DewPro MMY245
Installation and Operation Manual
GE General Eastern
8
2 Basic
Operation
The MMY 245 operation is simple and
intuitive. Provide the instrument with a
sample of gas and direct it to the
sensor using the handle on the side of
the instrument, apply power and let the
analyzer tell you when the
measurement is stable and should be
taken.
The instrument operates best when
measuring pressurized samples over a
range of 20-150 psig. Satisfactory
measurements can be made at lower
pressures, even at vacuum, although a
longer time may be required since
there are not as many exchanges per
minute at these lower pressures.
Techniques for these low-pressure
measurements will be discussed later
in this manual.
2.1 Operating
Controls
The electronic operating controls for the MMY 245 are found directly in front of the carrying handle
and the flow path control is located on the left side of the instrument. This “operating handle” of the
instrument puts the sensor into a desiccant environment or directs the flow of the sample across the
sensor.
The electronic controls provide access to the analysis of the sample. These electronic controls consist of
six membrane switches (see Figure 2) located below the digital display and are used to power the unit
and control the various functions of the unit. The POWER key will turn the unit on or off. The HOME
key will display the matrix position
V0 H0
or alternately
V4 H0
. Pressing the
V
and
H
keys advances
the vertical or horizontal position within the matrix and the display will show the contents of that
position. Pressing the + and – keys increments or decrements the value in the matrix cell described in
the right side of the display. These matrix and operating functions will be described on succeeding
pages.
2.2 Display
Elements
There are three distinct display elements consisting of a large
digital readout where values are shown, a smaller digital
section to the right where four characters are displayed
showing the location in the matrix where the values are
generated, and a bar graph across the bottom.
The MMY 245 takes the guesswork out of waiting for the
measurement to stabilize. The instrument display (see
Figure3) includes a rate-of-change bar graph indicating a
reading is changing or stable. A changing reading will cause
the bar graph to include additional segments in any portion
of the bottom of the display. The direction and amplitude
illustrated by the arrows indicate the required change in the
reading. This feature allows the operator to know the reading
has stabilized and can be recorded correctly. Below, several
different measurement techniques are discussed from the perspective of connecting the sample to the
unit; but the basics of operation remain the same.
-48.6
V H
0 0
-48.6
V H
0 0
Reading Still Changing
Stable Reading
Figure 3
Figure 2
-
V
0
HOME
V
H
+
-
POWER
