BANNER BES58-6 series incremental encoder selection and troubleshooting guide

Cable too long leads to voltage drop: For 5V TTL, the signal amplitude may drop below the receiving threshold after the cable exceeds 10 meters. You can use a line driven repeater or HTL encoder instead.

Practical troubleshooting: a complete repair case

Fault phenomenon: The X-axis position of a CNC machine occasionally jumps by+10mm and then returns to normal. The servo drive did not alarm, but the displayed actual position deviates too much from the commanded position.

Troubleshooting steps:

Observation of symptom characteristics: The position jump is sudden and irregular. This implies that it is not a mechanical clearance issue (which can lead to consistency hysteresis), but rather electrical noise or encoder pulse loss.

Check the mechanical coupling: manually rotate the screw after power failure, while observing whether the encoder shaft rotates synchronously. It was found that the fastening screws of the coupling were not loose, ruling out pure mechanical slippage.

Measurement of power supply voltage: Measure VCC and 0V at the encoder terminal. Rated 24V, actual measurement fluctuates between 23.5V and 24.5V, normal. But when observed with an oscilloscope, it was found that there was a high-frequency ripple with an amplitude of about 1V (from servo driver PWM feedback). Ripple may interfere with NPN output.

Analysis output type: The on-site encoder model is 6N (NPN open collector). NPN output is more sensitive to ripple because low-level signals may be misjudged as high-level under noise.

Capture A-phase waveform with oscilloscope: Set the oscilloscope to rising edge trigger and scan time to 10ms/div. When the machine tool is running normally, the waveform is a clear square wave. But when the fault occurred, an abnormal low-level spike was captured - a low level lasting about 20 microseconds, equivalent to losing several pulses.

Diagnostic root cause: Due to the need for a pull-up resistor for NPN output, the controller used on site is internally pull-up (2.2k Ω to 24V). Due to the length of the cable reaching 30 meters and the large distributed capacitance, coupled with power ripple, the rising edge of the signal becomes slower and more susceptible to interference. Push pull or HTL differential output has stronger driving capability.

Solution: Replace with a push-pull output encoder (6H). Reconnect the wires (no need to pull up), run again, the position jump disappears, and the oscilloscope displays sharp edges of waveforms A and B without burrs.

Preventive measures:

In long-distance or strong interference situations, HTL differential output (6T) is preferred.

The encoder cable should be routed in separate slots from the power line, with a minimum spacing of 20cm.

Install ferrite magnetic rings or power filters at the input end of the encoder power supply.

Environmental factors and maintenance cycle

According to environmental specifications, the working temperature of the encoder is -10 ℃~+70 ℃, and the storage temperature is -20 ℃~+80 ℃. In high temperature, high humidity, or dusty environments, additional measures should be taken:

High temperature: If the equipment is close to an oven or engine, the environment may exceed 70 ℃. In this case, a high-temperature resistant encoder or thermal isolation should be selected.

Oil pollution: IP65 can resist slight oil mist, but if oil is directly sprayed (such as gearbox leakage), the oil may seep into the interior along the shaft seal, causing contamination of the encoder. Regularly check whether there is oil accumulation at the shaft seal.

Vibration: Long term vibration can cause internal welding points to loosen or code discs to shatter. It is recommended to conduct signal waveform testing every 6 months to check for any abnormal jitter.

Suggested maintenance plan

Monthly: Check if the cable skin is worn and if the connectors are securely fastened.

Quarterly: Manually rotate the shaft and check for any jamming or abnormal noise (signs of bearing wear).

Every year: Use an oscilloscope to record the A, B, and Z waveform benchmarks, compare them with the initial waveform, and identify early degradation trends.