Line Pressure reading unstable at zero psi

[mcneil]

Using the Measurement Specialties M3431 from Digikey (the 0-5V sensor in the build guide), my pressure reading is erratic at zero psi. See below plot from the log



Bench setup, looks like this:


In the first part of the log, the cal points are 20 psi/.489V and 480 psi/ 3.951V. It gives good values when I apply shop air pressure to the sensor, but about 20 psi low. When I put in the actual sensor calibration values, line pressure is erratic at zero applied pressure. When I apply 100psi, it settles down and line pressure = applied pressure.

Is line pressure gauge or absolute? Should I not use 0psi as a cal point?

[Bernard Fife]

mcneil,

Thanks for spotting this. It looks like something is messed up in the code. In the meantime I would use the table value rather than the 2-point calculations. I will have a look in the line pressure sensor code and post test code here for you to try shortly.

Lance.

[Bernard Fife]

mcneil,

This code should be better (it is on my bench):

Monitor_5095t1.abs.s19

(78.61 KiB) Downloaded 860 times

GPIO_MShift_5095.ini

(261.03 KiB) Downloaded 823 times

Let me know if this doesn't fix it for you.

Lance.