Are thermocouples and thermal resistances the same kind of objects? Today, the editor tells you clearly that they are not. Although both thermocouples and thermal resistances are used as temperature sensing elements, their principles and functions are different. Today I will share with you how to distinguish thermocouples and thermal resistances.
The first method of distinguishing between thermocouple and thermal resistance: Determine whether it is a thermocouple or thermal resistance according to the label. There will be specific product and specification information of the thermocouple or thermal resistance on the nameplate. We only need to observe and distinguish it carefully. The thermocouple is still a thermal resistance.
The first method of distinguishing between thermocouple and thermal resistance: distinguish between thermocouple and thermal resistance according to the structure. Thermocouples are generally composed of thermal electrodes, insulating tubes, protective sleeves and junction boxes. Thermal resistance is the load and power source output by the sensor. Are connected in series.
The first method of distinguishing between thermocouple and thermal resistance: It is determined by the wiring board. The thermocouple is distinguished by the positive and negative poles, and the thermal resistance is not distinguished by the positive and negative poles. This distinction method is relatively simple, you can try it.
The first method of distinguishing between thermocouple and thermal resistance: judge by compensation wire, thermocouple needs to choose different compensation wire according to different models, connect the compensation wire to increase the temperature stability of thermocouple, and thermal resistance does not need compensation wire, but heat The resistance is also divided into different models.
Thermocouple and thermal resistance are two different components, we need to distinguish carefully, don’t make a mistake, we have to be clear about what the components we need are for, and choose according to our actual needs. The actual thermal resistance or thermocouple
Identification method of thermocouple and thermal resistance
Instrument novices are often confused about how to distinguish thermocouples and thermal resistances. The editor of the Electrician Learning Network introduces the identification methods of thermocouples and thermal resistances in this article. This method is simple, quick and practical, and it is worth collecting.
The appearance of industrial thermocouple and thermal resistance protection tube is almost the same. Some temperature measuring elements have very small appearance, such as armored type. The appearance of the two is basically the same. In the absence of a nameplate and no known model , Can be identified by the following methods.
The first is to look at the lead wires of the temperature measuring element. Usually a thermocouple has only two lead wires. If there are three lead wires, it is a thermal resistance. But for the four lead wires, the resistance value needs to be measured to determine whether it is a dual thermocouple or a four-wire thermal resistance. First find out the two pairs of lead wires with almost zero resistance from the four lead wires, and then measure the resistance between the two pairs of lead wires. If it is infinite, it is a double thermocouple, and the resistance value is almost zero. The lead wire is a thermocouple. If the resistance of the two pairs of lead wires is between 10-110, it is a single four-wire thermal resistance, and its resistance value is closest to the thermal resistance of which graduation number, then it is the thermal resistance of that graduation number .
If there are only two lead wires, you can use a digital multimeter to measure the resistance value to judge. Because the resistance value of the thermocouple is very small, the thermal resistance is almost zero; if the resistance value is very small during the measurement, it may be a thermocouple.
At room temperature, the minimum resistance value of the thermal resistance will also be greater than 10. Commonly used thermal resistances are Pt10, Pt100 platinum thermal resistance, Cu50, Cu100 copper thermal resistance four graduation numbers, at room temperature 20 ℃, the resistance value of Pt10 is 10.779, Pt100 is 107.794, Cu50 is 54. 285, Cu100 is 108.571. The resistance value is greater when the room temperature is greater than 20°C, and most of the resistance values can be judged by comparing the two resistance values. If it is a thermal resistance, you can also know what the graduation number of the thermal resistance is.
You can also find an easily available heat source, and judge and identify it by heating the temperature measuring element. If you can connect a cup of hot water from a water dispenser, put the measuring end of the temperature measuring element into the hot water, and use the DC millivolt block of the digital multimeter to measure whether it has thermoelectric potential. If there is thermoelectric potential, the thermocouple finds it according to the thermoelectric potential Thermocouple index table, you can determine what thermocouple is the index number. When there is no thermoelectric potential, measure whether the resistance value has changed. If there is a rising trend of resistance value, it is the thermal resistance. You can also use an electric soldering iron or an electric oven to heat the measuring end of the temperature measuring element to judge and identify.