Comparison between two-wire thermal resistor and three-wire thermal resistor

Ore dressing enterprises inevitably have many detection instruments on their equipment, including oil pressure, oil flow, vibration, temperature and other measuring sensors. Among them, temperature detection is an important parameter for detecting whether the equipment is normal. Its accuracy directly affects our judgment of the equipment operation status, so the authenticity and reliability of temperature detection must be guaranteed. During use, we found that the detection temperature sensor model used on the lubrication station of the blower is: WZP-231, two-wire system. It often happens that the temperature detected by the thermal resistor is 5-10℃ higher than the actual temperature, causing the equipment to trip, especially on hot days. Due to the high temperature, the measured temperature is higher, which will cause the equipment to fail to start.

Difference between two-wire thermal resistor and three-wire thermal resistor

Two-wire system: The lead method of the two-wire thermal resistor is relatively simple. Only one wire needs to be connected at each end of the thermal resistor for the lead-out of the resistance signal. However, due to the lead resistance of the wire, the resistance value of the thermal resistor is affected by the resistance, which makes the resistance value of the wire resistance have a large error. At the same time, the quality and length of the wire material will have a direct impact on the size of the resistance value error. Therefore, this lead method can only be used for testing in occasions with low precision requirements.

Three-wire system: The three-wire system refers to connecting a lead wire at one end of the thermal resistor and two lead wires at the other end. In most cases, the three-wire system will be used at the same time as the bridge. Two wires are connected to the back of the bridge and one lead wire is connected to the power supply of the bridge, so that the error of the lead resistance is minimized. It can eliminate the influence of the lead resistance on it. This method is also a more common lead resistance in control.

Methods for judging the quality of thermal resistors

(I) You can use your hands to actually feel how many degrees Celsius the temperature of the device is, and then compare it with the temperature actually measured by the thermal resistor to see if there is a large difference. If there is an obvious gap, it can be judged that the thermal resistor has a problem.

(II) Use an infrared thermometer to measure the actual temperature of the device, then use an ordinary multimeter to measure the resistance value of the thermal resistor, and then find the corresponding temperature on the thermal resistor scale to compare with the actual temperature to judge whether it is good or bad.

(III) You can use a multimeter to directly measure the signal terminal of the thermal resistor, measure the temperature measured by the thermal resistor, and then compare it with the temperature measured by the infrared thermometer to judge whether it is good or bad.

Problems and solutions when using two-wire thermal resistors

(I) When using two-wire thermal resistors, the measured temperature has been 5-10℃ higher than the actual temperature. Solution: Try to reduce the resistance effect of the line, and increase the cable as much as possible to reduce its impact.

(II) When increasing the cable, sometimes we cannot achieve the expected effect. We can choose to replace the thermal resistor, replace the two-wire thermal resistor with a three-wire thermal resistor, and replace the cable at the same time. The effect can be achieved.