Ametek Land 4500 MKIII, User Manual

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Opacity and Dust Monitor
User Guide
Model 4500 MkIII
B - 20
B5 Periodic Modes of Operation
B5.1 Calibration Check
Transceiver
1 LED light source 6 Measurement Detector
2 Flood LED 7 Reference Detector
3 50/50 Beam Splitter 8 Concave Mirror
4 Collimating Lens 9 Upscale Filter
5 Collimated Beam 10 Zero Point Reflector
The transmissometer periodically performs a two step calibration check. In
the first step, a zero-point reflector (10), mounted within the air purge of the
Transceiver is placed into the optical axis. In the second step, the upscale
filter (9) is also placed in the light path. The monitor reads the difference in
light between the current zero–point and the zero–point established during
the last clear stack calibration, and notes this value as the amount of drift
and optical dust build-up. The opacity value of the upscale filter (9) is shown
on the calibration certificate which accompanies the instrument.
As required by ASTM D6216-07, the model 4500 MkIII indicates the PLCF
value on the current loop output for 90 s at the end of each calibration
check. The value is scaled 0.0 to 10.0. For example PLCF = 1.2; the output
value will be 4 + (1.2/10) x 16 = 5.92 mA. This function can be disabled by
setting the output to hold during calibration (parameter 188=1).
If fail-safe shutters are fitted, the shutters close during the zero phase of
the calibration check. This demonstrates that the shutters are functioning
correctly and ensures that they cannot become stuck in the open position.
During this time, the purge air will escape around the edge of the rubber
sealing ring.
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