Model 1500
Dew Point Monitor
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3.0 FUNCTIONAL DESCRIPTION
The front panel of the Model 1500 Battery Powered DPM consists of an LED Display and two
push-buttons.
1.) MABC- Manual Automatic Balance Cycle
2.) DISPLAY “SCAN”- Allows viewing of all Parameters or selection of desired measurement.
3.1 Display
The eight character alphanumeric LED display is used to display dew point data
and status messages.
Dew point data is displayed as “DP 34.8 F”, with the units in degrees C or F. (See Set-Up
section)
When a status message is necessary, the display will alternate between the data and the
message at about 2 second intervals.
The possible status messages and their meanings are:
“ABC CYCL” : Indicates that an Automatic Balance Cycle is in progress.
During an ABC Cycle;
The mirror is heated above the ambient temperature for a period of 1 to 3
minutes as determined by the last measured dew point.
After sufficient time has elapsed to ensure that the mirror is dry, the reflected light level of
the mirror is measured and if necessary, adjusted to the reference level.
After the adjustment is made, the instrument will begin cooling and seeking the dew
point. When a stable lock on the dew point is achieved, the “ABC CYCL” message will
disappear, and normal operation will resume.
The analog output is held to the dew point value just before the cycle started until the
completion of the ABC cycle.
If an alarm condition is present when the ABC cycle begins, the audible alarm and the
ALARM display are disabled but the Alarm Relay remains energized.
“ ALARM”: The Alarm Set Point has been exceeded. The Alarm Relay will be energized.
“CLN MIRR”: During an ABC Cycle, the condition of the sensor mirror and optics are
analyzed and a correction is made for changes in the reflectivity since the last cycle. If the
mirror reflectivity has decreased beyond the automatic correction range, this message will
appear at the end of the ABC cycle and indicates that the sensor mirror needs a manual
cleaning. Perform the “Mirror Cleaning Procedure” in the MAINTENANCE and
CALIBRATION Section.
Note: The instrument may appear to operate normally with this message present, but
the data should not be relied upon, until the appropriate maintenance is performed.
