SU872985A1 - Device for determination of thermocouple thermal lag index - Google Patents

Description

The invention relates to thermometry and can be used in devices for determining the thermal inertia index of thermocouples, mainly installed on the measured object. ⁵

A device for determining the thermal inertia index of thermocouples containing containers for hot and cold water and a recorder flJ.

The disadvantage of this device ¹⁰ is the low accuracy of measurement, which is due to the fact that when moving investigated thermocouple from one container to another trudnouchityvaemye occur errors in measurement .tem- ¹⁵ perature cold junctions.

The closest in technical essence and the achieved result to the proposed device is a device for determining the thermal inertia of thermocouples, containing a power source, a thermostat, an electronic key and a control unit connected to a power source, and a recorder connected to the electrodes of the G22 thermocouple.

A disadvantage of the known device is the low accuracy of the measurement due to the fact that the thermocouple is heated from a constant current source, therefore, the heating current is recorded on the recorder first, and then, after switching the relay of the control unit, the thermometer cooling process is recorded. Due to the lack of recording of the heating process, the accuracy of fixing the start of the cooling process is determined by the transient time in the relay. The functionality of the specified device is limited by the limit breaking parameters of the relay (current and voltage ^ therefore the device is used to study microthermocouples. The reliability of the device reduces the presence of electromechanical relays.

The aim of the invention is to improve the accuracy of measurement.

To achieve this goal, an alternating current bridge is introduced into the device, one diagonal of which is connected to the power source and the other to the thermocouple electrodes, with the middle point of the bridge connected between the cooling spacer — it is recorded by the recorder. After pressing the Reset button, the device is ready for operation again. The thermal inertia index is determined ₅ from the cooling curve of the thermocouple by known methods.

The proposed device allows you to determine the thermal inertia of the thermocouple.

The drawing shows a schematic diagram of a device.

The apparatus comprises a controlled object 1, the thermostat 2, the investigated thermocouple 3, AC bridge 4 is connected to the one diagonal ₁₅ used source of AC power supply 5, the other - the free electrodes of the thermometer at the midpoint of the bridge is connected between the junctions of the thermometer. The thermocouple is connected to the recorder 6, _2Q control unit 7 is connected with the registrar with bi bridge via an electronic switch 8. The electric bridge is balanced in such a way that the diagonal connected to the thermocouple ₂ $ The relative absent alternating component only Seebeck thermocouple is supplied to the registrar proportional to the temperature difference between the junctions.

The device operates as follows ₃ θ at a time.

When the device is turned on, the Start button is pressed, the electronic key 8 is activated, and power is supplied to the AC source 5. An alternating current flows through thermocouple 3, ³⁵ which heats the electrodes and junctions due to the release of Joule heat. The temperature of the free junction located in thermostat 2 is maintained constant. The temperature difference ⁴⁰ between the junctions varies. · The voltage between the junctions is fixed by the recorder 6. At the same time, the voltage drop signal through the control unit 7 is sent to the electronic key 8 and 45 when a certain value corresponding to the threshold of operation of the electronic key is reached, the latter breaks the power supply circuit of the AC source. The threshold of operation of the electronic key 50 is set by setting the gain selected in accordance with a given temperature difference. The heating current stops and the thermocouple begins to cool. Pro- tion thermometer 55, the temperature not exceeding the temperature of the controlled object more than 0.1 K. This eliminates the disturbing effect of the test thermometer for temperature controlled objective ⁴ ta. The proposed device has increased accuracy due to the introduction of an alternating current bridge, balancing it with respect to the variable component, obtaining only thermo-EMF at the output, which depends on the temperature difference at the junctions of the thermometer, i.e. a continuous heating-cooling process is recorded on the recorder. At the same time, the introduction of the bridge allows you to change the heating current over a wide range, i.e. measure the inertia of thermometers with a diameter of 0.03-0.5 mm or more.

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Claims (2)

(54) DEVICE FOR DETERMINING THE INDICATOR OF THERMAL INERTIA OF THERMOPARES The invention relates to thermometry and can be used in devices for determining the thermal inertia indicator of thermocouples, preferably installed on the measured object. A device for determining the thermal inertia index is a term steam containing containers for hot and cold water and a tl3 recorder. A disadvantage of the known device is the low measurement accuracy, which is caused by the fact that when the thermocouple under study is transferred from one container to another, inconceivable errors occur. in measurement. the temperature of the cold junctions. The closest in technical essence and the achieved result to the proposed device is a device for determining the thermal inertia index f pMonap, containing a power source, a thermostat, an electronic key and a control unit. connected to a power source, and a recorder connected to the thermocouple electrodes. A disadvantage of the known device is low measurement accuracy due to the fact that the heating of the thermocouple is conducted from a direct current source, therefore, the heating current is recorded first on the recorder, and then after the relay of the control unit switches, the temperature of the thermometer is recorded. Due to the absence of a recording of the heating process, the accuracy of fixing the start of the cooling process is determined by the transient time in the relay. The functionality of this device is limited by the limiting discontinuous parameters of the relay (the current and voltage are therefore used by the device to study microthermocouples. Reliable operation of the Device reduces the availability of electromechanical relays. The purpose of the invention is to increase the measurement accuracy. To achieve this goal, the AC bridge one diagonal of which is the connection to the power supply, and another to the electrodes of the thermocouple, with the middle point of the bridge being connected between the spans The drawing shows a schematic diagram of the device.The device contains a controlled object 1, a thermostat 2, a thermocouple under study 3, an alternating current bridge 4 connected by one diagonal to an alternating current power source 5 .other to the free electrodes of the thermometer, with the midpoint bridge connected between thermometer thermocouple thermocouple connected to the recorder control unit 7 is connected to the bis recorder by an electronic key 8. The electric bridge is balanced so that in the diagonal connecting In other words, the thermocouple is not variable in the thermocouple, only thermoEMF from the thermocouple is supplied to the recorder, which is proportional to the difference in temperature between the joints. The device works as follows. When the device is turned on, it presses the Start button, the electronic key 8 is activated, and the AC source 5 is energized. Through thermocouple 3 alternating current flows which heats the electrodes and junctions due to the release of Joule heat. The temperature of the free spa, which is located in the thermostat 2, is kept constant. The temperature difference between the spans varies. The voltage between the junctions is recorded by the recorder 6. At the same time, the voltage drop signal through the control unit 7 is supplied to the electronic key 8 and, when a certain value of the corresponding threshold of the electronic key is reached, the last break in the power supply circuit of the AC source. The threshold of the electronic key is set by setting the gain coefficient, selected in accordance with a given difference, temperature. The warm-up current stops and the thermocouple begins to cool. The cooling process is recorded by the recorder. After pressing the Reset button, the device is again ready for operation. The index of thermal inertia is determined from the thermocouple cooling curve by known methods. The proposed device makes it possible to determine the indicator of thermal inertia of a thermometer, the heating temperature of which does not exceed the temperature of the monitored object by more than 0 K. It eliminates the disturbing effect of the thermometer under investigation on the temperature of the monitored object. The proposed device has increased accuracy due to the introduction of an AC bridge, balancing it with a variable component, obtaining at the output only a thermo-emf depending on the temperature difference between the thermometer and the thermometer. The recorder records the continuous process of heating - cooling. At the same time, the introduction of a bridge allows varying the heating current over a wide range, i.e. measure the inertia of thermometers with a diameter of 0.03-0.5 mm or more. The invention The device for determining the indications of the bodies of thermal inertia of thermocouples installed on a measuring object, containing a power source, a thermostat, an electronic key and a control unit connected to a power source, a recorder connected to the thermocouple electrodes, in order to increase the measurement accuracy The AC bridge is inserted into it, one diagonal of which is connected to the power source, and the other to the teryrpary electrodes, with the average power point connected between the thermocouple junctions. Sources of information taken into account in the examination 1. USSR author's certificate number 384028, cl. Q 01 K 15/00, 1973. 2. Malgun, MM and others. Determination of the index of thermal inertia of microthermopar, - Instruments and experimental technique, 1977, No. 3, p. 198 (prototype).