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
4-20mA Output Hydrostatic Level Transmitters & Sensors - Explore industrial 4-20mA hydrostatic level transmitters for reliable liquid depth measurement. Ideal for tank gauging, borehole control & process monitoring applications.
DPS Low Differential Pressure Transmitter - Ultra low differential pressure transmitter for HVAC applications with 4-20mA current loop or amplified voltage output signal in pressure ranges from 0.1 mb up to 1 bar differential.
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
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.
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.
Related Help Guides
- How to get a 10 volt signal from a 4-20mA output pressure sensor
- How to Connect a 4-20mA Current Loop Pressure Transmitter
- Advantages and Disadvantages of using a 4 to 20 mA Signal
- Supply voltage and load resistance considerations for pressure transmitters
- Choosing calibrator for pressure transmitters
- How to create a list of specification parameters for a pressure sensor
- How do you measure flow rate with a dp cell
- Transforming a 2 wire Current Loop into a Voltage Output Signal
- 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
- Pressure Transmitter 4-20mA Current Output Calculator
- Flow Transmitter 4-20mA Current Output Calculator
- DP Flow Transmitter Output Calculator
- 4-20mA Signal to Measurement Reading Converter
- SqRt Extraction 4-20mA Signal to Measurement Reading Converter
- Temperature Transmitter 4-20mA Current Output Calculator
- Liquid Level Transmitter 4-20mA Current Output Calculator
- 0-20mA Signal to Measurement Reading Converter
- 4 to 20 mA Supply, Load, Shunt and Signal Calculator
- Pressure Transmitter 0-20mA Current Output Calculator
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- Sulfuric acid 12-15% conc. drop-in level probe for 10m high tank
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- 1013 to 1400 mbar barometric pressure transmitter & readout
- 180°C UHT milk compatible pressure transmitter
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