Calibration

Question 1

What is the purpose of checking the printer before calibration?

Answer 1

Ensure it has enough paper and ink and is correctly linked to the computer.

Question 2

How do you verify the date and time on the computer?

Answer 2

Open the time in the bottom right corner of the screen.

Question 3

What is the typical storage requirement for a routine EEG with video?

Answer 3

300-400mb.

Question 4

What is the default sampling frequency for EEG acquisition settings?

Answer 4

256Hz.

Question 5

What is the Nyquist Theorem?

Answer 5

It states that to accurately sample a signal, it must be sampled at a rate greater than twice its highest frequency.

Question 6

What should be checked regarding the notch filter during calibration?

Answer 6

Ensure it is functioning by checking if 50Hz interference attenuates from the trace.

Question 7

What does standard BF classification mean for EEG equipment?

Answer 7

It indicates body floating and is for use on the skin only due to the floating isolated output.

Question 8

What is calibration in the context of EEG equipment?

Answer 8

The activity of checking the accuracy of a measuring instrument by comparison with a standard.

Question 9

Why is calibration important for EEG equipment?

Answer 9

It ensures the equipment is performing to an agreed standard, making the EEG waveforms accurate representations of cortical activity.

Question 10

What is the Common Mode Rejection Ratio (CMRR)?

Answer 10

It refers to the ability of the differential amplifier to reject common signals and amplify differential signals.

Question 11

What are the standard settings for commonly used montages in EEG?

Answer 11

• LFF – 0.5Hz
• HFF – 70Hz
• Sensitivity/Gain – 10uV/mm
• Timebase – 30mm/sec

Question 12

What does internal noise in EEG refer to?

Answer 12

The frequency produced by the EEG machine itself, caused by thermal movements of electrons.

Question 13

What is the function of the Low Frequency Filter (LFF)?

Answer 13

It allows signals below a certain frequency to pass while attenuating higher frequencies.

Question 14

How is the time constant (TC) calculated?

Answer 14

TC = Distance (mm) / Time (mm/sec).

Question 15

What should the amplitude of internal noise not exceed?

Answer 15

2uV.

Question 16

What happens to the signal when the High Frequency Filter (HFF) is decreased?

Answer 16

There is a progressive increase in the rounding and attenuation of the peak.

Question 17

What is the purpose of photic stimulation in EEG?

Answer 17

To check the photic stimulator is flashing at the correct frequencies.

Question 18

How can chart speed be checked?

Answer 18

Using a stopwatch, an external signal generator, or inserting 50Hz known interference.

Question 19

What is sensitivity in the context of EEG?

Answer 19

The ratio of the input signal voltage to the output signal deflection produced on the trace.

Question 20

What should be done to check sensitivity?

Answer 20

Induce a square wave and measure deflection at multiple sensitivity values.

Question 21

Fill in the blank: Increasing LFF makes the rate of decay _______.

Answer 21

broader.

Question 22

Fill in the blank: The increase of the LFF makes the rate of decay _______.

Answer 22

steeper.

Question 23

What is a filter in EEG, and why is it necessary?

Answer 23

A filter is a device that allows certain frequencies to pass while attenuating others, necessary for isolating specific signals.

Question 24

What is the significance of linearity in EEG calibration?

Answer 24

It ensures that the machine responds accurately to a range of input signals.

Question 25

True or False: The CMRR should ideally be at a low setting.

Answer 25

False.

Question 26

What are steps of internal calibration 12

Answer 26

Check to see if cables are damaged and frayed, tuck away

Check if connections are secure and connected to main power supply

Check health and safety sticker and if equipment is classified as standard BF

Printer enough paper and working

Date and time

Storage

Default settings- check sampling frequency (256 Hz) and all headbox electrodes are turned ON

Check LFF, HFF, sensitivity and time base

Stimulate 50 Hz turn notch filter on

Check photic stimulation count flashes

Check chat speed

Sensitivity on square wave