Lecture 1 Flashcards
Requirements for a circuit
Closed Conducting Path and Energy Source
Magnitude of current is a function of what?
Vi, R tissues, and contact interference
Impedance of dry skin
100,000-300,000 ohms/cm2
Impedance of wet skin
1000-3000 ohms/cm2
Biological effects of current are a function of what?
frequency, magnitude, duration, individual size, type of contact
Let go current
5-20 mA
Threshold of perception
min 0.5 mA (0.083 mA with gel)
Severe Burns
greater than 10 amps
Current thresholds increase with what?
body mass
Macro shock occurs when?
current is applied at two points on the surface of the body
safety limit of macroshock
5 mA
Microshock occurs when?
when current is applied directly to the heart
Safety limit of microshock
10 microA
R patient
Rc1+Rb+Rc2
Leakage Current is?
Current flow between adjacent isolated conductors at different potentials
GFCI
Ground Fault Circuit Interrupt
Chassis leakage for device not intended for patient contact
500 microA
Chassis leakage for device with non-isolated patient leads
100 microA
Chassis leakage for device with isolated patient leads
100 microA
Patient lead leakage for device with non-isolated patient leads
50 microA
Patient lead leakage for device with isolated patient leads
10 microA
resistance between ground pin of plug and equipment and exposed metal objects
less than 0.15 ohms
leakage current should be:
less than 10 to 500 microA
