Manual / Auto Modes; Automatic Balance Compensation (Abc) - Michell Instruments 4000 Series User Manual

SERIES 4000 Precision Dewpointmeter (Remote, Climatic, RS and TRS)Users Guide
2.6

Manual / Auto Modes

The instrument may be operated in an automatic or manual mode of operation. The
switch on the front panel MANUAL / AUTO sets the mode of operation. The mode
may be changed at any time, but the front panel INITIATE push-button is only active
when the switch is in the MANUAL position.
In the automatic mode, the instrument initiates an ABC cycle automatically at pre-
determined user-definable intervals (refer to Section 2.8.).
In the manual mode, it is the responsibility of the user to manually initiate an ABC
cycle periodically.
The front panel OPTICAL BALANCE CONTROL is only active when the AUTO /
MANUAL switch is in the MANUAL position. The OPTICAL BALANCE METER is
always active.
Important Note:
2.7

Automatic Balance Compensation (ABC)

In Operation Mode, the optical components of the sensor (i.e. mirror, light guides
etc.) become progressively contaminated which results in a gradual loss of
sensitivity. To compensate for this, a compensation system is provided that heats the
sensor‟s mirror to evaporate the condensate and allow the system to measure the
mirror‟s contamination. This provides a new baseline for the dew point measurement
until the next ABC is initiated. The duration of the ABC is user definable from 1 to 8
minutes and is set using SW4 – refer to Section 2.9.
The AUTO/MANUAL switch enables automatic or manual initiation of the ABC. In
MANUAL an ABC is only initiated by pressing the ABC button, whereas it is initiated
periodically in AUTO.
The duration of the ABC is set as follows :
SW3-1
SW3-2
SW3-3
SW3-4
SW3-5
SW3-6
SW3-7
SW3-8
Note that only one switch may be in the ON position at any time.
If the Data Hold facility (see section 2.10) is not used to maintain the measured dew
point during an ABC, it is important that the instrument is allowed sufficient time to
settle before a dew point reading can be taken. This settling time is dependent on
the dew point of the sample gas and the particular application.
Automatic operation of the Balance Compensation System must
not be used if the dew point to be measured is lower than -60ºC,
or if the sensor temperature is lower than -30ºC.
ABC Duration
30 minutes
1 Hour
2 Hours
4 Hours
8 Hours
16 Hours
32 Hours
N/A
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