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Scaling

Helmut O'Brian

Posted on 04.03.2018 00:49

Hi Slovenia !

I was wondering if there is any documentation concerning SCALING in DEWESoft.

We are actually upgrading our data acquisition & conditionning system with DEWESoft hardware (SIRIUS STG) and until now, our customer uses a database which provides a polynomial scaling in mV (and not mV / V).

Apparently the scaling input units change with the type of measurement (voltage, gauges, etc) from mV, V to mV / V and with the supply voltage.

Do you guys can explain how is the scaling made ?

Since we use this database to generate the DEWESoft Analog Sensors database and XML setup files it would be great to have all the informations on how the scaling is made, what "calculations" are made, what is done with the supply voltage with the polynomial coefficients, etc.

Thank you !

Have a nice day !

DEWESoft Support
Technical support
Posted on 10.05.2018 11:23

Hi,

as discussed via email, I'm sorry that this response took such a long time. We don't really have any documentation on how the scaling is done. Usually, customers only look at the scaling factors provided by the sensor manufacturer, which can be entered directly in Dewesoft without having to worry how the underlying amplifier structure looks like.

With that being said, the scaling process is fairly complex, as there are multiple stages involved in the whole process. To simplify it, as the data passes through different stages, additional scale and offset factors are applied to, which in the end result in the correct data. Those factors are necessary to account for the ADC, the calibration, amplifier properties, adapters, sensors and finally zeroing/balancing corrections.

One thing to note is that the scaling in Dewesoft will always be linear. Even if you, for example, choose a sensor with polynomial scaling, Dewesoft will apply linearization to allow it to get the scale and offset factors.

In the specific case of bridge measurements, the scaling is done depending on the excitation voltage, as you've already figured out. More specifically, the input voltage will be divided by the excitation. If you, for example, measure 1 V between the IN+ and IN- pins, and you've used an excitation of 2 V, then Dewesoft will return the value of 500 mV/V.

In your bridge configuration, you'll probably use a sensor so its scaling will be done on top of your mv/V measurement. You can check the scaling effect in the data preview, where the left side of the screen will show the scaled data depending on your amplifier configuration, and the right side will contain the scaled values depending on your sensor (an additional scaling layer). As already mentioned, if you'll be using a polynomial scaling format, it will be linearized under the hood.

I hope this will be somewhat useful to you. If you'll require further information, please let me know.

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