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? 4-20mA strain gauge load cells
Posted by on 16 February 2012 11:29 AM

With 4-20mA loadcells it is not so straight forward, we commonly would not expect to see a difference in the site zero kN applied load and the calibration zero kN applied load, outside the accuracy of the sensor. If a difference is present and this is required to be removed, this difference would require to be calculated into KN and removed after all future readings are calculated into KN, rather than removal within the engineering calculation.

 

We can confirm that the temperature effect on the Strain gauge load cells from -10°C to +50°C is +/- 0.005% FS/°C. The temperature effect is therefore well within the sensors accuracy, please see the datasheet attached. In summary no temperature effect to worry about. 

Also as stated on the datasheet the load cells have a accuracy of ±0.5% FS, we would therefore expect a zero reading of a load cell to be within this ±0.5% FS compared to the calibration certificate provided. In the example presented, cell No. 200904255 with a 300kN range we would not expect the zero reading to exceed 3kN. 

On site with the load cell example above a zero reading (unloaded cell) recorded a value of 0.044mV which equates to 4.5kN. Should you accept that this was a valid reading and you wish to subtract this reading from any future readings you will require to convert the future reading into kN then subtract the 4.5kN offset.

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