Hi!
I am now working with Honeywell's pressure sensor PX2EN1XX200PSCHX.
Documentation
As you can see this sensors output is a current between 4 mA and 20 mA.
How would I go about getting this value?
I assume it is more complicated than just putting it into an analog pin and using analogRead().
I have also yet to figure out how I would convert the value I read into the actual pressure value, so if anyone has an idea for how that calculation would go I am very grateful.
If you put the 4 - 20 through a 250 Ohm resistor to GND, that will give you 1 to 5 volts for analog in.
Put a 10k resistor between analog in and load resistor for over voltage protection.
If you put the 4 - 20 through a 250 Ohm resistor to GND, that will give you 1 to 5 volts for analog in.
That would be the normal approach, but this sensor seems to work differently than most.
My reading of the data sheet for the "CH" sensor type is that the supply voltage (VS) must be between 8 and 30 volts, and the maximum value of the load resistor is (VS-8)*50 ohms.
So, the actual voltage output swing to be expected across the load resistor depends on how you are powering the device (which limits your choice of load resistors).
The voltage swing across the resistor will be proportional to the current.
For a 12 volt sensor power supply, the maximum load resistance would be 200 Ohms, and the expected voltage swing for 4 - 20 mA would be 0.8 - 4.0 V.
That doc is not easy to follow (for me anyway :-[). If the OP will select a power supply and load R we can go from there.
In fact the data sheet specifies that the full scale current swing of the "CH" device is 4-16 mA.
So, for a 12 volt power supply and a 200 Ohm resistor, the voltage across the resistor would range from 0.8 to 3.2 V. For a higher voltage power supply a larger resistor can be chosen, for a larger voltage swing.
I think that16 mA span is on top of the 4 mA zero so its 4 - 20???
Perhaps. The data sheet could be clearer.
Maybe better for 4-20mA sensors to use a 51ohm resistor, and measure with the more stable 1.1volt Aref enabled.
More protection for the pin as a bonus (100mA sensor current).
Still wise to use a (10k) resistor between sense resistor and analogue pin.
Leo..