Impedance, 1 & 2 channels

Question 1

material’s resistance to flow of electrical current (measured in ohms)

Answer 1

Electrode Impedance

Question 1

What is Electride Impedance

Answer 1

Impedance is a material resistance to flow of electrical current
* measured in ohms (Ω)

Question 2

opposition to alternating current flow between one electrode and another (~2 or less kOhms)

Answer 2

Interelectrode Electrical Impedance

Question 3

What is Interelectrode electrical impedance

Answer 3

Opposition to alternating current flow between one electrode and another.

Question 4

___ and ___ absolute electrode impedances contribute to high quality AER recording

Answer 4

Low and balanced absolute electrode impedances contribute to high quality AER recording

Question 5

Low and balanced absolute electrode impedances contribute to high quality AER recording by What?

Answer 5

• limiting internal amplifier noise
• Reduce External electrical interference
• Maintain high common mode rejection

Question 6

what is the desired electrode impedance range?

Answer 6

Desired impedance range: 1–5 kΩ
* Ideal target: 3–5 kΩ
* 0 kOhms is not desirable
* Differences between electrodes should be ≤2 kΩ (small as possible)

Question 7

Impedance must be checked:
when?

Answer 7

• Before the test
• During the test if interference, movement, or switching ears occurs

Question 8

What happens if impedances is too high or unbalanced?

Answer 8

High or unbalanced impedance can:
* Increase noise
* Decrease signal quality
* Cause electrical artifact

A 0 kΩ reading may signal:
* Electrodes too close together
* Short circuit risk

Question 9

Low inter-electrode impedance is very important for ____ ____ to work well.

Answer 9

Low inter-electrode impedance is very important for common mode rejection to work well.

Question 10

“Open” means the impedance is what?

Answer 10

“Open” means the impedance is greater than 80kOhm

Question 11

what is a major determinant of electrode impedance

Answer 11

Major determinant of electrode impedance is the contact between the skin and the electrode

Question 12

what causes “Open” impedance

Answer 12

Causes:
No electrode plugged in
Faulty/broken electrode
Montage mismatch (e.g., 1-channel setup selected for 2-channel)

Question 13

With two channel ABR recordings you can perform

Answer 13

With two channel ABR recordings you can perform both ipsi and contra ear recordings simultaneously

Question 14

One channel recording

Answer 14

• the inputs for channel 2 are not used and should be empty
• No jumper should be connected to the patient cable for one channel recording
• Leaving a jumper connect during one channel will result in noisy data

Question 15

What is the purpose of the 2 channel jumper cable

Answer 15

For two channel recording with a Cz or Fz site, to avoid placing two non-inverting electrodes on a patient, the receptacles are linked by a jumper cable
Jumper has both electrode pin and receptacle