Emerson Process Management 3000 - Manual (Page 120)

Instruction Manual
Appendix A Rev. 3.8
July 2002
A-22 Appendices Rosemount Analytical Inc. A Division of Emerson Process Management
World Class 3000
terminal strip could act as additional ther-
mocouple junctions. This could produce a
voltage that would affect the thermocouple
output signal.
Do not bend wires closer than 1/4 inch
(6.4 mm) from end of ceramic rod. Dress
wires so they do not touch sides of probe
junction box.
l. Slide assembled probe junction box and in-
ner probe assembly into probe tube. To
align calibration gas tube with correspond-
ing hole in backplate (A, B, Figure A-1), in-
sert scriber through hole in backplate and
into calibration gas tube. Secure with
screws. Reinstall hoses and probe junction
box cover.
m. Power up system. Monitor thermocouple
output. It should stabilize at set point mV
±0.2 mV. Recalibrate probe per Instruction
Bulletin applicable to your electronics
package.
A-14 REPLACEMENT OF HEATER, V-STRUT
AND BACKPLATE ASSEMBLY (INNER
PROBE ASSEMBLY; INCLUDES CONTACT
AND THERMOCOUPLE ASSEMBLY)
Use heat resistant gloves and clothing
when removing probe junction box
and inner probe assembly. Do not at-
tempt to work on these components
until they have cooled to room tem-
perature. Probe components can be as
hot as 800° (427°C). This can cause
severe burns.
Disconnect and lock out power before
working on any electrical components.
There is voltage up to 115 Vac.
NOTE
This replacement may be done without
removing the probe from the duct.
a. Disconnect and lock out power to electron-
ics. Using heat resistant gloves and cloth-
ing, remove probe cover. Squeezing tabs
on hose clamps and remove hoses from
probe junction box, Figure A-21. Remove
four screws and lockwashers (7, 10, Figure
A-24) that hold probe junction box and inner
probe assembly to probe tube. Pull probe
junction box and inner probe assembly free
from probe tube. Set on bench and allow to
cool to room temperature.
b. Disconnect cell extension wire (orange),
thermocouple wire (red alumel), and ther-
mocouple wire (yellow chromel) by cutting
bomb tail connections from the terminal
strip, Figure A-18.
c. Remove two screws, lockwashers, and flat
washers that connect probe junction box to
inner probe assembly. Remove and discard
inner probe assembly (heater, V-strut, and
backplate assembly). Replace with new in-
ner probe assembly. Reinstall screws, lock-
washers and flat washers.
d. Connect color coded wires to proper termi-
nals as shown in Figure A-18. Rosemount
recommends connecting the thermocouple
wires directly to the terminal strip. This is
because the junction of different metals at
the wires and lugs and at the lugs and the
terminal strip could act as additional ther-
mocouple junctions. This could produce a
voltage that would affect the thermocouple
output signal.
Do not bend wires closer than 1/4 inch
(6.4 mm) from end of ceramic rod. Dress
wires so they do not touch sides of probe
junction box.