Teledyne 326, 327 and 328 - Oxygen analyzers User Manual

Page 24

Teledyne Analytical Instruments

3-4

Per

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Section 3

The standard current output option is 4 to 20 mA dc (O-20 or I-20).

Other ranges can be negotiated. Refer to the Specific Application Data and/
or Special Addendum to determine the output signal magnitude for specials.

The appropriate terminal strip connections and polarizations are identi-

fied on the Schematic and Interconnection Diagram. Always observe the
polarity specified on the Schematic and Interconnection Diagrams; other-
wise, output indication will be lost, and circuit damage may be caused to the
instrument or other devices involved.

Two-conductor shielded cable is recommended for all signal inter-

connections for the best possible signal protection. For explosion-proof and
CENELEC-approved units, consult the control unit outline diagram for the
proper conduit access port to use for wiring.

Important:

Important: Make sure that the impedance of the external circuit does not

Make sure that the impedance of the external circuit does not

Make sure that the impedance of the external circuit does not
exceed the specified impedance of the current range provided.

exceed the specified impedance of the current range provided.

3.2.3 Alarm and/or Control Circuitry

Two relay-contact outputs with electronically controlled adjustable

setpoints are available for controlling customer-provided equipment, such as
an annunciator or shut-down circuitry. They ar available withe normally-
open or normally-closed contacts, Higher-than-setpoint or lower-than-
setpoint actuation, and for CENELEC models: 3 amperes maximum, non-
inductive contacts.

When this circuitry is installed, the model number includes a -2. The

operating characteristics described in the previous paragraph will be docu-
mented on the Specific Application Information and/or in an Addendum in
the front of the manual.

CAUTION: Consideration must be given to the energized state of the relays

(energized above or below setpoint, and normally-open/normally-

(energized above or below setpoint, and normally-open/normally-
closed) to ensure failsafe operation when desired.

closed) to ensure failsafe operation when desired.

Connections are made to the terminal strips provided, as labeled in the

Interconnection Drawings at the rear of the manual.

In models with intrinsic safety barriers, it is vital to know to which side

of the setpoint a given relay is energized so that the proper contacts of the
SPDT relay switch (normally closed or normally open) can be used in the
external circuit. The terms normally open (NO) and normally closed (NC)
refer to the position of the relay switch when its control solenoid is de-

the position of the relay switch when its control solenoid is de-

energized

energized. The NO and NC contacts share the C (for common) contact.
Any load connected across the NO and C contacts will always see an open
circuit (switched off) when the relay is de-energized. Any load connected