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
IWTxT Loop Powered 4-20mA Input to Wireless Transmitter - Power and measure the current loop signal output from any 4 to 20 milliamp transmitter, and wirelessly transmit it to a wireless receiver hub
Lube oil pressure sensor for use on ship engines to measure up to 10 bar - Marine approved pressure sensor for use on lube oil up to 10 bar with a maximum media temperature of 125°C and environment temperature of 85°C.
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.
DMP331 Precision Pressure Transmitter - Stainless steel pressure transmitter with ranges from 100mbar up to 40 bar gauge or absolute. Special options for ATEX , SIL2 and compound ranges.
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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- 0-20mA Signal to Measurement Reading Converter
- 4 to 20 mA Supply, Load, Shunt and Signal Calculator
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