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

There is a 24V HTL incremental rotary encoder 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. Using a multimeter, the voltage at the power terminal was measured at around 2V, which is significantly lower than expected. After removing the encoder, the output voltage from the CU310 was confirmed to be 24V, indicating that the issue likely lies with the encoder itself.

The error code 4 was triggered, and when only 24V was connected, the readings showed A=0V, A-=24V, B=24V, and B-=0V. This suggests an unusual signal pattern. According to the encoder manufacturer, the normal voltage should be around 15V. Several similar encoders exhibit the same behavior, making it difficult to determine if they are fully functional using just a multimeter.

While a multimeter can provide some basic diagnostics, it's not always sufficient to fully assess the condition of an incremental encoder. Here’s how you can check it more effectively:

• Power On Test: When the encoder is powered on, measure the output voltages of A, B, and Z. If there’s no voltage, the power supply or main chip might be damaged.
• Signal Check: Slowly rotate the encoder shaft and observe the A and B outputs. They should alternate between high and low levels as the shaft turns. The Z signal should produce a high pulse once per revolution. The high-level voltage for Z is typically 2V or higher than the input voltage.
• Phase Analysis: If one of the signals doesn’t switch to a high level, or if the output level is consistently low, that phase may be faulty.

If the multimeter test appears to pass, use an oscilloscope to inspect the waveform for distortion or missing pulses. This will give a clearer picture of the encoder’s performance and help identify any hidden issues that a multimeter might miss.