Load Cell Amplifier Calibration Always Reads About 83% of Actual Weight

Hey everyone,
I purchased an ATO-S-LCTR-DY610-A2 (Link: https://www.ato.com/digital-load-cell-amplifier-output-4-20ma-0-10v-rs485) and it's very precise, but I'm having a hard time getting it calibrated correctly. I’ve watched the official video multiple times and I’m pretty experienced with load cell calibration and electronics, but I can’t seem to get this one right.
I can zero it fine, but when I calibrate using a known 500g weight on a 1kg load cell, the reading ends up around ~415g. If I try a smaller weight (200g), I get about ~165g. It’s consistently about 83% of the actual value.
Has anyone run into this before or have suggestions on what I should check? Thanks!

Doub wrote:You mean that when using this amplifier ATO-S-LCTR-DY610-A2 to calibrate a 0–1Kg load cell, the span calibration is unsuccessful, right?

First of all, before calibrating, you need to make sure that the sensor is properly connected to the amplifier, and the number displayed by the amplifier must be a positive value (the load cell is slightly loaded) before calibration can be performed.

If the wiring is correct and the displayed number is positive, you can try another load cell.

That ~83% scaling error usually isn’t random. It often points to a gain/span mismatch rather than noise or wiring.
A couple of things I’d double check:
1. Make sure the rated output (e.g., 1.0 mV/V vs 2.0 mV/V) of your load cell matches what the amplifier expects
2. Confirm excitation voltage is stable (if it’s lower than expected, your readings scale down proportionally)
3. Try recalibrating using a weight closer to full scale (like 800–1000g instead of 200–500g)
I’ve seen similar behavior when the amplifier gain setting doesn’t match the sensor spec.

Ellertson wrote:I agree with you, but the consistency (always ~83%) makes me think it’s either:
Wrong sensitivity setting (mV/V mismatch), or mechanical setup issue (like load not applied fully vertically, or some friction/constraint). Also, check if the amplifier has any internal scaling or parameter that weren’t reset—sometimes factory settings don’t match your specific sensor.

In this case, it is possible that the load cell is damaged. You can replace it with another load cell and test it. Here is how to confirm if the load cell is faulty:
1. Find the connection terminals of the sensor in the weighing instrument (or amplifier).
2. When the connection circuit of the measuring sensor is normal, the red and black wires (EX+, EX-) of the sensor are at the excitation voltage, generally 5V power supply voltage.
3. Remove green and white lines (SIG+, SIG-) signal lines when the sensor is unloaded, set the multimeter to voltage mV gear, and then directly measure the mV voltage of the (SIG+, SIG-) signal lines.
4. If the measurement result does not exceed 0.3 mV, then press the sensor with your hand.
If you see obvious mV voltage changes, it means that the sensor is good; If you do not see any change in mV voltage, it means it’s bad.

Thanks for all the suggestions. The displayed value is still consistently about 83% even after checking wiring and repeating calibration. I’ll try testing with another load cell and follow the mV measurement method to rule out sensor damage.