SECTION 9 – SERVICE AND TROUBLESHOOTING
FORM QWC3-NM1
ISSUE DATE:11/20/2020
QUANTECH
157
9
CHECKING INPUTS AND OUTPUTS
Digital Inputs
See the Elementary Wiring Diagram on page 66. All
digital inputs are connected to J13-1 of the I/O board.
The term “digital” refers to two states – either ON or
OFF. As an example, when the flow switch is closed,
30VDC will be applied to J13, pin 5 (J13-5) of the I/O
board. If the flow switch is open, 0VDC will then be
present at J13-5.
Pin 1 of J13 is an unregulated 30VDC source used
to supply the DC voltage to the various user contacts,
Unit Switch, flow switch, etc. This DC source is fac-
tory wired to CTB1, terminal 13. Any switch or contact
used as a digital input would be connected to this ter-
minal, with the other end connecting to its respective
digital input on the microboard. Any time a switch or
contact is closed, 30VDC would be applied to that par-
ticular digital input. Any time a switch or contact is
open, 0VDC would be applied to that particular digital
input.
Typically, voltages of 24 to 36VDC could be measured
for the DC voltage on the digital inputs. This voltage is
in reference to ground. The unit case should be suffi-
cient as a reference point when measuring digital input
voltages.
Analog Inputs – Temperature
See the Elementary Wiring Diagram on page 66.
Temperature inputs are connected to the microboard
on plug J6. These analog inputs represent varying DC
signals corresponding to varying temperatures. All
voltages are in reference to the unit case (ground). The
following pages show the connections for the tempera-
ture sensing inputs.
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