Hach SP-510 Manuel D'utilisation page 22

10.1 Troubleshooting for a hard reading
When the red LED is on continuously and the instrument measures hard water, do the steps that
follow.
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.