Trouble shooting of torque sensor
Trouble shooting of torque sensor
The torque sensor works in obscurity at ordinary times. Once there is a problem, it can really affect the whole production line. Have you ever had a headache with inaccurate display, jumping data and no response? Today, let's take a look at some common troubleshooting of torque sensors.
When the screen starts to "dance"-abnormal display
You are staring at the control screen, and suddenly you find that the torque value can't stop up and down, or it is stable at an obviously unreliable value. At this time, don't rush to judge that the sensor is useless, let's follow the steps:
The first step: first "ask" the power supply, which is the source!
First, take out the multimeter and measure whether the power supply voltage supplied to the sensor is stable or not. The voltage is too low/too high. Many sensors are very sensitive to the power supply voltage. For example, if 24VDC is required, but you actually only have 22V or jump to 26, it may not work normally, so as to ensure that the power supply is within the allowable fluctuation range (for example, +5%). Power supply ripple is too large: this is hidden. The voltage value looks right, but there are too many "clutter" in it. It's like giving you water mixed with sand. Although it's also water, people will feel uncomfortable after drinking it. At this time, it may be necessary to consider adding a filter to the power supply, or check whether there are high-power devices nearby that frequently start and stop and interfere with the power grid.
Step 2: Check the line again, this is the bridge!
Is the power supply okay? Then let's follow the road. Check the wiring from sensor to display instrument or PLC. Focus on the inspection of connectors: I have encountered too many cases, and the problem lies in the looseness, oxidation or water vapor entering the connectors, which leads to the increase of contact resistance, and the signal is attenuated or distorted during transmission. Please treat the connectors with moisture-proof tape to tighten them one by one. Whether the cable has "internal injury": Check whether the cable has been smashed and cut, especially when passing near the moving parts, which may cause short circuit or open circuit inside after a long time.
The third step: finally "school" zero, this is the basic skill!
If the first two steps are all right, it is likely that the "feeling" of the sensor has drifted. At this time, zero calibration is our first choice weapon.
Key points of operation: under the condition of ensuring that the sensor is free from any external force (including the dead weight of the coupling), zero calibration is carried out according to the instructions. This operation can eliminate the accumulated error inside the sensor, and many seemingly complicated display problems can be eliminated by a simple zero calibration.
Remember this order: power supply, one line and one zero point. After this "combination boxing" is played down, more than 80% of abnormal display problems can be solved by us.
When the data is "enchanted"-interference problem
This question is even more maddening than the abnormal display! Overall, the torque value is stable, but there is always a regular or irregular small fluctuation, which goes hand in hand like a ghost, causing the equipment to be unable to control accurately. Nine times out of ten, this problem is caused by "interference". We can imagine the sensor signal as a calm river, and the interference is the "Naughty Child" that throws stones into the river.
"Naughty Child" No.1: Electromagnetic interference (EMI) is the most common culprit.
The frequency converters, servo drives, high-power motors, and even welding machines in the workshop are powerful sources of interference.
Stay away method: Try to keep the signal line of the sensor as far away from these interference sources as possible, maintaining a distance of more than half a meter. Never bundle the signal and power lines in the same cable tray just to save time, that's a big taboo!
Shielding law:Be sure to use double wire with shielding layer, and the shielding layer must be reliably grounded at one end! Note that it is single ended! If both ends are grounded, it may form a "ground loop" and introduce more troublesome interference, a detail that many beginners may overlook.
Install a "protective talisman": Install a signal isolator or filter at the entrance or exit of the signal line. This thing is like a "purifier" that can filter out the "impurities" mixed into the signal, and the effect is immediate.
"Naughty Child" No. 2: Grounding Interference
If the grounding is not done well, even immortals will find it difficult to handle. This is a systemic issue.
Check the 'system ground': Ensure that your display instruments, PLCs, and other equipment have a clean and reliable grounding. Sometimes, if the grounding pile of the entire equipment cabinet is loose or corroded, it can cause inconsistent ground potentials among the devices, resulting in common mode interference.
Point grounding principle: The entire measurement system should ensure "one point grounding" to avoid potential differences caused by multiple grounding points.
"Naughty Child" No. 3: Mechanical Vibration and Temperature Drift
Vibration: Intense vibration not only damages the sensor itself, but may also cause abnormal signals in the internal circuit. Check if the equipment base is secure and if the coupling is properly aligned. Don't underestimate alignment, alignment is not good, it is itself a periodic torque interference temperature; If the malfunction always occurs after the equipment has been running for a period of time and the temperature rises, then it should be suspected that it is temperature drift. Check if the working environment temperature of the sensor exceeds the standard, or if the temperature compensation coefficient of the sensor itself is poor.
When encountering problems, we need to:
1. From external to internal: Always start with the simplest power supply, wiring, and environment, and then doubt the sensor itself.
2. Be bold and meticulous: Dare to check with your hands, but your mind must be meticulous and not miss any detail.
3. Make good use of tools: A multimeter is our "stethoscope", and an oscilloscope (if available) is our "CT machine", which allows us to see the "electrocardiogram" of the signal and determine the type of interference.
Finally, if all methods have been tried and the problem persists, it may be that the internal components of the sensor are really aging or damaged. At this point, don't hesitate to contact the manufacturer's technical support. But before that, you have already provided a lot of valuable information to technical support through your own investigation, which can quickly locate the problem. This itself is also a manifestation of professional ability.