Choosing a Load Cell for microgram precision

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Hi there!

I am looking for a load cell + amplifier combination that can be interfaced with an Arduino Uno and be able to measure loads in the 0 - 100 g range with micro-gram precision (0.001 grams).

Now, due to that interesting precision requirement, there are two routes (both of which can either use a Load Cell / Wheatstone Amplifier Shield (2ch) or a HX711 Load Cell Amplifier), that come to mind based on products available here:

  1. We go with a 100 g Micro load cell from phidgets. My question he is if it can satisfy the precision requirement reliably.
  2. We use either the 5 kg/20 kg Micro Load Cell and use levers to amplify the source load x100 to get it upto the 100s of grams range. My question here is whether the 5 kg cell is more precise on its lower end than the 20 kg load cell. And if so, would this method allow for greater precision than the 100 g load cell approach.

I’ve used a hx711 before, but if there is an advantage of the shield over it, then I would definatelt be open to change.

A number of questions here, and so any help is greatly appreciated!

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A clearer way for me to pose this question would be:-

  1. Is there an advantage for choosing the Load Cell / Wheatstone Amplifier Shield (2ch) over a hx711 amplifier in terms of precision?

  2. Between the 100 g, 5 kg and 20 kg load cells that are available on robot-shop, Is there an advantage in using the 100 g micro load cell over the other two when measuring very small loads ? (0-60 g).

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Hello @CasualElectron and welcome to the forum,

Is there an advantage for choosing the Load Cell / Wheatstone Amplifier Shield (2ch) over a hx711 amplifier in terms of precision?

Yes, the Load Cell/Wheatstone Amplifier Shield (2ch) is based on the AD8426 amplifier which has lower offset and higher CMRR than the HX711 so it is a better option for your project (and the datasheet is way more detailed than the HX711 which could come in handy in your application).

Between the 100 g, 5 kg and 20 kg load cells that are available on robot-shop, Is there an advantage in using the 100 g micro load cell over the other two when measuring very small loads ? (0-60 g).

Yes, the 100 g micro load cell will be more precise than the two other options.
Here are some specs that might interest you:

100 g load cell
Cell Repeatability Error Max ± 50 mg
Cell Non-Linearity Max 50 mg
Cell Hysteresis Max 50 mg
Creep 100 mg/hr
Temperature Effect on Span 5 mg/°C

5 Kg load cell
Cell Repeatability Error Max ± 2.5 g
Cell Non-Linearity Max 2.5 g
Cell Hysteresis Max 2.5 g
Creep 5 g/hr
Temperature Effect on Span 250 mg/°C

20 Kg load cell
Cell Repeatability Error Max ± 10 g
Cell Non-Linearity Max 10 g
Cell Hysteresis Max 10 g
Creep 20 g/hr
Temperature Effect on Span 1 g/°C

  • Cell Repeatability Error Max: The maximum difference the sensor will report when the same stimulus is applied multiple times under the same conditions.
  • Cell Non-Linearity Max: The maximum amount by which the sensor′s response curve deviates from the linear.
  • Cell Hysteresis Max: The maximum difference in measurement when a force is being applied versus being removed.
  • Creep: The maximum amount the sensor value will change over time, while loaded at or near capacity at a constant temperature within the compensated range.
  • Temperature Effect on Span: The change in output due to change in ambient temperature.

I hope that information can help you!

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The information is quite helpful.

Thank you!

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