Credit Code for Temperature Transmitters
Based on the "Credit Code for Temperature Transmitters", the specification clearly states that the calibration of the temperature transmitter is required, and the working environment is required to meet the relative humidity of 45%to 75%and the temperature is (20 ± 5) ° C. There is no immersion in the constant temperature tank. The temperature field is based on the range of the meter, which adopts a multi -point form of a drawing.
In terms of laboratory calibration, the standards introduced by the environment and the standard device have a small uncertainty, and the conclusions are relatively accurate. The disadvantage, so online calibration is currently the main development direction in the application field. Generally, the temperature requirements of the working environment of the temperature transmitter are within the range of -40 ° C ~ 85 ° C. Based on the requirements proposed by the "Calibration Specification", the calibration environment of the temperature transmitter needs to meet at least 15 ° C ~ 35 ° C, and and the conditions, and the conditions of the temperature transmitter must meet the conditions of 15 ° C ~ 35 ° C. The relative humidity meets at least 85%, so that the calibration of equipment can be ensured that the equipment will not be affected by environmental factors.
The working temperature of carrying a portable warm field requires between the range of 50 ° C ~ 300 ° C, and the volatility of the temperature field is better than 0.03 ° C, and the uniformity of the temperature field is better than 0.01 ° C. The second -class standard platinum resistance thermometer and measurement range are 0 ~ 30mA, and the portable inspection device is required to meet the accuracy level of level 0.2 or higher. At the calibration stage, the temperature transmitter was disassembled, and the standard platinum resistance thermometer was placed in the portable temperature field.
The inspection instrument provided the instrument 24V voltage source, and the output current value was read. The constant temperature temperature field is based on the inspection point proposed in the "Calibration Specifications" in turn. When the temperature at about 30 minutes, the temperature in the temperature source is stable, and the calibration personnel are displayed in accordance with the standard platinum resistance thermometer. Detailed record.
Verify the uniformity of the temperature field and the lower limit of the stable time. The staff needs to test the 10 uniformly distributed temperature points for the upper and lower limit to observe whether the 10 temperature points reaches 0.01 ° C uniformity, and the minimum transition to 0.03 ° C within 10 minutes is the lowest. time limit. During the detection period, if the longest stability time is 40 minutes, the temperature source detection result is uniform, and the 40 min stability time is offline. At the calibration phase of this method, the laboratory environment is required, and the average temperature of the level is ≤0.01 ° C in the actual working conditions, and the 10 minutes change <0.04 ° C and the vertical temperature field <0.02 ° C stable constant temperature temperature field.
During the on -site calibration of the temperature transmitter, there are high requirements for heat dissipation and thermal insulation of thermal field. Therefore, the work unit needs to set up an independent portable warm field. At the same time, it is equipped with a computer operating system. A large number of staff members are required. Although the calibration results are reliable, it may cause obstacles to on -site production and the calibration rate is low.
