Electronics

Question 1

What is the maximum leakage current allowed at the chassis when the ground wire is open?

Answer 1

300 microamperes

Question 2

Maximum leakage current allowed to the electrodes?

Answer 2

10 microamperes

Question 3

Leakage into the amplifier, from the patient leads, must be…

Answer 3

10uA unattached, or 20uA with patient leads attached

Question 4

OR grounding must be…

Answer 4

across 1Kohm at 60Hz, less than 20mV

Question 5

Macroshock

Answer 5

Large deadly current such as “finger in an outlet”

Question 6

Microshock

Answer 6

Smaller current, but still lethal due to direct application to heart

Question 7

Ground loops

Answer 7

Occurs when more than one earth ground exists and a voltage difference exists across them

Current can potentially flow from one ground to the other (across the pt) forming a loop

Question 8

What is a line isolation monitor?

Answer 8

Device that measures combined leakage current to ground from all devices in the OR and alarms if it detects excess current

Question 9

What is an ammeter?

Answer 9

Measures current

Question 10

What is an ohmeter?

Answer 10

Measures resistance

Question 11

What is a voltmeter?

Answer 11

Measures voltage

Question 12

What is a safety analyzer?

Answer 12

Device used by biomed to perform electrical testing

Question 13

What do the colors in a power cord mean?

Answer 13

Green=ground
Black=hot
White=neutral

Question 14

Silver-silver chloride electrodes

Answer 14

surface

Question 15

Gold electrodes

Answer 15

long time constant, low drift

Question 16

Platinum electrodes

Answer 16

non-reactive, non-toxic even when current is applied

Question 17

Stainless steel electrodes

Answer 17

short time constant, has drift

Question 18

Silver electrodes

Answer 18

toxic to brain tissue

Question 19

Tin/lead/copper electrodes

Answer 19

All reactive to biochemistry with toxic by-products!

Question 20

What is Coulomb’s Law?

Answer 20

The force exerted between two charges is inversely proportional to the square of the distance between them

F=1/(distance)^2

Question 21

What is Ohm’s law?

Answer 21

Voltage (V) is equal to the product of the current (I) and the resistance (R)

V=IR

Question 22

How do you calculate the total resistance in series?

Answer 22

Rtotal=R1+R2+R3+…

Question 23

How do you calculate the total resistance in parallel?

Answer 23

Rtotal=1/R1+1/R2+…

Question 24

What is the gain of a differential amplifier?

Answer 24

the voltage out divided by the voltage in

Question 25

What is the required CMRR based on the guidelines?

Answer 25

10,000:1 or 80dB

Question 26

What should the input impedance be based on the guidelines?

Answer 26

Guidelines require greater than or equal to 100 MOhms

Question 27

What should the bin width be based on the guidelines?

Answer 27

<20uS/data point (sampling rate >50,000)

Question 28

Nyquist frequency

Answer 28

2x the fastest frequency in a recorded signal

Question 29

What is vertical resolution and what do the guidelines say?

Answer 29

The number of available discrete points (vertical resolution) is determined by the number of bits the system operates with, which is 2^N where N is the number of bits

guidelines require a minimum of 8 bits

Question 30

What equation do you use to calculate SNR after averaging?

Answer 30

SNRf=SNRi(sqrtN) where N is the number of averages

Question 31

Common Mode Rejection

Answer 31

The characteristic of a differential amplifier that allows it to cancel out signals that are common to both inputs