How to use a multimeter to easily judge whether the encoder is good or bad - Database & Sql Blog Articles

Programmable Package SG-8018CA(SG7050C) 0.67M~170M

Photocoupler

A 24V HTL incremental rotary encoder is connected to the X23 port of the CU310 via six lines: 24V, 0V, A, A-, B, and B-. However, the power supply isn't working properly. When measuring the voltage at the power terminal with a multimeter, it reads only 2 volts. After disconnecting the encoder, the output voltage of the CU310 is found to be 24V. It's suspected that the encoder might be faulty. The code 4 is connected only to 24V, and the measured voltages are A=0V, A-=24V, B=24V, B-=0V. Is the encoder functioning correctly? According to the manufacturer, the normal voltage should be around 15V. Several similar encoders behave in the same way. It's difficult to determine if the encoder is fully functional using just a multimeter.

A multimeter can help assess the quality of an incremental encoder by checking its output. When powered on, measure the voltage from the A, B, and Z outputs. If there’s no voltage, the power supply or main chip may be damaged. If there is a signal, slowly rotate the encoder shaft and observe the A and B signals. They should switch between high and low levels, with a 50% chance of either. The Z signal should produce a high level once per revolution. Normally, the high-level voltage should be at least 2V or higher than the input voltage. If the phase doesn’t show a high level, or if the output level is too low, it could indicate a fault in the phase circuit.

If the multimeter test shows everything is okay, then use an oscilloscope to check for waveform distortion or missing pulses. This will give a more accurate picture of the encoder's performance. Sometimes, even if the voltage readings look good, the signal quality might still be poor, which can cause issues in the system. So, always double-check with an oscilloscope when possible. This method helps ensure the encoder is not just showing correct voltages but also producing clean, accurate signals.