Teledyne 326, 327 and 328 - Oxygen analyzers User Manual

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Teledyne Analytical Instruments

Introduction

Model 326/327/328

1.5.1 Integral Alarm Circuitry

A number -1 or -2 appended to the model number indicates one or two

alarm and/or control relay circuits with setpoints that are adjustable over the
selected analysis range. The contacts of the relay are available for intercon-
nection with customer circuitry at the terminal strip provided.

The setpoint is set by a potentiometer with a calibrated-dial. The

integral control circuitry can be arranged so that the relay is energized
above or below the setpoint. Unless otherwise specified, the control relay in
a single setpoint instrument actuates (de-energizes) when the oxygen con-
centration rises above the setpoint, and the relays in a double setpoint
instrument actuate (de-energize) when the oxygen level is outside the
portion of the analysis range between the two setpoints. These configura-
tions can be used for power supply failure alarms as well as an oxygen
alarm. The Form “C” relay contacts are rated at 3 A (noninductive).

1.8.2 E to I Converter

TBE also offers a current output signal, so that current-to-pneumatic

devices, as well as low impedance current indicating and/or recording
equipment, may be driven directly without the need of accessory equipment.

The current output option is indicated by an “I” in the model number if

the instrument has a grounded current output option, or an “O” if the
output is isolated. This letter designation will be immediately followed by a
one or two digit number which specifies the maximum output. Thus, O-20
signifies an isolated 4 to 20 mA dc current output. The most common
current outputs used are 1 to 5, 4 to 20, and 10 to 50 mA dc.

By special order, isolated voltage outputs from 0–1 mV up to 0–1 V dc

can be provided.

Some common current outputs are:

1. 1–5 mA dc suitable for devices with from 0 to 6000 ohms impedance.

2. 4–20 mA dc suitable for devices with from 0 to 1500 ohms impedance.

3. 10–50 mA dc suitable for devices with from 0 to 600 ohms impedance.

1.8.3 Optional Feature Packaging

Both the integral-alarm and E-to-I converter options are plug-in printed

circuit boards for quick replaceability. When either or both the options are
employed in an instrument, a highly-regulated differential power supply
(also a plug-in type printed circuit board) is included to supply the positive
and negative voltage required by the semiconductor circuitry.