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Teledyne Analytical Instruments
20
Thermal Conductivity Analyzer Model 212R
5) Using a screwdriver that has a shaft diameter of 1/8” and a shaft
length of at least 6”, turn the “Reactive” balance adjustment all
the way counterclockwise (CCW) until the potentiometer stop
point is reached. Turn the adjustment back clockwise (CW) 5 full
turns to center the adjustment.
6) Turn the “Resistive” balance adjustment all the way clockwise (CW)
until the potentiometer stop point is reached.
7) Slowly turn the “Resistive” adjustment until the output reaches its
lowest value. If the reading is negative adjust to the most nega-
tive value possible.
8) Turn the “Reactive” balance adjustment slowly CW and CCW to
obtain the lowest possible output value. Again, if the reading is
negative adjust to the most negative value possible.
9) Repeat steps 6) and 7) until the output value is as low as these
adjustments can make it.
10) Detune the instrument by turning the “Resistive” balance adjust
ment ½ turn CW. This will bring the signal out of the baseline
noise, which could otherwise cause non-linear response at the
low concentration end.
NOTE: Due to minute differences between measuring cells
and the electronics in the bridge circuit found in vari-
ous instruments, some analyzers will have to be bal-
anced at a point higher than 10% of scale while others
can be balanced even closer to electrical zero. The
10% of scale recommended in step 6 of the procedure
is an arbitrary starting point. If the bridge circuit can
be easily balanced at this signal level, the procedure
should be repeated at a point even closer to electrical
zero. Conversely, if balance cannot be accomplished
at 10% of scale, the operator will have to select a
higher recorder set point for the procedure. In any
case, the object is to accomplish dynamic balance
with the lowest magnitude of analyzer cutout signal
attainable with the analyzer at Range #1 sensitivity.
6.3 Correct Operation.
If a stable recording is achieved when the analyzer is operated on zero
gas, erratic performance must be attributed to the customers sampling system