Great Lakes Instruments 692P, Руководство пользователя

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PART SIX - SERVICE AND MAINTENANCE SECTION 2 - TROUBLESHOOTING
Model 692P Rev. 9-898 -54-
Checking Instrument 1. Disconnect sensor or combination electrode wires from
the instrument. Simulate the pH and temperature inputs
by connecting:
A. A 1%, 1/4 watt, 301 ohm resistor across the yellow
and black terminals on TB2 (Figure 3-2).
B. A jumper across the green and red terminals on TB2.
C. A jumper across the green and black terminals on
TB2.
2. If a GLI 5-wire Differential Technique sensor was used,
make sure the following switches are at the listed set-
tings. If a combination electrode was used, place these
switches to these settings:
Control Setting
SWITCH 3 (Figure 3-2) .......... DIFF (off/right) position
TEMP. COMP. switch............. THERM position
(Figure 3-2)
3. In the pH measurement mode, the display should indi-
cate approximately “7 pH.”
4. Press DISP VAR key once to display temperature. The
readout should be approximately “25
°
C” or “77
°
F.”
5. Remove jumper from green and red terminals on TB2. In
its place, connect a millivolt generator (+) lead to red
terminal and (-) lead to green terminal and provide 175
mV DC.
6. Press DISP VAR key three times to return display to pH
measurement mode. The readout should be approxi-
mately “4 pH.”
If these checks are accomplished, the instrument is operat-
ing properly, but the sensor or interconnect cable (if
used) may be inoperative. Proceed with step 7. If these
readings cannot be attained, the instrument is probably
inoperative.
7. Remove the 301 ohm resistor and millivolt generator
from TB2. Reconnect the sensor directly to the instru-
ment (purposely excluding interconnect cable, if used).
For a combination electrode, place switches in appropri-
ate positions (refer to Part Two, Section 3.2).