What does a LOWSIG warning mean on the CL17 Chlorine Analyzer?

Document ID

Document ID TE1896

Published Date

Published Date 03/23/2018
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Question
What does a LOWSIG warning mean on the CL17 Chlorine Analyzer?
Summary
CL17 LOWSIG warning
Answer
LOWSIG is the most common SENSOR WARNING. The resolution is to either (1) clean the colorimeter or (2) replace the colorimeter. The manual provides a  colorimeter cleaning process in the Maintenance Section. A low signal (LOWSIG) warning is indicative of a dirty or failing colorimeter. If you go to Menu> Setup> REF, you should see a value displayed. Any number lower than 2000 will display this warning. Try to clean the colorimeter with the acid solution first.

Clean the colorimeter cell as follows:

1. Press the MENU key, then press the down ARROW key until the MAINT menu appears. Press ENTER.
2. Press the down ARROW key to scroll to the CLEAN option. Press ENTER.
4. Remove the rubber plug on the top of the colorimeter assembly.
5. Remove the magnetic stir bar using a bent steel paper clip as a retrieval tool.
6. Wait until CLEAN flashes on the status line of the display, then put 0.5 ml of the 19.2 N Sulfuric Acid (Catalog Number/Order Code 203832) in the colorimeter and fill the rest with clean water. Take caution as not to spill this solution or overflow onto any parts of the instrumentation as it will cause permanent damage.
Note: Lower normality sulfuric acid will NOT be sufficient for cleaning the colorimeter.
7. Allow the sulfuric acid to stand in the colorimeter for 15 minutes.
8. Insert a wooden or paper cotton-tipped swab* into the opening and move it up and down with a gentle scrubbing action, cleaning the interior surfaces of the colorimeter cell.
9. Clean the stir bar with the cotton swab. Reinstall the stir bar.
10. Replace the rubber plug on the top of the colorimeter assembly.
11. Press the EXIT key to immediately return to normal operation; the instrument will return to normal operation automatically after 60 minutes.
* Do not use a plastic swab when cleaning the colorimeter with sulfuric acid, the acid will dissolve the plastic.

There are three enhanced colorimeter cleaning methods if basic cleaning is not sufficient:
  1. Increase the acid concentration by suctioning out the residual sample water in the colorimeter after putting the CL17 into CLEAN mode. Also, make sure to use at least 2-3 dropper fulls of 19.2 N Sulfuric Acid to guarantee the sample cell is full.
  2. Extend the time the acid stands in the colorimeter. The manual suggests leaving the acid in the colorimeter for 15 minutes. To allow for additional cleaning leave the acid in the sample cell for 45 minutes. Do not exceed 60 minutes because the CL17 will flush the sample cell and returns to normal operation, which prevents you from swabbing the colorimeter while the acid is still inside.
  3. If the sample water contains Manganese or Iron, there is a solution that can clean the stains associated with these elements more effectively than the 19.2 N Sulfuric Acid. A solution of 2 parts household white vinegar and 1 part Hydrogen Peroxide can be used as a substitute for the Sulfuric Acid. Follow the same instructions in the manual however use this solution in place of the acid.
If none of these cleaning methods resolve the LOWSIG warning replace the colorimeter (Product # 6867000). If replacing the colorimeter does not resolve the LOWSIG warning Hach suggests to arrange for service.

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