04/12/23

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Types of IsolatorsTypes of Isolators

Output Loop Powered – 651T-0600

Input Loop Powered – 671T-0600

Self-Powered – 631T-0500

Steals powerfrom output loopw/ Sinking output

Steals powerfrom input loop

w/ Sourcing output

Separate Power Connection w/

Sourcing output

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Types of IsolationTypes of Isolation

Magnetic vs. Optical Isolation

An LED and a phototransistor are separated so that light may travel across a barrier but electrical current may not. As an electrical signal is applied to the input, photons are emitted from the LED which excite the phototransistor. When it activates, a proportional electrical signal is generatedat the output.

The primary and secondary coils are wrapped around a core of very high magnetic permeability such as iron. A current passing through the primary coil creates a magnetic field. The magnetic field lines pass through the iron core which produce a current in the output of the secondary coil.

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Reasons for Isolators / SplittersReasons for Isolators / Splitters

#1 – Prevent Ground Loops & Noise ProblemsA single ground poses no problem, but multiple grounds cause ground loops. In a ground loop, each ground is tied to a different earth potential. This allows current to flow between the grounds, interfering with the actual signal. If an extraneous current is produced from 50/60Hz AC power, noise is created. If this unwanted current is DC, it will create an offset.

An Isolator prevents unwanted currents by breaking ground loops. This eliminates noise problems and DC offsets.

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Reasons for Isolators / SplittersReasons for Isolators / Splitters

#2 – Isolate Bucking Power Sources

PLCH2S Analyzer / Monitor

4-20mA Sourced Output

Powered InputPassive Input

Loop Powered Output

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Reasons for Isolators / SplittersReasons for Isolators / Splitters

#3 – Amplification

Dewpoint Transmitter

AC Powered, 4-20mA Output up to 270 Ohms

Output Up to 1000 Ohms

Chart Recorder 250 Ohms Input Impedance

Panel Meter 100 Ohms Input Impedance

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Reasons for Isolators / SplittersReasons for Isolators / Splitters

#4 – Splitter for Isolating Loads

1000 feet

500 feet

2-wire Pressure

Transmitter

PLC

Display

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Reasons for Isolators / SplittersReasons for Isolators / Splitters

# 5 – Surge Protection

Flowmeter

Surge plus Isolation and Amplification

Field Instrument

Control Room

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Reasons for Isolators / SplittersReasons for Isolators / Splitters

#6 – Easy to Scale / Adjust Range

4-wire Optical Sensor

Optical InterfaceModify software to re-scale

One step Load-Trim Adjustment

+/-.75% Accuracy