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RAPIDPULSEDISSOLVEDOXYGENTROUBLESHOOTING

The Rapid Pulse DO sensor used in many 6-Series instruments can be quickly tested when a problem is

suspected. The three keys to proper operation are a good charge, good gain, and a successful probe

warm-up test. When a problem is suspected you must determine if it is the probe, the sonde, or both. The

steps below will take you through the actions necessary to determine the cause of the problem.

HIGH DO CHARGE (ACCEPTABLE RANGE 25 TO 75)

The first step is to isolate the problem. Remove the DO probe from the sonde, dry the port with a

Kimwipe, and confirm that the charge drops to a number that is in between -0.8 to +1.2. This number

can fluctuate with the typical value being 0.2. A charge number greater than 1.2 would indicate that the

DO port is contaminated and there is conductivity between the pins or that the circuit board is

malfunctioning. Usually connector contamination is the cause. See the cleaning instructions at the end of

this document for corrective action.

If the DO charge measured on the sonde (sensor removed) is within the acceptable range, then the

problem is in the probe. Remove the electrolyte from the sensor and rinse the electrolyte well with DI

water and dry with a Kimwipe. Now reinstall the sensor and re-test. If the charge remains outside the

-0.8 to 1.2 range, then the probe has internal leakage or contamination. You can try soaking the probe

per the cleaning instructions. If this is not successful and reconditioning with the 6035 Reconditioning

Kit is not successful, then the probe must be replaced.

DO WARM-UP FAILURE

The Rapid Pulse DO sensor, like other Clark DO probes, must warm up correctly for proper operation.

Failure of the probe to pass the warm-up test is grounds for probe rejection. When conducting the high

to low output test remember that the RS-232 Auto-Sleep function found in the sonde’s Advanced Menu

must be enabled. Also remember that the first two sonde readings taken at a four-second discrete sample

rate can be discounted. The first two warm-up samples can be erratic when the circuitry is first turned on

after a 60 second idle period.

Examples:

Good Test DO in % -44.0 104.4 99.2 97.1 95.3 94.4 93.0 92.9 92.8

Bad Test DO in %- -99.9 -99.9 30.9 49.2 54.9 57.5 59.7 61.2 62.5 65.7

The first step in isolating the cause of a bad DO warm-up is to test the sonde without the DO probe

installed. With the probe removed the DO charge should be between -0.8 and +1.2. If the charge is

greater, then clean both the probe and sonde bulkhead connector per the port cleaning instructions.

After cleaning, retest the sonde and probe after running the DO probe for 15 minutes in discrete mode.

Let the sonde sit idle for at least 60 seconds before beginning the high to low warm-up test. If you are

unsuccessful with the cleaning procedure and the probe still fails the DO warm-up test, then the probe

must be rejected.

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