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MPX5100DP problem with slope

Question asked by Dan Ponpon on Sep 23, 2019
Latest reply on Sep 23, 2019 by Jose Alberto Reyes Morales



I want to measure water level (+/- 2 m) in my tank using a pressure sensor MPX5100DP.

I use the schematic of AN1516 (figure 3) with a (air) pipe in water. The pressure in the air pipe is measured by the positive pressure inlet of the MPX5100DP.

When I try to calibrate the sensor (Vs = 5 V) I get a slope of 3,1 mV/cm water level.

If I read the data sheet, every 1kPa of pressure will give 45 mV Vout. But a pressure variation of 1 kPa is caused by a water height of 10 cm! So I must have a slope of 4,5 mV/cm...

How is it possible?