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CE > topic 4 > Flashcards

topic 4 Flashcards

1
Q

What is an anti-surge plug?

A

an anti surge plug has a varistor between live and neutral

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2
Q

What is a varistor?

A

varistor is used to protect equipment against excessive transient voltages. by blocking current from sensitve components.

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3
Q

What is macroshock?

A

currents that spread throughout the body

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4
Q

What is microshock?

A

all current flows through the heart

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5
Q

What are the effects of 50hz ac current on adults?

A 
<1 mA - imperceptible/tingling
>1 mA - mild painful sensation
>10 mA - unable to release grip
>20 mA - breathing stops
>75 mA - ventricular fibrillation
>1 A - paralyses the heart, burning of tissues
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6
Q

What are the factors that affect body’s susceptibility to shock?

A
  1. gender
  2. duration
  3. body weight
  4. points of entry
  5. frequency
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7
Q

What is capacitive leakage current?

A

Capacitive leakage current results from capacitance between two wires or between a wire and a metal chasis.

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8
Q

What is resistive leakage current?

A

Resistance leakage current comes from the lack of resistance of the insulation surrounding the power wires.

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9
Q

How is electricity distributed?

A

Transmission: High voltage enters the building via underground cable.

Substation: The secondary of a stepdown transformer develops 240V. This secondary has a grounded centre tap to provide two 120V circuits.

Domestic power supply: Ordinary wall receptacles and lighting are obtained from either one of the ungrounded hot transformer terminals and the neutral grounded centre tap.

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10
Q

What does line isolation monitor do?

A

It measures the total possible resistive and capacitive leakage current.

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11
Q

What to do when line isolation monitor’s alarm go off?

A

unplug one equipment at a time until alarm stop sounding to indentify faulty equipment.

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12
Q

What is ground fault circuit interrupter (GFCI)?

A

The GFCI acts like a circuit breaker when it senses an inequality of current between the hot and neutral wires. It shuts off the power supply within 15-100ms.

It is typically used in wet locations.

It is not used in patient care to prevent loss of power to life support.

senses current as small as 6mA

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13
Q

What are the 10 basic areas of safety testing in the IEC60601.

A
  1. Earth Leakage
  2. Enclosure leakage
  3. applied part leakage
  4. Chassis ground resistance
  5. dielectric withstand
  6. Residual voltage
  7. Accessible parts voltage
  8. Retained energy
  9. Current draw
  10. power consumption
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14
Q

What are the 3 types of applied part leakage?

A
  1. Patient leakage current
  2. Patient auxiliary current
  3. lead isolation current
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15
Q

What is patient leakage current?

A

current between applied part and protective earth

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16
Q

What is patient auxiliary current?

A

current between applied part and other appled parts

17
Q

What is lead isolation current?

A

current flow between iolated AC voltage applied between selected applied parts and earth.

18
Q

What is chasis ground resistance?

A

This test measures the power cord resistance and ensures that the chasis is connected to earth pin of socket.

can only test on 3 wire power cords.

19
Q

What is dielectric withstand?

A

High voltage is applied to insulated parts for a specified time, to make sure that the insulation can withstand high voltage.

20
Q

What is residual voltage?

A

test voltage one second after plug is disconnected.

voltage must be less than 60V. and if 60V is exceeded energy must be less than 2mJ.

21
Q

What accessible parts voltage?

A

voltage present in doors.

voltage between accessible parts and ground must not exceed 25VAC or 60VDC.

22
Q

What is retained energy?

A

When accessible parts voltage is more than 25VAC or 60VDC. Check that energy is less than 2mJ.

23
Q

What is current draw?

A

current draw of equipment is withing 10-25% of the rating of the equipment. test measure current from power cord.

24
Q

What is power consumption?

A

power that is consumed by the product must not be more than 10-15% of rating.

adjust equipment to max power to measure max power.

CE (6 decks)

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