Issues regarding the loop testing of temperature transmitters
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I have a temperature sensor here with a calibration code of PT100; I use a resistance box to measure temperature changes. How exactly should I proceed? How to calculate the relationship between resistance value and current. Can we use Ohm’s law?
If it is a simple temperature transmitter without a thermal resistor, then connect the resistance box to the temperature transmitter (for the thermal resistor signal input); the output terminal needs to be connected to a power supply and for current detection. The resistance value of the resistance box should be adjusted (using the calibration table for PT100, which is available online). This does not require Ohm’s law. After understanding the principle of thermal resistors, a temperature transmitter converts signals into 4-20mA; in this measurement method, the resistance box is treated as a thermal resistor.
Having a resistance box is not enough; a 24V power supply and an ammeter capable of measuring currents between 4 and 20mA are also required. For specific procedures, refer to the JJF 1183-2007 standard for the calibration of temperature transmitters, which is available online.
PT100 – it doesn’t seem to be a scale number. The one at the back is the graduation mark
The temperature value corresponding to the resistance value can be calculated based on the scale number. You didn’t provide the scale number; it should be PT100 _ 385, right?
Materials needed: 24V power supply, multimeter, resistance box, temperature sensor, and several wires. Steps: 1. Wiring: Connect the positive and negative terminals of the temperature sensor (24V) to the corresponding positive and negative terminals of the 24V power supply (connect the multimeter in series with the negative terminal and set it to the DC current setting). Connect the terminals of the resistance box to the temperature input terminals of the sensor (usually a three-wire connection; be sure to identify the common terminal). After verifying that the wiring is correct, power on the system for testing. 2. Testing: Use a resistance box to simulate a PT100 temperature probe in order to test temperature changes. The resistance box is adjusted starting from 100 ohms (based on your temperature range and the corresponding temperature table), and then the current value is recorded to check whether it corresponds to the resistance value.
In accordance with the wiring requirements for temperature-sensitive PT100 sensors, a resistance box is used to simulate the PT100 sensor and connect it to the instrument; the resistance value of the resistance box is set according to the temperature range (the resistance value corresponding to each temperature point), and the current output is measured.