SU1543251A1 - Arrangement for measuring temperature - Google Patents

Abstract

The invention relates to temperature measurements, namely to multichannel devices for measuring temperature using thermoelectric converters, and makes it possible to improve the measurement accuracy. The signal from each thermoelectric converter 1 is fed through an operational amplifier 8, which serves to decouple the input circuits, and an operational amplifier 6, which serves to separate the parasitic voltage compensation signal, to the inputs of the operational amplifier 7, the output of which produces a voltage independent of the magnitude of the interference signal and the magnitude of the parasitic voltage caused by leakage currents of field-effect transistors 4.5. 1 il.

Description

The invention relates to temperature measurements, namely, multichannel devices for measuring temperature using thermoelectric converters.

The aim of the invention is to improve the accuracy and noise immunity of the device.

The drawing shows a diagram of the proposed jq device for measuring temperature. The device for measuring temperature contains η measuring channels 1.1, ..., 1, p (only two measuring channels are shown in the drawing), each of which includes thermoelectric converters

2.1 ,,. ,, 2.p, the first field effect transistor 3.1, ..., 3. η with an isolated gate - £ 0 thief, the second field effect transistor with | 4.1, ..., 4.n with an isolated gate and a compensating field effect transistor '5.1, ..., 5.η with an isolated gate, three operational amplifiers 6-8 Five 25 resistors 9-13. The gates of the transistors' acting as keys of each measuring channel are connected to i corresponding control buses • 14.1, ..., 14.P. Stocks of all the first '

П 1 О transistors J.1, ..., 3.η are connected to the potential bus 15 of the device, and; drains of all second field-effect transistors - with a common bus 16 of the device.

The device operates as follows. 35

A change in temperature affects thermoelectric converters, causing a change in their thermopower E _t . With the arrival of the control signal to the control bus 14 of each measuring drop, the junction transistors of this channel are opened both at the input of the operational amplifier 7 through the operational amplifier 8, which serves to decouple the input circuits and the summation point on the operational amplifier 7, and through the operational amplifier 6, which serves to isolate spurious voltage compensation signal, voltage U d and U £

U, = E _t ± U _n ;

= + U, where and _p is the magnitude of the interference voltage emitted by the field effect transistor 5.1 and caused by the presence of a general disturbance between the ground point on the housing of the test object 'of the measuring device and the housing point of the test object with which the transformer is galvanically or capacitively coupled; - voltage at the output of the operational amplifier 8; U ^ is the voltage at the output of the amplifier 6.

In this case, the output of the operational amplifier 7, which is the output of the device, will be a voltage, np depending on the magnitude of the interference signal ^to <"<* M -" A.

where K is the gain of amplifier 7. Thus, the proposed device, in addition to compensation for interference, provides compensation for stray voltage on the resistance of transistors connecting the output terminal of the transformer to the common bus of the device caused by the leakage current of the transistors.

The presence of an operational amplifier 8 having a high input resistance eliminates the influence on the measurement result, changes in the resistances of wires and internal resistance of thermoelectric converters, which allows the use of various types of converters, including high-impedance ones, significantly reduces the requirement for the resistances of open transistors, which is fundamentally important when implementing microelectronic devices, as well as breaking the ashes of the contour of the occurrence of toicob caused by induced signals, increases the noise immunity of the measuring circuit.

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Claims (1)

Claim A temperature measuring device containing η measuring channels, each of which includes a thermoelectric converter, the terminals of which are connected respectively to the sources of the first and second field effect transistors with insulated gates connected to the control bus, the drains of all first field effect transistors are connected to the potential bus of the device, and the drains of all second field-effect transistors are connected to a common bus of the device, characterized in that, in order to increase the accuracy of measurement5, three there are five operating resistors and five resistors, and each measuring channel is equipped with a compensating field effect transistor with an isolated gate, the source of which is connected to the source of the second field effect transistor, and the gate is connected to the control bus. Moreover, the drains of all compensating field effect transistors are interconnected and connected through the first a resistor to the first terminal of the second resistor and the input of the first operational amplifier, the output of which is connected to the second terminal of the second resistor and through the third resistor it is connected to the inventory input of the second operational amplifier, the non-inventing input of which is connected 5 to the non-inverting input of the first operational amplifier and connected to the common bus, and the output being an informative output of the device, through the fourth resistor is connected to its inventory input connected through the fifth resistor to the output and inventory input a third operational amplifier, the non-inverting input of which is connected to the potential bus of the device.