Service manual

PN 4237242C
2.5-5
INSTRUMENT DESCRIPTION
DATA ACQUISITION
2
The vacuum measurement is the difference between these two reference readings. During a
sample analysis cycle, one zero reference is taken prior to the first count period, and a high
reference voltage reading is taken for each of the 12 count periods. This produces a vacuum
measurement for each of the count periods.
Figure 2.5-2 Vacuum Sensor Card Block Diagram
The input and output connectors and test points for the Vacuum Sensor card are shown in
Figure 2.5-3 and the test points are summarized in Table 2.5-4.
Inputs
r J1 - ±15 V
r J2 - solenoid LV1
r J3 - solenoid LV2
Outputs
J1 - VAC OUT
Adjustments
R2 - The Gain adjustment calibrates the card and requires an accurate vacuum measuring
device to set it. It is a factory adjustment that cannot and must not be adjusted in the field.
7242045A
REFERENCE
VOLTAGE
SOURCE
OFFSET
REDUCTION
SOURCE
SUMMING
AMPLIFIER
PRESSURE
TRANSDUCER
LOW PASS
FILTER
GAIN
ADJUST
8.000 V
-+
LV2
LV1
VAC
OUT
+24 V
SIG1
+24 V
SIG2