CA1184604A - Continuous variable frequency measurement apparatus - Google Patents
Continuous variable frequency measurement apparatusInfo
- Publication number
- CA1184604A CA1184604A CA000419000A CA419000A CA1184604A CA 1184604 A CA1184604 A CA 1184604A CA 000419000 A CA000419000 A CA 000419000A CA 419000 A CA419000 A CA 419000A CA 1184604 A CA1184604 A CA 1184604A
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- CA
- Canada
- Prior art keywords
- signal
- frequency
- pulse
- successive
- measured
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
- G01R23/10—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage by converting frequency into a train of pulses, which are then counted, i.e. converting the signal into a square wave
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
Abstract
ABSTRACT
A method and apparatus of measuring the frequency of an input signal comprising providing a first signal having a frequency related to the frequency of the signal to be measured, totalling the cycle periods of the signal over a predetermined number of cycles successively once each cycle as a moving total, whereby the totals are successive representations of the frequency of the input signal.
A high resolution determination of the frequency of the input signal at a high sampling rate is the result.
A method and apparatus of measuring the frequency of an input signal comprising providing a first signal having a frequency related to the frequency of the signal to be measured, totalling the cycle periods of the signal over a predetermined number of cycles successively once each cycle as a moving total, whereby the totals are successive representations of the frequency of the input signal.
A high resolution determination of the frequency of the input signal at a high sampling rate is the result.
Description
01 This invention relates to an apparatus and 02 method for continuously measuring the frequency of a 03 variable frequency signal having a period which varies 04 with slower frequency than the frequency itself, with 05 a high degree of precision.
06 It is sometimes required to measure the 07 fre~uency of a ~requency varying signal with high 08 resolution on a continuous basisO For example, 09 variations in frequenc~ of radiation from the earth as detected by a magnetometer or the like during an 11 airplane scan of the terrain can indicate the present 12 of magnetic ore bodies. The speed by which the 13 scanning is conducted is usually dependent on the 14 ability of the frequency determining apparatus to de-termine frequency variation of the detected input 16 signal as anomolies are overflown. By increasing the 17 resolution of the frequency determining apparatus and 1~ by increasing the signal sampling rate, a much faster 19 scan of the terrain could be achieved. This would reduce the cost of conducting the scan, or would 21 facilitate conducting the scan over a much greater 22 area during a given scanning interval.
23 Present frequency determining methods 24 require the use of relatively slow propeller driven survey airplanes to conduct the scanO This invention 26 increases the sampling rate of the frequency 27 determining apparatus to such a great extent that it 28 is believed that fast jet airplanes can be used to 29 conduct the scan, at much greater speeds than before.
An understanding of this invention will be 31 obtained by a consideration of the description below, 32 of the general concept and of a preferred embodiment 33 of the invention, in conjunction with the following 34 drawings in which:
Figures 1-4 are waveform diagrams used to 36 explain prior art forms of the invention, 37 Figure 5 is a waveform diag~am used to 01 explain the present invention, 02 Figure 6 is a block diagram of the basic 03 form of the present invention, and 04 Figure 7 is a block diagram illustrating 05 the preferred form of the present invention.
06 Turning to Figure 1, a received signal 07 whose frequency is to determined is shown as waveform 08 1, which has been corrected into squarewave form.
09 Within a certain period P, there are n pulses which can vary in number according to variations in 11 frequency. According to one prior art technique Eor 12 determining the frequency of an input signal, the 13 number of pulses within a period P (e.g. 1 second) is 14 counted, thereby representing the ~requency. In this 1~ technique it ta~es a full second (assuming that is the 16 time interval of the count) to determine the frequency 17 of the input signal.
18 In order to increase the resolution and 19 thus the accuracy of the described technique, the number of input pulses is sometimes multiplied by a 21 predetermined factor, and then the number of pulses is 22 measured over a defined period of time (e.g. 1 23 second), as before. However this also requires a long 24 time period to perform the frequency determination.
According to a technique for decreasing 26 the required period of time for frequency 27 determination, the time period of a single input pulse 28 2 is measured (Figure 2). However this measurement is 29 very limited in re~olution.
To increase the resolution of the period 31 measurement technique, a period measurement of a large 32 number n cf periods is measured as shown in Figure 3.
33 The total time period required to determine the 34 frequency is nxT, where T is the period of each pulse (assuming equal pulse periods). ~owever this 36 increases the required time period while i~ increases 37 the resolution.
01 The technique of Figure 3 is also used in 02 the technique shown in Figure 4, in which successive 03 pulse group ~ntervals of the input signal are 04 measured, to determined changes in frequency. For 05 example, six pulses during the period nxTl are 06 measured, followed by the measurement of a similar 07 number of pulses during the interval nxT2. Thus it 08 may be seen that two successive time periods, each six 09 pulses long are required to detect any change in frequency. Clearly this is a relatively slow and 11 ineffective technique for determining the frequency 12 change of a terrestrial signal caused by a stationary 13 ore body, from a fast moving airplane, particularly 1~ when the ore body is small.
According to prior art techniques, 16 increases in resolution result in decrease in speed of 17 frequency determination, and vice versa.
18 The present invention achieves high 19 resolution obtained by the multiple pulse period measurement technique, but simultaneously achieves a 21 fast sampling rate similar to that of the single pulse 22 measurement technique. A consideration of Figure 5 23 will illustrate the technique.
24 The -time period for n pulses (shown as six in number ~or example), each having its own time 26 period, for example, To-Ts, is measured, as in the 27 technique described with reference to Figure 3. The t 28 total time for the six periods is nPl. Then the 29 ~irst-in pulse time period To is dropped, and the time period of the next pulse T6 is added to time periods 31 Tl-T5, to provide a total time period of nP2.
32 Following this the next first-in pulse time period P2 33 is dropped and the time period T7 is added to 34 establish the total time period nP3. It may be seen that should the frequency change~ the period of each 36 new incoming pulse also changes~ and thus the total 37 changes. Accordingl~ we have a moving total 01 representing the frequency of a given number of 02 pulses.
03 It should be noted that while the total 04 over a predetermined number of pulses provides a 05 relatively high re~solution result, a sample is taken 06 each pulse period. Consequently the sampling rate is 07 as high as the pulse rate. Thus we have the result of 03 high resolution at the same time as a high sampling ~9 rate.
While the actual pulse rate of the input 11 signal can be used~ it is preferred, Eor ease of 12 design and stablity of the circuitry to divide the 13 relatively high frequency input signal by a factor 14 whereby the pulse rate which is measured is of the order of 100 hertz. This also provides time for 16 relatively inexpensive processors to generate the 17 average calculation.
1~ It may be seen that the method of the 19 present invention provides a substantially improved freguency measurement technique, which provides the 21 desirable result of high resolution at the same time 22 as high sampling rate, which was not possible in the 23 aforenoted prior art techniques. Accordingly a high 24 speed scanning survey airplane can be used to conduct the survey.
26 The apparatus of the invention, in 27 general, is a continuous frequency measurement 28 apparatus comprising apparatus for providing a first 29 signal having frequency related to the frequency of the signal to be measured, and apparatus for totalling 31 the pulse period of the first signal over a 32 predetermined number of the pulses successively as a 33 moving total.
34 More particularly, the invention is a continuous variable frequency measurement apparatus 36 comprising apparatus for providing a first signal 37 having a frequency related to the frequency of a 38 _ ~ _ 01 signal to be measured, a source of a calibration 02 signal having a prede~ermined constant frequency which 03 is greater than the frequency oE the ~irst signal, 04 apparatus for coun~ing the number of cycles of 05 calibration signal occurring during each successive 06 pulse of the Eirst signal, to provi~e successive count 07 signals, apparatus ~or s-toring a predetermined number 08 of the successive count signals, apparatus for 09 totalling the values of the stored count signals to provide an output signal representative of the average 11 frequency to be measured over a period of the 12 predetermined number of successive count signals, 13 apparatus for deleting a first-in count signal and 14 adding a new count signal with each successive pulse of the first signal, and apparatus for successively 16 totalling the values of the stored count signals each 17 time a new count signal has been stored, whereby the 1~ output signal is continuously representative oE the 19 average Erequency of the signal to be .neasured updated each pulse of the first signal.
21 It should be noted that the average time 22 for a predetermined number of pulses can be used, 23 rather than the to~al (i.e. the time divided by the 24 number of pulses). Alternatively, a running average of a prede~ermined number of totals could be used, to 26 smooth a curve defined by the totals.
27 Thus the me~hod and apparatus provides an
06 It is sometimes required to measure the 07 fre~uency of a ~requency varying signal with high 08 resolution on a continuous basisO For example, 09 variations in frequenc~ of radiation from the earth as detected by a magnetometer or the like during an 11 airplane scan of the terrain can indicate the present 12 of magnetic ore bodies. The speed by which the 13 scanning is conducted is usually dependent on the 14 ability of the frequency determining apparatus to de-termine frequency variation of the detected input 16 signal as anomolies are overflown. By increasing the 17 resolution of the frequency determining apparatus and 1~ by increasing the signal sampling rate, a much faster 19 scan of the terrain could be achieved. This would reduce the cost of conducting the scan, or would 21 facilitate conducting the scan over a much greater 22 area during a given scanning interval.
23 Present frequency determining methods 24 require the use of relatively slow propeller driven survey airplanes to conduct the scanO This invention 26 increases the sampling rate of the frequency 27 determining apparatus to such a great extent that it 28 is believed that fast jet airplanes can be used to 29 conduct the scan, at much greater speeds than before.
An understanding of this invention will be 31 obtained by a consideration of the description below, 32 of the general concept and of a preferred embodiment 33 of the invention, in conjunction with the following 34 drawings in which:
Figures 1-4 are waveform diagrams used to 36 explain prior art forms of the invention, 37 Figure 5 is a waveform diag~am used to 01 explain the present invention, 02 Figure 6 is a block diagram of the basic 03 form of the present invention, and 04 Figure 7 is a block diagram illustrating 05 the preferred form of the present invention.
06 Turning to Figure 1, a received signal 07 whose frequency is to determined is shown as waveform 08 1, which has been corrected into squarewave form.
09 Within a certain period P, there are n pulses which can vary in number according to variations in 11 frequency. According to one prior art technique Eor 12 determining the frequency of an input signal, the 13 number of pulses within a period P (e.g. 1 second) is 14 counted, thereby representing the ~requency. In this 1~ technique it ta~es a full second (assuming that is the 16 time interval of the count) to determine the frequency 17 of the input signal.
18 In order to increase the resolution and 19 thus the accuracy of the described technique, the number of input pulses is sometimes multiplied by a 21 predetermined factor, and then the number of pulses is 22 measured over a defined period of time (e.g. 1 23 second), as before. However this also requires a long 24 time period to perform the frequency determination.
According to a technique for decreasing 26 the required period of time for frequency 27 determination, the time period of a single input pulse 28 2 is measured (Figure 2). However this measurement is 29 very limited in re~olution.
To increase the resolution of the period 31 measurement technique, a period measurement of a large 32 number n cf periods is measured as shown in Figure 3.
33 The total time period required to determine the 34 frequency is nxT, where T is the period of each pulse (assuming equal pulse periods). ~owever this 36 increases the required time period while i~ increases 37 the resolution.
01 The technique of Figure 3 is also used in 02 the technique shown in Figure 4, in which successive 03 pulse group ~ntervals of the input signal are 04 measured, to determined changes in frequency. For 05 example, six pulses during the period nxTl are 06 measured, followed by the measurement of a similar 07 number of pulses during the interval nxT2. Thus it 08 may be seen that two successive time periods, each six 09 pulses long are required to detect any change in frequency. Clearly this is a relatively slow and 11 ineffective technique for determining the frequency 12 change of a terrestrial signal caused by a stationary 13 ore body, from a fast moving airplane, particularly 1~ when the ore body is small.
According to prior art techniques, 16 increases in resolution result in decrease in speed of 17 frequency determination, and vice versa.
18 The present invention achieves high 19 resolution obtained by the multiple pulse period measurement technique, but simultaneously achieves a 21 fast sampling rate similar to that of the single pulse 22 measurement technique. A consideration of Figure 5 23 will illustrate the technique.
24 The -time period for n pulses (shown as six in number ~or example), each having its own time 26 period, for example, To-Ts, is measured, as in the 27 technique described with reference to Figure 3. The t 28 total time for the six periods is nPl. Then the 29 ~irst-in pulse time period To is dropped, and the time period of the next pulse T6 is added to time periods 31 Tl-T5, to provide a total time period of nP2.
32 Following this the next first-in pulse time period P2 33 is dropped and the time period T7 is added to 34 establish the total time period nP3. It may be seen that should the frequency change~ the period of each 36 new incoming pulse also changes~ and thus the total 37 changes. Accordingl~ we have a moving total 01 representing the frequency of a given number of 02 pulses.
03 It should be noted that while the total 04 over a predetermined number of pulses provides a 05 relatively high re~solution result, a sample is taken 06 each pulse period. Consequently the sampling rate is 07 as high as the pulse rate. Thus we have the result of 03 high resolution at the same time as a high sampling ~9 rate.
While the actual pulse rate of the input 11 signal can be used~ it is preferred, Eor ease of 12 design and stablity of the circuitry to divide the 13 relatively high frequency input signal by a factor 14 whereby the pulse rate which is measured is of the order of 100 hertz. This also provides time for 16 relatively inexpensive processors to generate the 17 average calculation.
1~ It may be seen that the method of the 19 present invention provides a substantially improved freguency measurement technique, which provides the 21 desirable result of high resolution at the same time 22 as high sampling rate, which was not possible in the 23 aforenoted prior art techniques. Accordingly a high 24 speed scanning survey airplane can be used to conduct the survey.
26 The apparatus of the invention, in 27 general, is a continuous frequency measurement 28 apparatus comprising apparatus for providing a first 29 signal having frequency related to the frequency of the signal to be measured, and apparatus for totalling 31 the pulse period of the first signal over a 32 predetermined number of the pulses successively as a 33 moving total.
34 More particularly, the invention is a continuous variable frequency measurement apparatus 36 comprising apparatus for providing a first signal 37 having a frequency related to the frequency of a 38 _ ~ _ 01 signal to be measured, a source of a calibration 02 signal having a prede~ermined constant frequency which 03 is greater than the frequency oE the ~irst signal, 04 apparatus for coun~ing the number of cycles of 05 calibration signal occurring during each successive 06 pulse of the Eirst signal, to provi~e successive count 07 signals, apparatus ~or s-toring a predetermined number 08 of the successive count signals, apparatus for 09 totalling the values of the stored count signals to provide an output signal representative of the average 11 frequency to be measured over a period of the 12 predetermined number of successive count signals, 13 apparatus for deleting a first-in count signal and 14 adding a new count signal with each successive pulse of the first signal, and apparatus for successively 16 totalling the values of the stored count signals each 17 time a new count signal has been stored, whereby the 1~ output signal is continuously representative oE the 19 average Erequency of the signal to be .neasured updated each pulse of the first signal.
21 It should be noted that the average time 22 for a predetermined number of pulses can be used, 23 rather than the to~al (i.e. the time divided by the 24 number of pulses). Alternatively, a running average of a prede~ermined number of totals could be used, to 26 smooth a curve defined by the totals.
27 Thus the me~hod and apparatus provides an
2~ advantage over prior art techniques for both short 29 lasting but constant frequency samples and for continuous and drifting frequencies. The accuracy of 31 the scanned frequency in proton continuous types of 32 magnetometers, such as helium or cesium and the 33 reliability of the result Erom the freguency 34 distribution, is considerably improved. The technique and apparatus is of course not limi~ed to the 36 geophysics field, and can be used in any field in 37 which a varying frequency is to be measured with high 3g - 5 -6~
01 resolution.
02 A block diagram of the basic form of the 03 preferred embodiment o~ the invention is shown in 0~ Figure 6. An input signal is received at input 3 at a 05 signal condltioner 4. The signal conditioner reduces 06 the frequency of the input signal. For example, the 07 input signal from a proton magnetometer typically 08 would be between l kHz and 5 kHz, the output of a 09 helium ma~netometer would be typically between 200 kHz and l megahertz, while the input signal from a cesium 11 magnetometer might be twice as high as from the latter 12 magnetometer. The signal conditioner, which could be 13 a phase locked loop or counter, provides an output 14 frequency of the order of lO0 hertz. This signal is applied to a moving totalizer 5. An output signal of 16 the moving totalizer is obtained at port 6.
17 The moving totalizer stores the time 18 periods of a first predetermined number of pulses l9 output from the signal conditioner 4. A total ti~e period is then determined, which is representative of 21 the average frequency of the first predetermined 22 number of pulses ~e.g. 6 in number). Then the time 23 period of the first-in pulse is dropped from the total 24 time and the time period of the next pulse output from signal conditioner 4 is measured and is added with the 26 remaining total of the time periods. The time period 27 for the next first-in pulse is then dropped and the 28 time period of the next-in pulse received from signal 29 conditioner 4 is stored and added with the time periods of the remaining pulses. Each total is 31 determined and a signal designating the total is 32 output at port 6. Each total is of course 33 representative of the frequency of the input signal.
34 A total i9 struck once each pulse.
As the frequency of the input signal 36 changes, the time periods of the pulses of the output 37 signal from signal conditioner 4 change, and 01 consequently the time period signal output from moving 02 totalizer 5 changes, which provides an output signal 03 indicative of the frequency and of the changeO
04 Accordingly an output signal representative of the 05 frequency of the input signal is produced having high 06 resolution which corresponds to a large number of 07 pulses, but with a sampling rate corresponding to the 08 frequency of single pulses output from the signal 09 conditioner.
Figure 7 shows a more detailed block 11 diagram of the preferred form of the invention. An 12 input signal is received at input 3 to a signal 13 conditioner 4. The reduced frequency output signal of 14 signal conditioner 4 is applied to a two output di~ide by two counter 7, which can be in the form of a J-K
16 flip-flop.
17 A calibration signal fcAL having a constant 18 frequency much higher than the output signal of the 19 signal conditioner is applied to a lead 8 which is connected to the inputs of a pair of switches 9 and 21 10. The outputs o~ switches 9 and 10 are connected 22 respectively to counters 11 and 12. The outputs of 23 divide by two counters 7 and 8 (each of which is high 24 during successive alternate pulses of the input signal from the signal conditioner1 are connected to the 26 enable inputs of corresponding switches 9 and 10.
27 Consequently when one output of counter 7 is high, 28 switch 9 is caused to close and when the other input 29 of counter 7 is alternately high, switch 9 is caused to open and switch 10 is caused to close.
31 During one output pulse from signal 32 conditioner 4, the signal fcAL is applied to the 33 input of counter 11, while during the next output 34 pulse of conditioner 4, the signal fcAL is applied to the input o~ counter 12. The number of fcAL
36 signal pulses stored in counters 11 and 12 are thus 37 representative of the corresponding time periods of 01 two succeeding output pulses of signal conditioner ~.
02 The output ports of the counters 11 and 12 03 are connected via a processor 14 to a memory 15, which 04 stores a predetermined number of pulse time data 05 signals from the counters, from which an total can be 06 taken by the processor.
07 When one output of counter 7 goes high, an 08 enable circuit 13 is caused to input an interrupt 09 signal to processor 14, having inputs connected to the outputs of counter 11 This interrupt causes 11 processor 14 to receive the count signal stored in 12 counter 11 and to reset lt. Processor 14 causes 13 memory 15 to erase the data stored at a first memory 14 location in memory 15 if necessary, to shift the data stored in each of a predetermined number of locations 16 te.g. the following five locations for six pulses) to 17 lower numbered locations including the erased 18 location, and to store the count data signal from 19 counter 11 in the last or freed memory location of memory 15.
21 Since at the beginnin~ of operation all of 22 the memory locations of memory 15 will be empty or 23 have non-sensible values stored therein, until the 24 count outputs from the counters are stored in all memory locations, the data stored in memory 15 will 26 not have validity as a whole.
27 With the next pulse leading edge from 28 counter 7 input to enable circuit 13, processor 14 is 29 interrupted causing it to receive output data ~rom counter 1:2 and to reset counter 12. The data stored 31 in the first-in location of memory 15 is erased or 32 otherwise deleted if necessary, and the data stored at 33 the second to the sixth memory locations are shifted
01 resolution.
02 A block diagram of the basic form of the 03 preferred embodiment o~ the invention is shown in 0~ Figure 6. An input signal is received at input 3 at a 05 signal condltioner 4. The signal conditioner reduces 06 the frequency of the input signal. For example, the 07 input signal from a proton magnetometer typically 08 would be between l kHz and 5 kHz, the output of a 09 helium ma~netometer would be typically between 200 kHz and l megahertz, while the input signal from a cesium 11 magnetometer might be twice as high as from the latter 12 magnetometer. The signal conditioner, which could be 13 a phase locked loop or counter, provides an output 14 frequency of the order of lO0 hertz. This signal is applied to a moving totalizer 5. An output signal of 16 the moving totalizer is obtained at port 6.
17 The moving totalizer stores the time 18 periods of a first predetermined number of pulses l9 output from the signal conditioner 4. A total ti~e period is then determined, which is representative of 21 the average frequency of the first predetermined 22 number of pulses ~e.g. 6 in number). Then the time 23 period of the first-in pulse is dropped from the total 24 time and the time period of the next pulse output from signal conditioner 4 is measured and is added with the 26 remaining total of the time periods. The time period 27 for the next first-in pulse is then dropped and the 28 time period of the next-in pulse received from signal 29 conditioner 4 is stored and added with the time periods of the remaining pulses. Each total is 31 determined and a signal designating the total is 32 output at port 6. Each total is of course 33 representative of the frequency of the input signal.
34 A total i9 struck once each pulse.
As the frequency of the input signal 36 changes, the time periods of the pulses of the output 37 signal from signal conditioner 4 change, and 01 consequently the time period signal output from moving 02 totalizer 5 changes, which provides an output signal 03 indicative of the frequency and of the changeO
04 Accordingly an output signal representative of the 05 frequency of the input signal is produced having high 06 resolution which corresponds to a large number of 07 pulses, but with a sampling rate corresponding to the 08 frequency of single pulses output from the signal 09 conditioner.
Figure 7 shows a more detailed block 11 diagram of the preferred form of the invention. An 12 input signal is received at input 3 to a signal 13 conditioner 4. The reduced frequency output signal of 14 signal conditioner 4 is applied to a two output di~ide by two counter 7, which can be in the form of a J-K
16 flip-flop.
17 A calibration signal fcAL having a constant 18 frequency much higher than the output signal of the 19 signal conditioner is applied to a lead 8 which is connected to the inputs of a pair of switches 9 and 21 10. The outputs o~ switches 9 and 10 are connected 22 respectively to counters 11 and 12. The outputs of 23 divide by two counters 7 and 8 (each of which is high 24 during successive alternate pulses of the input signal from the signal conditioner1 are connected to the 26 enable inputs of corresponding switches 9 and 10.
27 Consequently when one output of counter 7 is high, 28 switch 9 is caused to close and when the other input 29 of counter 7 is alternately high, switch 9 is caused to open and switch 10 is caused to close.
31 During one output pulse from signal 32 conditioner 4, the signal fcAL is applied to the 33 input of counter 11, while during the next output 34 pulse of conditioner 4, the signal fcAL is applied to the input o~ counter 12. The number of fcAL
36 signal pulses stored in counters 11 and 12 are thus 37 representative of the corresponding time periods of 01 two succeeding output pulses of signal conditioner ~.
02 The output ports of the counters 11 and 12 03 are connected via a processor 14 to a memory 15, which 04 stores a predetermined number of pulse time data 05 signals from the counters, from which an total can be 06 taken by the processor.
07 When one output of counter 7 goes high, an 08 enable circuit 13 is caused to input an interrupt 09 signal to processor 14, having inputs connected to the outputs of counter 11 This interrupt causes 11 processor 14 to receive the count signal stored in 12 counter 11 and to reset lt. Processor 14 causes 13 memory 15 to erase the data stored at a first memory 14 location in memory 15 if necessary, to shift the data stored in each of a predetermined number of locations 16 te.g. the following five locations for six pulses) to 17 lower numbered locations including the erased 18 location, and to store the count data signal from 19 counter 11 in the last or freed memory location of memory 15.
21 Since at the beginnin~ of operation all of 22 the memory locations of memory 15 will be empty or 23 have non-sensible values stored therein, until the 24 count outputs from the counters are stored in all memory locations, the data stored in memory 15 will 26 not have validity as a whole.
27 With the next pulse leading edge from 28 counter 7 input to enable circuit 13, processor 14 is 29 interrupted causing it to receive output data ~rom counter 1:2 and to reset counter 12. The data stored 31 in the first-in location of memory 15 is erased or 32 otherwise deleted if necessary, and the data stored at 33 the second to the sixth memory locations are shifted
3~ down one memory location to the first to the fifth memory loc:ations. The data output from counter 12 is 3~ then stored at the sixth memory location of memory 15.
37 In similar manner, each successive pulse 01 output from signal conditioner 1~ causes the count 02 data representing the time of one pulse period 03 alternately from counter 11 and counter 12 to be 04 stored at the sixth memory location in memory 15, 05 after the data in the second to sixth memory locations 06 are shifted to the first to the fifth memory locations.
07 Each time a data signal is stored in the 08 sixth memory location of memory 15, processor 14 is 09 caused to read the data in the six memory locations and to total them. Alternatively it can merely 11 average the time value data signals. This provides an 12 indication of the time period of six pulse periods 13 output from signal conditioner 4. The total or 14 average signal is output from output port 6 to an output line, and can be plotted on a graph or 16 displayed on a meter or digital display, as a 17 representation of the absolute and varying frequency 13 of the input signal.
19 As noted earlier, the average of a predetermined number of totals can also be used, to 21 smooth the output signal.
22 Since the total is determined each time 23 the sixth memory location is written, the output 24 signal representative of the input frequency is updated at the frequency of each pulse output ~rom 26 signal conditioner 4. It is clear that the sampling 27 rate is very high. Since the number of pulses 28 measured can be predetermined, the resolution can also 29 be established, and can be very high. The larger the number of pulses and the higher their frequency, 31 however, the faster the processor required.
32 Appendix A illustrates the algorithm 33 performed by processor ~, which is believed to be 34 self-explanatory. The variable m represents the number of pulses during a totalling period, while n is 36 the count number stored in a counter. The variable C
37 is a constant multiplied by the total count from the 38 _ 9 _ 01 counters over the totalizlng period, divided by the 02 reference frequency. A consideration of Appendix A
03 with respect to the description noted above will make 04 clear the manner of operation of the processor. It is 05 of course assumed that a person skilled in the art 06 understanding this invention will also understand the 07 techniques of preparing a program for operation of the 08 processor according to the algorithm described above.
09 It will be understood that since signals representing the time periods of each of the pulses 11 within a totalizing period are stored in the memory, 12 other operations can also be performed based on these 13 values~ such as determining the statistical 14 distribution of the samples, obtaining parameters such as signal to noise ratio, establishing the reliability 16 of the readings, etc.
17 Further, it should be noted that the 18 system can be used to provide a first indication of 19 the presence of ore bodies during a fast exploration scan of a territory. Should an interesting anomoly be 21 located, a slow pass can be initiated to pinpoint its 22 location more accurately or, alternatively, the 23 resolution of the system can be changed by increasing 24 the number o~ samples totalized.
A person understanding this invention may 26 now conceive of other embodiments or variations and 27 additions, using the principles described herein. All 28 are consi~ered to be within the sphere and scope of 29 the inven~ion as defined in the claims appended hereto.
~ APP~.~DIX A
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37 In similar manner, each successive pulse 01 output from signal conditioner 1~ causes the count 02 data representing the time of one pulse period 03 alternately from counter 11 and counter 12 to be 04 stored at the sixth memory location in memory 15, 05 after the data in the second to sixth memory locations 06 are shifted to the first to the fifth memory locations.
07 Each time a data signal is stored in the 08 sixth memory location of memory 15, processor 14 is 09 caused to read the data in the six memory locations and to total them. Alternatively it can merely 11 average the time value data signals. This provides an 12 indication of the time period of six pulse periods 13 output from signal conditioner 4. The total or 14 average signal is output from output port 6 to an output line, and can be plotted on a graph or 16 displayed on a meter or digital display, as a 17 representation of the absolute and varying frequency 13 of the input signal.
19 As noted earlier, the average of a predetermined number of totals can also be used, to 21 smooth the output signal.
22 Since the total is determined each time 23 the sixth memory location is written, the output 24 signal representative of the input frequency is updated at the frequency of each pulse output ~rom 26 signal conditioner 4. It is clear that the sampling 27 rate is very high. Since the number of pulses 28 measured can be predetermined, the resolution can also 29 be established, and can be very high. The larger the number of pulses and the higher their frequency, 31 however, the faster the processor required.
32 Appendix A illustrates the algorithm 33 performed by processor ~, which is believed to be 34 self-explanatory. The variable m represents the number of pulses during a totalling period, while n is 36 the count number stored in a counter. The variable C
37 is a constant multiplied by the total count from the 38 _ 9 _ 01 counters over the totalizlng period, divided by the 02 reference frequency. A consideration of Appendix A
03 with respect to the description noted above will make 04 clear the manner of operation of the processor. It is 05 of course assumed that a person skilled in the art 06 understanding this invention will also understand the 07 techniques of preparing a program for operation of the 08 processor according to the algorithm described above.
09 It will be understood that since signals representing the time periods of each of the pulses 11 within a totalizing period are stored in the memory, 12 other operations can also be performed based on these 13 values~ such as determining the statistical 14 distribution of the samples, obtaining parameters such as signal to noise ratio, establishing the reliability 16 of the readings, etc.
17 Further, it should be noted that the 18 system can be used to provide a first indication of 19 the presence of ore bodies during a fast exploration scan of a territory. Should an interesting anomoly be 21 located, a slow pass can be initiated to pinpoint its 22 location more accurately or, alternatively, the 23 resolution of the system can be changed by increasing 24 the number o~ samples totalized.
A person understanding this invention may 26 now conceive of other embodiments or variations and 27 additions, using the principles described herein. All 28 are consi~ered to be within the sphere and scope of 29 the inven~ion as defined in the claims appended hereto.
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Claims (17)
1. A continuous variable frequency measurement apparatus comprising:
(a) means for providing a first signal having a frequency related to the frequency of a signal to be measured, (b) means for generating signals having values related to the time of each pulse of the first signal, (c) means for successively storing a predetermined successive number of said generated signals, (d) means for summing the values of the stored signals to provide a first totalized signal, (e) means for repetitively deleting a stored signal representing the earliest of the stored generated signal and with each deletion storing a further one of the successively generated signals, and (f) means for repetitively summing the values of the predetermined numbered of the stored signals each time a further successive generated signal is stored to provide successive totalized signals, whereby said first and successive totalized signals are indicative of the variable frequency of the signal to be measured.
(a) means for providing a first signal having a frequency related to the frequency of a signal to be measured, (b) means for generating signals having values related to the time of each pulse of the first signal, (c) means for successively storing a predetermined successive number of said generated signals, (d) means for summing the values of the stored signals to provide a first totalized signal, (e) means for repetitively deleting a stored signal representing the earliest of the stored generated signal and with each deletion storing a further one of the successively generated signals, and (f) means for repetitively summing the values of the predetermined numbered of the stored signals each time a further successive generated signal is stored to provide successive totalized signals, whereby said first and successive totalized signals are indicative of the variable frequency of the signal to be measured.
2. A continuous variable frequency measurement apparatus comprising:
(a) means for receiving a first pulse signal having a frequency related to the frequency of a signal to be measured, (b) means for summing the pulse periods of said first signal over a predetermined number of said pulses successively as a moving total to provide a signal indicative of the frequency of the signal to be measured.
(a) means for receiving a first pulse signal having a frequency related to the frequency of a signal to be measured, (b) means for summing the pulse periods of said first signal over a predetermined number of said pulses successively as a moving total to provide a signal indicative of the frequency of the signal to be measured.
3. A measurement apparatus as defined in claim 2, in which the summing means is comprised of means for summing said predetermined number of pulse periods once each pulse period.
4. A measurement apparatus as defined in claim 2 or 3 in which the predetermined number of pulses is fixed.
5. A continuous variable frequency measurement apparatus comprising:
(a) means for providing a first signal having a frequency related to the frequency of a signal to be measured, (b) a source of a calibration signal having a predetermined constant frequency which is much greater than the frequency of the first signal, (c) means for counting the number of cycles of calibration signal occurring during each successive pulse of the first signal, to provide successive count signals, (d) means for storing a predetermined number of the successive count signals, (e) means for summing the values of the stored count signals, to provide an output signal representative of the average frequency of the signal to be measured over the period of the predetermined number of successive count signals, (f) means for deleting a first-in count signal and adding a new count signal with each successive pulse of the first signal, (g) means for successively summing the values of the stored count signals each time a new count signal has been stored, whereby said output signal is continuously representative of the average frequency of the signal to be measured updated with each pulse of said first signal.
(a) means for providing a first signal having a frequency related to the frequency of a signal to be measured, (b) a source of a calibration signal having a predetermined constant frequency which is much greater than the frequency of the first signal, (c) means for counting the number of cycles of calibration signal occurring during each successive pulse of the first signal, to provide successive count signals, (d) means for storing a predetermined number of the successive count signals, (e) means for summing the values of the stored count signals, to provide an output signal representative of the average frequency of the signal to be measured over the period of the predetermined number of successive count signals, (f) means for deleting a first-in count signal and adding a new count signal with each successive pulse of the first signal, (g) means for successively summing the values of the stored count signals each time a new count signal has been stored, whereby said output signal is continuously representative of the average frequency of the signal to be measured updated with each pulse of said first signal.
6. A measurement apparatus as defined in claim 5, in which the means for counting is comprised of a pair of counters having inputs connected to the source of calibration signal, means for switching the source of calibration signal to the input of one counter to store pulses thereof during the interval of every second pulse of said first signal, means for switching the source of calibration signal to the input of the other counter to store pulses thereof during every alternate pulse of said first signal, memory means for storing output signals of each alternate counter representing a calibration signal cycle count stored therein at the leading edge of each pulse of the first signal, and processor means for controlling the storage of the cycle count signals in the memory means, the deletion of the first-in count signal, the summing of the predetermined number of successive count signals and the provision of said output signal.
7. A measurement apparatus as defined in claim 6, including means for applying said first signal to the input of a flip-flop, switch means connecting the source of calibration signal to the inputs of the counters, and means for applying individual outputs of the flip-flop to corresponding control inputs of the switches, whereby each switch is closed during alternate pulse periods of said first signal.
8. A measurement apparatus as defined in claim 5, 6 or 7 in which said means for providing said first signal is comprised of a frequency divider for receiving the signal whose frequency is to be measured and providing said first signal reduced in frequency by a predetermined factor.
9. A measurement apparatus as defined in claim 5, 6 or 7 in which said means for providing said first signal is comprised of a divider for receiving the signal whose frequency is to be measured and providing said first signal reduced in frequency by a order of about 10, and in which the calibration signal is an order of about 105 times the frequency of said first frequency.
10. A continuous variable frequency measurement apparatus comprising:
(a) means for providing a first pulse signal having a frequency related to the frequency of a signal to be measured, (b) means for totalling the pulse periods of said first signal over a predetermined number of said pulses successively as a moving total once each pulse or low multiple thereof which is much smaller than said predetermined number, whereby a signal representative of the frequency of the signal to be measured is generated.
(a) means for providing a first pulse signal having a frequency related to the frequency of a signal to be measured, (b) means for totalling the pulse periods of said first signal over a predetermined number of said pulses successively as a moving total once each pulse or low multiple thereof which is much smaller than said predetermined number, whereby a signal representative of the frequency of the signal to be measured is generated.
11. A measurement apparatus as defined in claim 10, including means for averaging a predetermined number of moving totals to provide a smoothed representation of said signal representative of the frequency of the signal to be measured.
12. A method of measuring the frequency of an input signal comprising:
(a) measuring and storing signals representing the time invervals of each pulse of a predetermined constant number of successive pulses of said signal, (b) summing the time interval signals of said predetermined number of pulses, (c) measuring the time intervals of successive pulses of said signal, (d) successively deleting the time interval signal of the earliest pulse in said total and adding the time interval signal of a new pulse, each time the time of a new pulse is measured, whereby a running total of the time periods of a predetermined constant number of pulses is obtained, said total being representative of the frequency of said input signal, and (e) providing an output signal of said total, representing the frequency of said input signal, having a resolution based on the predetermined constant number of pulses, and a sampling rate which is the pulse rate of the pulses of said input signal.
(a) measuring and storing signals representing the time invervals of each pulse of a predetermined constant number of successive pulses of said signal, (b) summing the time interval signals of said predetermined number of pulses, (c) measuring the time intervals of successive pulses of said signal, (d) successively deleting the time interval signal of the earliest pulse in said total and adding the time interval signal of a new pulse, each time the time of a new pulse is measured, whereby a running total of the time periods of a predetermined constant number of pulses is obtained, said total being representative of the frequency of said input signal, and (e) providing an output signal of said total, representing the frequency of said input signal, having a resolution based on the predetermined constant number of pulses, and a sampling rate which is the pulse rate of the pulses of said input signal.
13. A method of measuring the frequency of an input signal comprising:
(a) providing a first signal having a frequency related to the frequency of the signal to be measured, (b) averaging the cycle periods of the signal over a predetermined number of cycles successively as a moving average, whereby said averages are successive representations of the frequency of the input signal.
(a) providing a first signal having a frequency related to the frequency of the signal to be measured, (b) averaging the cycle periods of the signal over a predetermined number of cycles successively as a moving average, whereby said averages are successive representations of the frequency of the input signal.
14. A method as defined in claim 13, in which the cycle periods are averaged with each new cycle of said first signal.
15. A method of measuring the frequency of a signal comprising:
(a) providing a first signal having a frequency related to the frequency of the signal to be measured, (b) totalling the cycle periods of the signal over a predetermined number of cycles successively as a moving total, whereby said totals are successive representations of the frequency of the input signal.
(a) providing a first signal having a frequency related to the frequency of the signal to be measured, (b) totalling the cycle periods of the signal over a predetermined number of cycles successively as a moving total, whereby said totals are successive representations of the frequency of the input signal.
16. A method as defined in claim 15 in which the cycle periods are summed with the arrival of each new cycle of said first signal, the predetermined number of cycles being successive cycles and being fixed in number.
17. A method as defined in claim 15 or 16 including the steps of averaging a predetermined number of successive totals to provide an output signal representative of the frequency of said input signal.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419000A CA1184604A (en) | 1983-01-06 | 1983-01-06 | Continuous variable frequency measurement apparatus |
| AU20895/83A AU2089583A (en) | 1983-01-06 | 1983-11-02 | Continuous variable frequency measurement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000419000A CA1184604A (en) | 1983-01-06 | 1983-01-06 | Continuous variable frequency measurement apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1184604A true CA1184604A (en) | 1985-03-26 |
Family
ID=4124271
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000419000A Expired CA1184604A (en) | 1983-01-06 | 1983-01-06 | Continuous variable frequency measurement apparatus |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU2089583A (en) |
| CA (1) | CA1184604A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0484975A2 (en) * | 1990-11-09 | 1992-05-13 | Hewlett-Packard Company | Continuous overlapping frequency measurement |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AR241336A1 (en) * | 1987-09-30 | 1992-05-29 | Siemens Ag | Procedure for determining the frequency of a sampled symmetrical signal |
-
1983
- 1983-01-06 CA CA000419000A patent/CA1184604A/en not_active Expired
- 1983-11-02 AU AU20895/83A patent/AU2089583A/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0484975A2 (en) * | 1990-11-09 | 1992-05-13 | Hewlett-Packard Company | Continuous overlapping frequency measurement |
| EP0484975A3 (en) * | 1990-11-09 | 1992-09-23 | Hewlett-Packard Company | Continuous overlapping frequency measurement |
Also Published As
| Publication number | Publication date |
|---|---|
| AU2089583A (en) | 1984-07-12 |
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