SU1158873A1 - Digital thermometer - Google Patents

Abstract

A DIGITAL THERMOMETER containing a frequency output thermocouple connected to the first input of the clock unit, the output of which is connected to the key input, and the second input connected to the output of the reference frequency generator and through the frequency divider connected to the first input of the control unit, the first output of which is connected to I will give the key input, and the second output is connected to the installation input of the result counter, the output of which is connected to the input of the indicator register and the first input of the certification circuit is smaller, the second input Which are connected to a source of constant logic levels, a group of AND circuits whose outputs are connected to the inputs of an OR scheme, a second OR circuit, three, AND circuits, a second more-less circuit, the first inputs of which are connected to sources of constant reference levels, characterized in that, in order to simplify the process of calibrating the thermometer, two additional OR schemes are added to it, an additional counter, a single-selector, an AND-NOT element, a trigger, two inverters and a decoder, the inputs of which are connected to the outputs of the result counter, and the outputs connected to the inputs of the AND circuit group and the inputs of the second RSHI circuit, the output of which is connected to the first input of the NAND circuit and through the first inverter connected to the first input of the first AND circuit, the second input of which is connected: to the second input of the NAND circuit and output a one-shot, the input of which is connected to the output of the first circuit H) W and the first input of the third OR, the second input of which is connected to the control input of the indicator register and the second output of the control unit, and the output is connected to the installation input of the additional counter, the outputs of which with the 00 inputs of the AND groups, and the counting input is connected to the output of the second AND circuit, the first input of which is connected to the output of the first circuit is more-less and the third input of the AND-NOT circuit, and the second input is connected to the output of the key and the first input of the fourth circuit OR, the second input of which is connected to the output of the first circuit AND, and the output is connected via the second inverter to the first input of the trigger, the second input of which is connected to the output of the AND-NOT circuit, while the inputs of the third circuit AND are connected respectively to the output of the trigger OR ,

Description

and the output is connected to the counting input of the result counter, the setup inputs of which are connected to sources of constant logic levels,

The second input of the second circuit is more or less connected to the intermediate output of the frequency divider, and the output is connected to the second input of the control unit.

The invention relates to devices for measuring temperature, in particular the creation of digital thermometers with piezoquartz temperature transducers with a frequency output signal.

Digital known, oh thermometer containing temperature sensor with frequency output, key, result counter, result indicator register, reference frequency generator, reference frequency divider, AND circuit and control unit

However, this thermometer does not take into account the nonlinearity of the characteristics of thermocouples, which leads to inaccuracy in the readings of the thermometer, especially when measuring E over a wide temperature range.

The closest to the proposed technical essence and the achieved effect is a digital thermometer containing a thermal converter with a frequency output, connected to the first input of a clock unit, the output of which is connected to the input of the key, and the second input connected to the output of the reference frequency generator and through a frequency divider connected to the first input of the control unit, the first output of which is connected to the control

l Kits entrance key, and the second output

connected to the installation input of the result counter, the output of which is connected to the input of the indicator register and the first input of the first circuit is more or less, the second inputs of which are connected to a source of constant logic levels, a group of AND circuits, whose outputs are connected to the inputs of the first OR circuit, the second OR circuit , three circuits And, the second circuit is more-less, the first inputs of which are connected to the sources of constant reference levels, as well as the memory block and the pulse distributor 2.

The known thermometer makes it possible to eliminate the influence of non-linearity of the characteristics of thermal converters on the temperature measurement result, there is no error due to non-linearity in it, however, its scheme is too complicated, and the calibration process is complicated and takes a long time. This is explained by the fact that the thermometer is equipped with setting elements and memory devices in the volume necessary to memorize the complete piecewise linearly approximated characteristics of the thermocouples, which allows you to adjust the thermometer to all parameters of the piecewise linearly approximated characteristic of the thermocouple generator in the form of connection tables And, and the numbers written to the memory for changing the number in the counter, one by one for the approximation area. All this complicates the temperature calibration process when replacing thermocouples.

The purpose of the invention is to simplify the process of calibrating a thermometer.

The goal is achieved by the fact that a digital thermometer containing a thermocouple with frequency output connected to the first input of the clock unit, the output of which is connected to the key input, and the second input is connected to the output of the reference frequency generator and connected to the first input control unit, the first output of which is connected to the control to the key input, and the second output is connected to the installation input of the result counter, the output of which is connected to the input of the indicator register and the first input of the first more-less circuits, the second inputs of which are connected to a source of constant logic levels, a group of AND circuits whose outputs: 3 are connected to the inputs of the first OR circuit, the second OR circuit, three AND circuits, the second circuit is more-less, the first inputs of which are connected to sources of constant reference levels, two OR schemes are added to it, an additional counter, a single vibrator, an NAND element, a trigger, two inverters and a decoder, whose inputs are connected to the outputs of the result counter, and the outputs are connected to the inputs of the AND group and the second inputs schemes OR,, the output of which is connected to the first input of the NAND circuit and through the first infertor is connected to the first input of the first AND circuit, the second input of which is connected to the second input of the AND-NOT circuit and the output of the odouvibrator, the input of which is connected to the output of the first OR circuit and the first input of the third circuit OR, the second input of which is connected to the control input of the indicator register and the second output of the control unit, and the output is connected to the installation input of the additional counter whose outputs are connected1 to the inputs of the AND circuit group, and the counting input is connected to the output the second AND circuit, the first input of which is connected to the output of the first circuit is more or less and the third input of the AND – NO circuit, and the second input is connected to the output of the key and the first input of the fourth OR circuit, the second input of which is connected to the output of the first AND circuit, and the output is connected via the Second Inverter with the first input of the trigger, the second input of which is connected to the output of the NAND circuit, while the inputs of the third AND circuit are connected respectively to the trigger output and the output of the fourth OR circuit, and the output is connected to the counting input of the result counter, setting entrances to orogo connected to sources of permanent logic levels, a second input of the second moreless circuit connected to the intermediate output of the frequency divider, and an output connected to a second input of the control unit. FIG. 1 shows a digital thermometer; in fig. 2 diagram of the clock unit. A 1-meter thermometer contains a thermo converter 1 with a frequency output, a clock unit 2, a key 3, a generator 4 of the reference frequency, a divider 5 frequency, and a block 6 of the control. 734 counter 7 of the result, on the installation inputs of which the number N is supplied in the form of constant logic levels, the indicator register 8, the first circuit is more or less 9, for the first time the inputs of which are the number N in the bidet of constant logic levels, the second circuit is more or less 10, the second inputs of which are in the form of constant logical levels are given the number N, a decoder 11, n outputs of which (where n is the number of approximation nodes of the error curve from nonlinear piezoquartz thermal conversions, on which the correction to the measurement result is positive) n Connected to the first inputs of all AND I 2 groups, py, and m outputs (where ha is the number of approximation areas where the correction to the measurement result is negative) to the inputs of the first OR 13 circuit, additional counter 14, the second OR circuit 15, . single-pulse 16, first circuit AND 17, third OR 18, AND-NOT element 19, fourth circuit OR 20, trigger 21, first inverter 22, second circuit AND 23, third circuit AND 24 and second inverter 25. As an indicator register. 8 uses a register with a reversible display system. The control unit contains a trigger 26, the inputs of which are the first and second inputs of the control unit, and a one-shot 27 connected to the trigger output. The outputs of the trigger and the one-shot are simultaneously the first and second outputs of the control unit. The clock unit 2 is designed to bind the pulses from the thermal converter 1 at any time to the pulses of the reference generator, which is necessary, for example, so that the transfer of information from counter 7 to the register 8 does not occur at the time when the counter 8 counts the next pulse from the sensor . The clock unit (Fig. 2) can be implemented on two GR-triggers 28 and 29 and element 30, the output of which is the output of the clock block, and the inputs are connected to the forward output of the trigger 28 and the inverse output of trigger 29. The clock inputs of both The trigger is connected to the output of the optional generator, the D input of the trigger 28 under 5 G keys to the output of the thermal converter, and the trigger 29 to the trigger trigger 28. The circuits greater than or less 9 and 10 are devices for subtracting two numbers with the output only sign of the result and can be implemented on the basis of Artney chips. The operation of a digital thermometer is based on the fact that it first converts the frequency into a code that depends only on temperature and does not depend on the spread of the characteristics of the thermal converter on the nominal frequency and slope, and then linearizes the number thus obtained by introducing an amendment. This uses the fact that after converting the frequency of the thermocouple into a code, taking into account the nominal frequency of the thermocouple and the slope, the nature of the nonlinearity for all piezoquartz thermal converters becomes the same, i.e. after, combining the initial and final points of the characteristic by shifting all its points perpendicular to the abscissa axis and multiplying each ordinate by a factor individually for each thermal converter, the characteristics at the other points will be. Therefore, in the proposed thermometer, in contrast to the prototype, at first, two points of characteristic are combined, and then linearization of the overall program. It is very important that in the proposed thermometer the process of combining two points of the characteristic of the thermal converter ends with to Toroj, as the counting process ends, which allows starting and ending linearization in the process of counting the pulses from the thermal conversion of bodies r without increasing the measurement time. In other words, a feature of the proposed thermometer is the lack of conversion of the already received code, in which the variations in the characteristics of the thermal converters are eliminated, but the error from nonlinearity remains, in the OTHER code, in which there is no error from nonlinearity. The process of obtaining the result in the proposed thermometer is carried out as follows. As a result of the next overflow of the divider 5, the trigger 26 of the control block 6 is set to O, closes the key 3 and starts the one-shot 27, impinges on the output of which (the second output of the control block) transfers the result from the count 7 to the indicator register 8. At the same time 7, the number N is entered, and the counter 14 through the OR circuit 18 is set to O. The frequency divider 5 is then set to O and the output of the circuit 10 is also set O, since the number in the divider (all zeros) is less than the number Nj. When in the divider 5 of the reference frequency, as a result of continuous counting of the pulses of the reference frequency generator 4, the number N is greater than 10, the pulse is sent to control unit 6, the trigger 26 of the control unit is set to 1, key 3 is unlocked. The pulses from the temperature sensor 1 through the clock unit 2, the key 3, the circuit OR 20 and the circuit AND 24 begin to arrive at the input of the counter 7 of the result. In the clock unit, after the arrival of 1 to the D input of the trigger 28 from the thermal converter, the nearest front pulse of the reference generator sets the trigger 28 to 1. At the same time, the output pulse of the AND 30 element is 1. The next pulse of the reference generator sets the 1 trigger 29 and 30 Wits O. At the end of the input pulse, the triggers 28 and 29 are alternately set to O by the pulses of the reference generator. Since in O first there is a trigger trigger 28,. impulse from the output of the element I 30 is not in accordance with Wits. Thus, in response to a single pulse of a thermal converter, having an arbitrary duration and arriving at an arbitrary time, the clocking unit produces one narrow positive pulse whose duration is equal to the period of the reference generator signal, and the beginning and end coincide with one of the edges of this signal. The result counter counts the incoming pulses to its input. The pulses from the output of the clock unit will flow into the counter 7 of the result until the number in the counter 7 becomes equal to N. After that, the input pulses from the output of the key 3 will start through the AND 23 circuit to the input of the counter 14. Counter 14, AND diagrams 12, an OR 18 circuit and a single vibrator 16 represent a hundred controlled frequency divider that is controlled by the outputs of depot generator 11. The set of dividing coefficients of the controlled divider determines c by the generalized nonlinearity characteristic of piezoquartz thermal converters e depending on the number corresponding to the temperature, the number recorded in the meter 7 ,, excluding exp. wok that a controlled divider must produce (i.e., in the form of an error curve from nonlinearity). In this case, it is taken into account that N and N are selected for each thermal converter individually, depending on the zero (nominal) frequency and average slope of the thermal converter between the calibration wheelbarrows. When the number in the counter 14 becomes equal to the number, at which the output of the selected circuit of the circuit 12 and tc 1, the one-shot 16 turns on and the mode OR 18 sets the counter 14 to 0, if at the output of the circuit OR 15 o, 17, 20 and 24 will add 1 to the count of 7 results. If the output of the OR 15 circuit is 1, this means that the soda: you don’t need to add the counter, but to subtract 8 in this case, the pulse from the output of one vibrator 16 sets the trigger 21 to O and the input of the counter 7 results not passed. The next pulse of the code code 3 does not pass to the input of counter 7 by the falling edge of the same pulse, trigger 2 is set to 1, thereby allowing the passage of the next counting pulses from the output of key 3 through circuit 24 to the input of counter 7 of the result. The number Nj sets the counting time from the condition that the difference in thermometer readings when temperature is different at two points in the temperature range corresponds to the temperature difference at these two points. The number sets the temperature in one of the range points. 38 The number N is chosen outside the temperature range (e.g. 180 ° C). When the number N appears in the result counter, the measurement result is corrected. This number is constant for all thermocouples and a few "L-P1" x s larger than the largest NT of all that may be needed for this family of thermocouples, but at the same time less, which will appear in the result counter when measuring the minimum temperature Ni, N Np ,. Since N is constant, and after a result is measured in the counter, a number depends on the temperature and does not depend on the zero frequency of the thermal converter and the average steepness of its thermal-frequency characteristics, since this dependence is eliminated by the appropriate choice for i-rp - NH Nj5 thermal converter, the number of pulses received by the counter from the output of the key 3 during the time from the moment of the appearance of the number N in the counter to the counting interval also depends only on the temperature and does not depend on the zero frequency of the thermal converter and cf one of the steepness of its thermal characteristics. . Thus, by the end of the counting interval, i.e., at the moment of the overflow of divider 5, the result is set in counter 7. measurement, which, firstly, does not depend on the spread of the characteristics of the thermal converter, since this variation is eliminated by an appropriate choice of the number N, the preset of the counter 7 and the number Ngj-select; the measurement time depending on the average slope of the thermal frequency characteristic 1 of the thermal converter, and secondly, it is linearly related to the measured temperature, since the error of nonlinearity is eliminated in the counting process by adding pulses from a controlled frequency divider to the counter or prohibiting the addition of pulses to the counter ignalami this divider of advance: by law. The proposed device in comparison with the prototype allows for a new way to organize signal processing with

9 1158873

thermoelectric converter and eliminate the time-consuming process of determining and entering the individual thermal characteristics of the thermal converter, which simplifies its operation and allows for calibration with

less hardware and labor costs. In addition, the proposed thermometer is cheaper because it contains a smaller number of microcircuit cases with the same measurement accuracy.

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Claims (1)

A DIGITAL THERMOMETER containing a thermal converter with a frequency output connected to the first input of the clock unit, the output of which is connected to the key input, and the second input is connected to the output of the reference frequency generator and connected to the first input of the control unit through the frequency divider, the first output of which is connected to the control input key, and the second output is connected to the installation input of the result counter, the output of which is connected to the input of the indicator register and the first input of the first circuit is larger, the second inputs of which connected to the source of constant logic levels, a group of AND circuits, the outputs of which are connected to the inputs of the first OR circuit, the second OR circuit, three, AND circuits, the second circuit is more or less, the first inputs of which are connected to the sources of constant reference levels, characterized in that , in order to simplify the process of calibrating the thermometer, two additional OR circuits are introduced into it, an additional counter, a single vibrator, an NAND element, a trigger, two inverters and a decoder, the inputs of which are connected to the outputs of the result counter, and the outputs are connected to the inputs the group of AND circuits and the inputs of the second OR circuit, the output of which is connected to the first input of the AND circuit and through the first inverter is connected to the first input of the first AND circuit, the second input of which is connected: to the second input of the AND circuit and the output of the one-shot, the input of which is connected to the output of the first circuit or and the first input of the third OR circuit, the second input of which is connected to the control input of the indicator register and the second output of the control unit, and the output is connected to the installation input of an additional counter, the outputs of which are connected to the inputs of the groups chem And, as a counting input connected to the output of a second AND gate having a first input connected to the output circuit of the first high-low and the third input of AND-NO element, and the second SI 00 m 00 the input is connected to the key output and the first input of the fourth OR circuit, the second input of which is connected to the output of the first AND circuit, and the output is connected through the second inverter to the first trigger input, the second input of which is connected to the output of the AND-NOT circuit, while the inputs of the third circuit AND are connected respectively to the trigger output and the output of the fourth OR circuit, and the output is connected to the counting input of the result counter, the installation inputs of which are connected to sources of constant logic levels, the second input of the second circuit is more or less connected to the industrial daily output of the frequency divider, and the output is connected to the second input of the control unit