How to Measure Using the Ohm Range on a Digital Multimeter
Thermocouple is a commonly used temperature measuring element in temperature measuring instruments. It directly measures temperature and converts the temperature signal into a thermoelectric potential signal, which is then converted into the temperature of the measured medium through electrical instruments (secondary instruments). The appearance of various thermocouples often varies greatly due to their needs, but their basic structures are roughly the same. They are usually composed of main parts such as hot electrodes, insulation sleeves, and junction boxes, and are usually used in conjunction with display instruments, recording instruments, and electronic regulators.
Method of using a multimeter to check the quality of thermocouples
1. Before using a multimeter for testing, we first observe with the naked eye whether the protective tube is corroded, penetrated, or leaking. Then use a multimeter to measure the continuity. The resistance of the assembled thermocouple is generally not greater than 2 ohms, and the resistance of the network cable is generally not greater than 50 ohms. Generally, if it is greater than 1K, it can be determined that it is broken.
2. Measure the resistance value with a multimeter, and if the resistance exceeds 100K, it is considered faulty.
3. Use a multimeter ohmmeter to measure the thermocouple, adjust the resistance, connect both ends, and use a lighter to slightly heat it. If the multimeter pointer significantly increases or decreases, it indicates that it is good. If the pointer does not move, it indicates that it is already broken. You can use a multimeter to measure the voltage at both ends in millivolt range. If there is no voltage, it will malfunction.
Common faults and maintenance methods of multimeters
1. The pointer swings abnormally, with intermittent oscillation and resistance
Solution:
(1) Open the watch case and use tweezers and a screwdriver to adjust the mechanical swing part, making the pointer swing flexibly;
(2) Re weld the header wire, reconnect the shunt resistor when it is disconnected, and replace it with a shunt resistor of the same model when it burns out;
(3) Use tweezers to readjust the shape of the balance spring, making its outer ring smooth and evenly arranged;
(4) Repair the supporting parts
2. No indication in resistance mode
(1) Reinstall the multimeter battery or replace it with a new one;
(2) Re weld the connection and adjust the center contact of the potentiometer to ensure good contact with the resistance wire;
(3) Clean the oil stains on the contact points and repair the contact pads. If the welding connection wire is disconnected, it needs to be re welded;
