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If your readings are within these values, go on to Step 5.
HRD
GND
N2 Bus Terminal Block
on ASC
NCU
6 3
SFT
GRD
5
SFT
GRD
2
N2(-)
ZBus
REF
N2+ to REF
+2.45 to 2.98 VDC
N2- to REF
+2.06 to 2.54 VDC
N2 +
4 1
N2(+)
N2AREF
N2 -
DMM
N2+ to N2+0.36 to 0.92 VDC
DMM
Note: For best reading, place probe on metal
plate inside terminal, not on screw.
VOLTAGE2
Figure 23: Measuring N2 Voltages at PHX
5.
Before connecting the three N2 Bus wires to the PHX, identify the
correct voltage and polarity of each wire with the DMM. The
voltages should match the following:
N2+ to REF = +2.45 to 2.98 VDC
N2- to REF = +2.06 to 2.54 VDC
REF to earth ground = ≤1.0 VDC/VAC, referenced to earth ground
with 100K ohm resistor across the DMM
If the voltages are not within the above ranges, end-of-line termination
may not be set correctly. Locate and fix the problem.
6.
Connect the N2 Bus wires to the PHX and continue to the next PHX.
Perform Steps 4 and 5 until you have connected each PHX to the
N2 Bus.
These steps comprise the simplest and most thorough N2 Bus test.
3-42 Laboratory Controls––Phoenix Interface