Tips for measuring contactor coils with a multimeter
Low-voltage coils are generally milliohm level, with a multimeter can not measure the exact resistance value (error is very large), you need a special direct resistance tester. However, we can not say that the measured value is the same or almost the same as the design value, we can conclude that the coil is good, sometimes the coil turn-to-turn or layer-to-layer insulation damage can not be measured with a multimeter, you need to use frequency tester, such as 3x frequency generator set, etc., in order to find out the failure point.
Measure the coil with a digital multimeter with an ohmmeter of 2K or less to see if the coil is disconnected, if it is disconnected, it proves that the coil is bad.
Use the multimeter ohm 200 to measure the normally closed and normally open (measure the normally open by hand or electrified suction) auxiliary contact pass or not, if the contact contact is not good, this time the measurement resistance is very large. Indicates that the contact contact is not good, if the auxiliary contact is connected to the load, when measuring the voltage, the voltage will not reach the rated voltage.
Use a multimeter to measure the normally open and closed terminals to see if it is normal, coil with a multimeter is not good, the best way is to directly add the rated voltage into the test action.
Diode general multimeter adjusted in that gear
The digital multimeter has a diode symbol is the diode gear. Buzzer file is to measure the on-off circuit, generally diode file and buzzer file combined into one. There are also separate ones.
In this gear can be used to measure the diode's forward conduction voltage, thus inferring the diode's good or bad. Measurement must be placed in the red pen on the positive side of the diode, the black pen on the negative side of the diode. Good silicon diode forward voltage of about 0.5-0.7 volts, most of the ordinary light-emitting diode is 1.7 volts for the right.
Multimeter diode file is to measure the diode. Pointer multimeter generally do not have a diode file, the former pointer meter years, measuring diodes are used resistance file, and then look at the LV that a scale, read the diode downstream voltage, but also look at the LI that a scale, read the diode downstream current at that time. Silicon diodes will be around 0.6~0.7V, germanium diodes will be around 0.2~0.3V, and Schottky diodes will be around 0.2V.
