1 Thermocouple temperature sensor length
JJG351-1996 "Operational cheap metal thermocouple temperature sensor" verification routine clearly defines the length of the thermocouple temperature sensor is not less than 750mm, so the length of the thermocouple temperature sensor is delineated, due to the consideration of the thermocouple temperature sensor There must be a sufficiently wide temperature gradient zone after separating the temperature measurement zones. The thermoelectromotive force of the thermocouple temperature sensor also occurs in this area. It is necessary to ineffectively prohibit the heat from the hot end (measuring end) of the thermocouple temperature sensor from being transmitted to the cold end (terminal). The most fundamental method is the thermocouple temperature sensor. The cold end should have sufficient spacing to keep the hot end away. Individually, the deviation due to the length of the thermocouple temperature sensor is negative, and the modified value is positive. The shorter the length, the greater the deviation, so the length of the thermocouple temperature sensor must be determined before the furnace calibration.
2 thermocouple temperature sensor wire twist
The thermocouple temperature sensor is thin and soft, and is easily deformed. When the filament is deformed by plastic deformation such as folding and distortion, the thermocouple characteristics of the thermocouple are changed, so that the thermocouple temperature of the thermocouple temperature sensor is changed, thereby deforming the thermocouple temperature. The accuracy of the sensor measurement results is affected. Therefore, the thermocouple temperature sensor wire must be straightened before verification.
3 thermocouple temperature sensor wire is infected
The thermocouple temperature sensor wire is infected and even oxidized, which will cause the hot electrode wire to be bright, dark and black. At this time, the thermoelectric characteristics of the hot electrode are extremely unstable, and the accuracy of the measurement data is poor. There are infected electrodes that dispel the infection layer.
4 Responding to the influence of time
The fundamental reason for the snoring method is that the temperature measuring element should reach the thermal equilibrium with the tool to be tested. Therefore, in the temperature measurement, it is necessary to adhere to the timed light, so that the two can reach the thermal equilibrium. Adhere to the right and wrong of time, related to the heat response time of the temperature measuring component. The hot response time depends on the structure of the sensor and the premise of measurement. The difference is extremely large. Therefore, in the same normal verification process, the thermoelectric temperature sensor according to the differential example is selected to select a suitable heating rate and heat equalization time.
5 insulation resistance
When the thermocouple temperature sensor is at a low temperature, its insulation resistance drops sharply with the decrease of temperature, so a current will flow out. This current flows through the insulation flow, which has been reduced by the insulation resistance , into the meter , causing the instrument to be unstable or to cause measurement deviation. Therefore, do not neglect the test of the insulation resistance of the thermocouple temperature sensor before it is installed. Only when the satisfactory verification routine requests it, the temperature tolerance test is stopped.
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