SU1728679A1 - Digital thermometer - Google Patents

Abstract

The invention relates to thermometry and permits an increase in the response rate while simultaneously improving the measurement accuracy. The period of the difference frequency signal is measured by filling it with the pulses of the reference oscillator 2. The accumulated number of pulses goes to the counter. 9 results. The accumulated body of pulses is corrected by eliminating some of them, which is determined by the output code of the persistent storage device 10. 2 Il.

Description

The invention relates to temperature measurement by contact methods using thermocouples with a frequency output signal, in particular piezo quartz thermocouples.

Known digital thermometer containing thermocouple with frequency output signal, the reference frequency generator, mixer, switching element, the result counter, the display system.

The disadvantage of this digital thermometer is the low measurement accuracy due to the fact that not in all cases the non-linearity of the period-frequency characteristic compensates for the non-linearity of the characteristic of the temperature sensor.

Closest to the present invention is a digital thermometer containing a temperature output temperature transducer and a first input mixer associated with it, a reference frequency generator, the output of which is connected to the second input of the mixer, a frequency divider, a key, a result counter with a register, the inputs of which are connected to the outputs counter and digital indicator, the inputs of which are connected to the outputs of the register.

The disadvantages of this thermometer are low accuracy, caused by the non-recoverable error of the sensor from non-linearity, and low speed. Poor performance is compounded by the use of sensors with low sensitivity to temperature. Miniature sensors have a slope of thermal frequency characteristics of 2 0.15 Hz / ° C, and the nonlinearity reaches half the slope. When trying to implement such a thermometer according to the principle of the prototype, the speed does not exceed 50 seconds per measurement to obtain a sensitivity standard of 0.01 ° C.

The purpose of the present invention is to improve the accuracy and speed of a digital thermometer.

VI GO 00 ON XI O

This goal is achieved by having a digital thermometer containing a frequency output thermocouple connected to the first input of a mixer, a second input connected to the output of a reference frequency generator, a frequency divider, a key, a result counter, outputs connected to the inputs of a register connected by outputs to a digital indicator , the first and second one-shot one-shot, 1-K-flip-flop, an inequality element and a permanent storage device connected by address inputs to the counter outputs are entered in series and the result, and the output connected to the first input of the inequality element and the I, K and R inputs of the IK trigger, connected by the output to the second input of the unequality element, and C input to the C input of the result counter and the output of the key connected by the input to the output of the generator the frequency input, and the control input of the output-connected frequency divider connected between the mixer output and the first one-channel input, the output of the inequality element is connected to the output of the counter of the result counter, the reset input of the connected to the output of the second one-shot, connected by the input to the input of the register.

Introduction of new connections between elements allows to increase the thermometer speed, the presence of ROMs - eliminate the error from nonlinearity of the resulting sensor characteristic together with the nonlinearity of frequency versus period, communication ROM, inequality element and l-K-trigger - simplify the device due to the possibility of using one-time this ROM and combining the functions of the address counter and the result counter.

Fig, 1 shows a diagram of the proposed digital thermometer; 2 shows timing diagrams for his work.

Digital thermometer contains sensor 1, reference generator 2 (reference frequency generator), mixer 3 with filter and driver at the output, divider number 4, one-shot 5, key 6, one-shot 7, result register 8, result counter 9, read only memory (ROM) 10, result indicator 11, 1-K-trigger 12 and unequal element 13.

The temperature sensor 1 and the reference generator 2 are connected by their outputs to the inputs of the mixer 3, the output of which through the divider 4 is the number of pulses fed to the input of the single vibrator 5 and the control input of the key 6. The output of the single vibrator 5 is connected

to the input of the one-shot 7 and to the input of the TRANSFER of the register 8. The output of the one-shot 7 is connected to the input of the zero setting of the counter 9 of the result, the outputs of which are parallel

connected to the inputs of the register 8 and to the address inputs of the ROM 10. The outputs of the register 8 are connected to the inputs of the digital indicator 11. The output of the reference generator 2 is connected via a key b to the counting input of the result counter 9 and to the C input 1-K-flip-flop 12, the output of which connected to the first input of the element 13 inequality, to the second input of which and to the inputs, K and R of the trigger 12 is connected to the output of the ROM. Item 13 exit

inequalities connected to the input of the resolution of the counter 9 result.

Digital thermometer works as follows. Temperature sensor 1 generates a signal whose frequency depends

from the temperature, the reference oscillator 2 generates a signal of a constant frequency, the mixer 3 with a low-pass filter and a driver generates pulses, the frequency of which is equal to the difference

frequency sensor 1 and generator 2, Divider 4 divides the difference frequency of the signal at the output of the mixer 3. The pulses coming from the output of the divider 4, turn on time

its key duration 6, m pulses from the generator 2 output go to the counting input of the result counter 9 and to the C input of the trigger 12. The falling edge of the pulse of the divider 4 starts a chain of one-shot 5 and 7,

which produce two short pulses, one after the other. The one-shot impulse 5 transfers the result from counter 9 to the register 8 with its rear edge, then the single-shot impulse 7 sets the result counter 9 to the initial state. When counting the pulses of the generator 2, the counter 9 switches the addresses of the ROM 10. If there is a zero at the output of the ROM, the trigger 12 is held in the zero position by the presence of a zero at its R input, while the output of the non-unequal element 13 also has 0. entrances. This zero, coming from the output of the element 13 to the input of the resolution of the counting of the counter 9, allows it to calculate the next pulse. Thus, if there is a zero at the output of the ROM, the counter counts the next pulse. If, after counting the next input pulse

ROM will set the address where 1 is written to it, then the unit is wits at the ROM output, as a result, the trigger 12 will no longer be held in the zero position, and at the output of the element 13 it will be wound 1, which

will prevent counter 9 from counting the next pulse. This next impulse will set the trigger 12 to 1, since its I and K inputs will have 1 output from the ROM, allowing the trigger 12 to operate in the counting mode. After installing the trigger 12 in 1 at the output of the element 13, the zero turns on, allowing the counter 9 to count the next pulse. This next pulse will be counted by counter 9. In addition, this pulse will set trigger 12 to 0. At the output of the ROM, the next bit of information recorded in it is read, and if this is zero, trigger 12 will be confirmed in the zero state with a signal to R -input, and counter 9 will be prepared to calculate the next pulse, which will not set to 1 trigger 12. If the next bit of information is 1 again, the next pulse will set to 1 trigger 12, and counter 9 will not calculate this pulse. Thus, a zero at the output of the ROM allows counter 9 to count all the pulses arriving at its input, and the unit allows the installation of a trigger 12 to 1 and prohibits counting this pulse by the counter 9. After installing the next trigger pulse 12 to 1, the next pulse sets the trigger 12 to 0 and will be counted by counter 9. In other words, the zero at the output of the ROM allows counting all the pulses of the generator 2, and one through one. Therefore, in the case of recording in the ROM of all zeros, the counter will count all input pulses, and in the case of recording all the units, the counter will count the pulses after one, i.e. the frequency of the counted pulses will be halved. Writing zeros and ones in the ROM, it is possible to double the counting frequency of the pulses by the counter 9 in accordance with the sensor characteristics and obtain a readout of the measured temperature.

Figure 2 shows the process of counting pulses by the counter 9 of the result. Figure 2, and shows the pulses of the reference generator 2; in Fig.2, in - the signal at the output of the ROM, which can move from 1 to 0 and back only at the moments of counting the next pulse by the counter 9 (fig.2c). In Fig. 2c, the signal at the output of the inequality element 13, which is resolving (zero) or prohibiting. (One) for counting the pulses by the result counter 9, and immediately after the pulse arrives at the input of the result counter this level can change, it does not result To failure in operation, as the counter 9 responds to the state of the control input immediately before the arrival of the counting pulse.

2, d shows the signal at the output of the trigger 12. The trigger 12 is set to 1,

when counter 9 skips - it does not count the next input pulse, i.e. depending on the output state of the ROM, the input pulse either sets to 1 5 trigger 12, or is counted by counter 9. Figure 21 shows the process of increasing the number in counter 9. When recording all zeros in ROM, counter 9 counts all input pulses of line 1 by chart when writing

0 in the ROM of all I accumulation, the numbers in the counter 9 are twice as slow - line II in the time diagram. The required characteristic can be obtained by writing the ones and zeros in the ROM 10. It lies between

5 lines I and II and its steepness should never go beyond the slopes of lines I and II. Thus, unlike the prototype and other thermometers, the proposed instrument eliminates the error from the nonlinearity of the total characteristic — the sensor and the period-frequency characteristics by writing 1 and 0 to a single-bit ROM, and the address counter of the ROM and the result are the same however, the simplification of the device, the increase in accuracy and speed are achieved.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION Digital thermometer comprising a frequency output thermal converter. 0 connected to the first input of the mixer, the second input connected to the output of the reference frequency generator, frequency divider, key, result counter, outputs connected to the inputs of the register connected by the outputs to the digital indicator, which, in order to increase speed while improving accuracy measurements, the first and second one-shot one-shot, IK-trigger, inequality element and permanent memory connected by address inputs to the outputs are entered into it. Meters withstand result, and the output element 5 with the first input of the inequality element and the I, K and R inputs of the I-K-flip-flop connected by the output to the second input of the unequality element, and the C input to the C input of the result counter and 0 to the output of a key connected by the input to the output of the reference frequency generator, and a control input connected to the output of a frequency divider connected between the output of the mixer and the input of the first single-frequency device . connected by the input to the register input.