VICI 450 Dynacalibrator - Manual (Page 8)

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Figure 2 summarizes the Model 450 output flow configurations. When the mode
selector switch is in the REMOTE po sition with no remote inputs, the calibrator
defaults to the STANDBY mode. Remote inputs can then change the mode to
ZERO, SPAN 1 or SPAN 2.
Referring again to Figure 1, note that the dilution stream passes through scrub-
ber #2 and feeds into differential pressure regulator DPR2. The Model 450 con-
tains two separate dilution flow control valves and flowmeters, corresponding
to SPAN 1 and SPAN 2, for three-point calibration of analyzers. Solenoid control
valve SV1 routes the dilution stream to either set depending on the position of
the front-panel MODE CONTROL switch. Differential pressure regulator DPR2
maintains a fixed 3.2 psi pressure differential across the selected flow con trol
valve and meter. The flow rate through the selected flowmeter is then a func-
tion of this fixed pressure differential and the setting of the selected flow control
valve. Both flow control valves are adjustable at the front panel. The calibrated
output of the selected dilution flowmeter is mixed in a tee with the permeation
chamber output to provide the final output concentration.
The Model 450 has five operation modes – STANDBY, ZERO, SPAN 1, SPAN 2, and
RE MOTE. The STANDBY mode allows the calibrator to be permanently plumbed
to the sample inlet of an analyzer; the sample to be tested passes through the
calibrator and ultimately into the analyzer sample input. When the calibrator
mode is changed – either locally or remotely – to ZERO, SPAN 1, or SPAN 2, a two
position valve in the cali brator interrupts the sample input and substitutes the
calibrator output to the analyzer.
The ZERO, SPAN 1, and SPAN 2 modes provide a three-point calibration setup. The
ZERO mode vents the permeation chamber output through an exhaust port so
that only the dilution stream passes through the mixing tee to the stream outlet
port and into the analyzer for zero point calibration. The SPAN 1 mode mixes
the carrier stream with the dilution stream from a high-flow control valve and
flowmeter for low output con centrations of the trace gas. In the SPAN 2 mode, a
low-flow control valve and flowmeter are substi tuted for the high flow compo-
nents in the dilution stream to produce high output concentrations of the trace
gas. Front panel access to the control valves for each of the two dilution fiowme-
ters permits the user to accurately set both a low and high output concentration
and switch between them and zero air for the 3-point check.
Figure 3 illustrates a remote application of the Model 450. The calibrator is
initially set up and plumbed to the analyzer at the remote monitor ing station.
The analyzer requires neither a separate calibration inlet port or remote capabil-
ity. With the calibrator in REMOTE and the mode switch at the control station in
STANDBY, the sample under test passes through the calibrator into the analyzer.
The operator at the control sta tion can perform a 3-point calibration check by
successively placing the local mode switch in the ZERO, SPAN 1, and SPAN 2 posi-
tions and recording the results. Like the Model 340, the Model 450 may also be
automatically sequenced through its modes with an external timer/sequencer.
Figure 4 shows a Model 450 in a remote application with two separate analyz-
ers. In this application, the STANDBY position of the control station switch places
the calibrator in STANDBY and the analyzers in CALIBRATE. Sample gas passes
directly through the calibrator to the input ports of the two analyzers. The ZERO,
SPAN 1, and SPAN 2 remote modes interrupt both input samples and route the
Introduction