Fig 3a Simplest circuit with one side of
20mA current loop connected to
earth.
Also illustrates resetting from safe area.
Fig 3b
Two Zener barrier channels are
required if the 4/20mA current loop
can't be earthed at the barrier busbar.
Also shows optional resetting from
hazardous area
Fig 3c Galvanic isolator can be used with any
4/20mA current loop.
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