ADC Offset vs. Pressure guage

Falcon

Hello,

I am trying to interface an SSI Technologies P51 pressure sensor (Digikey P/N 734-1027-ND) to a BS2 to eventually measure the water pressue from my home's water boost pump. I'm currently using an ADC0834 with several LM34 temp sensors and that is working good with the REF voltage set to 2.56VDC (thank you Chris Savage).

This P51 Pressure sensor is a gage-type sensor with an output of .5 - 4.5 VDC over a range of 0-100 PSI. I have the pressure sensor breadboarded to my BS2 through one channel of the ADC0834. With no external pressure source (just atmosperic pressure), it is reading ~ 01100011 (DEC 99) from the ADC0834. I expected it to read 00000000 with no external pressure applied.

My first thought was to adjust the REF voltage for that one channel but there is only one REF input so it affects all four channels since the 2.56V offset could be the problem. I also have an 11-channel TLC2543 ADC that I could use but that also appears to have just one REF input that would affect all 11 channels.

Would the best approach be to use a 1-channel ADC0831 on this pressure sensor so I can tailor the REF voltage for it, and leave the LM34s on the ADC0834 with the REF set to 2.56 VDC since it is working good?

Has anyone used this P51 pressure sensor before?

falcon

kwinn

With no external pressure the sensor will output 0.5V so the ADC should output approximately decimal 51. The 99 you are getting is higher than expected and may be due to some offset or other problem with your circuit. Check the output of the sensor with a meter.

You can use a voltage divider to reduce the output voltage by 50% so the input to the ADC would be 0.25 – 2.25V for 0 – 100 PSI. That should give an output reading from the ADC of decimal 25 – 225 for 0 – 100 PSI. This makes calculating the pressure very simple.