Q1: Which reasons would cause OFL or –OFL millivolt value from load cell?
A: Prior to unload material when begin to check the possible causes:
1. Failure from the load cell connection. (Checking whether terminal connection is loose or not; or whether the connection mode is correct or not.)
2. Enter the millivolt value interface, then pull/push the load cell, if the millivolt value display was changing into normal, which means the scale body was overweight or underweight; if the display was remaining OFL or –OFL, continue the checking.
3. Turn up the maximum scale value and check whether it became normal.
4. Measure the voltage of SIG+ & SIG with the multimeter in DC voltage profile. (The normal was between 0 and 24mv).
5. Check it with another good load cell.
6. It would become normal with the multimeter connecting the SIG+ and SIG, if the reason was static electricity.
7. Check whether the load cell was damaged or not.
8. Check if there were any serious vibration during the scale was running. (Shutting the discharging valve and Packing action can produce larger retraction force moment, which may cause OFL display and then closing down.
9. The analog-digital converter was broken, only depot repair.
10. Test each load cell individually if the scale contains more than one load cell. Check the failure was from load cell.
11. The load cells were not balanced.
Q2: The indicator cannot light up or all the digital characters light up.
A: 1.Pull up all I/O port and serial port, only connect
the electricity power, check the indicator can turn on normally. (This operation was for checking whether other signal from other equipment result in indicator working abnormal)
2. Reboot the indicator, check the indicator cannot light up after flash”8” or never light up. If it cannot light up after the indicator flash”8”, then check the GM Logo light up or not, if the logo was lighting up, which means the indicator locked itself, contract us to get the password and unlock it.
3. Measure the power voltage with multimeter. The instable voltage or overloading voltage would cause indicator can"t start or burn out.
4. Check the working conditions. If the working condition was quite adverse, the indicator would be short circuit due to being affected with damp and cause shot circuit of chip.
Warning: The normal working voltage of indicator was 220V±20%, Instantaneous over voltage range may not damage the indicator, but over voltage for a long time would burning internal components.
Q3: Hop-count of indicator
A: 1. Re-calibration;
2. Connection problems: check whether the display reading would change or not when touching the load cell connections, if
the changes were existed, need to reconnect the load cell.
3. Check the vibration around the indicator, especial for the equipment connected the indicator.
4. Check if the problem was from the load cell using another good load cell.
Q4: Serial port cannot communicate with other equipment.
A: The below were the possible problems:
1.Parameter settings.(Including Data format, Calibration method, Communication mode, Baud rate and other parameters related to communication)
2. Check the communication mode was RS232 or RS485. ( Generally, the indicator internal have the corresponding dial switch, dial to the right tap)
3. Check whether the adapter was normal or not if the communication mode was RS485.
4. Connection problems. (Check the serial port connection way was correct, such as inversely connecting of transmission and reception; inspect whether connecting the ground in RS232 Mode)
5. Check the serial tool of the other side was right or not.(Including check whether thevtransmit mode of the other side data and the data after verification were right or not)
6. Check whether the serial port line was too long.(Check the communication would become normal after replace it with a short serial port line)
Special tips: If the indicator was installed another system, need to reset again.
Q5: Serial port can’t import the data.
A: 1. Check if the communication was normal or not. (Check whether the indicator and equipment can normal communicate well, if not, as the serial port should not read-in data.
2. Check whether the order of transmitter data was correct.
3. Check the input values if there are other restricted conditions.(Such as no greater than maximum capacity or less than the minimum division)
Note for the Modbus communication: Distinguish between the PLC address and display address according to the use manual. The display address read-in data starting from 0, while the PLC address was from 40001, select the correct read-in approach during communication due to the two addresses just stagger one number.
Q6: The measure weight was not accurate.
A: The below were the possible problems:
1. Calibration is not accurate, need to re-calibrate.
2. The linearity of load cell was not stable. Which could be tested from measuring the weight of two objects of equal weight, check whether the weight of loading them together was twice of only put one weight, if not, that means the linearity of load cell was not good, need to replace it.
3. Uneven loading due to containing more than one load cell, which could also cause inaccurate measuring weight.(Test method: Put a same weight at different positions of scale and measure it, if got a same measuring weight, which means no need calibration, if got different measuring weight, that means need calibration or change another good load cell. Calibration method: Adjust the load cell junction box until get a same weight of different position of scale.)
4. Check it with replacing another good load cell, if the measure weight was accurate after changing a good load cell, which means the load cell was damaged.
Q7: Restart the indicator
A: 1. Reset the indicator, possible failure was internal program error.
2. Unplug all external terminals and then re-up electricity, which can clear external disturbance.
3. Check if the voltage was stable.