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I have purchased one of these and I've connected it to a pressure sensor. I now need to convert the digital values to pressure. However, my maths is all forgotten. Can anyone help me out?

The discrete values I get back from the sensor are between 0 to 3750. 750 is equal to 0 bars pressure. The top pressure the sensor can goto is 250 (which is 3750) and the values are linear.

Any help appreciated.

  • Hello, since I didn't know what "4 to ma" was going to say I have tried to edit your title to be more descriptive. Feel free to change as you see fit. – Ghanima Oct 11 '18 at 17:37
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Linear for the win!

y = (slope * x) + intercept is the classic linear formula, in your case, x=sensor, y=bars, so the formula becomes

bars = (slope * sensor) + intercept

... and you have two data points of this formula, sensor@750, and sensor@3750

equation 1: 0 = (slope * 750) + intercept
equation 2: 250 = (slope * 3750) + intercept

... lets rearrange the 1st equation in terms of the intercept, so

- (slope*750) = intercept

... and use this intercept equation in the 2nd equation, so

250 = (slope * 3750) + (-(slope*750))

... continue by solving for the slope

250 = 3750slope - 750slope
250 = (3750 - 750) slope
250 = 3000 slope
250 / 3000 = slope
1/12 = slope

... use this in equation 2 to find the intercept

250 = (1/12 * 3750) + intercept
250 - 312.5 = intercept
- 62.5 = intercept

... and you have your final conversion equation!

bars = (sensor / 12) - 62.5

Which is valid with the 2 examples you started with.

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since a picture is worth a thousand words:

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