A simple judgment method 1. Macroscopic observation, whether protecting tube corrosion penetration, whether water leakage, etc. 2. Is measured with a multimeter on and off, prefabricated thermocouple thermocouple is generally not greater than 2 ohm, cables are rarely more than 50 ohm resistor. Generally greater than 1 k can determine is broken. More than a simple judgment, the long-term work under high temperature environment, prone to temperature drift, such as K type work for a long time in more than 1000 degrees, E work for a long time in more than 800 degrees, S type thermocouple work for a long time in more than 1250 degrees, will occur drift, drift 2-1000 degrees 5 c see very often. According to the requirements of technical specification is compulsory verification standard measuring instruments, involving energy saving and safe production, general use a year must send measurement test verification. Resistance is measured with a multimeter. More than 100 k is bad resistance. Measurement method to measure the multimeter ohms, adjusted the amount of resistance, connected to both ends, with a lighter under a little bit hot, if the multimeter pointer significantly larger or smaller suggesting that this is good, pointer that have gone bad. Can use a multimeter millivolt voltage on both ends of the gear measurement, such as no voltage is measured with a multimeter bad resistance to see your request, Using the environment, etc. ) , the stand or fall of galvanic couple couldn't determine different demands, with reference to your request to do experiments, achieve good precision thermocouple use for a long time after the fault is mainly: joint aging and breakpoint ( 1) Using a multimeter to measure resistance method is a simple and fast. Thermocouple resistance generally under 10 ohm, dozens of ohm or infinite are defective. （ 2) Thermocouple mv value is measured with a high-precision multimeter, check that the table I know use multimeter voltage profile measured voltage signal, but for the thermocouple, if only a multimeter can be measured is good or bad? The thermocouple is the multimeter resistance measured resistance signal or a dc voltage profile measuring voltage signal? 1. With the resistance. 2. Is assumed to be PT100: at 0 degrees Celsius to 100 ohms, at 20 degrees for 107. 7935 ohms. Differential resistance is about 0. 39 ohm/c. According to your site, environmental temperature, calculate the resistance value should be how much, and then use a multimeter resistance measure, then use lighter heating thermocouple, whether its value is rising. 3. Thermocouple accuracy, is need special instrument to detect the parameters such as multimeter testing only good or bad. That is to say, as a user, as long as the judge thermocouple no short circuit, there is no open circuit, resistance changes with the temperature, can think thermocouple is good.