Why we mainly use 4-20 mA current and 3-15 psig pressure and not use from zero to 20 mA or 15 psig?
For 4-20mA devices there is a single loop which is used to provide the signal and power to the device. If the signal was zero then there would be nothing powering the device. 0-4mA is used to power the device.
If you have an offset signal at zero reading it is good for failure mode indication: If the signal is 0 mA or 0 psi then there is fault with the equipment.
For a pneumatic 3-15 psi signal it is difficult to control very low pressures accurately with a simple regulator, plus you have to provide vacuum to allow for calibration and measurement hysteresis & repeatability errors.
Featured 4-20ma signal related products
DPS200 HVAC Differential Pressure Transmitter - Differential air pressure sensor with a 10 volt or a 4-20mA output for building ventilation applications. Ranges from 0 to 6 mbar up to 0 to 1000 mbar.
LMP307 Submersible Level Transmitter - Submersible level transmitter for measuring liquid level with a 4-20mA current loop or a 0-10V voltage output plus optional ATEX approval for intrinsically safe use in hazardous areas in ranges from 1mH2O up to 250mH2O. The LMP307 is suitable for use on potable water with no leaching, and can be supplied with a drinking water certificate according to DVGW and KTW.
Advantages of 4-20 mA vs 0-20 mA
- Using 2 instead of 3/4 wires reduces cost of wiring
- Power supply and signal circuit is combined into one
- Distinguish between zero signal and a fault
- Zero offset can be adjusted without need for polarity change of signal
Advantages of 3-15 psi vs 0-15 psi
- Easier to regulate pressure from 3 psi
- No need to provide vacuum when regulating zero signal at 3 psi
- Distinguish between zero pneumatic signal and a pressure failure
Featured 0-20ma signal related products
Universal Strain Gauge Bridge Input Transmitter – STRAIN - Simplify your strain measurement setup with the STRAIN Universal Strain Gauge Bridge Input Transmitter. This versatile device converts mV signals from strain gauges, load cells, and pressure transducers into 0-10Vdc, 0-20mA, or 4-20mA outputs.
DPS300 User Switchable Pressure Range, Volts or Current Output Low DP Sensor - The DPS 300 is a low range HVAC differential pressure sensor. The lowest possible pressure range is 0...100 pascals. 2 or 3 switchable pressure ranges, plus volts or current output are included with most standard configurations.
Related Help Guides
- Choosing calibrator for pressure transmitters
- Advantages and Disadvantages of using a 4 to 20 mA Signal
- How to create a list of specification parameters for a pressure sensor
- How do you measure flow rate with a dp cell
- Supply voltage and load resistance considerations for pressure transmitters
- How to Connect a 4-20mA Current Loop Pressure Transmitter
- Transforming a 2 wire Current Loop into a Voltage Output Signal
- How to get a 10 volt signal from a 4-20mA output pressure sensor
- What is the difference between a pressure transducer and a transmitter
Related Technical Terms
- 2 Wire
- 4 to 20 mA Current Loop Output Signal
- HART®
- Square Root Extraction
- Stainless Steel Pressure Sensors
- Transmitter
- Turndown Ratio
Related Online Tools
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