# Reading and interpreting output sensitivity of a load cell from data sheet

I'm given these ratings /spec for load cell / sensor:

• Range: 0-200kg
• Output sensitivity: 0.7 ± 0.15mV / V
• Nonlinear: 0.05% F.S
• Hysteresis: 0.05% F.S
• Repeatability: 0.05% F.S
• Creep: 0.05% F.S/3min
• Zero output: ±0.1mV/V
• Input impedance: 1050±10Ω/1050±10Ω (self-compensation) Output impedance: 1050 ± 10Ω
• Operating temperature: -10~+45°C
• Wiring method: red (power positive), black (power negative), green (signal positive), white (signal negative)
• Zero temperature drift: 0.05% F.S/10°C
• Temperature sensitivity drift: 0.05% F.S/10°C
• Insulation resistance: ≥2000MΩ
• Excitation voltage: 3~10VDC
• Four-corner error: ±0.05% F.S

I know this is likely dumb question, but is the sensitivity there 0.7V +/- 0.15mV, or is this 0.7mV +/- ..? Probably 700mV/V is too much, but 0.7mV/V sounds too little .. ? (or does it..)

If 0.7mV/V, if I'm applying 5V input - that's my plan - this will be output range 0 - 3.5mV, which seems too low ?

• From the information that you provide, the only conclusive answer that can be given is that; The output sensitivity is 0.7 [NO UNIT] +- (0.15 mV/V).. So the output sensitivity here has no unit, but it varies with 0.15mV pr. V, That seems strange. I would bet that there is some more information in the datasheet which when put together with this makes everything make sense. I think that the output sensitivity is relative to the supply voltage, so you probably can't just equate 0.7 to 700mV or 0.7mV, it probably depends on your supply voltage. Sep 21 '19 at 7:10
• Hey @Vinzent, don't have datasheet but supplier (seller) just has description as i c&p above. The item is as here : link
– v01d
Sep 21 '19 at 7:20

I think that what they mean by "Output Sensitivity" is what is also sometimes referred to as the "Full-Scale Deflection", and the reason that they are not giving it a unit is because it is relative to the supply voltage, or here "Excitation Voltage", which they require to be between 3V and 10V.

So in other words, this is how I would calculate the parameters I need to use this sensor;

First we choose a supply voltage between 3V and 10V, lets use 3V for this example.

Vcc = 3v

Now we calculate the Full-Scale Deflection voltage, ie. the voltage out of the sensor when the sensor is under full load.

Vfsd = Vcc * 0.7 = 2.1V

Now we look at the range of the sensor which is 0-200kg, from this I would assume that Vfsd corrosponds to 200kg of load on the sensor, so to calculate the output voltage (Vo) pr. kg of load on the sensor we simply divide;

Vo = Vfsd / 200kg = 2.1V / 200kg = 10.5 mV/kg

To this we have to add an error of +- 0.15 mV/V, so at the full scale deflection the error will be;

Vfsd * 0.15mV/V = 2.1V * 0.15mV/V = 0.315mV

• Oh i see. So if I want to use 5V, then that's Vfsd = 3.5V, or Vo = 17.5mV/kg.
– v01d
Sep 21 '19 at 7:50
• Btw, about Output Sensitivity. This is how Sensitivity explained in relation to load cell (for weighting scale) : "The sensitivity of a load cell is defined as full load output voltage in relation to the excitation voltage. It is generally expressed in mV/V. This value corresponds to the voltage deviation caused by the load cell at full load when excited by a 1V source. The sensitivity of load cells is very low (generally about 2mV/V). If a system has a 3.3V excitation voltage then at full load, the output voltage will be 6.6mV" (source: EE times, weighting scale design)
– v01d
Sep 21 '19 at 7:53
• sorry but I looked more at how they generally specify these load cells, and I think, apologies for this, your interpretation is not / shouldn't be right. See here for example : link. Thus I think it should be 0.7mV/V +/- error for my bar.
– v01d
Sep 22 '19 at 18:07