If you are running a signal cable over a long distance or have a spare current output pressure transmitter, it is possible to convert the output signal to a voltage type to make it compatible with voltage only input devices.
A typical current output is 2 wire 4 to 20 mA which is designed to be connected in a series with the power supply and other components included in the circuit. The pressure transmitter acts as a current source regulating the current at a particular pressure for a range of load impedances as long as there is sufficient supply voltage to power it.
If a load resistor is added to the circuit in series this will cause a voltage drop across the resistor which is directly proportional to the current being generated by the pressure transmitter. The potential of this voltage drop can be easily measured by connecting two voltmeter probes or an analog to digital converter to the circuit on either side of the resistor.
HART® Pressure Transmitters
High Temperature Pressure Transmitters
DMP331 Precision Pressure Transmitter
4-20mA Output Hydrostatic Level Transmitters & Sensors
The voltage output generated by different values of load resistance on 4 to 20mA current loop are as follows:
| Load Resistor (Ω) | Min Volts | Max Volts |
|---|---|---|
| 50 | 0.2 | 1 |
| 100 | 0.4 | 2 |
| 150 | 0.6 | 3 |
| 200 | 0.8 | 4 |
| 250 | 1.0 | 5 |
| 300 | 1.2 | 6 |
| 350 | 1.4 | 7 |
| 400 | 1.6 | 8 |
| 450 | 1.8 | 9 |
| 500 | 2.0 | 10 |
| 550 | 2.2 | 11 |
| 600 | 2.4 | 12 |
| 650 | 2.6 | 13 |
| 700 | 2.8 | 14 |
| 750 | 3.0 | 15 |
| 800 | 3.2 | 16 |
| 850 | 3.4 | 17 |
| 900 | 3.6 | 18 |
| 950 | 3.8 | 19 |
| 1000 | 4.0 | 20 |
- Hydrostatic Liquid Level Voltage Output Pressure Transducers
Steam Pressure Transducers
High resolution minus 150 mbar range pressure transducer
IWR-1 Single Channel Wireless Sensor to 4-20mA or 1-5Vdc Output Signal Receiver