Hach SP-510 Basic User Manual page 22

Problem
The HARD LED is flashing.
The SOFT LED is flashing
continuously for more than
5 minutes after the power is set
to on.
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.
22 English
Possible cause
The instrument could not
save the calibration
information.
The instrument could not
save the disabled alarm
status.
The optical path has a
blockage or the optical
switch does not work.
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.
Solution
Contact technical support.
• Let the instrument complete the
cycle.
• Make sure that the motor
operates.
• Set the power to off and then to on
and wait for 5 minutes.
• Contact technical support.