SU1379752A1 - Device for measuring thermoelectric efficiency of thermocouple - Google Patents

Abstract

The invention can be used to measure the thermoelectric performance of semiconductor materials. The purpose of the invention is to improve the accuracy of measuring the thermoelectric efficiency of thermoelement SI by taking heat transfer from its side surface into account. The heat-conducting unit 22 is installed in a position where it has no contact with the plate 3, Switches 13, 12 and 11 respectively connect the thermocouple 1 with the current output of the resistor 15, the output of the AC source with the resistors 14 and 17, the output of the thermocouple 8 and the common point resistors 14 and 17 with the input of the indicator of the zero AC. Then, the switch 12 connects the output of the DC source 18 to the resistors 14 and 17, and after establishing the stationary mode, the switch 11 is connected in series with the input of the device 21, Koropbtfi measures the potential difference and temperature. In the same position, the measurement switches are turned on with the reverse direction of the current. Thermoelectric efficiency is calculated using the above formula, 1 e, p. f-ly, 1 ill. (L with co SP

Description

The invention relates to thermal physical measurements and can be used to measure the thermoelectric performance of semiconductor materials.

The purpose of the invention is to improve the accuracy of measuring the thermoelectric efficiency of thermoelements by taking into account heat losses from the side surface of the thermoelement.

The drawing shows the electrical circuit of the proposed device.

The device contains thermoelement 1, additional thermoelement 2, first 3, second 4, third 5 and fourth 6 metal plates, first 7, second 8, third 9 and fourth 10 thermocouples, first 11, second 12 and third 13 switches, variable 14, exemplary 15, the first additional 16 and the second additional

17resistors, sources of constant

18 and AC 19 current indicator

20 zero alternating current, measuring instrument 21 direct current, heat CONDUCTING unit 22 and thermal insulation base 23.

The measurement of the thermoelectric efficiency Z of the thermoelement is carried out as follows.

First, the heat-conducting unit 22 is installed in a position where it does not have contact with the plate 3. Switches 13, 12 and 11 respectively connect the thermocouple 1 with the current output of the resistor 15, the output of the AC source with the resistors 14 and 17, the copper output of the thermocouple 8 and the common point of resistors 14 and 1 with the input of the indicator of the zero of the alternating current. The resistance of the variable resistor 14 is set such that the signal at the input of the device 20 is zero. Then, switch 12 connects the output of DC source 18 to resistors 14 and 17, and after establishing a stationary mode, switch 11 serially connects to the input of device 21 a copper lead of a thermocouple 8 and a common lead of resistors 14 and 17, a copper lead of a thermocouple 7 and a common lead resistors 14 and 17, potential leads of resistor 15 and leads of thermocouples 8 and 7. At the same time, the device 21, respectively, measures the potential difference U, i / и, l and temperature T ,,, T,. In the same position of the switches is measured

They are not repeated with the reverse direction of the current (the value of the direct current remains the same), while the device 21 accordingly measures U,

and and t t

Ii. 11 g 11

Next, the heat-conducting unit 22 is connected to the plate 3 and these measurements are repeated, the device 21 measuring the temperatures T,, T (in the forward direction of the current) and T, T (in the opposite direction of the current), then all are the same Measuring operations, including setting zero at the output of the device 20, are performed for the second thermoelement 2, which is connected by the switch 13. In this case, the thermocouples 9 and 10 turn on in the measuring circuit using switch 11 instead of thermocouples 7 and 8 by analogy with the first thermoel ment in the absence of a heat sink difference po- ten1Schalov U,, and s temperature

7i

And T ,, for the direct direction

l to current, potential difference, U,

and temperatures TJ, and, for the reverse direction of the current and in contact with the heat conducting unit 22, the temperatures Tj, and Tj for the forward direction of the current and the temperature T ,,, and T 7g FOR the reverse direction of the current.

Thermoelectric efficiency is calculated by the formula

„1 and“ X „X ,, -1

f 1 f ff

T, and,

X, LH "-X" -2)

where t

Ti + Til

About O i-i-Ujk.,

15 2

X, e :, e;

 P

0: (e; ,,) 0 „(b ;, c;,) e ;; T0T bTG

2J

„Sh (Arch at,)

X, o-Arch y,

G, and,; + and;, Un 2

y- uW + Ujrf

ja - 2

f T7, -t- t ;,

T 2

Yr

SkR (e:, 0; rp; x H0 ei, i

2d, 0, y.

Tk (ek, b; ,,

- t t

kg i k, ki

„IIY

c,

d I rr, HJ,

a t rpiK

kr42 Ki I

d is the length of thermoelements;

S is the cross-sectional area of thermoelements;

R - exemplary resistance

resistor 15,

 for the first thermoelement, for an additional thermoelement.

The design formulas are given for the case when the product of the length by the square root of the ratio of the perimeter of the cross section to the cross-sectional area of the first thermoelement is twice as large as this value of the additional thermoelement.

Claims (2)

1. A device for measuring thermoelectric efficiency of thermoelements containing a controlled thermoelement with current contacts located on its ends, the first, second and third switches, two thermocouples, the working junctions of which are installed at the ends of the thermoelement, and their free ends are connected through the first switch to the measuring DC device, DC power source, O TL and 10 15 20 25 thirty 35 40 In order to ensure the accuracy of the measurement by taking into account heat losses from the side surface of the thermoelement, an additional thermoelement made of the material of the controlled thermoelement and different from it in size is introduced into it, two additional thermocouples, AC source, zero indicator an alternating current, a quadruple resistive measuring bridge and a heat-conducting unit mounted for movement relative to the ends of the thermoelements, with both thermoelements with their current contacts are connected separately via the third switch to one of the arms of the resistive measuring bridge, the measuring diagonal of which is connected via the first switch to the null indicator of alternating current and the measuring instrument of direct current, and its supply diagonal is connected via the second switch separately to the sources of alternating and permanent current. 2. A device according to claim 1, characterized in that both thermocouples are cylindrical or rectangular in shape and their dimensions are interconnected by the relation J / PIV s; - 2 where d and d are the lengths P, and P - perimeters of the transverse S sections, and S, - cross-sectional area thermocouple sections.