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21 Calibration
Regular calibration is essential to maintain the accuracy of the CO measurement,
and also to demonstrate that the sensor is functioning correctly. The choice of
calibration interval needs to balance a number of factors:
•
Frequent calibration gives the best accuracy and reliability:
•
The analyzer is not measuring sample during calibration, so it is unable to
perform its early warning function. Therefore frequent calibration reduces the
safety coverage offered by the Millwatch or Silowatch analyzer;
•
Calibration gas is expensive and frequent calibrations consume a significant
amount of gas;
•
If the calibration gas is not permanently connected to the instrument, an
operator must go to the instrument and connect the gas cylinder.
In most cases, a calibration interval between 1 day and 7 days gives good results.
21.1 Automatic Calibration - Quick Start
Although a number of detailed calibration options can be selected, the following
procedure is sufficient for most calibration requirements.
1)
Check the display does not show "Zero calibrating" or "System Settling". You
must wait until those have been completed before calibrating.
2)
Press CAL
3)
Set entry code 4 then press CAL
4)
Check cursor is on the top line (AUTO CAL)
5)
Press CAL
6)
In the next screen, press "SETUP" to change the value on the top line and
press SETUP again to save it. Set the following parameters:
a)
Type: Manual
b)
GAS1 SETTLE: 300
c)
GAS1 SPAN: Cal gas concentration for first cal gas
d)
GAS3 SPAN may also be required
e)
CAL METHOD: 2 POINT
7)
Press CAL to begin calibration
8)
Display should show AUTO
CALIBRATING on the bottom line
9)
If the system aborts the calibration
after a few seconds, check the cal
gas pressure. If the pressure switch
on the calibration module is not
active, the instrument will abort the
calibration. As a diagnostic, in case
the pressure switch is not functioning,
place a jumper wire across the
terminals (circled).
User Guide
Millwatch / Silowatch
33
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