SU1397747A1 - Device with frequency output for measuring temperature - Google Patents

Abstract

The invention relates to temperature measurements. The purpose of the invention is to increase the reliability of the device during its operation in remote measurement systems. When measuring the positive temperature at the output of the amplifier 5 there is a negative. voltage proportional to the measured temperature. At the output of the sign determining comparator 9, a positive voltage arises, which is fed to the input of the voltage converter 12 to the frequency. The frequency of the pulse sequence at the output of the latter is proportional to the resistance value of the thermometer, and the trace, to the measured temperature. The frequency divider 15 converts the frequency signal from the inverter 12 nprp) frequency to the meander, which is transmitted to the communication line through the cascade 16. At a negative temperature, the analog key 11 opens, and through it the negative voltage enters the voltage converter 12 at the frequency . 1 il. -.

Description

the first 10 and second 11 analogue clg-20 neyb) its conversion occurs

chi, the converter 12 for example / year to the frequency, made, for example, according to the scheme of double 1 and integration with ftpsirovm the integrating discharge, is analogous to that when measuring positive temperature

In case of a cal device, the device is in place of a thermometer;

bones containing tuned resis- tions of a highly resistive shop of high precision 13 and 14 J divider 15 years; .., matching cascade 16, made, for example, 5 an open collector with a transistor switch.

The device works with a cool-about-30 Trim coarse resistors coarse

at once.

The resistance of thermometer 1 is transformed into voltage by converter 2 and is amplified by a differential amplifier 1. When measured: and a positive temperature at the output of differential amplifier 5 there is a negative voltage proportional to the measured temperature. A positive voltage appears at the output of the sign determining comparator 9, which when entering the device output, it indicates that a positive temperature measurement is taking place and opens the analog key 10. Lpa-i key 11 is closed at this time, eg The output from the differential amplifier 5 is fed to the input of the voltage converter 12 to the frequency, which converts the input voltage to a sequence of pulses whose frequency is proportional to the resistance value of thermometer 1 and, therefore, to the measured temperature.

Frequency divider 15 converts a frequency signal from a voltage converter 12 to a frequency signal, which is transmitted

TI;

40

50

55

Bridges, Using the grading table on the resistance box, set the value corresponding to the resistance of the thermometer at 0 ° C;

settings 3 and fine tuning 4 at the output of the differential amplifier 5 set the ground potential. After that, the value of the store corresponding to the heating

meter at +50 C. To the output of the device connect the frequency meter and a stand-up resistor coarse tuning 13 and fine tuning 14 set the output frequency of 500 Hz. Then, on the resistance box, expose C5: the measurement corresponding to the resistance of the thermometer at -50 ° C. The resistor 8 sets the output frequency to 500 Hz,

After calibration, the measurement accuracy is checked at several intermediate points. When the device is beating, when measuring the positive temperature by trimming resistors 13 and 14, the resistance of the open key 10 is compensated, and when measuring negative temperature - compensation of the resistance of the public key 11 by trimming resistor 8,

Claims (1)

Claims An apparatus for measuring temperature with a frequency output, comprising a resistance thermometer connected to a thermometer's resistance to voltage converter connected by its output to the input of a differential amplifier, a voltage to frequency converter and a matching stage that differs that, in order to increase the reliability of remote temperature measurements, an inverting amplifier, a comparator, has been introduced into it. two analog switches and a frequency divider; the output of the differential amplifier is connected to the input of the first analog switch, the input of the inverting amplifier and the comparator input, the output of the inverting amplifier is connected to the input of the second analog switch, the output of the comparator is connected to the control inputs of analog switches whose outputs are connected to the input of a voltage to frequency converter, between the output of which a frequency divider is connected to the input of the matching stage.