VICI 340 Dynacalibrator - Manual (Page 7)

3
Introduction
The flow rate through the flowmeter needle valve is a function of the differential
pressure across it and the setting of the dilution flow control valve. This differen-
tial is maintained at 3.2 psi by DPR2. The needle valve is adjustable at the front
panel. The calibrated output of the dilution flowmeter mixes with the perme-
ation chamber output to provide the final output concentration.
When the non-pressurized internal pump option is included, the rear-panel zero
outlet port is internally connected to a passive scrubber which functions identi-
cally to those previously described. In operation, the zero outlet is plumbed
either to the analyzer sample intake port or to the zero air intake port, so that
analyzer suction provides flow through the scrubber.
The Model 340 features zero air capability for easy two-point calibration. It can
be remotely switched between the zero air and span output modes. A front
panel switch permits selection of the ZERO, SPAN, or REMOTE mode. In the ZERO
mode, a two position valve directs the permeation chamber output to an exhaust
vent. Only the dilution stream passes through the mixing tee to the outlet port,
permitting the analyzer to be calibrated at its zero point.
In the REMOTE mode, the Model 340 can be used to calibrate a remote analyzer
equipped with a separate calibrate input port and remote control capability.
Figure 2 illustrates this application. The calibrator is initially set up and plumbed
to the analyzer at the remote monitoring station. The operator may then periodi-
cally check the calibration of the analyzer by simply switching it to the calibrate
mode and selecting the ZERO and SPAN outputs of the calibrator, or the calibrator
may be automatically sequenced at fixed time intervals. The calibrator requires
only a single contact clo sure to switch between the two modes.
Remote monitoring station
340 Dynacalibrator Gas analyzer
Remote control panel
Span Sample
Zero Remote Remote Cal.
Cal.
inlet
Stream
outlet
Span Sample
Zero Cal.
Recorder
Figure 2: Model 340 in remote mode