I'm dealing for the first time with two sensors, of pressure and temperature. Both have output of 4-20mA, then I'm using a 47 ohms 1% to convert to voltage. When flows 20mA, 20mA * 47 ohms = 940mV, and my ADC has a positive reference of 1V.
My doubt is about how to convert the mA value (or voltage on the resistor) to temperature (degrees) and pressure values (psi). I just didn't found documentation about that on both manufacturer's webpage.
Do they have linear relationship? For example for the temperature sensor, 4mA would mean 0°F, 20mA would mean 400°F and 12mA would mean 200°F?
These are the sensors:
TEMPERATURE SENSOR: OMEGA OS136A-1-MA Range is from -18 to 202°C (0 a 400°F).
PRESSURE SENSOR: KELLER PA-21Y Its body show "range of 0 to 200 psi".