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Why use 4-20mA and 3-15 psi rather than 0-20mA & 0-15psi

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

  • LMP305 Borehole Level Transmitter
  • Chemical Resistant Pressure Sensor Elements for Electronic Devices & Embedded Product Design & Development
  • SIL 2 Approved Safety Rated Pressure Transmitters
  • HART® Pressure Transmitters

Advantages of 4-20 mA vs 0-20 mA

  1. Using 2 instead of 3/4 wires reduces cost of wiring
  2. Power supply and signal circuit is combined into one
  3. Distinguish between zero signal and a fault
  4. Zero offset can be adjusted without need for polarity change of signal

Advantages of 3-15 psi vs 0-15 psi

  1. Easier to regulate pressure from 3 psi
  2. No need to provide vacuum when regulating zero signal at 3 psi
  3. Distinguish between zero pneumatic signal and a pressure failure

Featured 0-20ma signal related products

  • DMP343 Low Range Pneumatic Pressure Sensor
  • Universal Strain Gauge Bridge Input Transmitter – STRAIN
  • Low Differential Pressure Transmitters DPS300 User Switchable Pressure Range, Volts or Current Output Low DP Sensor
  • DMP331 Precision Pressure Transmitter

Related Help Guides

  • Transforming a 2 wire Current Loop into a Voltage Output Signal
  • 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
  • Advantages and Disadvantages of using a 4 to 20 mA 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
  • Choosing calibrator for pressure transmitters
  • How to create a list of specification parameters for a pressure sensor

Related Technical Terms

  • 2 Wire
  • 4 to 20 mA Current Loop Output Signal
  • HART®
  • Isolation Diaphragm
  • 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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Wirelessly Measure & Log 4-20mA

Use this battery powered wireless 4-20mA wireless transmitter to transmit readings to a receiver connected to USB, RS485, RS232, cellular network or analog output

Use this battery powered 4-20mA wireless transmitter to transmit readings to a receiver connected to USB, RS485, RS232, cellular network or analog output

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  • Level
  • Temperature
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