Converting Pressure Sensor ADC Value into Pressure Value in PSI?

Other Hardware Sensors
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So I have a pressure sensor that outputs a 4-20mA signal. I am using an ESP8266, and have converted that 4-20mA signal to be a 0-3.3V signal for the 10 Bit ADC to read. I get the ADC to display a value, but I know that is the ADC value, not the pressure. How would I convert that ADC value into a pressure range of 0 PSI to 250 PSI?

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See datasheet. No doubt it's explained in detail how the output (in mA) of the sensor relates to the pressure it reads. From there it's a matter of calculation: ADC reading to V to mA to pressure.

3

wvmarle:
See datasheet. No doubt it's explained in detail how the output (in mA) of the sensor relates to the pressure it reads. From there it's a matter of calculation: ADC reading to V to mA to pressure.

The datasheet is on this website. This is the sensor in use, and the datasheet says nothing about the conversion. Currently I am thinking I can go from ADC output > Voltage > to pressure?

4

0--250 psi, 4--20mA current loop output.

0psi = 4mA
250pis = 20mA.

As its a current output you'll need a shunt resistor to convert this to a voltage in the
range 0..5V.

5

MarkT:
0--250 psi, 4--20mA current loop output.

0psi = 4mA
250pis = 20mA.

As its a current output you'll need a shunt resistor to convert this to a voltage in the
range 0..5V.

So the range of the ADC pin on this board is 0 - 3.3V. I added a 150 ohm resistor to limit the 4-20mA signal to 0.6V to 3.0V.

6

queenlexi13:
Currently I am thinking I can go from ADC output > Voltage > to pressure?

No.
Go from A/D values directly to pressure.

  1. Write a simple sketch that only prints the A/D values, and see what values you're getting without pressure.
    That offset value must of course be subtracted from the A/D readings.

  2. Max pressure, as a result, must have a value five times that value (4-20mA).
    See if it's within the range of the A/D, near it's max. Otherwise your sense resistor is wrong.

  3. Formula is now:

(float) pressure = (analogRead(A0) - offset) * someFactor;

someFactor depends on what you want to display. BAR, PSI, KPa.
In your case, for the 250PSI readout, 250/(4*offset)= ~0.3125
Leo..

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