How to wire 4 - 20mA Transmitter? Wiring Types: 2 -Wire, 3 - Wire & 4 - Wire

Standards and Definitions for 4-20 mA Transmitters 

Per the ANSI & Instrumentation Systems and Automation Society (ISA), type numbers with suffix letters are used as transmitter identifiers. Type number is the number of wires necessary to provide transmitter power. Shields and IO wires are excluded. Suffix letters identify the load resistance capability. 

We have three basic 4-20 mA transmitter types: 

• Type 2 Transmitter
• Type 3 Transmitter 
• Type 4 Transmitter

Type 2 Transmitter

Type 2 is a 2-wire transmitter that is energized by the loop current where the loop source voltage is included in the receiver. The transmitter floats and signals ground is in the receiver. 

Type 2 Transmitter

Photo : Type 2 Transmitter

Type 3 Transmitter 

This is a 3-wire transmitter energized by a supply voltage at the transmitter. The transmitter sources the loop current. The transmitter common is connected to the receiver common. 

Type 3 Transmitter

Photo : Type 3 Transmitter

Type 4-wire Transmitter 

This is a 4-wire transmitter that is energized by a supply voltage at the transmitter. The transmitter sources the loop current to a floating receiver load. 

Type 4 Transmitter

Photo: Type 4 Transmitter

Another Case Study:-

4 - 20mA Transmitter Wiring Types: 2 -Wire, 3 - Wire & 4 - Wire

Today’s electronic process transmitters - pressure, temperature, flow and level are connected in different wire types or configurations. These connection methods are of great concern to the instrument engineer/technician. The 2 - Wire, 3 - Wire and 4 - Wire types are often used to describe the method of connection of electronic transmitters. However in today's rapidly evolving technological world, the 2 - Wire type transmitter is by far the most common. Evidently so because of the huge savings in wiring and other advantages it possess over the other transmitter wire configurations.

Two wire transmitters:

These are the simplest and most economical and should be used wherever load conditions will permit. They are often called loop powered instruments. In a 2 -wire system, the only source of power to the transmitter is from the signal loop. The 4 mA zero-end current is sufficient to drive the internal circuitry of the transmitter and the current from 4 to 20 mA represents the range of the measured process variable. The power supply and the instruments are usually mounted in the control room. The schematic diagram below shows the wire transmitter configuration:

Three wire transmitters:

Some transmitters require more power than the signal loop ( 4-20 mA. etc) can supply their internal circuitry. A DC common wire is run from the instrument to the transmitter. This permits the transmitter to draw whatever power it needs from the power supply and produce the desired signal current at the transmitter output. The schematic diagram for a 3 -wire transmitter is shown below:

  

Four wire transmitters:

4-wire transmitters have their own internal power supply hence they are often referred to as self-powered instruments. They require no connection to the DC power supply. A 120 Vac sources is connected only to the receiving instrument. These are often used where an instrument is added to the load of the DC supplies. The disadvantage is the need for AC power at the instrument site. Below is shown the wire configuration of a four wire transmitter:

Note that in all the transmitter wire configurations shown above, a load resistor of 250Ω is used. Usually process controllers used in instrumentation systems are not equipped to directly accept milliamp input signals, but rather voltage signals. For this reason a precision resistor is connected across the input terminals of the controllers to convert current signals from transmitters into standardized analog voltage signals that controllers can understand.

A voltage signal range of 1 to 5 volts is standard, although some models of controllers use different voltage ranges and therefore require different precision resistor values. If the voltage range is 1-5 volts and the current range is 4-20 mA, the precision resistor value must be 250 ohms.

In the transmitter wire configurations discussed above, it is assumed that a voltage signal range of 1-5V and a standard current signal of 4-20mA are used.

4-20 mA Transmitter Types With Wiring Illustrations

If you are involved in the installation, setup and maintenance of process measurement instruments in the field or in plant process control applications, it is imperative for you to know the three types of 4-20 transmitters (2, 3, 4 wires) and how each is wired. This knowledge may be useful when you are troubleshooting for a problem in the loop where you need to know beforehand how the transmitter is energized. Although 2 wires 4-20 transmitters are common in applications, you may encounter an application with 3 or 4 wires transmitters, where you have to troubleshoot for a measurement error and fix it. 

credit to : https://www.instrumentationtoolbox.com/

#instrumentation #processcontrol #4to20mawiring #4-20mawiring

#custronics #ledsafetyscoreboard #safetyfirst #OSHAscoreboard

LED Display System Design & manufacturer 
CUSTRONICS
Engineered & Assembly in Malaysia
https://www.facebook.com/JTTechtronics/
https://www.custronics.com

Jim Loo https://Www.wasap.my/60163199391

#custronics #jttechtronicssdnbhd #PPMdisplaypanel #MPMDisplaypanel #KPIdisplaypanel #productiondisplaypanel #leddisplaypanel #malaysialed #leddisplaypanelmalaysia #leddisplaymalaysia #leddisplayboardmalaysia #leddisplayboard #productiondisplayboard #productiondisplaymalaysia #rs232display #rs485display #mqttdisplay #andonsystem #andondisplay #andonleddisplay