I have a 4 to 20mA output pressure sensor, is there a way of converting the current output into a 10 volt output signal so I can use a voltage input data acquisition card?
Typically a 4-20mA output pressure sensor is configured as 2 wire current loop and with this type of signal circuit it is possible to add load resistance without affecting the current signal. At a particular pressure the pressure sensor behaves like a constant current source regardless of the load resistance connected in series to the circuit. If a 500 Ohm load resistor is added in series to the loop circuit, it is possible to generate a voltage drop across the resistor which will vary from 2 to 10 volts according to the current output variation of 4 to 20mA. So a 2-10Vdc output signal can be sent to the data acquisition card connecting the input wires across the load resistor.
A 4-20mA pressure sensor has a low and high limit of load resistance that must not be exceeded. the limits vary depending on the product type and supply voltage. The resistance limits are normally specified on the product data sheet. This is important to consider since by generating a 2-10Vdc signal you have added an additional 10V max to the circuit which will be deducted for the power supply. Therefore you need to ensure there is sufficient voltage left to power the 4-20mA pressure sensor without exceeding the maximum supply voltage for the circuit.
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