Preserving Probes, Protecting Pockets

  

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Rugged, reliable, easy to use, easy to read.  Four ways to describe YSI’s handheld multimeters, like the YSI-556. These may be true, though I do have some other descriptors that would make you think I was talking about Kim Kardashian or Paris Hilton: fussy, temperamental, expensive, demanding, fickle, and not to be left out: high maintenance.  Don’t get me wrong, the YSI-556 is way better than the Horiba multimeter that we used to refer to as the “Horrible” during groundwater sampling events, but we realized very quickly with the YSIs, if not properly maintained, they could be relied on...well, about as much as a politician.     

I’ve put together a step by step instruction sheet on how to keep and maintain YSI sensors based on on-site training with a YSI vendor.  

NOTE: These instructions were made specifically for the YSI-556 model. Other models may differ.

Dissolved Oxygen Sensor

1. The sensor is held in by a set screw. Using an allen/hex wrench, unscrew it and take the sensor out.
2. Unscrew the membrane.
3. Remove residual material on the probe using 400 grit damp sandpaper. Use different pieces of sandpaper for the anode (silver) and cathode (gold). Rinse with clean water after sanding, then wipe with a wet paper towel.
4. Fill with an electrolyte solution prior to screwing the membrane back onto the sensor. A small amount of the solution should overflow.  Bubbles will cause artificially low readings.
5. Inspect the plastic cap regularly (every 2-3 weeks) and change if there is a buildup of debris.
6. When reattaching the sensor to the module, make sure that there is no moisture between them. Moisture will cause the sensor to short out.

Conductivity and temperature sensor

1. Remove by inserting the sensor installation tool into one of holes at the base of the sensor and twisting counterclockwise.
2. Wet a cleaning brush with clean water, and insert it into both holes 15-20 times. Twist as you do this.
3. Rinse out each hole with DI water or clean tap water.
4. Blow out the holes with compressed air.
5. Line up the three prongs to reinsert the sensor back into the bulk head. Make sure there is no moisture in between them.

1. Remove by inserting the sensor installation tool into one of holes at the base of the sensor and twisting counterclockwise.
2. Wipe the glass bulb gently with a cotton swab soaked in clean water. Do not use a dry swab; the static electricity can short out the sensor.
3. Remember to wipe the glass bulb very gently. A new pH probe costs around $300.
4. Use a new dental brush to clean underneath the glass bulb.
5. Make sure there is no moisture between the bulk head and sensor before you screw the sensor back in.

• Use regular water, not DI water to keep the sensors moist.
• A YSI-5511 kit is a good thing to have, it includes all the equipment necessary to properly maintain the sensors.

Pictured Left: The contents of a YSI-5511 maintenance kit.

Sensor Installation/Removal Tool
Cleaning Brush
DO port plug
Hex wrench
O-Rings
Set Screw
Tube of O-Ring Lubricant

• Consider getting confidence solution. This is not used to calibrate, but you will be able to see if all your sensors are functioning properly.
• Check out YouTube. YSI has posted a number of videos on YSI maintenance and use.
• Calibration logs - It is important to routinely record the instruments response to calibration standards and/or the confidence solution to help make sure the system response is not degrading (and to show to the visiting EPA official).