SU624121A2 - Temperature sensor - Google Patents

Description

one

The invention will be adapted to the field of temperature measurement.

Known temperature sensor., On author.St. No. 1,83430, containing a temperature-sensitive element and a transistor blocking generator, which converts temperature into a sequence of pulses whose frequency is proportional to temperature, while a varistor connected to the base circuit of the blocking transistor generator l is used as the temperature-sensitive element.

The disadvantage of such a sensor is the low accuracy of converting the temperature to the pulse frequency, which is associated with a low thermal stability of the circuit.

The aim of the invention is to improve the accuracy of converting temperature to pulse frequency.

This is achieved by introducing an adjustable voltage divider on the resistors, connected in parallel to the power source, additional condensate and two additional transistors, the first additional transistor connected to the emitter circuit os2

The main transistor is connected to the emitter of the main transistor, the base is connected to the midpoint of the voltage divider, the second additional transistor is connected to the base of the main transistor and the timing plate of the master capacitor, and the base is connected via an additional capacitor The time of the master capacitor is connected to the second plate.

A schematic diagram of the temperature sensor described is shown in

5 drawing.

The temperature sensor contains the main transistor 1, 2.3 additional transistors, the temperature-sensitive element - varistor 4, the transformer

0 5, voltage divider across resistors 6.7, time setting capacitor 8, additional capacitor 9.

The temperature sensor works as follows.

five

Claims (2)

When the temperature changes, the resistance of the sensing element 4 changes. A change in the resistance of the sensitive element causes a change in the pulse frequency of the blocking generator. The emitter junction of the tray 3 is connected in the forward direction along the charge circuit of capacitors 8.9. By this, additional capacitor 9 is charged almost to the same level as capacitor 8. When capacitor 8 is discharged after the transistor 1 is locked, the emitter junction of transistor 3 is turned on in the blocking direction and reverse current 1 flows through it, which provides the charge capacitor 8, This makes it possible to effect the compensation of the current 1 of the locked state; the transistor 1 is discharged by the capacitor 8. The auxiliary transistor 2 performs the Zener diode function with a stabilization voltage determined by the voltage drop across the resistor 7. Like a Zener diode, this transistor 2 has a positive temperature coefficient of voltage (TKU). At the same time, the TKU of the threshold for unlocking the main transistor 1 is negative. For the proposed device, the period of the generated rectangular pulses is defined as,, (-1) where t is the duration of the pulse removed from the output winding of the pulsed transformer 5; tpaj discharge time capacitor 8, determined in accordance with the dependence E-Ue-u where T is the base resistance of the transistor 1, C is the capacitance of the capacitor 8, EP is the natural logarithm, is the voltage of the condensate charge E is the voltage. power supply UQ-threshold unlock transistor 1 with a non-zero voltage on its collector, and about the threshold unlocked transistor 1 with zero voltage-on its collector, and-voltage stabilization of the transistor 2. The temperature coefficients with respect to voltage for electron-hole transitions in direct switching and for zener diodes are opposite and close to each other. Due to this, the change in voltages UQ, ui, U under the influence of changes in the ambient temperature practically does not affect the discharge time of the capacitor 8. Thermal stabilization of the circuit based on the reverse current IK of the locked transistor 1 and on its threshold of unlocking allows to significantly improve the accuracy of conversion temperature in the frequency of the generated pulses. The proposed invention makes it possible to increase the accuracy of converting the temperature to the frequency of the generated pulses, to simplify the temperature measurement control systems, since it eliminates the need to develop additional devices that provide the required accuracy of the conversion. Claims of the temperature sensor according to auth.St. No. 183430, characterized in that, in order to increase the accuracy of temperature conversion to the pulse frequency, an adjustable voltage divider on the resistors, connected in parallel with the power supply, an additional capacitor, and two additional transistors are introduced; the first additional transistor is connected to the emitter circuit of the main transistor, its collector is connected to the power source, the emitter is connected to the emitter of the main transistor, the base is connected to the midpoint of the voltage divider, the emitter of the second additional transistor is connected to the base of the master capacitor and the base is connected to the second plate via an additional capacitor, the time of the master capacitor. Sources of information taken into account in the examination: 1. USSR Author's Certificate No. 183430, cl. C01 C 7/32, 1965.