therefore also based on the object of a telemetry period measurement method to develop so that measurement signals of higher frequency can be detected. This object is also achieved by a telemetry period measurement method according to claim 1. In the method according to the fourth aspect of the invention as set out in claim 17, a check is carried out to detect measurement signals of higher frequency after reading out the table to determine whether the number of measurement periods exceeds a limit value. If this is not the case, the clock pulses are counted over the number of measuring periods and then the counter reading together with the number of measuring periods are transmitted to the telemetry receiver for evaluation.

However, if the number of measuring periods exceeds the limit and the measuring signal is classified as high-frequency, a comparison frequency pulse counter is first set to a value corresponding to the number of measuring periods, then the counter is reset and started, then the comparison frequency counter is decremented with each edge of the comparison frequency signal and the counter is stopped as soon as the count value of the comparison frequency pulse counter is zero, whereupon the counter reading and the information representing the measurement period are transmitted to the telemetry receiver, which determines the frequency of the measurement signal from the transmitted counter reading, the reciprocal of the number of measurement periods and the reciprocal of the period of the comparison frequency signal.

Preferred developments of the telemetry period duration measuring method according to the invention are specified in the remaining subclaims.

A preferred embodiment of the telemetry period measurement method according to the invention is explained in more detail below with reference to the accompanying drawings.

Fig. 1

ein Flußdiagramm einer ersten bevorzugten Ausführungsform des erfindungsgemäßen Telemetrie- Periodendauer-Meßverfahrens; und

Fig. 2

ein Flußdiagramm einer zweiten bevorzugten Ausführungsform des erfindungsgemäßen Telemetrie- Periodendauer-Meßverfahrens.

Show it:

Fig. 1

a flow diagram of a first preferred embodiment of the telemetry period measurement method according to the invention; and

Fig. 2

a flowchart of a second preferred embodiment of the telemetry period measurement method according to the invention.

As shown in FIG. 1, a first method step 1 forms the start of the measuring method according to the invention. A program operating according to the method according to the invention can be a subroutine for controlling a microprocessor of a telemetry measuring system which, in a cyclically repetitive manner, processes the output signals from a plurality of telemetry sensors with a plurality of subroutines in a time-multiplexed manner and sends them to a telemetry -Receiver transmits.

In this case, the first method step 1 is the program step with the execution of which the microprocessor of the telemetry measuring system begins when the time window for the processing and transmission of a sensor with a frequency output signal has been reached, this output variable being to be recorded by means of the period duration measuring method according to the invention .

In a second method step 2, a counter is loaded with a start value. In the preferred embodiment, the starting value is 7800H. This start value of the counter is selected such that when the counter is counted up with a clock signal which is derived from a CPU clock, there is just no counter overflow for a period of a measurement signal with the lowest frequency to be detected.

In step 3, the counter is started, whereupon the start value is incremented with each clock pulse.

In method step 4 it is checked whether a counter overflow has occurred. If this is the case, the measurement signal to be checked can already be classified as too low-frequency for evaluation by means of the measurement method according to the invention, so that the measurement is defined as invalid. In this case, the program goes to step 6 to be explained later.

In the subsequent method step 5 it is checked whether a signal edge indicating the end of a period of the measuring signal has occurred. In the preferred embodiment, the microprocessor responds to falling edges of the signal to be measured and generates an interrupt when a falling edge occurs. As long as no signal edge occurs, the microprocessor remains in a waiting loop, in which it returns to program step 4.

If the counter overflows, the counter reading is set to zero in a sixth method step, whereupon an error message is transmitted in a method step 7 to the receiver of the telemetry system, which indicates the invalid character of the measurement carried out. In this case, the measuring cycle is ended with the subsequent method step 8.

Steps 4 and 5 serve, on the one hand, to wait for the next falling edge for the purpose of synchronizing the start of the period measurement, and on the other hand, in the case of signals which are too low-frequency, an error message indicating this fact can be transmitted to the receiver of the telemetry system.

If the signal frequency is too low, the available time can already be exceeded in steps 4 and 5 when synchronizing with the start of the measurement. The starting value of the counter, which is selected in method step 3 already explained and method step 9 still to be explained, is dimensioned such that the time until the counter overflow just permits the measurement of the longest possible period of the measurement signal. In the configuration according to the exemplary embodiment, the start value is 7,800H, so that the time of 8,800H counter readings passes until the overflow, which corresponds to the counter reading FFFFH according to OOOOH. This corresponds to a time period of 40.8 ms or a lowest measuring frequency of 24.5 Hz.

The same time limit applies during the measurement of the first period to be explained with reference to the method steps from the ninth method step. In this case too, the counter must be set to the explained starting value in a ninth method step.

In the worst case, which corresponds to the start of measurement immediately after the occurrence of a falling edge, 40.8 ms have to be waited for the first falling edge. The subsequent measurement of a period takes the same time. The resulting maximum time for the period measurement is 81.6 ms. If a signal with a longer period is present, this leads either to waiting for the first edge already explained with reference to steps 4 and 5 or to waiting for the second edge to be explained using method steps 10 and 11 to a counter overflow which leads to a termination of the measurement program due to process steps 6 to 8.

Steps 6 to 8 therefore ensure that the next following signal edge is not waited for in the event of a counter overflow, since otherwise the permissible measurement time could be exceeded.

Steps 10 and 11 correspond identically to steps 4 and 5, with the determination of the overflow at Step 10 leads to a jump to method step 6.

After detection of the signal edge in the eleventh method step due to the interrupt event occurring here, the counter is stopped in a twelfth method step 12, whereupon in the subsequent method step 13 the current counter status is subtracted by the starting value, since this difference only corresponds to the duration of the measured period.

The counter reading determined in this way, which in a first approximation represents the period of the signal to be measured, is used to read out a table in which a predetermined number of measuring periods b and a specific coding messper are assigned to each of the predetermined counter reading ranges. The number of measuring periods b is chosen so that the counting of the clock pulses by means of the counter does not lead to a counter overflow even with the longest period of a signal belonging to the period of this value b. According to a particularly preferred concept of the invention, the measurement period numbers b are stored in such a staggering with the associated coding messper in the table for the respective counter readings that such a measurement counter number b is assigned to a specific counter reading and thus to a specific, already approximately recorded period of the measurement signal is that this is the next smaller value, which can be represented by a power of two, below the value which results from the counter reading and thus the approximate period already determined divided by the period of the clock pulses and divided by the maximum permissible counter reading. In a preferred, practical embodiment of the invention, the measurement period number b is assigned the coding messper as follows:
b = 2 ^meas .

In other words, the measurement period numbers are defined as powers of two with the exponent measper. Possible values of the number of measuring periods b are therefore 1, 2, 4, 8, 16, 32, 64, ....

This staggered assignment of the measuring period numbers to the approximate period duration previously classified by steps 1 to 15 makes it possible to count the counter up to a relatively high value regardless of the period duration of the signal to be measured, before the next interrupt occurs, regardless of the period duration. Signal after the last period stops the counter. The high counter reading enables, as will be explained later, a period duration measurement for each signal regardless of its period duration with a high resolution.

Due to hardware limitations of the system that can be used, it is not possible to use a single counter to record more than 256 falling signal edges and thus 256 measurement periods of the signal.

In order to be able to measure such high-frequency signals with regard to their period duration, for whose period duration measurement with high resolution more than 256 measuring periods are required, a check is first made in the sixteenth method step 16 as to whether the number of measuring periods is greater than 256. If this is the case, it is replaced in a seventeenth method step 17 by a value which corresponds to the number of measuring periods divided by a loop counter value of 32. As will be clarified later, another quotient can also be used instead of the value of 32 if the loop counter explained later has a different end value.

If the distinction in the sixteenth method step 16 leads to the number of measuring periods not exceeding the value 256, this value is reduced by one in an eighteenth method step 18.

In a nineteenth method step 19 it is checked whether the coding has a value of zero. If this is the case, this means that a single measurement period is sufficient to measure the input signal, which in this case is very low frequency, with a high resolution. In this case, the program goes to the twentieth step 20, in which the counter reading from the fourteenth step 14 is adopted and in a subsequent twenty-first step 21, together with the associated coding messper = 0, is transmitted to the receiver of the telemetry measuring system. In this case, the measuring cycle is ended in a twenty-second method step 22.

If the check in the last-mentioned query 19 is negative, the microprocessor checks in the next query step 23 whether the number of measurement periods b is even. If this is not the case, then this indicates a signal to be measured of not high frequency.

If, in the course of the subsequent measurements of several period durations, the signal frequency drops sharply or fails, an interrupt is also triggered in the process steps 24, 25 or 32, 33 following the twenty-third method step and the measurement overflow is terminated and the measurement is ended as invalid. In this case, when the counter overflow is determined in the twenty-fourth and thirty-second program steps 24, 32, the program jumps to the forty-fifth program step in which the counter reading is reset to zero, whereupon the error message is transmitted to the receiver of the telemetry system in the forty-sixth program step, to end the measuring cycle at the forty-seventh program step.

The counter is started in the twenty-sixth step 26 following the twenty-fifth program step. Then, at the twenty-seventh step 27, it is checked again whether a counter overflow has occurred. In in this case there is a jump to the forty-fifth program step 45. Otherwise, by means of the twenty-eighth program step 28, the program runs through a waiting loop in which the interrupt is waited for as an indication of the next signal edge. As long as this does not occur, the program returns to the twenty-seventh program step. When the falling signal edge occurs, the signal edge counter is incremented in the twenty-ninth program step, whereupon it is checked in the thirtieth program step whether the measured number of signal edges already corresponds to the number of measuring periods b. If not, the program returns to the twenty-seventh program step. Otherwise, the counter is stopped in the next method step 31.

The program then goes to the step 21 already mentioned, in which the meter reading with the associated coding messper is transmitted to the receiver of the telemetry system.

If it turns out when checking step 23 that the number of measuring periods is an even value, this means that the signal to be checked is a high-frequency signal (cf. steps 16 to 18).

Method steps 32, 33 serve, in the manner already explained, to detect a measurement signal with a period that is too long, which leads to the triggering of an interrupt due to a counter overflow.

If the signal is judged to be in the permissible frequency range, the program goes to the following program step 34.

In this step 34, the counter is set to zero and started in step 35. Then the Step 36 set a loop counter to zero. This loop counter has a fixed value up to which it can be counted up before it overflows. In the present exemplary embodiment, this value is the number 32.

If a counter overflow is detected in the thirty-seventh step, the program continues with the forty-first program step 41 after triggering a corresponding interrupt.

At the next interrupt, which indicates a falling signal edge, which is detected by a query step 38, the loop counter is increased by one in method step 39. As long as no signal edge occurs, the program remains in a waiting loop at program steps 37 and 38.

As long as the loop counter has not yet reached its end value, which is checked in the subsequent query step 40, the program returns to step 37. As soon as the loop counter has reached its final value, the counter value, which indicates the detected number of signal edges, is increased by one in a forty-first method step 41. It is obvious to a person skilled in the art that in this embodiment the counter value is only increased on every thirty-second signal edge.

As soon as the number of signal edges equals the number of measuring periods b, the counter is stopped in a subsequent step 43. However, as long as this is not the case, the program returns to the thirty-second program step, in which the loop counter for the inner loop is reset.

After the counter has been stopped in the forty-third method step 43, the counter reading is stored in the subsequent step 44 and in the one already explained Step 21, to which the program now proceeds, is transmitted together with the coding messper to the telemetry receiver.

In the exemplary embodiment described, a signal edge is detected by triggering an interrupt. It is obvious to the person skilled in the art that the detection of a signal edge by querying or polling can also be considered. A processor's response to an interrupt takes longer than waiting for an edge through polling, but better resolution is possible by using an interrupt. A conditional jump in the event of a bit being queried takes so long that two counter readings of the counter are run through during this time, while the waiting state for an interrupt signal occurs in one of the described idle loops (idle mode), so that every counter reading reacts can be. The use of interrupts to detect the edges thus enables a resolution of a counter reading of the counter.

Furthermore, the program described puts the processor in the so-called "idle mode" while waiting for a falling edge, in which it does not execute any commands, but only waits for the next interrupt signal. In this state, the current consumption of the microprocessor is reduced considerably. In a practically implemented embodiment, the current consumption drops from 17 mA to 5 mA.

In order to detect high-frequency signals, the program according to the preferred embodiment uses a loop counter, the final value of which is 32 in this embodiment. It is obvious to the person skilled in the art that loop counters with other values can also be considered. In this case, the quotient must be adjusted accordingly in step 17.

In the preferred exemplary embodiment, two complete periods of the signal to be measured are measured for the initial, approximate determination of the period by means of method steps 1 to 14. It is obvious to the person skilled in the art that the measurement of two half-periods as well as a multiple of this value is also conceivable, even if the measurement of two whole periods is preferred for the reason of the interrupt signals that can then be used to indicate falling signal edges.

As shown in FIG. 2, a first method step 1 forms the start of the second embodiment of the measuring method according to the invention.

In a second method step 2, a counter is loaded with a start value. In the preferred embodiment, the starting value is 7800 H. This starting value of the counter is selected such that when the counter is incremented with a clock signal which is derived from a CPU clock over a period of a measuring signal with the lowest frequency to be detected no counter overflow takes place.

In step 3, the counter is started, whereupon the start value is incremented with each clock pulse.

In method step 4 it is checked whether a counter overflow has occurred. If this is the case, the measurement signal to be tested can already be classified as too low-frequency for evaluation by means of the measurement method according to the invention, so that the measurement is to be defined as invalid. In this case, the program goes to step 6 to be explained later.

In the subsequent method step 5 it is checked whether a signal edge indicating the end of a period of the measurement signal has occurred.

In the event of the counter overflow, which is detected in the test according to method step 4, the counter status is set to zero in a 6th method step 6, whereupon the program jumps to method step 19, which will be explained later and which transmits the counter status and the coded number of periods ldn serves. In this case, the measuring cycle ends with the subsequent method step 20.

Steps 4 and 5 are used, on the one hand, to wait for the next falling edge for the purpose of synchronizing the start of the period measurement, and on the other hand, for signals that are too low-frequency, an error message indicating this fact, which may consist, for example, of the information cnt = 0 to which the receiver of the telemetry system can be transmitted.

If the signal frequency is too low, the time available for a measuring cycle can be exceeded already in the synchronization with the start of measurement in method steps 4 and 5. The starting value of the counter, which is selected in method step 3 which has already been explained and method step 9 which is yet to be explained, is dimensioned such that the time until the counter overflow just allows the measurement of the longest possible period of the measuring signal.

In the configuration according to the exemplary embodiment, the start value is 7800 H, so that the time of 8800 H counter readings passes until the counter overflows, which corresponds to the counter reading FFFFH after 0000 H. This corresponds to a time period of 40.8 ms and thus a lowest measuring frequency of 24.5 Hz.

The same time limit applies during the measurement of the first period, which is still to be explained with reference to the method steps from the ninth method step. In this case too, the counter must be set to the explained starting value in a 9th method step 9.

In the worst case, which corresponds to the start of measurement immediately after the occurrence of a falling edge, 40.8 ms have to be waited for the first falling edge. The subsequent measurement of a period takes the same time. The resulting maximum time for the period measurement is 81.6 ms. If a signal with a longer period is present, this leads to a counter overflow either when waiting for the first edge already explained with reference to steps 4 and 5 or when waiting for the second edge to be explained, which leads to a termination of the measuring program jumps to step 19.

As mentioned, in step 9, the counter is preassigned with a start value, which in the preferred embodiment has the value 7800 H.

The method steps 10 and 11 correspond identically to the method steps 4 and 5, the determination of the overflow in the 10th method step 10 also leading to a jump to the 6th method step 6.

After detecting the signal edge in 11th method step 11 due to the interrupt event occurring here, the counter is stopped in a 12th method step 12. Stopping the counter in this step of the method enables the manipulation of a 16-bit counter with 8-bit instructions, as explained below, to be carried out in processors from the 8051 family. If one were to carry out manipulations with 8-bit commands while a 16-bit counter was running, a carry could take place between the manipulation of a low-order bit group of the counter and the manipulation of a high-value bit group of the counter, which would lead to an error. This problem is eliminated in the method according to the invention in that the manipulation of the 16-bit counter is stopped before each of the manipulations explained below, as is also the case in the 12th method step 12.

In the subsequent 13th method step, the counter reading is reduced by the start value and stored as the input counter reading cnt1. As mentioned, this storage takes place in that, when the counter is stopped, the least significant byte and then the most significant byte are stored in succession under the address cnt1.

In the 14th method step 14, the counter is set to a further start value (start value *), which has the value 15 here. This default setting of the counter with a starting value of 15 counter values instead of resetting the counter to the value zero has the following background. The time that has elapsed during the interruption of the counter must be taken into account. In the exemplary embodiment shown, this takes place in that the start value *, which is stored in the 14th method step 14, the interruption during the 12th and 13th method step with 9 counter readings and an interruption to be explained later in a 22nd and 23rd method step with 6 meter readings is taken into account.

In the subsequent method step 15, the counter is started again starting from the start value mentioned.

The counter reading cnt1 stored in the 13th method step 13 is used to access a first table during a 16th method step 16. The determined counter reading cnt1 represents in a first approximation the period of the signal to be measured and is used as an input variable for reading out the first table, in which a predetermined number of measuring periods n and a specific coding ldn are assigned to each predetermined counter reading range. The number of measuring periods n is chosen so that the counting of the clock pulses by means of the counter does not lead to a counter overflow even with the longest period of a signal belonging to the period of this value n. According to a particularly preferred concept of the invention, the measurement period numbers are n in such a graduation with the associated coding ldn stored in the first table for the respective counter readings cnt1, which is associated with a certain counter reading cnt1 and thus with a certain, approximately already recorded period of the measuring signal such a number of measuring periods n that this is the next is a smaller value, which can be represented by a power of two, below the value which results from the counter reading and thus the approximate period duration already determined divided by the period duration of the clock pulses and divided by the maximum permissible counter reading. In a preferred, practically implemented embodiment of the invention, the number of measuring periods n is assigned the coding as a logarithm duales ldn.

In other words, the measurement period numbers n are defined as powers of two with the exponent ldn. Possible values for the number of measuring periods n are therefore 1, 2, 4, 8, 16, 32, 64, ....

Through this staggered assignment of the measurement period numbers to the approximate period duration previously classified by steps 1 to 15, it is possible to count the counter up to a relatively high value regardless of the period duration of the signal to be measured, before the next interrupt occurs, regardless of the period duration. Signal after the last period stops the counter. The high counter reading enables, as will be explained below, a period duration measurement for each signal regardless of its period duration with a high resolution.

A particularly important aspect of the telemetry period duration measuring method according to the invention can now be seen in the fact that the counter in the 15th method step 15 is started before the method step 16 of reading out the first table and thus runs for the duration of the table reading out. In other words, in this aspect of the invention, in contrast to the configuration according to FIG Main patent application of the counter is not stopped for table access, but runs during the period of table access, whereby at least the time for measuring a period of the measurement signal is gained. Since the measuring time is limited, this leads to an increase in measuring accuracy, especially when measuring in the range of low frequencies.

After the table has been accessed in the 16th step, the number of measurement periods n is checked in the 17th step to determine whether it is equal to 1. If this is the case, the input counter reading cnt1 stored in the 13th method step is adopted as counter reading cnt, whereupon the method ends the measuring cycle with the method steps 19 and 20 already explained.

If the test in the 17th method step is negative, it is checked in a 21st method step 21 whether the number of measuring periods n is less than or equal to 32. If this is not the case, the counter is stopped in a 22nd method step 22 and then the counter reading is increased by an overflow counter reading cntov read from the first table during the 16th step. As explained above, this addition also takes place with two successive 8-bit additions of a higher-order bit group of the overflow counter reading and a lower-order bit group of the overflow reading cntov to the current counter reading cnt, whereupon the counter is started again in the 24th method step 24. This overflow counter reading cntov is dimensioned such that the counter overflows shortly before the maximum permissible measurement time is reached and then the measurement is ended at the latest. This measure is necessary in the case of rapidly falling measurement signal frequencies. If one were not to add up the overflow counter cntov, the value of which depends on the period, to the current value of the counter, the measurement over the number of measuring periods n, which is obtained by reading the first table in the 16th step 16, could lead to an overshoot of the measuring time because the current period of the measuring signal has increased during the measuring period after reading out the table in the 16th method step 16 and no longer corresponds to the preliminary estimate. In a 25th method step 25, a loop counter b is pre-assigned with the number of periods n reduced by 1. In the subsequent method step 26, the counter overflow is checked. If this occurs, the program jumps to 19th step 19.

Otherwise, the occurrence of a signal edge of the measurement signal is checked in the subsequent method step 27. If no signal edge occurs, the program returns to method step 26. If this is the case, however, the loop counter is decremented in the 28th method step 28. In the subsequent method step 29, it is checked whether the loop counter b has reached the value zero. If this is not the case, the program returns to method step 26. Otherwise, in the subsequent method step 30, the counter is finally stopped, whereupon in the 31st method step 31, the counter reading cnt is again reduced by the overflow counter reading cntov by means of two 8-bit subtractions in order to obtain the true measured value. In this case, the measuring cycle is completed with a jump to the 19th method step.

If the test in the 21st method step 21 is positive, the program continues with a further test step 33, in which it is checked whether the measurement period number n is greater than or equal to 512. If this is not the case, the measurement signal is classified as a signal of a medium frequency range. In this case, in a 34th method step 34, the number of measurement periods n is divided by a loop counter value of an inner loop counter to be explained, which is 32 in the example. In the subsequent method step 35, the counter is checked for overflow. If an overflow occurs, go the program for the 19th method step 19. Otherwise, the following method step 36 checks whether a signal edge occurs. If this is not the case, the program goes back to the 35th method step 35. If a signal edge occurs, the counter status is set to zero in the next method step 37. The method steps 38 to 44 explained below form an inner loop counter.

First, in a 38th method step 38, the loop counter status is set to zero, whereupon in the subsequent method step 39 it is checked whether a counter overflow takes place. If this is the case, the program goes to method step 19. Otherwise, it is checked whether a measurement signal edge has occurred. After this check in method step 40, the program returns to method step 39 if no signal edge has occurred. If a measuring signal edge occurs, the loop counter status is incremented in the subsequent method step 41.

In the subsequent step 42, it is checked whether the current loop counter reading has reached the end value 32. If this is not the case, the program returns to the 39th step. Otherwise, the measuring period counter is decremented in a 43rd method step. In the subsequent method step, it is checked whether the number of measuring periods n has reached the value zero. If this is not the case, the program returns to the 38th method step 38. Otherwise, the counter is stopped in the subsequent method step 45 and the counter content is stored as counter reading cnt, whereupon the program continues with the 19th method step 19.

As already mentioned, it is checked in the 33rd method step 33 whether the number of measurement periods n is greater than or equal to 512. If this check leads to a positive result, the program continues with the 47th method step 47 continues, where the counter is checked for overflow. If an overflow occurs, the program jumps to step 19.

Otherwise, it is checked in the subsequent method step 48 whether a signal edge of the measurement signal occurs. If this is not the case, the program returns to the 47th method step 47. Otherwise, the counter status is set to zero in the subsequent method step 49, whereupon a loop counter status is set to zero in the method step 50. The program routine explained below with the method steps 49 to 57 serves to achieve a higher accuracy in determining the number of measuring periods for high frequencies of the measuring signal. In other words, the initial measurement of a single period to determine the number of measuring periods is fraught with uncertainties because of the low meter readings at high frequencies, which can only be countered in an initial measurement over a single period by taking the table values for the number of measuring periods into account of the measurement inaccuracy. However, this would lead to a loss in the achievable accuracy. Therefore, in the program routine explained below, the period of the measurement signal is estimated over several periods.

For this purpose, the loop counter reading is set to zero in the 50th method step 50, whereupon the counter is checked for overflow in the 51st method step 51. If an overflow occurs, the program jumps to method step 19. Otherwise, it is checked whether a signal edge of the measurement signal has occurred. If this check at step 52 is negative, the program returns to step 51. Otherwise, a loop counter reading is incremented in the subsequent method step 53. In the subsequent method step 54, it is checked whether the loop counter reading is a number of periods for the initial check of 20 periods. If this is not the case, the program routine returns to the 51st step. Otherwise the counter is stopped in the subsequent 55th method step 55 and its value is stored in the following method step 56 as counter reading cnt1. In a 57th method step 57, this is used to access a second table from which the number of measurement periods, their coding ldn and the overflow counter reading cntov are read out for the high frequency range present here.

In the subsequent method step 58, it is checked whether the coding ldn is greater than or equal to 14. If this is not the case, the measured signal is assigned to the upper range of medium frequencies, so that the program carries out the period duration measurement by jumping to the 34th program step 34.

If the test at step 58 is positive, this means that the measurement signal is classified as the highest-frequency measurement signal. In this case, the method according to the invention does not carry out a period duration measurement in the subsequent method steps 59 to 67, but rather a frequency measurement.

The upper limit frequency of the period measurement is determined by the speed of the processor used. Interrupt must be processed for each edge of the measurement signal. The period must not be less than the processing time required to process an interrupt, as otherwise individual edges cannot be registered. This would severely limit the upper limit frequency, so that not all frequencies occurring in a telemetry measuring method could be covered.

When using the 8051 microcontroller, however, it is possible to count hardware pulses. The cut-off frequency is a 24th of the processor clock frequency, because the measurement signal is sampled at a 12th of the processor clock frequency.

In the preferred embodiment that has been implemented, the cut-off frequency of the period measurement is 106 kHz, while that of the frequency measurement is 426 kHz.

The combination of the two methods provided according to the invention enables the measurement of frequencies between 25 Hz and 426 kHz, the maximum permissible measurement time of 80 ms being never exceeded. The resolution of the frequency measurement is 13 bits at frequencies around 100 kHz and rises to 15 bits at the upper limit frequency.

With a method adapted to the maximum measuring time of 160 ms, a period measurement between 13 Hz and 106 kHz with a resolution between 15 and 16 bit is possible. The frequency measurement achieves a resolution of 14 to 16 bits at signal frequencies between 106 kHz and 418 kHz.

To carry out the frequency measurement, the measurement signal must be present at input T0 (timer 0) of the processor (not shown). Each falling edge then increases the count of timer 0. A signal with a fixed frequency must be present at input INT1 (interrupt 1) as the time base for frequency measurement. The counting of the timer 0 can be controlled by the bit TRO (timer run 0). Counting with this bit is made possible for a certain predetermined time for frequency measurement. This time is counted as a corresponding number of edges at input INT1.

In the exemplary embodiment implemented, the comparison frequency at input INT1 has a frequency of 1.25 kHz, which corresponds to the period duration of 800 »s. The measurement is carried out over 98 such periods, so that a measurement time of 78.4 ms results. This, together with the preliminary dimension already explained, results in the maximum measuring time of 80 ms observed.

If, as explained in the 58th program step, the presence of high-frequency measurement signals is determined, a comparison frequency pulse counter with the number of measurement periods n is loaded in the subsequent method step 59. A check is then carried out in method step 60 to determine whether there is an edge of the comparison frequency at input INT1. If so, the program goes back to step 60. Otherwise, the counter, which now serves as a signal edge counter, is set to zero in the subsequent step 61. If the occurrence of a signal edge is detected in the subsequent method step 62, the counter is incremented in the 63rd method step 63. Otherwise, the program goes directly to the subsequent method step 64, in which it is checked whether there is an edge of the comparison frequency.

If this is the case, the comparison frequency pulse counter b is decremented in the 65th method step 65. Otherwise this program step is skipped, whereupon the program checks at the 66th program step 66 whether the comparison frequency pulse counter b has meanwhile reached the count value zero. If not, the process goes back to the 62nd step. Otherwise, the current counter reading is stored as counter reading "cnt" in the subsequent program step 67, whereupon the transmission of the counter reading "cnt" and the coded number of periods "ldn" takes place in the 19th process step before the process is ended in the 20th process step.

In the preferred embodiment, the following data is transmitted between the telemetry transmitter and the telemetry receiver:

On the one hand the counter reading cnt as a 16-bit word and on the other hand the coding of the number of pearls ldn as a 4-bit word.

The processor clock frequency fcpu of 10.24 MHz is known.

On the part of the telemetry receiver, two cases must be distinguished for the calculation of the signal frequency:

On the one hand, the case of the period measurement, which is present in the preferred exemplary embodiment when the coding ldn lies in the value range between 0 and 13. Since the two logarithm of the number of periods is transferred with ldn, the number of periods is determined as follows: n = 2 ^ldn .

In this case, the frequency f is calculated as follows: $$\text{f =}\frac{\text{n}}{\text{cnt}}\text{·}\frac{\text{f-cpu}}{\text{12th}}$$

If the coding ldn has the value 14 or 15, this indicates that a frequency measurement has been carried out. The number of periods n in this case is 98 for a value of ldn = 14 or 196 for a value of ldn = 15. The frequency is then calculated as follows: $$\text{f =}\frac{\text{cnt}}{\text{n · 800 »s}}$$

An invalid measurement is coded as cnt = 0. Falling below the lower limit frequency is coded as ldn = 0.

It is obvious to the person skilled in the art that the numerical values given serve only to explain a case distinction and thus depend on the application.

Claims (17)

1. A telemetric method for measuring the duration of a period
   comprising the following method steps:

   - counting, by means of a counter, clock pulses over at least half the period duration of a signal to be measured so as to determine a period duration count indicating the approximate period duration of the signal to be measured,

   - reading a number of measuring periods (b), which is associated with a period duration range within which the period duration count lies, from a table by means of the period duration count, the number of measuring periods being selected such that, even in the case of the longest period duration of this period duration range, counting of the clock pulses by means of the counter will just not yet result in counter overflow, the number of measuring periods (b) read from the table being the next lower value which can be represented by a power of 2 below the value resulting from the approximate period duration, which is represented by the period duration count, divided by the period duration of the clock pulses as well as divided by the maximum count,

   - counting the clock pulses over the number of measuring periods (b) of periods of the measuring signal, and

   - transmitting the count and an information (messper) representing the number of measuring periods (b) to a telemetric receiver.
2. A telemetric method for measuring the duration of a period according to claim 1, wherein the information representing the number of measuring periods (b) is additionally read from said table by means of the period duration count, in the form of a code (messper), and
   wherein the following relationship exists between the code (messper) representing the number of measuring periods and the number of measuring periods (b):
   b = 2^messper.
3. A telemetric method for measuring the duration of a period according to one of the claims 1 or 2, wherein at the beginning of each measurement cycle the counter is counted up with the clock pulses starting from a start value, the measurement cycle being finished when counter overflow occurs before the next signal edge of the signal to be measured appears, and wherein,
   when no counter overflow occurs, the counter is again counted up starting from the start value when the signal edge appears, the measurement cycle being finished when counter overflow occurs before the subsequent signal edge appears.
4. A telemetric method for measuring the duration of a period according to claim 2, wherein, in the case of a code (messper) corresponding to a single measuring period (messper = 0), the initially determined period duration count is transmitted together with the code (messper).
5. A telemetric method for measuring the duration of a period according to one of the claims 1 to 4, wherein the number of measuring periods (b) is compared with a maximum count value (256) of a measuring period counter and wherein, when said maximum count value is exceeded, the number of measuring periods (b) will be divided by a loop counter value (32) or otherwise reduced by 1.
6. A telemetric method for measuring the duration of a period according to claim 5, wherein, in the case of an uneven number of measuring periods (b), the counter is counted up with the clock pulses over the number of measuring periods (b), whereupon the count value thus determined is increased by the initially determined period duration count prior to transmitting the count thus determined together with the code (messper).
7. A telemetric method for measuring the duration of a period according to one of the claims 1 to 6, wherein, in the case of an even number of measuring periods (b), a measuring period counter is incremented only if an inner loop counter has reached its loop counter final value by counting up by means of the signal edges, and that the counter will be stopped as soon as the measuring period counter has reached a value which is equal to the number of measuring periods (b), whereupon the count thus determined is transmitted together with the code (messper).
8. A telemetric method for measuring the duration of a period according to one of the claims 1 to 7, comprising the following method steps:

   - storing (13, cnt1) of the count after having counted clock pulses over at least half a period duration when a signal edge of the measuring signal has occurred (11); and

   - resetting (14) and renewed starting (15) of the counter prior to the method step of table reading (16), the counter continuing to run while the table is being read.
9. A telemetric method for measuring the duration of a period according to claim 8, wherein the method step of storing comprises the following method steps:

   - stopping (12) the counter when the signal edge of the measuring signal occurs (11);

   - storing (13, cnt1) a more significant bit group of the count;

   - storing (13, cntl) a less significant bit group of the count;

   - setting (14) the counter to a start value corresponding to the period of time for which the counter is stopped; and

   - starting (15) the counter.
10. A telemetric method for measuring the duration of a period according to one of the claims 1 to 9, comprising the following method steps:

    - reading an overflow count (cntov) from the table;

    - adding (23) the overflow count (cntov) to the instantaneous count (cnt);

    - finishing (22, yes) the measurement when a counter overflow occurs (26, yes); and,

    - when no counter overflow occurs, subtracting (31) the overflow count (cntov) from the count (cnt) after counting of the clock pulses over the number of measuring periods (n) prior to the method step of transmitting to the telemetric receiver the count and the information (ldn) representing the number of measuring periods (n).
11. A telemetric method for measuring the duration of a period according to claim 10, wherein the method step of adding the overflow count (cntov) comprises the following method steps:

    - stopping (22) the counter after having read (16) the table;

    - adding (23) a more significant bit group of the overflow count (cntov) to the count (cnt);

    - adding (23) a less significant bit group of the overflow count (cntov) to the count (cnt); and

    - starting (24) the counter.
12. A telemetric method for measuring the duration of a period according to claim 10, wherein the method step of subtracting (31) the overflow count (cntov) comprises the following method steps:

    - stopping (30) the counter after having counted the clock pulses over the number of measuring periods (n);

    - subtracting (31) a more significant bit group of the overflow count (cntov) from the count (cnt); and

    - subtracting (31) a less significant bit group of the overflow count (cntov) from the count (cnt);
13. A telemetric method for measuring the duration of a period according to one of the claims 11 or 12, wherein each period duration range has associated therewith a value of the overflow count (cntov).
14. A telemetric method for measuring the duration of a period according to claim 13, wherein the value of the overflow count (cntov) is zero for period duration ranges which are associated with the signal frequencies above a limit value (1 kHz).
15. A telemetric method for measuring the duration of a period according to one of the claims 1 to 14, comprising the following method steps between the method step of reading (16) the first table and the method steps of counting the clock pulses as well as of transmitting (19) to the telemetric receiver the count (cnt) and the information representing the number of measuring periods (n):

    - examining (33) whether the number of measuring periods (n) obtained when the first table is read (16) exceeds a limit value (512);

    - if the result of the examination (33) is negative, continuing with the method steps of counting the clock pulses and of transmitting (19) the count;

    - if the result of the examination (33) is positive,

    - renewed counting (47 to 54) of clock pulses over a plurality (20) of period durations of the measuring signal by means of a counter for determining again a period duration count (cnt1) indicating the approximate period duration of the measuring signal;

    - renewed reading of a number of measuring periods (n), which is associated with a period duration range within which the period duration count lies, from a second table by means of the period duration count, the number of measuring periods being selected such that, even in the case of the longest period duration of this period duration range, counting of the clock pulses by means of the counter will just not yet result in counter overflow, and

    - continuing with the method step of counting the clock pulses over the number of measuring periods thus ascertained and with the method step of transmitting (19) to the telemetric receiver the count (cnt) and the information (ldn) representing the number of measuring periods (n).
16. A telemetric method for measuring the duration of a period according to claim 15, wherein the method step of renewed counting (47) of the clock pulses over the plurality of period durations comprises the following method steps:

    - resetting and renewed starting (49) of the counter (cnt: = 0);

    - resetting (50) a loop counter;

    - incrementing (53) the loop counter in response to each edge of the measuring signal; and

    - stopping (55) the counter as soon as the count of the loop counter corresponds to said plurality (20) of period durations.
17. A telemetric method for measuring the duration of a period according to one of the claims 1 to 16, comprising the following method steps after the method step (57) of table reading:

    - examining (58) whether the number of measuring periods (n) obtained when the table is read exceeds a limit value (ldn = 14);

    - if the result of the examination (58) is negative,
       -- continuing with the method steps of counting the clock pulses and of transmitting (19) the count;

    - if the result of the examination (58) is positive,

    -- setting (59) of a reference frequency counter to a value (b: = n) corresponding to the number of measuring periods (n);

    -- resetting and starting (61) the counter so as to count the clock pulses of the measuring signal;

    -- decrementing (65) the reference frequency counter in response to every edge of a reference frequency signal;

    -- stopping (67) the counter as soon as the count (b) of the reference frequency counter is zero;

    -- transmitting (19) to the telemetric receiver the count (cnt) and the information (ldn) representing the measuring period duration (n); and

    -- determining the frequency of the measuring signal in accordance with the following equation: $$\text{f =}\frac{\text{cnt}}{\text{n * TREF}}$$

    

    wherein cnt is the count transmitted, n is the number of measuring periods and TREF is the period duration of the reference frequency signal.

Images