Use this guide when the TD100 4–20 mA loop output is low, unstable, absent or does not match the measured tank level.
Low or no loop output
If the loop output is low, unstable or absent, work through the conditions below.
Output does not track properly near full scale
The output becomes inaccurate near the upper end of the measurement range.
The voltage supplied to Pin 4 is too low. The transmitter electronics do not have enough operating voltage to meet both the transmitter and PLC input requirements.
- Verify the supply voltage.
- Check the loop resistance.
- Ensure adequate headroom is available.
- Increase the supply voltage if required.
Output measures below 4 mA but above 3 mA
The measured current is less than 4 mA but remains above 3 mA.
This condition typically indicates that the loop is reporting an error.
- Inspect the transmitter wiring.
- Verify probe operation.
- Check the transmitter programming and configuration.
Output is stuck at 22 mA when the tank is empty
The loop output remains fixed at approximately 22 mA, even when the tank or vessel is empty.
The loop has entered an error state, usually because of a transmitter fault.
- Inspect the transmitter for faults.
- Check the wiring connections.
- Verify that the module is operating correctly.
Output reading is incorrect
The loop output does not match the actual level being measured.
System accuracy depends on the strapping table programmed into the transmitter. A difference between the programmed strapping table and the actual probe length will produce inaccurate measurements.
- Verify the probe length.
- Verify the tank dimensions.
- Confirm that the correct strapping table is loaded into the transmitter.
- Reprogram the strapping table if necessary.
Calibration cannot be adjusted using CAL mode
The desired calibration cannot be achieved using CAL mode.
The TD100 4–20 mA transmitter module cannot be adjusted through CAL mode.
Make all calibration corrections by modifying the strapping table loaded into the transmitter.