4-20mA Signal Isolators

4-20mA Signal Isolators

Signal isolators receive 4-20mA process current inputs and provide an isolated 4-20mA output signal. One multi-channel units, each channel operates independently and is isolated from the others to prevent interaction between channels. Galvanic isolation eliminates ground loops, reduces noise, and blocks transient signals. Products include

  • 2 Wire loop powered isolators
  • 3 Wire DC Powered isolators
  • 4 Wire AC/DC Powered isolators

Read on below to learn more.

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Signal Isolators

Acromag manufactures 4-20mA Signal Isolators. There are several different types to choose from:

2 wire loop isolatorsThis is an image of a DC Voltage Current Input Transmitters 611T 612T. This unit is also known as a signal isolator and is made by Acromag.Current/millivolt Input DC Power Transmitter
 

2 Wire Loop Powered Isolators

3 Wire DC Powered Isolators

4 Wire AC / DC Powered Isolators

4-20mA Loop-Powered Isolators, 2-Wire Models get power from the 4-20mA output or input loop (sinks or sources current). Typical uses are as a current repeater or to drive resistive loads.

DC-Powered Isolators – These models are used to drive resistive loads (sources current). The 4-20mA output signal and DC power share a common lead which is wired directly to the PLC/DCS’s internal ground.

4-Wire AC/DC-Powered 4-20mA Isolators – These isolators provide 3-way isolation to separate input, output, and power circuits. They are safest for retrofitting or expanding systems where instrument isolation or the grounding schemes are unknown.

For more information on the different signal isolators 4-20mA ; please see below or contact us.

Or to learn how to choose the right isolator for your application – check out this blog titled “Selecting the right signal isolator”

4-20mA Loop Powered Isolators, 2 Wire

Models get power from the 4-20mA output or input loop (sinks or sources current). Typical uses are as a current repeater or to drive resistive loads

651T and 250T models are ideal for applications that require an isolator with a power supply in series with the output signal. Power is obtained from the output loop. The isolator must control current draw from the power supply in the output loop which is the 4-20mA signal. Since output and power share the same two wires, this type of isolator can be placed anywhere between the field sensing device and the PLC/DCS or monitoring device. Usually, the isolator is located close to the field device. Since both the input and output signal are 4-20mA, location of the device is not critical.

670T and 270i models are useful when adding and isolating a monitoring instrument to an existing current loop. When adding a field device such as a recorder or display, no additional power source is required for the added loop or for the isolator. The isolator’s output is powered by the input loop power and drives passive loads only.

Series available

Thermocouple / millivolt Input 2-Wire Transmitter TT2332 Wire Loop Powered Isolators 651T, 652T, 653T4-20mA 2 Wire Multi Channel Isolators
TT 230 Series: 2 Wire Loop Powered 4-20mA Isolators, Rail Mount

Model: TT236

600 Series: 2 Wire Loop Powered 4-20mA Isolators, DIN Rail Mount

Model: 650T

600 Series: 2 Wire Loop Powered 4-20mA Isolators, DIN Rail Mount

Model: 670T

Transmitter/Isolator, Current/Millivolt Input, Loop-Powered

  • Multi-range ±20mA or ±500mV input
  • 4-20mA output (sink/source)
  • 12-32 V DC loop/local power

The TT236 model is a space-saving two-wire transmitter that isolates and converts a DC current or low voltage input to a proportional 4-20mA control signal

651T / 652T: Isolator, Single/Dual Channel

  • 4 to 20mA DC input
  • 4 to 20mA DC output
  • Output loop powered
  • Low cost isolator
  • Up to two independent channels in a single unit with channel-to-channel isolation

These units receive 4-20mA process current inputs and provide isolated 4-20mA output signals. Each channel operates independently.

671T / 672T / 674T: Isolator, Single/Dual/Quad Channel

  • 4 to 20mA DC input
  • 4 to 20mA DC output
  • Input loop powered
  • Low-cost isolator
  • Up to four independent channels in a single unit with channel-to-channel isolation

These units receive 4-20mA process current inputs and provide isolated 4-20mA output signals.

Loop, DC or AC Power Transmitter 250T-TCLoop Power Isolator4-20mA Signal Isolator DT236
Flat Pack Series: 2 Wire Loop Powered 4-20mA Isolators, DIN Rail Mount

Model: 250T-DC; 350T-DC; 450T-DC

Flat Pack Series: 2 Wire Loop Powered 4-20mA Isolators, DIN Rail Mount

Model: 270i

DT236 Current/Millivolt Input 2 Wire Transmitter

Model: DT236

250T-DC: Transmitter, Output Loop Power

350T-DC: Transmitter, DC Powered

450T-DC: Transmitter, AC Powered

These models convert sensor inputs to proportional process current or voltage output signals.

270i: Isolator, Input Loop Power

  • 4-20mA DC input
  • 4-20mA DC output
  • 1500V AC peak isolation DC prevents ground loops

The 270i accepts a process current input and provides an isolated 4 to 20mA process current output signal. Power is received from the input signal current.

DT236: Two Wire Transmitter that isolates and converts DC Current or low voltage into 4-20mA

  • Multi range +/-20mA or +/-500Mv
  • 4-20mA Output
  • 12-32 V DC Loop or Loc Power

These models are used to drive resistive loads (sources current). The 4-20mA output signal and DC power share a common lead which is wired directly to the PLC/DCS’s internal ground.

3 Wire DC Powered Signal Isolators

Acromag’s 340i model is ideal for applications requiring multiple isolators at a single location where all isolators share the same power supply. PLCs and DCSs usually have 24V DC power available at their input terminals.

4-20mA Signal Isolator TT2364-Wire DC Powered IsolatorDC Voltage Current Input Transmitters 611T 612T
TT200 Series: 3 Wire DC Powered 4-20mA Isolators, Rail Mount

Model: TT-236

Flat Pack Series: 3 Wire DC Powered 4-20mA Isolators, DIN Rail Mount

Model: 340i

Single or Dual Channel DC Voltage / Current Input DC Powered Transmitter

Model: 611T, 612T

Transmitter/Isolator, Current/Millivolt Input, DC-Powered

  • Multi-range ±20mA or ±500mV input
  • 4-20mA ouput (sink/source)
  • 12-32 V DC power

The TT236 model is a space-saving 3-wire transmitter that isolates and converts a DC current or low voltage input to a proportional 4-20mA control signal.

340i: Isolator, DC-Powered

  • 4 to 20mA DC input
  • 4 to 20mA DC output
  • 10-36V DC power
  • 1500 AC peak isolation prevents ground loops

Calibration is independent of the load to eliminate load compensation adjustments

The 340i accepts a process current input and provides an isolated 4 to 20mA process current output signal.

Single (611T) or Dual Channel (612T)

  • ±100V DC, 0 to 100mA DC, 0 to 20A AC (with optional sensor) input
  • 0 to 20mA, 0 to 10V DC output
  • 10-36V DC power
  • Universal DC I/O transmitters with auto-configuration and self-ranging capabilities

Receive DC current or voltage input signals, provide isolation, and output proportional DC current or voltage signals.

4 Wire AC / DC Powered Signal Isolators

These isolators provide 3-way isolation to separate input, output, and power circuits. They are the safest choice when retrofitting or expanding systems where instrument isolation or the grounding schemes are unknown.

These 3-way signal isolators source current out and do not use a separate output power supply. The outputs are designed to drive purely resistive loads.

The isolator can be located several or hundreds of metres away from the PLC/DCS and obtain power from an external AC or DC source. This source may have a different ground potential than the PLC/DCS or field device. In this case, the power ground must be isolated from both the input and output. Across long distances, the ground potential at a sensor is likely different from the power source and PLC/DCS. Consequently, input to output isolation is also necessary.

Additionally, these units can isolate 4-20mA control outputs from the PLC/DCS to field actuators. In the case of analogue outputs, the PLC/DCS output is wired to the isolator input and the isolator output is wired to the field device/actuator.

Single/Dual Channel IsolatorsCurrent/millivolt Input DC Power Transmitter
600 Series: 4-Wire AC/DC-Powered 4-20mA Isolators, DIN Rail-Mount

Model: 630-T

TT300 Series: 4-Wire DC-Powered 4-20mA Isolators, DIN Rail-Mount

Model: TT336

631T / 632T: Isolator, Single/Dual Channel

  • 4 to 20mA DC input
  • 4 to 20mA DC output
  • 15-36V DC SELV, 90-250V AC power
  • Single or dual I/O with a dual output model and full isolation

These units receive 4-20mA process current inputs and provide isolated 4-20mA output signals. Each channel operates independently

Transmitter/Isolator, Current/Millivolt Input, DC Power

  • Multi-range ±20mA or ±500mV input
  • 4-20mA, ±20mA, 0-10V, or ±10V DC output
  • 12-32V DC power

The TT336 model is a space-saving four-wire transmitter that isolates and converts a DC current or low voltage input to a proportional control signal.

4-Wire DC Powered Isolator4-Wire DC Powered Isolator
Flat Pack Series: 4-Wire AC/DC-Powered 4-20mA Isolators, DIN Rail-Mount

Model: 330i

Flat Pack Series: 4-Wire AC/DC-Powered 4-20mA Isolators, DIN Rail-Mount

Model: 430i

330i: Isolator, DC-Powered

  • 4 to 20mA DC input
  • 4 to 20mA DC output
  • 10-36V DC power
  • Three-way isolation

Series 330i isolators provide 3-way isolation and do not require recalibration for different loads. They accept a 4 to 20mA process current input and provide a 3-way isolated process current output.

430i: Isolator, AC-Powered

  • 4 to 20mA DC input
  • 4 to 20mA DC output
  • 115V AC or 230V AC power
  • Three-way isolation
  • Zero and span adjustment enable precise calibration

Series 430i isolators provide 3-way isolation and do not require re calibration for different loads. The 430i accepts a 4 to 20mA process current input and provide a 3-way output.

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