Heyer Modular+, Service Manual

Page: 97 / 114

Preventive Maintenance
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10 With the Patient Module still warm, disconnect any breathing circuit that may be attached and
verify that there is no gas flow at the Expiratory or Inspiratory ports on the Patient Module.
11 Increase the DAC value using the increment keys until the bar indicator for AVM 3-2 shows
50.0 ± 0.2.
12 Measure the DC voltage between the junction of R35 and R19 on the Module 2 AVM 3-2 board
and the boards ground pin.
13 Record the voltage at the junction of R35 and R19 as U1.
14 Measure the DC voltage between V13 Pin 8 and ground.
15 Record the voltage between Pin 8 of V13 and ground as U2.
16 Adjust P3 on the Module 2 AVM 3-2 board as necessary to obtain a 1:1.4 ratio between
reading #1 and reading #2, as seen in the example below.
Example:
Measure U1 = 1.45 VDC
U2 = 1.91 VDC
Calculate 1.91 / 1.45 = 1.32
Evaluate the ratio is too small. The target ratio is 1.4
Correct Turn P3 clockwise to increase the ratio.