Autocal - Alpha Moisture Systems SADPmini Instruction Manual

11.1.4 AutoCal

Description – AutoCal allows the user of the SADPmini to ensure accuracy between
laboratory calibrations by checking the span of the instrument and correcting for any
deviation.
The AutoCal facility uses the fact that each sensor is designed and manufactured to give no
further increase in response when it reaches its maximum moisture level. For example an
SADPmini with a full-scale value of -20°C dewpoint will read -20°C dewpoint when
exposed to a gas with this moisture concentration, and will continue to read -20°C
dewpoint as the moisture concentration rises above -20°C dewpoint. The SADPmini can,
therefore, be adjusted to read -20°C dewpoint on any gas with a moisture concentration
wetter than -20°C dewpoint, ambient air for instance, thus setting the span to match the
original calibration.
AutoCal should be operated periodically, every 2 to 3 months, say, or can be used to
verify operation of the SADPmini if confirmation of an unexpected result is required.
Operation – of SADPmini units with full scale values of -20°C or 0°C dewpoint
1. Select AutoCal from the Set-up Menu
2. Follow the on-screen instructions, i.e.:
i)
ii)
iii)
iv)
v)
vi)
Note - Avoid carrying out the AutoCal procedure on a SADPmini with a full scale value of
Inst Reading
Extend the desiccant head and press the '' key.
The SADPmini will display a moving bar until it assesses that the
sensor has stabilised. (Up to 10 mins.)
The SADPmini will now display the full-scale value of the unit, either
-20°C or 0°C. If the unit is being checked against a known moisture
level such as from a moisture generator the scroll and ▲ and ▼ keys
can be used to enter the known moisture level, otherwise leave it set at
the full-scale value and press the '' key.
The SADPmini will display a moving bar whilst the calibration data is
modified. (Up to 5 mins.)
Close the desiccant head when instructed to do so and press the ''
key.
The SADPmini will return to the Set-up Menu with the "EXIT" option
highlighted. Pressing '' key again will return the instrument to
operational mode.
0°C dewpoint on days when the ambient dewpoint may to be below this value, for
example a dry day when the ambient temperature is below around 12°C.
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ACAL adjusts slope of curve.
New settings stored in SADPmini.
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