Arduino and Load Cell ( INA125P or HX711 ?)

Hello,

I am trying to measure milli gram loads using a 100g load cell from Phidgets: http://www.phidgets.com/products.php?category=34&product_id=3139_0

I could not find a load cell which measures deci grams or smaller loads. There are such load cells from ATI but they cost thousands of dollars :frowning: If anyone can suggest me a cheaper source, that would be really helpful.

From other forum topics it seems like INA125P and HX711 are popular choices for amplifiers. For measuring such small loads (deci or milli grams) which one is better? Can someone share a connection diagram or a schematic and a sample code? Or are there ready made modules?

Thank you!

Dakujr

Both should be working. The HX711 provides a digital interface and has a built in amplifier with fixes gain settings. The INA125 is an analog instrumentation amplifier. Therefore you can adjust its amplification and you get an analog signal from it which you can adjust further if necessary (e.g. for filtering). For the INA125 you would need an additonal ADC with a high resolution as the ones built in the Arduinos are not sufficient for that.
I would first try it with the HX711 as they are cheap and you don't need an additional ADC which makes it easier to handle.

I hope that helps you
Daniel

I think you may have some difficulties just based upon the sensor and nothing to do with the electronics downline. You are trying to measure differences of a milligram with a sensor that has a maximum rating of 100g, 1 milligram = 1.0e-3 g which is 100,000 times smaller than 100g. You are expecting some amazing performance out of a budget sensor, at least that is my thought.

wade

Thank you Daniel and Wade.

I have Arduino Due (12 bit ADC resolution) and INA125p handy. I will try out the load cell measurement s/m with those and let you know how things went.

All the load/torque cells I found are in very high $$ range.Do you have any ideas for measuring milli gram forces / mill N-m torques? Have you come across and DIY load cells with milli gram range?

Regarding the resolution I had a question like that and got the following answer:

After some additional research the resolution (1/10000 to 1/50000 of the maximum load) mentioned in the post seems possible for this type of sensors. Transfering this to your load cell 10mg resolution should be possible, maybe even something below that.