I. Typical Failure Manifestations
1. Abnormal Protection Function
When the belt slips at low speed, breaks, or overspeeds, the sensor does not trigger an alarm or stop the machine.
After pressing the self-test button, the fault indicator light does not illuminate, indicating that the alarm circuit has failed.
2. Abnormal Signal Output
The measured current at the constant current output terminal deviates from the set value (e.g., not 5±0.5mA), or there is no signal output.
The main unit does not receive a speed signal, but the wiring connection is normal, initially suspecting a fault in the sensor itself.
3. Decreased Environmental Adaptability
Frequent false alarms or malfunctions in humid or dusty environments may be due to poor sealing or circuit aging.
II. On-site Testing Methods
1. Resistance Testing
After powering off, use a multimeter to measure the resistance of the sensor's internal coil. The normal value should be between 0.7 and 1.2kΩ (taking the GS4(A) model as an example). If the resistance is infinite or zero, it indicates that the coil is open-circuited or short-circuited.
2. Voltage and Signal Test
Measure the voltage at the power supply terminal to ensure it is between DC 12V and 24V while the device is powered on.
Use an oscilloscope to check the output waveform at the signal terminal: a normal output should be a stable pulse signal; if the waveform is chaotic or there is no signal, the sensor may be damaged.
3. Manual Simulation Test
Rotate the sensor roller by hand and observe whether the host receives the corresponding speed signal. If the host does not respond, but the wiring is intact, the sensor is faulty.
4. Substitution Method Verification
Replace the sensor with a known good sensor of the same model. If the system returns to normal operation, the original sensor was confirmed to be faulty.
III. Diagnosis Based on Fault Codes
Some systems record relevant fault codes, such as:
P0500 series: Indicates an abnormal or no signal from the vehicle speed sensor.
"Fault Code 11": Some mining protection devices indicate a speed sensor fault.
Reading the fault codes with a dedicated diagnostic tool can quickly pinpoint whether the problem lies with the sensor itself or the transmission line.
