Different load cells can be connected to the architecture selected by us. For this reason, it is possible to store a calibration for each connected scale in the maintenance mode.
Since version v1.0 a guided calibration mode has been introduced. This simplifies calibration so that the text below is no longer necessary.
The calibration consists of two values. On the one hand from the “Offset” and on the other hand from the “Scaling“. If, for example, the connected load cell always measures 3kg too much, the offset can simply be used to correct this value downwards. The offset can also be negative, i.e. the result can be corrected upwards. The scaling value is similar, if the scale measures only 90% of the real weight when the weight is added, this value can be corrected.
For simplicity we have created the following Excel file. Three successive measurements are entered there. This allows the required offset and scaling to be calculated automatically. In order to edit the Excel table locally, the file can be saved in the desired format via “File”=>”Download as”.
The following screenshot shows the maintenance mode setting fields. The values previously calculated in the Excel table can then be entered here.
The procedure in detail
To calculate the calibration values “Offset” and “Scaling value”, proceed as follows using some example numbers:
First of all, you need a calibration weight where you know exactly what it weighs. Let’s take a 5kg weight plate.
After you have started everything correctly, the scale will show you a weight of 5246.38kg (5246380g). However, you only have 10kg (10000g) lying on it.
So you enter the weight difference (offset) of “5236380” in the web interface.
In the next step we calculate the scaling value, because if you now place the 5kg weight plate on your scale, you will notice that the weight has not increased exactly by 5kg. Since the new measurement now shows only 13.5kg, the value must be scaled correctly. We calculate 13500g/15000g = 0.9. This scaling value can be entered as “0.9” in the web interface. Based on these two calibration values, the exact weight is now always displayed.
Depending on the model, some load cells may have a temperature-dependent measurement error. This is especially noticeable with cheap load cells. In concrete terms this means that the load cell measures a different weight at 5°C than at 20°C, for example. These deviations are often around 25 grams per °C.
We have built in temperature compensation by software. This allows the use of cheap load cells. You can use the following Excel sheet to calculate the necessary correction value and enter it into the input field in maintenance mode:
Translated 11.08.2019 by JK