Wiring Inductive Loads; Driving High-Current Loads; Fig. 2-18: Suppressor Diode For Inductive Loads; Fig. 2-19: Driving High-Current Loads - Emerson Rosemount Analytical X-STREAM Enhanced Series Short Form Manual

X-STREAM XE
2.7.2

Wiring Inductive Loads

Switching inductive loads creates electromag-
netic interference:
When an inductive load (e.g. relay, valve) is
switched off, the magnetic field resists the
change in current; this induces a high volt-
age across the coil contacts (several hundred
volts). This impulse propogates through the
connected cables and can influence any
electrical devices nearby or destroy signal
inputs and outputs. This can be avoided with
a simple precaution:
• A silicon diode is connected in parallel
to the load's contacts. The induced im-
pulse is thus short-circuited at its source.
The cathode must be connected to the
positive end of the coil, the anode to the
negative end (Fig. 2-18).
Compatible filter components for standard
valves are available on request.

Fig. 2-18: Suppressor Diode for Inductive Loads.

2-26
2.7 Installation - Notes on wiring
2.7.3

Driving High-Current Loads

Loads which draw a current in excess of the
specifications for X-STREAM series analyzer
outputs (>30 mA / >1 A) may not be directly
driven from digital or relay outputs.
Such loads require external relays serving as
de-coupling modules: the X-STREAM output
drives the external relay, which in turn drives
the load.
In order to avoid interference, we recommend
supplying the analyzer and the high-current
loads from different sources (Fig. 2-19).
As previously described, the use of sup-
pressor diodes for inductive loads is highly
recommended.
External relay
Analyzer output

Fig. 2-19: Driving High-Current Loads

Emerson Process Management GmbH & Co. OHG
Short Form Manual
HASXEE-SFM-HS
05/2017
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