2101510 Rev. AG
Page 6–25
The NGC uses pulse width modulation technology to drive its
heaters and valves. Due to this feature, a DMM may not show
the voltage present at the NGC termination panel accurately.
However, in no case, even under load, should the DMM
indicate a voltage less than 11.5 VDC (or 22 VDC for 24 VDC
system) if the proper cables are used. It may be necessary to
have a digital volt meter capable of capturing fast transients
(less than 1 ms in duration).
For example: While using a DMM with fast transient capture
capability, set the DMM to capture the minimum voltage
(sometimes this is a min/max measurement) using its fast
transient capability. Then let it monitor the NGC while operating
for a few minutes. This should provide a good indication of the
minimum voltage appearing at the NGC terminals.
2)
Is the voltage within limits? If not, continue to the next step. If yes, no physical
problem is found.
3)
Is the external equipment, such as a radio or other device, being powered from
the NGC termination panel? If not, return to
sequence. If yes, continue to the next step.
4)
Disconnect the peripheral equipment from the NGC.
5)
While the NGC is operating, verify that the voltage at the NGC termination panel
is between 11.5 VDC-16 VDC (for 12 VDC systems) or 22 VDC to 28 VDC (for
24 VDC systems).
6)
Is the voltage within limits? If not, return to
sequence. If yes, the external equipment is drawing excessive current. Check the
equipment and related wiring. Correct and retest, if necessary.
6.5.4
NGC Module Isolation Test
This test isolates the NGC modules to pinpoint equipment failure.
This procedure assumes that the previous power supply voltage test and
equipment isolation test was performed and that no errors were found.
6.5.4.1
Instructions
1)
With power still supplied to the termination panel J1 connector, disconnect the
power supply cable at the termination panel.
2)
Using instructions in, Removing Digital Controller Assembly
remove the digital
controller and disconnect the termination panel to the digital controller cable.
3)
Using instructions in,
remove the analytical
module.
4)
With power still disconnected from the NGC, measure the voltage at the J1
connector screw terminals. Record the value as power supply voltage (open
circuit).
5)
Reconnect the power supply cable at the NGC termination panel J1.
6)
Measure voltage at the termination panel J1 connector screw terminals. Voltage
should be within 0.1 VDC of the power supply voltage (open circuit).
i.e., only 0.1 VDC drop max. between the PS and the NGC.
7)
If the voltage drop is greater than 0.1 V, replace the termination panel using
instructions in,
, and return to step 6. If the voltage
drop is again greater than 0.1 V, call Totalflow technical support, following the
instructions in the Introduction to this manual, Getting Help.
