Coarse Adjustment
The coarse adjustment is only necessary if one of the two following cases is found during Std. Control
adjustment.
1. Both the Std. Control trimmer (VR-2), and the Coarse Span trimmer (VR-3), are at maximum
(both fully clockwise), and the analyzer cannot be calibrated high enough to match the chlorine
residual test.
2. Both the Std. Control trimmer (VR-2), and the Coarse Span trimmer (VR-3), are close to minimum
(both almost fully counterclockwise), and the analyzer Std. Control is too sensitive to match the
chlorine residual.
To adjust the input range, it is necessary to return the Std. Control and Coarse Span trimmers (VR-2
and VR-3) to normal starting positions.
1. Turn both VR-2 and VR-3 fully counterclockwise to their “clicking” endpoints (or 30 full turns).
2. Adjust VR-2, 15 turns clockwise.
3. Adjust VR-3, 10 turns clockwise.
Follow the directions for setting ZERO Control on page 26, but use the following adjustment for span
(Std. control), instead of the normal procedure. See
Figure 37
(page 29) for trimmer locations.
After determining the actual chlorine residual with an accurate chlorine residual test instrument, make
the adjustment on the Input Range trimmer (VR-4), instead of the Std. Control, but set it higher than
necessary to give the input potential some working range. This will leave room to go up, if necessary,
on any future calibration adjustments. Counterclockwise = up. Clockwise = down.
Example
: if the new analyzer range is 0-1.00 ppm and the actual residual test shows 0.70 ppm, then
set the Input Range trimmer VR-4 to read 1.00 ppm. Then make the final adjustment to match the
actual residual (ex: 0.70 ppm) on the Coarse Span adjustment VR-3. Fine adjustments, if necessary,
can now be made on the Std. Control trimmer. The analyzer is now ready for use. Future calibration
adjustments can be done as per normal “Setting Std. Control and Setting Zero Control” directions.
In some rare cases of low range calibration (usually 0-2 ppm or below) in conjunction with very high
sample pH, total alkalinity, calcium hardness, or a combination of these, there may not be enough
cell potential to get a high enough standard calibration. In these cases, VR-3 should be carefully
desoldered and removed from the amplifier board. This should not be attempted, however, until all
other procedures have been exhausted. In these cases, factory consultation is recommended.
In high total alkalinity samples there may still not be enough sensitivity to reach the desired set-point
even after the VR3 trimmer is removed. A modification to existing amplifier boards is available to
resolve this problem. New chlorine residual analyzers with 0-1 ppm operating range or less include
this Low Range Sensitivity option (
Figure 36
, below).
Calibration
27
FX-1000p
