Help with pressure sensor.

[erice1984]

I have a similar problem, I got everything to work, except translating the math.

My lowest ADVAL is 0 and it's also the HIGHEST pressure.

I saw how the math worked out for him, but I am lost.

[erice1984]

AD Res 1024

Lowest voltage = .085v = 100psi = ADVal 18

Highest voltage = .999v = 10psi = ADVal 205

In order to switch everything around all I did differently was subtract my highest voltage (1volt) from lowest voltage (.085volt) and went from there!

[erice1984]

So then I thought it out a little more, and instead of converting to voltage etc.. ADVal represents that value...

SO

highest ADVal = 205

205 - whatever the adval is at for the input from the sender = x

x * .5347 = pressure

on my 187 resolution scale here.

[erice1984]

didnt work very well... lost again

[mackrackit]

AD Res 1024

Lowest voltage = .085v = 100psi = ADVal 18

Highest voltage = .999v = 10psi = ADVal 205

In order to switch everything around all I did differently was subtract my highest voltage (1volt) from lowest voltage (.085volt) and went from there!

Can you give the make and model or data sheet for the sensor?

Maybe show your code too.

If that voltage range is correct I would go with 8 bit resolution and a reference voltage. Are you really getting a lower reading with a higher pressure?

[erice1984]

yes, its an autometer 2242 pressure sender unit. its really annoying.

all I have is
15 ohms = 100psi
175 ohms = 10psi


What I am doing right now is using regulated current. ~5mA

[erice1984]

reason why I am not using the 8bit adc is because I would have to use a lot more current to get it up out of the 19mV range, and not really wanting to do that since it seems to vary more, its probably my hardware tho, LM317T current reg.

[mackrackit]

I think I see the problem.

The ADC is for measuing a voltage.

Use the sensor for R1 of a voltage divider and a fixed resistor for R2. The feed that output to the PIC.

http://en.wikipedia.org/wiki/Voltage_divider