Using a multimeter to test thermocouple performance good or bad judgment method

Everyone is no stranger to the use of thermocouple testing should be, but the detection of a thermocouple is good or bad there are a variety of methods. Don't know several people know? The following three chang first explain thermocouple multimeter is used to inspect the specific is what to do.

if the condition of the scene of the working condition of the absence of thermal treasure dian, how to judge the stand or fall of thermocouple?

simple judgment method: first of all, with the naked eye observation, protecting tube corrosion penetration, whether water leakage, etc. Thermocouple with universal table can only be measured at room temperature on and off. Because one of thermocouple temperature measurement conditions for different choice on both ends of the thermocouple temperature all table resistance wire is negative, respectively, by the thermocouples are negative resistance have shown to make otherwise to break. Resistance heat resistance with a multimeter, then heated, the resistance for change; Thermocouple with a multimeter to measure voltage, measure range to choose a little bit small, heating at one end, for voltage change. Prefabricated thermocouple resistance is generally not more than 2 ohm, cables are rarely more than 50 ohm resistor.

1, the thermal resistance sensor output is resistance signal, namely ohm ( Ω ） Resistance measurement, using a multimeter. At ambient temperature measurement, the output resistance value in line with the index value, such as Pt100, output 111 at 30 ℃. 67Ω ；

2, thermocouple sensor output is a voltage signal, namely the millivolt ( mV） Resistance of judge is generally the multimeter measure the on/off. If you want to check, will the heating test. Under the environment temperature measurement output of millivolt values is no potential output ( Because of hot and cold end temperature)

3, if measured on and off as long as the two thermocouple wire connected to the multimeter probe doodle of the ring is of general principles of not broken

4, if the measuring thermocouple Howe v value table transferred to hao on transmission line

generally greater than 1 k can determine is broken. But it is worth noting that the above is just 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 work for a long time in more than 1250 degrees, will occur drift, drift 2-1000 degrees - - - - - - 5 c see very often.

in accordance with the relevant requirements, the technical specification is compulsory verification standard measuring instruments, involving energy saving and safe production, general use a year must send measurement verification test center. Resistance is measured with a multimeter resistance more than 100 k is bad. 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 milli v 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 is the basis of the principle of thermoelectric effect testing temperature of common tools. In the conventional instrument, to solve the problem of cold junction compensation of thermocouple and linearity problems, must take some measures to add some additional equipment, can obtain the more accurate readings. Hold the tube furnace at the allowable maximum temperature, and keep the stable range. At that time with tested qualified hui sten potentiometer, measure standard and the thermoelectric potential difference under test and record.

according to the records of thermoelectric potential difference, fish respectively corresponding to the temperature of the look-up table, if poorly under test, can be judged to be unqualified. This kind of tube furnace, not analytical chemistry with silicon carbon tube furnace. For the unqualified, can cut off a little from the hot end, welding again. Welding method is simple, the ordinary nickel-chromium, can use autotransformer to low voltage, and with two root silk into a pole, the other with the carbon rods, direct ignition arc, two wire will melt into a small ball in the head. The operation is easy, can adjust voltage, will soon be master. This welding using the autotransformer, must pay attention to the insulation to secure them. Welding of expensive platinum rhodium, is another method. Insert after regulating power as a sodium chloride aqueous solution, the other is screwed together, with insulating pliers clamp, tap the solution surface, both ends can fuse. These two kinds of welding methods, pay attention to safety and practice, easy to master. To welding, can detect, determine the qualified or not. You say, VCC - Resistance - Thermocouple - The ground. 。 。 This answer. Normal middle certainly wouldn't be VCC. When broken accidentally. They became VCC in the middle. In voltage way affect thermocouple performance? Broken accidentally testing? Refers to the thermocouple disconnect? Broken accidentally detection refers to the thermocouple off state, we use a type B platinum-rhodium wires, use voltage method for testing, afraid influence the performance of platinum-rhodium wires, platinum rhodium wire will go into too many process can be used for accurate temperature measurement. Don't know how you thermocouple receiving circuits, we buy the thermocouple acquisition module, platinum rhodium wire at both ends is receiving module +, - directly Signal at the input, it is not clear how the acquisition module is broken accidentally detection. General AD inside there is a super small current current source, the thermocouple can be broken accidentally detection without affecting performance. For example, hundreds of nA small constant current source. Is that so? 广告- - - - - - MCU pin output zero, in AD + pin read input values, when the thermocouple didn't disconnect, AD + read logic 1, attend to logic 0 when disconnected.

through the above details, hope you can help to you more profound understanding of the thermocouple with the testing points of the multimeter, if you have any problems you can feel free to contact us three cheong instrument.