envea STACK 710, User Manual

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5 Periodic Mode of Operation STACK 710
40
(PC-000878-MA Issue 7, December 2021)
ENVEA UK Ltd
5.
Periodic Mode of Operation
5.1 Calibration Check
1 LED light source 7 Reference Detector
2 Flood LED 8 Concave Mirror
3 50/50 Beam Splitter 9 Span Filter
4 Collimating Lens 10 Zero Point Reflector
5 Collimated Beam
6 Measurement Detector
Figure 16: STACK 710- Transceiver.
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 span 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 span filter (9) is shown on the calibration certificate which
accompanies the instrument.
As required by ASTM D 21 -07, the STACK 710 indicates the PLCF value on the
current loop output for 90 s at the end of each calibration check. The value is
scaled from 0.0 to 10.0. For example, PLCF = 1.2; the output value will be 4 +
(1.2/10) x 1 = 5.92 mA. This function can be disabled by setting the output to
hold during calibration (parameter 188=1).
Caution
Do not attempt to move the zero point reflector by hand. The
precision gearbox will be irreparably damaged.