Load cell signal calculator
A load cell output is millivolts per volt of excitation. That is a very small signal, which is why the amplifier matters more than the cell.
kg
mV/V
V
kg
Signal at that load
0.600 00mV
- Output at full capacity
- 10.0000 mV
- After the amplifier
- 0.076 80 V
- ADC least significant bit
- 0.002 33 microvolts
- Theoretical resolution
- 0.4657 g
- Usable scale divisions Allowing a factor of ten for noise.
- 429 497
- Total capacity
- 2000.0 kg
- Load per cell
- 30.00 kg
Show the working
- Load cell capacity = 500
- Sensitivity = 2
- Excitation voltage = 5
- Applied load = 120
- Amplifier gain = 128
- ADC bits = 24
- Number of cells = 4
- Output at full capacity = 2 * 5 = 10
- Total capacity = 500 * 4 = 2000
- Signal at that load = 2000 > 0 ? 10 * 120 / 2000 : 0 = 0.6
- After the amplifier = 0.6 / 1000 * 128 = 0.0768
- ADC least significant bit = 5 / 128 / 2^24 * 1e6 = 0.002 328 31
- counts_full = 10 * 1000 / (5 / 128 / 2^24 * 1e6) = 4 294 970
- Theoretical resolution = 4 294 970 > 0 ? 2000 / 4 294 970 * 1000 : 0 = 0.465 661
- Usable scale divisions = 0.465 661 > 0 ? 2000 * 1000 / 0.465 661 / 10 : 0 = 429 497
- Load per cell = 4 > 0 ? 120 / 4 : 0 = 30
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- output = sensitivity x excitation x load / capacity
- a 2 mV/V cell at 5 V excitation gives 10 mV at full load
Theoretical ADC resolution is always far better than usable resolution. Noise, drift and mechanical effects cost an order of magnitude.
Four cells under a platform share the load only if the platform is rigid and level.