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#1 2017-12-12 22:25:13

mcarroll
Member
From: Australia
Registered: 2017-02-14
Posts: 18

Sensor calibration curve

Hi all, I need some help in adding a calibration curve to some sensors.  Basically, I'm looking for a differential measurement between two identical sensors and I'm trying to rule out differences in values, that come from the manufacture of the devices.

For example, if I pick the two temperature sensors, I currently have a fixed calibration value (offset) of 2.2 degrees, which does bring them pretty close in tracking values, with respect to each other.  However, what I would like to do is be able to set the calibration to 2.2 degrees at 25C and 2 degrees at 30C and so on, creating a calibration curve that more accurately reflects how the sensors track, with respect to each other.

Any thoughts smile ?

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#2 2017-12-13 15:08:54

tomáš čechura
Administrator
Registered: 2016-02-22
Posts: 371

Re: Sensor calibration curve

Hi mcarroll,

you can define your calibration curve using CNDR function block - for more details see documentation: https://www.rexcontrols.com/media/doc/E … /CNDR.html

Hope the above is useful for you.

Regards, Tomas

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#3 2017-12-17 23:59:35

mcarroll
Member
From: Australia
Registered: 2017-02-14
Posts: 18

Re: Sensor calibration curve

Thanks Tomas!

Hmmm that block is a little complicated... smile 

Are you able to provide a quick example, or point me in the direction of where I might find some that I can reference?

For instance how would I put the configure the block (or multiple blocks) for the following example:

Temperature | Calibration Value
10 degrees:     -0.5
15 degrees:     -0.3
20 degress:     -0.2
30 degrees:     +0.2
40 degrees:     +0.5

and so on.

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#4 2017-12-18 10:16:00

tomáš čechura
Administrator
Registered: 2016-02-22
Posts: 371

Re: Sensor calibration curve

Hi mcarroll,

setup the CNDR function block according to the screenshot below. Remember also to set parameter "n" (number of (u,y) node pairs) to 5 and parameter "SATF" according to your needs (probably set to 0).

CNDR_settings.png

Hope it helps.

Cheers, Tomas

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#5 2017-12-20 01:17:40

mcarroll
Member
From: Australia
Registered: 2017-02-14
Posts: 18

Re: Sensor calibration curve

Thanks Tomas, that makes sense now.  I'll give it a go and see if I can get it to work!

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