Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: Transmitters 4-20mA Current Failure Alarm Limits
Share
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Basics > Transmitters 4-20mA Current Failure Alarm Limits

Transmitters 4-20mA Current Failure Alarm Limits

Last updated: March 4, 2021 4:02 pm
Editorial Staff
Basics Control Systems PLC Tutorials Standards
5 Comments
Share
4 Min Read
SHARE

4-20 mA instrumentation and controls usually support a signal range slightly below 4 mA and above 20 mA.

Contents
Transmitters 4-20mA Current Failure Alarm LimitsSmart Valve Positioners

For transmitters, current values below 4 mA and above 20 mA are used to signal a fault such as a thermocouple burnout, Signal cable broken, Cable Low/High Resistance, Transmitter Failure or other sensor failure.

The transmitter can be configured for failure indication low or high.

Unfortunately manufacturers use different signal levels to indicate failure which prevents tight analog signal integration and interpretation in single loop controllers, control systems, and safety systems.

Transmitters 4-20mA Current Failure Alarm Limits

Transmitters 4-20mA Current Failure Alarm Limits

Image Source : eddl.org

Some transmitters may use 3.75 mA while others may use 3.6 mA or less. Some transmitter may use 21.75 mA or more while other use 23 mA.

This inconsistency of signal levels for failure indication makes it difficult to take full advantage of the failure information in control strategies.

The NAMUR NE43 “Standardization of the Signal Level for the Failure Information of Digital Transmitters” recommendation was created to standardize failure indication from transmitters and interpretation in control systems to enable better analog integration.

NE43 defines 3.8 to 20.5 mA as a valid (‘Good’) measurement value where 3.8 to 4 and 20 to 20.5 mA indicates saturation.

A signal of <3.6 mA or >21 mA indicates a transmitter failure (‘Bad’).

4-20mA Alarms Ranges NE43

Image Source : eddl.org

By using transmitters and systems that both conform to the NE43 recommendation, it is possible to flag faults to the operators and control strategies.

However, note that all device errors, severe and trivial, are flagged the same way so the operator cannot tell the difference and that if any error occurs it is flagged and the measurement value is not provided.

FOUNDATION fieldbus and PROFIBUS-PA transmitters use digital communication with separate status indication for each measurement including measurement validity flagged in realtime as ‘Good’, ‘Bad’, or ‘Uncertain’.

This allows operators and control strategies to severe problems from trivial issues. This allows the control strategy to put the loop in manual in case of failure, with the option to trip. For non-severe issues the value is still displayed with ‘Uncertain’ status.

Smart Valve Positioners

Smart valve positioners are not in the scope of NAMUR NE43.

However, signals <4 mA and >20 mA also have specific meanings. Control systems and single loop controllers with 4-20 mA output use a similar scheme to achieve tight shut-off for control valves. That is, they may set current <<4 mA or >>20 mA.

Some control systems set the output current to 0 mA to achieve tight shutoff. This is impractical in the case of smart valve positioners since they need 3.6 mA to operate and will be completely switched off at 0 mA.

Therefore make sure to configure the control system or single loop controller to provide at least 3.6 or 3.8 mA for tight shutoff to ensure that the smart valve positioner can continue to operate and respond to HART communication.

Source : Eddl.org

If you liked this article, then please subscribe to our YouTube Channel for PLC and SCADA video tutorials.

You can also follow us on Facebook and Twitter to receive daily updates.

Read Next:

SIS, PLC and BPCS

Pressure Transmitter Tips

Selector, Override control

Calculate Process Variable

Instrument Air Manifold

Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

Difference Between PLCSIM and PLCSIM Advanced? – Siemens PLC
PLC Sinking and Sourcing Explanation
Moving Data between PLCs – Siemens Basics – TSEND TRCV
Tuning a Temperature Process Control Loop
Selector Control Functions
PLC Application for Stamping Operation – Example Programming
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
5 Comments
  • Bhagath says:
    August 30, 2016 at 6:33 am

    Please share topics on floating voltages and grounded voltage… Thanx.

    Reply
  • Paulo R M Monteiro says:
    December 20, 2016 at 10:37 am

    Excellent.

    Reply
  • surendra says:
    April 8, 2017 at 8:28 am

    very good ..article…!!!…Thanks

    Reply
  • Shan Ahmad says:
    September 18, 2018 at 11:40 pm

    Fine tips

    Reply
  • Minhaj alam says:
    February 14, 2019 at 8:44 pm

    Inst video is very good

    Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

List of Instrumentation Project Engineering Documents
Compare Online and Offline PLC Programs
Multiple Pumps Control using PLC
#3 PLC Best Practices – Leave Operational Logic in the PLC wherever feasible
PLC Programming to Control Lights in a Sequence
What is Integral Wind Up ?
Feedforward Control with Dynamic Compensation
PLC Light Sequence Control using Bit Shift Registers

Keep Learning

DCS Alarm and Setpoint

Setpoints and Alarms in Control System

PLC Program for Filling Operation

PLC Program for Continuous Filling Operation

PLC Program for Food Processing

PLC Program for Food Processing Industry

Latched and Momentary Operation of Motor PLC Program

Latched and Momentary Operation of Motor PLC Program

Transistor Output Wiring

PLC Output Types

PLC Instruction List Example for Level Control of Tank

PLC Instruction List Example for Level Control of Tank

Car Parking System PLC Program Example

Schneider Electric: Car Parking System with Calculations in PLC

Things to Take Care of When Designing SCADA System

Things to Take Care of When Designing SCADA System

Learn More

Sensors and Transducers Test

Sensors and Transducers Test

Why does SMPS Need isolation - Switch Mode Power Supply

Why does SMPS Need isolation? – Switch Mode Power Supply

Difference between Transmitter and Transducer with Examples

Difference between Transmitter and Transducer with Examples

Hydraulic versus Pneumatic Systems

Hydraulic versus Pneumatic Systems

What is the consumed tag in Studio 5000 software?

Produced Tags and Consumed Tags in Studio 5000

Linear Heat Detector Working Principle

What are Linear Heat Detectors?

What is FAT and SAT?

What is FAT and SAT? Difference between them

Switch or Transmitter

Switch or Transmitter

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?