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that new value is entered, the SADPminiEx automatically reverts to the ‘Exit’ option in
the ‘Setup Menu’.
Note – 1) The only way to leave this menu without altering any values is to press the ‘ ’ key
twice, accepting the current values for both the upper and lower settings.
2) The 4-20mA range settings are reset to full span whenever the moisture units are
altered.
3) The 4-20mA output should not be operated while the instrument is charging.
11.1.4
AutoCal
Description – AutoCal allows the user of the SADPminiEx 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
SADPminiEx 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 SADPminiEx 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 SADPminiEx if confirmation of an unexpected result is required.
Operation – of SADPminiEx 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)
Extend the desiccant head and press the ‘ ’ key.
ii)
The SADPminiEx will display a moving bar until it assesses that the
sensor has stabilised. (Up to 10 mins.)
iii)
The SADPminiEx 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.
iv)
The SADPminiEx will display a moving bar whilst the calibration data is
modified. (Up to 5 mins.)
ACAL adjusts slope of curve.
New settings stored in SADPmini.
Inst Reading 100%
