C-2
If the customer has a working sensor, measuring those
voltages is a good reference.
The listed voltages for WHT and BLU are typical.
Voltages outside the ranges specified do not necessari-
ly indicate Electronics Module failure. The voltage
between WHT and BLU should be at least 1.5v.
With the Common probe of the DMM on a BLK sensor
wire, expect the following sensor wire voltages:
Sensor Voltage
Wire (VDC)
WHT +4.50 to +5.50
BLU -0.10 to +0.10
RED +4.75 to +5.50
ORG -4.75 to -5.80
For the entire terminal block, with DMM probe at TB2-3:
Sensor TB2 Voltage
Wire (VDC)
WHT 1 +4.50 to +5.50
BLU 2 -0.10 to +0.10
RED 4 +4.75 to +5.50
ORG 5 -4.75 to -5.80
SHLD 6 0
WHT 7 +4.50 to +5.50
BLU 8 -0.10 to +0.10
BLK 9 0
RED 10 +4.75 to +5.50
ORG 11 -4.75 to -5.80
Voltages for WHT and BLU are typical.
If any voltage is out of range, remove all sensors.
Check the voltages on the pins of the analyzer, which go
through the terminal block. If the voltages are still bad,
see if there are any stray bits of wire that are causing a
short. Make sure that all analyzer pins go through the
terminal block; the ends of all the pins should appear. If
there is nothing apparent to cause an open or short,
remove the Electronics Module from the case. Check
for bent pins. If there are none, the Electronics Module
is probably defective.
With all sensors removed, if all voltages are now in
range, there is probably a bad sensor or a fault in the
sensor wiring. Check the wiring. Connect the sensors
one at a time, to isolate the bad one.
1.4.2 Sensors connected to the Analyzer are not list-
ed as AVAILABLE
The troubleshooting approach is similar to that for NO
SENSORS ARE DETECTED.
Check Sensor signals.
Equipment Required: Digital Multimeter (DMM)
Connection check
• For three or more sensors
See if the good sensors are all connected to one
“main” line, and bad sensors on the other.
Suppose, for example, that there are five sensors in
the system. Four sensors are connected to a
Junction Box, which is in turn connected to the
Analyzer at TB2-1 to TB2-5. The fifth sensor is con-
nected to TB2-7 to TB2-11. If the fifth sensor is list-
ed as AVAILABLE during start-up, then one of its
wires may not be securely connected to TB2.
Note that TB2-1 to TB2-5 is not isolated from TB2-7
to TB2-11. The +5v on the RED at TB2-4, for exam-
ple, should be the same at TB2-10. If not, and there
are no sensors connected, then the Electronics
Module is defective. If the +5v is OK for the Module
alone but out of range with sensors connected, then
there is a fault in the sensor wiring or a bad sensor.
• Good-vs-Bad Check
This is a thorough test for determining if the “bad”
sensor is really bad.
Voltages for the communication points TB2-1/TB2-2
and TB2-7/TB2-8 are typical. Voltages outside the
ranges specified do not necessarily indicate
Electronics Module failure. The voltage between
TB2-1 and TB2-2 and between TB2-7 and TB2-8
should be at least 1.5v.
Remove all sensors. Check the following voltages:
With DMM probe at TB2-3
TB2 Voltage
(VDC)
1 +4.50 to +5.50
2 -0.10 to +0.10
4 +4.75 to +5.50
5 -4.75 to -5.80
60
7 +4.50 to +5.50
8 -0.10 to +0.10
90
10 +4.75 to +5.50
11 -4.75 to -5.80
Power down the Analyzer. Attach the good sensor.
Power up the Analyzer. During the AVAILABLE display,
the Analyzer is waiting for keypad input. There is digital
sensor communication. Check the voltage at the WHT
wire. The voltage should be steady at about +0.07
VDC.
Press keys to accept the sensor. During the Process
Measurement display, check the WHT voltage. It should
vary abruptly, indicating that the Analyzer is communi-
cating with the Sensor.
MODEL 2700 APPENDIX C
TROUBLESHOOTING GUIDE
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