RU2534384C1 - Pulse-frequency temperature variation rate meter - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: proposed meter comprises differential thermocouple 1 composed by thermocouples 2 and 3 with different time constants, amplifier 4, electronic switch 5 with memory 6 at its output. Unit for isolation of module 7 and controlled frequency generator 8 are connected to the device output and, via delay unit 9, to control input of electronic switch 5 while via generator 8, pulse standardiser 10 and inverter 11, with selectable peak detectors 12, 13, with electrodes of thermocouple 2. Output of standardiser 10 is connected via detector 13 while inverter output is connected via detector 12 Output of switch 5 with memory 6 is connected via comparator 14 with sign output of the device that controls the input of detector 12 and via logical circuit "NO" 15 with control input of detector 13.

EFFECT: higher precision and fast response.

1 dwg

Description

The present invention relates to the field of temperature measurements.

Known measuring the rate of change of temperature, containing a temperature sensor, such as a thermocouple, connected in series with an adjustable differentiating element made according to a bridge circuit, a modulator, an isolation transformer, an indicator unit and a normalizing converter (Auth. Certificate. USSR No. 378732, G01K 7/02. Bull. No. 19, publ. 04/18/1973).

The disadvantage of this device is the relatively low speed and significant measurement error.

Also known is a temperature change rate meter adopted as a prototype (Auth. Certificate. USSR No. 403972, G01K 7/22, publ. 10/28/1973, Bull. No. 43), containing a thermocouple, hot sealed through a DC amplifier connected to double gates MOS transistors, one of which is switched by a key and to which storage capacitors are also connected, and load resistors are included in the drain circuits of MOS transistors, between which an indicator of the rate of change of temperature is connected.

The disadvantage of this meter is the relatively low speed and accuracy.

The technical essence of the invention consists in introducing negative feedback into the device to compensate for changes in the temperature of the thermocouple.

The technical result of the invention is to increase the speed and accuracy of the device.

The technical result is achieved by the fact that the frequency-pulse meter of the rate of change of temperature, containing a thermocouple, an amplifier, a storage capacitance and an electronic key, is additionally equipped with a second thermocouple, a module allocation unit, a controlled frequency generator, a delay unit, a pulse standardizer for duration and amplitude, an inverter, two selectable peak detectors, a comparator and a logic circuit “NOT”, while the second thermocouple is counterclockwise connected to the first with the connection of a differential term pairs to the input of the amplifier, the output of which through a series-connected electronic key with a storage capacity at the output, the module allocation unit and the controlled frequency generator is connected to the meter output and, through the delay unit, connected to the control input of the electronic key, as well as through a series-connected controlled frequency generator, standardizer pulses in duration and amplitude and the inverter are connected through the first and second selectable peak detectors with the electrodes of the second thermocouple, while the output is standard the isator is connected through the second peak selectable detector, and the inverter output is through the first peak selectable detector, and the output of the electronic key with the storage capacitance at the output is connected through a series-connected comparator with the sign output of the meter that controls the input of the first selectable peak detector and through the logic circuit “NOT” with the control input of the second selectable peak detector.

The structural diagram of a pulse-frequency meter of the rate of change of temperature is shown in figure 1.

The meter contains a differential thermocouple 1 of two counterclockwise thermocouples 2 and 3 with different time constants, connected to the input of the amplifier 4, the output of which is through a series-connected electronic key 5 with a storage capacity 6 at the output, a module allocation unit (BVM) 7 and a controlled frequency generator (GUCH) 8 is connected to the output of the meter and through the delay unit (BZ) 9 is connected to the control input of the electronic key 5, as well as the negative feedback circuit through the series-connected output of the generator frequency 8, a pulse and pulse standardizer (SAD) 10 and an inverter 11 connected through selectable peak detectors (SPD) 12 and 13 to the electrodes of the thermocouple 2 and the input of amplifier 4, while the output of SAD 10 is connected through SPD 13, and the output inverter 11 through SPD 12, and the output of the electronic key 5 with a storage capacity of 6 is connected through a sequentially connected comparator 14 with the sign output of the meter, the control input of the SPD 12 and through the logic circuit “NOT” 15 with the control input of the SPD 13.

The purpose of the newly introduced elements: thermocouple 2, allocation unit 7, controlled frequency generator 8, delay unit 9, pulse standardizer for duration and amplitude 10, inverter 11, selectable peak detectors 12 and 13, comparator 14, logical circuit “NOT” 15 backward from their names.

Frequency-pulse measuring rate of temperature changes is as follows.

In terms of transient dynamics, thermocouples 2 and 3 are first-order aperiodic links. The time constant T _{3 of} thermocouple 3 is greater than the time constant T _{2 of} thermocouple 2 (T ₃ > T ₂ ), and the sensitivity coefficients K ₂ and K _{3 of} both thermocouples are the same K ₂ = K ₃ = K.

When the controlled temperature ϑ varies, the output signal of the differential thermocouple 1 in the Laplace form has the form

, $$\vartheta \left(p\right)\left(\frac{K}{T_{2}p+\mathrm{one}}-\frac{K}{T_{3}p+\mathrm{one}}\right)=\vartheta \left(p\right)\frac{\left(T_3-T_2\right)p}{\left(T_{2}p+\mathrm{one}\right)\left(T_{3}p+\mathrm{one}\right)}\cdot K$$

,

where p is the Laplace operator.

Thus, at the input of the amplifier 4, the output signal of the differentiating-smoothing link of the second order (difermopair) acts.

, а частота F_вых - о величине этой производной. Время задержки БЗ 9 выбирается из условия замыкания ключа 5 во время паузы между импульсами с выходов САД 10 или инвертора 11. Генератор ГУЧ 8 изменяет свою частоту так, чтобы ликвидировать разность напряжений на выходе дифференциальной термопары 1.The output signal of the amplifier 4 through a closed key 5 is stored with a capacity of 6 and through the BVM 7 controls the frequency F of the _{output of the} GUCH 8. The pulses from the output of the GUCH 8 are standardized for the duration and amplitude of the CAD 10 and are inverted by inverter 11. Depending on the sign of the voltage (polarity) on the storage capacitance 6, the comparator, the second input of which is connected to the case (not shown conditionally), forms a logical unit “1” or “0” at its output, opening SPD 12 for passing pulses of negative polarity or through the logic circuit “NOT” 15 SPD 13 for ozhdeniya pulses of positive polarity. In this case, a pulsed current flows from the SAD 10 to one side through the hot junction of the thermocouple 2 or from the inverter 11 to the other. Based on the Peltier effect, when the current flows in one direction, the hot junction is heated, and in the other, it is cooled. The value of the output signal of the comparator 14 carries information about the sign of the temperature derivative with respect to time $$sign\frac{d\vartheta }{d\tau }$$

And the frequency F _O - on the value of this derivative. The delay time BZ 9 is selected from the condition of closing the key 5 during a pause between pulses from the outputs of the CAD 10 or inverter 11. The generator GUCH 8 changes its frequency so as to eliminate the voltage difference at the output of the differential thermocouple 1.

SPD 12 and 13 can structurally be performed like an electronic key 5.

Thus, the proposed automatic control tracking system provides high accuracy and speed of the temperature change speed meter by maintaining the temperature equalities of the hot junctions of thermocouples 2 and 3 at their different values of the time constant with an error determined by the static error of the tracking system (inversely proportional to its gain) .

Claims (1)

A pulse-frequency temperature change rate meter containing a thermocouple, an amplifier, a storage capacitance and an electronic key, characterized in that it is additionally equipped with a second thermocouple, a module selection unit, a controlled frequency generator, a delay unit, a pulse standardizer in duration and amplitude, an inverter, two selectable peak detectors, a comparator and a logic circuit “NOT”, while the second thermocouple is connected in a differential circuit with the first with the connection of counterclockwise a jar to the input of the amplifier, the output of which through a series-connected electronic key with a storage capacity at the output, the module selection unit and the controlled frequency generator is connected to the output of the meter and through the delay unit is connected to the control input of the electronic key, the meter also contains a negative feedback circuit through series connected by a controlled frequency generator, a standardizer of pulses in duration and amplitude and an inverter connected through the first and second selectable detectors with the electrodes of the second thermocouple, while the standardizer output is connected through the second peak detector, and the inverter output is connected through the first peak detector, the output of the electronic key with the storage capacitance at the output is connected through a sequentially connected comparator with the sign output of the meter controlling the input of the first selectable peak detector and through logic circuit “NOT” - with the control input of the second selectable peak detector.