New! ppb DO Sensor Maintenance and Calibration

• Unscrew the membrane cap that holds the membrane module
• Rinse the old membrane module and cap with deionized water.
• Remove the o-ring and shim from the oring groove
• Inspect the sensor tip and coils of the sensor. Should be bright and not tarnished. (If tarnished see sensor cleaning section below)
• Place the new membrane module in the membrane cap with the membrane facing down
• While holding the sensor upside down (tip facing upwards), install the shim, followed by the o-ring into the o-ring groove
• Place the membrane module inside the membrane cap
• Fill the center cavity with fill solution so the liquid is about 1/8″ (3.175mm) over the membrane module
• While holding the sensor with the tip facing down, tilt the sensor to approximately 60° with the flat facing up, refer to Figure 2
• Slowly screw the membrane cap back onto the sensor (you should see liquid escaping through the “flat”)

An instructional video of the charging procedure can be seen here:

Cleaning the Sensor

Recovery of a failing D.O. sensor can sometimes be achieved by cleaning using, D.O. sensor cleaning solution (P/N A1100194)
Caution: The cleaning solution is acidic

• • Remove the membrane cap exposing the coils and tip
  • Immerse in cleaning solution for 5 minutes, refer to Figure 3
  • 
  • Remove the sensor and rinse it in deionized water; use a soft cloth to wipe in the same direction as the coils are wound
  • Repeat until coils and tip look clean and have a gray shine, refer to Figure 4
  • If the tip of the sensor has become tarnished, as seen in Figure 5 use a 400 to 600 grit piece of sandpaper and your finger to apply even pressure to the tip and lightly move the sandpaper back and forth to remove the tarnish
  • Rinse with deionized water

Inserting the Sensor into the Flow Cell

Ensure the flow cell is vented to an atmospheric drain line so as not to create a vacuum which would cause the membrane to stretch. Best practice is to have the flow cell outlet at atmospheric pressure.

Refer to Figure 6 for flow cell component identification

• Inspect the inside of the flow cell for any foreign matter; wipe out if necessary. It should appear clean, shiny, and bright
• Insert the assembled sensor through the nut and sealing PTFE ferrule
• Press slowly all the way down until the sensor firmly reaches the stop
• By hand, tighten the nut firmly to get a good seal. This should be sufficient for 5 to 10 psi pressure. Give the nut an extra quarter turn beyond finger tight to keep out tramp oxygen

NOTE: The flow cell is not intended for use at high pressure. The sealing PTFE ferrule is not designed to hold against high pressure.

Removing the Sensor from the Flow Cell

Removal of the sensor from a sealed flow cell will create a vacuum and stretch the thin sensing membrane. Stretching the membrane can cause loss of contact with the sensor tip causing slow response, high and/or erratic readings.

To remove the sensor from the flow cell:

• Stop the sample flow to the dissolved oxygen sensor and vent the sample drain line to atmosphere
• Unscrew the nut and gently remove the dissolved oxygen sensor
• When the dissolved oxygen sensor has been fully removed, using a soft lint free laboratory cloth, blot the tip of the sensor dry. Then proceed to calibrate the sensor or perform maintenance as necessary

Calibrating the Sensor

For optimal results the entire calibration procedure should be performed within 100 seconds.

The calibration frequency depends on the application and the use of the analyzer. In permanent installations for continuous online measurement (model 865-25) of clean water, calibrations can be done less frequently. In portable continuous on-line measurement (model 869-21 or 869-22), calibrations may need to be done more frequently due to intermittent use and varying sample conditions.

Typically a calibration should be done at least once every three to six months. After replacing the membrane module, it is best practice to allow the sensor 12 – 24 hours to condition itself in a low oxygen environment before proceeding with a calibration. If the sensor is being used for the first time, it is best practice to allow the sensor 24 – 48 hours to condition itself in a low oxygen environment before proceeding with a calibration.

• Remove the sensor from the flow cell as described above
• Place the sensor approximately 1 inch (25 mm) over a beaker of tap water
• Allow reading to stabilize, should be around 8000 ppb (8.00 ppm)
• Press the button on the analyzer and wait for the display to stop flashing
• Once the display has stopped flashing, note the efficiency of the sensor, it should be between 75 – 125%
• An efficiency outside of this range means the sensor requires maintenance, or replacement
• Insert the sensor back in the flow cell, as described above, and restore flow
• Increase the flow rate to the flow cell (200 – 300 mL/min) to purge any air bubbles that could be trapped
• Allow the higher flow rate to run for 1 – 5 minutes. (Helpful tip: Turning the inlet valve on and off a few times can help to release
  any air bubbles)
• Reduce the flow rate to 50 – 200 mL/min

An instructional video of the calibration procedure can be seen here:

Sample Interruption / Shutdown
If no sample flow is expected for less than 72 hours, but will have low ppb sample in the flow cell, the instrument should be left on. During this time the measurement should be neglected or the analyzer should be put into standby. If no sample flow is expected for more than 72 hours, the following shutdown procedure should be performed. This procedure will prevent possible build-up of oxidation products in the sensor and flow cell.

1. Leave the analyzer power on.
2. Turn off sample flow prior to the flow cell inlet.
3. Close the drain valve from flow cell to prevent oxygen from entering.
4. Keep flow cell full of low ppb dissolved oxygen water or zero D.O. solution. Since the sensor consumes small quantities of dissolved oxygen, it will store for months in a sealed flow cell if the power is on.

If it is necessary to power off the analyzer for an extended period of time, there are three ways this can be done.

1. Disassemble and dry out the sensor.

• Remove and disassemble the sensor over a drain while it is still wired to the analyzer
• Rinse the tip and coils of the sensor with pure water and wipe dry to remove any trace of internal fill solution
• Using a soft lint free laboratory cloth, wipe the lead coils in the same direction as the coils are wound, to a bright condition. (Use the analyzer display reading to indicate the sensor is clean when it drops to 0.00 to 0.05 ppb.) Refer to Figure 4, for what the tip should look like
• Turn the power off to the analyzer. A disassembled sensor stored in a clean dry container can keep for years

2. For model 865-25, short the sensor leads

• Turn off sample flow prior to the flow cell inlet
• Close the drain valve from flow cell to prevent oxygen from entering flow cell
• Keep flow cell full of low ppb dissolved oxygen water
• Turn the power off to the analyzer
• Unscrew the D.O. positive lead (black & orange) and D.O. negative lead (braid) from the analyzer and short them together

3. For model 869-21 or 869-22

• Turn off sample flow prior to the flow cell inlet
• Close the drain valve from flow cell to prevent oxygen from entering flow cell
• Keep flow cell full of low ppb dissolved oxygen water
• Turn the power off to the analyzer, thisalso shorts the D.O. positive lead and D.O. negative lead.

Note: A new membrane module and fresh fill solution should be used when the sensor is put back into service.
IC Controls can perform the annual maintenance and calibration of your portable analyzers. Contact us about this service

450 Richardson Road, Orangeville, Ontario
Canada L9W 4W8
Phone (519) 941-8161
Toll Free (800) 265-9161
FAX (519) 941-8164
E-mail service@iccontrols.com
Web Site www.iccontrols.com