Thermoelectric measuring device

Abstract

The invention relates to measuring technology, and can be used for measuring the root-mean-square values of electrical quantities of direct current and high-frequency alternating current, such as current, voltage and power. A thermoelectric measuring device comprises a resistive element and a thermoelectric module, wherein the resistive element is designed to be capable of emitting heat when an electrical signal to be measured is supplied thereto, and is in thermal contact with a sensitive side of the thermoelectric module, and the thermoelectric module is designed to be capable of measuring the heat emitted by the resistive element and is disposed on a heat dissipating base. The thermoelectric measuring device is highly sensitive to heat flux and provides highly accurate measurement of electrical quantities.

Description

[0001] THERMOELECTRIC METER

[0002] Field of technology

[0003] The invention relates to measuring equipment and can be used to measure the effective values ​​of electrical quantities of direct current and high-frequency alternating current, such as current, voltage, power, and in particular can be used as detectors of the power of high-frequency signals.

[0004] State of the art

[0005] A class of high-frequency signal power detectors is known that convert electrical power into heat and measure it using various principles. Thermal power meters are considered to have low measurement errors. Their high accuracy is due to the high stability of calorimetric and related measurement methods. Thermal sensors measure average power regardless of the signal waveform. Therefore, such thermal sensors are used as reference sensors for the effective power of radio frequency and microwave signals.

[0006] In modern thermal sensors, thermocouples or thermocouple batteries (thermocouple thermal power sensors), bolometers and other recording methods are used as recording elements.

[0007] The thermal power sensor contains a resistive element in which the measured signal is converted into thermal power (Joule heat) according to the classical Ohm's law - proportional to the measured signal and the electrical resistance of the resistive element.

[0008] In a thermocouple sensor, a hot junction of a thermocouple or junctions of a battery of thermocouples are located in close proximity to the heater, in which a thermoelectric power is generated proportional to the local heating by the heat released.

[0009] In bolometric thermal sensors, the generated heat changes the resistance of the bolometer's temperature-sensitive element. The change in this resistance is proportional to the change in temperature, and therefore proportional to the generated thermal power.

[0010] In the known patent documents US 7705582 B2, published 27.04.2010, Cl. G01R 23 / 04, G01R 25 / 02, G01N 25 / 00, G01J 5 / 00, DE 102008057607 A1, published 27.05.2010, Cl. G01R 21 / 02, G01R 29 / 08, devices use not one, but several and even series of thermocouples, with the aim of increasing the sensitivity of the sensors per thermocouple.

[0011] Still, modern thermocouple thermal power sensors, for example, those known from the Internet source https: / / scdn.rohde-schwarz.com / ur / pws / dl downloads / dl common library / dl brochures and datasheets / pdf 1 / SL MESS E PDF, have a low integral volt-watt sensitivity to the measured power at the level of 0.2 V / W.

[0012] In the devices known from patent documents US 4789823 A, published 06.12.1988, Cl. G01R 21 / 02, G01R 21 / 00, US 5393351 A, published 28.02.1995, Cl. H01L 35 / 04, US 7705582 B2, published 27.04.2010, Cl. G01R 23 / 04, G01R 25 / 02, G01N 25 / 00, G01J 5 / 00, attempts were made to increase sensitivity by reducing the loss of emitted detectable heat into the environment and structural elements through the use of thin substrates.

[0013] In view of the complex correlation between the measured electrical power, the heat generated and the measured signal proportional to the heating temperature of the sensitive elements, in the devices known from patent documents US 2007 / 0176768 A1, published 02.08.2007, Cl. G08B 1 / 08 and US 2024 / 0053389 A1, published 15.02.2024, Cl. G01R 22 / 04, it is proposed to calibrate the sensors or even introduce reference heaters into their design that simulate reference signals.

[0014] The disadvantages of known devices lie in the fact that thermal sensors do not directly measure thermal power, but only its manifestation, expressed as the degree of heating of the structural elements—the film or substrate on which the sensing element (thermocouple, thermistor, etc.)—by the generated heat. Consequently, the dissipation of the generated power introduces parasitic losses into the measurements and complicates the correlation with the measured power. Additionally, extraneous heat flows distort the measurements and reduce sensitivity to the useful signal.

[0015] The closest analogue of this invention is a thermoelectric power meter, known from US Patent Application No. 2024 / 0053389 A1, published February 15, 2024, Class G01R 22 / 04. The device converts a frequency electrical signal into heat in a resistor, which is measured by a thermocouple or thermocouple array. A key drawback of this known thermoelectric power meter is the sensitivity of the thermocouple or thermocouple array to the substrate temperature, which changes due to the heat generated by the electrical signal being measured. Thus, the device measures not the heat itself—that is, the converted power of the measured signal—but its derivatives, which depend on many design factors. In general, the sensitivity of thermocouple sensors is limited by the thermoelectric power of the thermocouples.Thermal losses of the measured signal, such as natural dissipation of thermal power, reduce the sensitivity of sensors, make the correlation of the output signal and the measured power difficult, introduce nonlinearity into the measurements, and the measurements are not correct.

[0016] The devices known from the prior art have common drawbacks, expressed in the negative impact of external heat sources on measurements and the low sensitivity of the sensors to the measured power.

[0017] Disclosure of invention

[0018] The problem addressed by the present invention is to eliminate the shortcomings of technical solutions known from the prior art, to increase the sensitivity of sensors and to improve the accuracy of measuring the characteristics of high-frequency signals and direct current, such as current, voltage, and power.

[0019] The technical result achieved by the present invention consists in increasing the accuracy of measurements of the values ​​of electrical quantities of direct current and high-frequency alternating current.

[0020] The technical result is achieved thanks to a thermoelectric measuring device, including a resistive element and a thermoelectric module, wherein the resistive element is configured to generate heat when a measured electrical signal is supplied to it and is in thermal contact with the sensitive side of the thermoelectric module, and the thermoelectric module is configured to measure the heat generated on the resistive element and is placed on a heat-dissipating base.

[0021] A thermoelectric meter, characterized by the given set of features, ensures high accuracy of measurements of electrical quantities.

[0022] The technical problem is solved, and the technical result is also achieved, in the following specific embodiments of the thermoelectric meter. In one embodiment of the invention, the resistive element is a resistive film.

[0023] In one embodiment, the thermoelectric meter includes an additional similar resistive element in thermal contact with the sensing side of an additional similar thermoelectric module. The thermoelectric modules are located on the same heat-dissipating base and electrically connected in opposite directions. This reduces the influence of parasitic thermal effects and further improves measurement accuracy.

[0024] In one embodiment of the invention, the thermoelectric meter includes a thermoelectric module consisting of two or more cascades connected in series, which makes it possible to increase its sensitivity and further improve the measurement accuracy.

[0025] Brief description of drawings

[0026] Fig. 1 shows a schematic representation of a thermoelectric meter.

[0027] Fig. 2 shows a schematic design of a thermoelectric meter in an embodiment with a reference channel.

[0028] Fig. 3 shows a schematic version of a two-stage design of a thermoelectric meter with a reference channel.

[0029] Fig. 4a, 4b show graphs of the dependence of the output signal of a thermoelectric meter on the power of the supplied electrical signal, released in the form of heat.

[0030] In Figs. 1 - 3 the following notations are used:

[0031] 1 - resistive element,

[0032] 2 - thermoelectric module,

[0033] 3 - additional resistive element,

[0034] 4 - additional thermoelectric module,

[0035] 5 - heat-dissipating base.

[0036] Implementation of the invention

[0037] A schematic representation of a thermocouple sensor is shown in Fig. 1. The thermocouple sensor includes a resistive element 1 in thermal contact with the sensitive surface of a thermocouple module 2. Resistive element 1 has a resistance R and can serve as a matched load when measuring high-frequency electrical signals or have a different resistance value. The resistive element generates heat when an electric current is applied to it. A resistive film, deposited on the sensitive surface of the thermocouple module, can serve as the resistive element. The resistive element can be any resistive heater.

[0038] A thermoelectric module is a Peltier element, i.e., a thermoelectric converter whose operating principle is based on the Peltier effect. The thermoelectric module directly measures the heat generated by the resistive element. The heat flow passes through the thermoelectric module, where it is converted into an electrical signal, which is then measured. The thermoelectric module directly converts the heat passing through it into an electrical signal. Therefore, the thermoelectric module has a direct correlation between its output signal and the heat flow. The thermoelectric module has a high integral sensitivity to heat flow. The integral sensitivity of the recording element—the thermoelectric module—is the integral sensitivity of the entire thermoelectric measuring device.Consequently, by using a thermoelectric module as an element that records the heat released on the resistive element, the sensitivity of the device and the measurement accuracy are increased.

[0039] Integral sensitivity S a thermoelectric module is calculated using formula (1):

[0040] „ l

[0041] S a a = - x - (1) f k v ' where f is the form factor of the thermoelement of the thermoelectric module, f = - is the ratio of the cross-sectional area S of the thermoelement to the height h, a is the thermoelectric coefficient (Seebeck coefficient), k is the specific thermal conductivity of the thermoelement.

[0042] Although a thermoelectric module may consist of one or a series of pairs of thermoelements, its sensitivity does not depend on the number of these pairs, but is determined by the fundamental relationship between the parameters of the material of the constituent thermoelements and the form factor of these thermoelements (Gromov G.G., Glazer S.A., Zakhartsev Yu.V. Thermoelectric heat flow sensors. Thermoelectricity No. 6, 2015, pp. 88-98).

[0043] With typical thermocouple geometric dimensions, high integral sensitivity of a thermoelectric module can be achieved. Table 1 presents the integral sensitivity values ​​for thermoelectric modules with thermocouples of different form factors, calculated according to formula (1).

[0044] Table 1

[0045] The use of a thermoelectric module as a heat flux recording element significantly increases the integral sensitivity of a thermoelectric meter by 10 or more times compared to the similar characteristic of a typical thermocouple sensor, which ensures increased measurement accuracy.

[0046] Calibration of the thermocouple sensor does not require the use of reference signal sources. Integral sensitivity S a the thermoelectric module is determined by measuring its standard characteristics using formula (2): Where

[0047] 2N is the number of thermoelements in the thermoelectric module, and is the thermoelectric coefficient (Seebeck coefficient),

[0048] ACR is the intrinsic electrical resistance of a thermoelectric module measured with alternating current (AC).

[0049] Z is the thermoelectric figure of merit of the thermoelectric module.

[0050] The resistive element 1 and the thermoelectric module 2 form a measuring channel, the operating principle of which consists of the release of electrical power of the supplied signal in the form of heat on the resistive element and its measurement by the thermoelectric module, which ensures high sensitivity and increased accuracy of measurement of the supplied signal.

[0051] Thermoelectric module 2 with resistive element 1 on its surface is mounted on heat-conducting base 5. Heat-conducting base 5 can be, for example, any standardized housing for semiconductor devices of any type.

[0052] A completely analogous structure can be mounted on the heat-conducting base 5 in close proximity to the measuring channel—an additional thermoelectric module 4 with an additional resistive element 3 on its sensitive surface, constituting the reference channel (Figs. 2, 3). In this case, thermoelectric modules 2, 4 of the measuring and reference channels are electrically connected in opposite directions. The reference channel performs measurements similar to the measuring channel. In the presence of parasitic thermal influence, equally affecting both channels, the parasitic signal generated by the reference channel will compensate for the parasitic signal in the main measuring channel. Thus, the reference channel compensates for thermal drift and the influence of parasitic heat flows, increasing the stability of measurements, i.e., additionally ensuring increased measurement accuracy.

[0053] A thermoelectric meter can include a two-stage or more multi-stage thermoelectric module for the measuring and reference channels (Fig. 3). A thermoelectric meter with a multi-stage thermoelectric module will have a significantly higher integral sensitivity than one with a single-stage module, which further improves measurement accuracy. The integral sensitivity of a multi-stage thermoelectric module increases proportionally to the number of stages according to formula (3): S a = St xn (3) where n is the number of cascades. If the measuring module is implemented with a cascaded thermoelectric module, the reference channel can also be implemented in cascades, i.e. include the same number of cascades.

[0054] The thermoelectric meter works as follows.

[0055] A DC or high-frequency current signal I to be measured is applied to a resistive element of the measuring channel. As a result, the electrical power of the applied signal is released as Joule heat across the resistive element, which has a resistance of R. The effective power of the measured signal P, released as heat, QR, can be calculated using Ohm's law according to formula (4):

[0056] P = Q R = / 2 x R (4) where I is the applied current, R is the resistance of the resistive element. Here, the parameter QR (BT) determines the heat (heat flux) that can be released in the resistive element when the measured electrical signal is applied to it; i.e., this is the electrical power P, which is correspondingly released as heat.

[0057] The heat flow then passes through the thermoelectric module, generating an electrical output signal. Accordingly, the thermoelectric meter's output registers an electrical signal—thermal emf UR—directly proportional to the electrical power, i.e., the effective power of the electrical signal being measured and the integral sensitivity of the thermoelectric module. Thermoelectric emf UR can be calculated theoretically using formula (5):

[0058] UR = QR XS a (5) where QR is the heat released on the resistive element under the action of electric power P and passing through the thermoelectric module, i.e. this is the heat flow through the thermoelectric module, which generates thermoEMF UR in it.

[0059] S a - integral sensitivity.

[0060] The thermoelectric module may be affected by parasitic heat flows from the external environment, such as thermal conductivity within the structure, heat exchange with the environment, and others. Therefore, the thermoelectric module of the measuring channel can simultaneously record parasitic heat flows of 5QR. Consequently, the measured signal may contain a component of parasitic heat flows (QR + 5QR), which will interfere with accurate measurements. However, the thermoelectric measuring device includes a reference channel that measures the same parasitic heat flows of 5QR. Because the measuring and reference channels are electrically connected in opposite directions, the component of the electrical signal from parasitic heat flows in the measuring channel is completely compensated by a similar electrical signal in the reference channel. Therefore, at the thermoelectric module's output, the useful signal UR is measured ONLY from the measured power.Thus, the reference channel reduces the influence of parasitic thermal effects and ensures increased measurement accuracy.

[0061] An example of the invention.

[0062] A thermoelectric measuring device is manufactured in accordance with the design shown in Fig. 1. The resistive element 1 is made in the form of a resistive film deposited on the surface of the thermoelectric module 2. The electrical resistance of the resistive element is R = 3.2 Ohm. The thermoelectric module 2 is used as a recording element - a Peltier element including 8 pairs of n- and p-type semiconductor thermoelements, each with a cross-section of 0.2 x 0.2 mm 2 and a height of 0.8 mm. A thermoelectric module with a resistive film deposited on its sensitive surface serves as the measuring channel. The thermoelectric module is mounted on a heat-conducting base, a TO-8 metal-to-glass housing.

[0063] Based on the results of the calibration, the integral sensitivity of the manufactured thermoelectric meter S a amounted to 2.21 V / W according to formula (2). The designed thermoelectric meter can be used to measure effective electrical quantities, in particular, the effective power of direct or alternating current, preferably in the range of up to 100 mW (20 dBm).

[0064] A current I in the range from 0 to 60 mA was applied to resistive element 1 of the measuring channel. As a result, electrical power P was released in the form of heat QR (4) across resistive element 1, with values ​​ranging from 0 to 11.5 milliwatts (mW) or up to 10.6 decibel-milliwatts (dBm). The output signal—thermoelectric power UR—was measured experimentally at the output of thermoelectric module 2. The values ​​of thermoelectric power UR were also calculated theoretically using formula (5).

[0065] Fig. 4a, 4b show the results in the form of graphs of the dependence of the thermoelectric power values ​​obtained experimentally UR3 and calculated theoretically UR P FROM the effective power of the supplied signal.

[0066] For comparison, the calculated output curve of URO, 2 of a typical thermal thermocouple power sensor with a sensitivity of approximately 0.2 V / W is shown.

[0067] The obtained results are presented in standard units of power - watts, in particular milliwatts (mW), in Fig. 4a and logarithmic units - decibel-milliwatt (dBm) in Fig. 4b.

[0068] From the graphs it can be seen that the experimental curve shows a practically linear dependence of the measured output signal on the power of the supplied measured signal.

[0069] The presented results demonstrate almost complete agreement between the experimental data and the calculated data, and the correspondingly high performance of the thermoelectric meter. The calculated curve, with the integrated sensitivity measured during calibration, yields a slightly higher value than the experimentally measured one. This slight deviation is due to inevitable heat loss to the environment due to the thermal conductivity of the resistive element's supply wires and heat transfer to the surrounding environment.

[0070] In comparison with the data on the measuring capabilities of a typical thermocouple thermal sensor with an integral sensitivity of 0.2 V / W (UROT), it is obvious that the sensitivity (output signal UR3) of the thermoelectric module is several times higher, and accordingly, the measurement accuracy of the thermoelectric meter is significantly higher. and

[0071] An example of implementation shows that the invention solves the problem of significantly increasing the sensitivity to heat flow and the accuracy of measuring the electrical characteristics of high-frequency signals and direct current signals.

[0072] Thus, the present thermoelectric meter reduces the influence of external factors on measurements, has high sensitivity to heat flow and accuracy in measuring electrical quantities.

Claims

The amended claim was received by the International Bureau on May 8, 2026 (08.05.2026) Invention claims (as amended in accordance with Article 19 of the PCT) 1. A thermoelectric measuring device comprising a resistive element and a thermoelectric module - a Peltier element, wherein the resistive element is configured to generate heat as a result of the electrical signal being measured being supplied to it and is in thermal contact with the sensitive side of the thermoelectric module, and the thermoelectric module is configured to measure the heat generated on the resistive element and is placed on a heat-dissipating base.

2. A thermoelectric meter according to claim 1, wherein the resistive element is a resistive film.

3. A thermoelectric meter according to claim 1, in which the thermoelectric module is multi-stage.

4. A thermoelectric meter according to paragraph 1 or paragraph 3, including an additional similar resistive element that is in thermal contact with the sensitive side of an additional similar thermoelectric module, wherein the thermoelectric modules are located on the same heat-dissipating base and are electrically connected in opposite directions. AMENDED SHEET (ARTICLE 19)

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