A6 Bucket Test

Bucket Test

Test to be performed monthly

*Post the results of the test in this spreadsheet.

Before the Bucket Test

1.  Make the EEG solution: pour one scoop of Potassium Chloride into the plastic bucket, then fill it up to the “2” line with water

2.  Place the net in the solution and fully submerge it, agitating it slightly to ensure that all sponges are wet

• Keep the connector dry away from the water at all times

• Have hand towels nearby in case any water drips – it is critical to keep the connector, and cord to the best of your ability, dry at all times.

• Ensure that all electrodes are submerged

3.  Allow the net to soak for 10 minutes

4.  Perform a visual inspection of the EEG net

• Remove all rings, watches, other jewelry that may get caught on the net

• Look specifically for any torn elastomers (rubber cords between electrodes that create net appearance on cap - it's important that any broken cords are caught early!)

• Check for any broken or loose wires

• Flip the net inside out, and inspect the sponges, check that they are all situated with the electrodes within the outer plastic

• Check the sponges for discoloration or to see if any are missing

• Check for any green build up or bent pins on the connector plug

5.  Plug in net. Do not force the connector. If it is not going in smoothly, make sure the toggle switch is pointing left. Insert, then turn toggle to the right to lock the connection

Running the Test

1.  On the mac: Open Net Station Acquisition. Turn the amplifier “on” by toggling the button in the upper left corner

2.  Enter the date as the participant ID

3.  Measure net noise (repeat 3 times): Tools > Net Diagnostics

• In the Net Diagnostics pop up window, press start, then wait for the blue bar at the bottom to load—this is the indicator that the test has run. In the columns on the right side, values will appear for each electrode

• Sort the values on the right side from largest to smallest. In the graph, hover mouse over the peaks in the green box to see any noisy electrodes, if there are any, see "electrode problems" below.

  • • • Note: “bad” net noise values are anything > 1.5. Don’t rely on the graph alone to determine “bad” values, as the left-hand axis changes based on the values obtained through the test. Rely on chart on the right to sort by high val

• Targeting the problematic electrodes, put your hands into the water and squish the sponges of the “bad” electrodes a few times. This will help the sponge be fully saturated with water and improve the net noise values.

  • • • Re-test the net two more times, making note of which electrodes are bad (if any) each time in the EEG Binder

      • Try to improve the net noise values between each test by squishing the problematic electrodes

      • Always measure net noise before impedances

4. Measure impedances: Tools > Show impedances

• Press "Measure Impedances" and in the menu that appears check to see that the electrodes have impedance levels that are <10kΩ (Kohm)

• If any electrodes are above that threshold, select that specific electrode and click “Measure Impedances” and let it run for 5 cycles

5. Record appropriate information from the tests in the EEG binder (make a note of any red electrodes)

• Generally observe the baseline signals of the electrodes: looking to see some activity but overall signal from the channels should be relatively flat. Take note of any especially noisy signals - especially large peaks in the waveform (see electrode problems)

• Adjust the amplitude if necessary to gain a better view

After the Bucket Test

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1.  At the sink pour out the solution, remove the cap and dab it gently on a towel

2.  Place the cap in the bucket under the sink and rinse it until it is submerged

• Dunk the net in and out of the bucket ~10 times, agitating it intermittently

• Pour the water out and repeat the rinsing and dunking process three times

• Carefully rest the cord and connector around the back of your neck during this process to ensure that it stays dry

Electrode Problems

1.  During Net Diagnostics, if any electrodes have signals that are especially noisy locate that electrode on the EEG cap

2.  While submerged under the water in the bucket, repeatedly squeeze the target electrode (to remove air bubbles)

3.  Ensure that the rest of the electrodes in the net are re-submerged

4.  Run “Measure Impedances” again for 5 cycles and observe the signal

• If the problem persists, make a note and notify a grad student postdoc -- the electrode may need to be replaced