Dilutor; Pump Test - Hach QC8500 Series 2 User Manual

Troubleshooting

6.10 Dilutor

6.11 Pump test

1 Revolving index mark
2 Front of pump
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To test the accuracy of the dilutor, run five manually-diluted and five autodiluted
standards. Compare the results to determine if the problem resides in the dilutor
or elsewhere.
Run a dye test. Use the dilutor to make a series of standards from the stock Universal
dye. Use any manifold. Make sure the concentrations entered into the Sample tab
correspond to the dilutions being performed. Make sure the filter wavelength is 480 to
660 nm and the sample loop is 20 to 25 cm. Also make sure the calibration curve
obtained is linear and the residuals is less than 1 percent.
If the dilutor leaks, contact the manufacturer to have it repaired.
Note: Make sure the high standard peak amplitude is less than 5 V. If it is higher, dilute the stock
Universal Dye 1:2 with deionized water. Otherwise, the calibration will not be linear. Make sure the
wavelength of the filter used is less than 660 nm. An 880 nm filter will not produce peaks.
If the pump is not running at the proper speed, determine if a calibration is needed:
1. Use an accurate watch or chronometer to measure the time the pump takes to make
ten revolutions.
2. Remove all pump cartridges from the pump. Look for the index marks as shown in
Figure 64. Index marks allow the pump revolutions to be counted. Manually move the
rollers in order to find the revolving index mark on the roller mounting. If either mark
has faded away, make new index marks with a marker.
1
Figure 64 Index marks—angled top view of pump
3. Clamp down a new green-green pump tube. Make sure the tension lever is set
correctly at the 12 o'clock (vertical) position.
2 3
3 Stationary index mark