Hach SP-51 Manual Básico Del Usuario página 22

Cause
If the flow is too low, the
sample cell does not flush
completely all the color out
of the colorimeter. This
causes a zero reading. If
the flow is too high, some of
the water will bypass the
pinch block and cause the
color to be diluted.
The sample line is pinched
off in the pinch block.
No stir bar is installed or
more than one stir bar is
installed.
The instrument does not
receive any buffer or
indicator solution.
The chemistry does not
operate correctly.
The instrument does not
operate correctly.
22 English
Solution
Make sure to set the flow rate to 200 mL/minute.
• Pull the sample line from the colorimeter. Water that is already in
the line could leak out. Examine and adjust the flow rate when a
steady water stream comes out while the line is pinched. Set the
flow rate to 200 mL/minute.
• Make sure that the pressure plate of the pinch block is not
overtightened.
• Examine the back of the pinch blocks and make sure that they do
not have grooves.
• Make sure that a stir bar is installed.
• Use a paper clip to retrieve the stir bar from the colorimeter and
make sure that multiple stir bars are not installed.
• If the stir bar does not operate, mix the sample manually after the
reagents have been added. Use the end of a wooden Q-tip and
mix the reagents approximately for 10 seconds. If the instrument
gets a reading, the mixing is not sufficient. Replace the stir coil.
Additional information is available on the manufacturer's website.
Remove the two reagent lines from the Y connector. Only one drop
of reagent comes out per cycle. If no reagent comes out, examine
the pressure plate. Make sure that the pinch block is not
overtightened and the reagent lines are not pinched. Examine the
back of the pinch block for grooves. Replace the pinch block if
necessary.
Mix 1-mL of each reagent and 80-mL of sample. A color change
must show. If no color change shows, replace the reagents.
Pinch the sample inlet line to stop the sample flow. The next cycle
reads soft. If it does not read soft, examine the LED if it shows an
orange light. Examine the photocell and clean if necessary. After this
cycle, the instrument reads hard again.