HX711 Giving Constant High Voltage

Sensors Force & Weight
1

I have a 0.78 kg load cell connected to a HX711 amp connected to a USB-6009 oem NI card. If the load cell is directly connected to the NI card, and I average over enough measurements, the load cell force can be properly measured (around 1mV signal). However, the signal is fairly low, so I would need an amplifier to get more precise measurements. Once I attach the HX711, the signal becomes much higher, but it is always constant at around 1.3V, even though I apply a force on the load cell.

I followed the HX711 hookup guide on the SparkFun website. The vcc and vdd are therefore shorted to 5V. The measurement rate in LabView is set to 10 Hz, which I believe is the proper rate for the HX711.

Vcc->5V

Vdd->5V

DAT->Ai0+ (NI card GPIO)

CLK->Ai0-

Any idea why the signal isn’t changing?

2

Hi alars.

The output from the HX711 is digital data, not an analog signal. You need to send commands to the HX711 to get back the digital data. A microcontroller like an Arduino is usually used to do this. Please see our [hookup guide for details on how to connect the HX711 to an Arduino if you want to learn how to access data from the HX711 digitally.

In your case it sounds like you’re probably needing an analog load cell amplifier for your NI card. Sadly we don’t carry one, but an internet search for ‘analog load cell amplifier’ should turn up something that would work for you.](https://learn.sparkfun.com/tutorials/load-cell-amplifier-hx711-breakout-hookup-guide)

3

Sounds good, I’ll have to look into that. Thanks a lot for the help!