XI] Electrical safety

Question 1

Who is concerned for protection for technical safety of medical device ?

Answer 1

Patients and operators

Question 2

How much Amperes for let go current ?

Answer 2

10mA-100mA

Question 3

How much amperes for begining of physical discomfort ?

Answer 3

100mA to 100A

Question 4

what is the relashionship between the percieved mA and frequency of the excitation ?

Answer 4

Low treshold for low frequency

Question 5

Name risks factors for the heart by electrical current

Answer 5

route in the body
frequency of the applied current
duration
moment within the cardiac excitation (vulnerable Tphase)
tritial state of the heart

Question 6

what are the subcategorization fo laws for patient and operator protection ?

Answer 6

general instruction
special instruction for operators
special instructions for manufacturers
persecution and penalty of criminal facts
public authorities, tsting centern authorized experts

Question 7

Cite the main ressources for device safety

Answer 7

MPG
MDD
AIMD
IEC/EN 60601
EN ISO 14971
DIN EN ISO 13485

Question 8

Cite the 3 main axes for protection against electronic shock

Answer 8

B(ody)
B(ody) F(loating)
C(ardiac) F(loating)

Question 9

What current for housing leakage current without contact to patient ?

Answer 9

500

Question 10

What current for housing leakage current with external contact to patient ?

Answer 10

100

Question 11

What current for housing leakage current with direct contact to heart ?

Answer 11

100

Question 12

What current for patient leakage current in µA when external patient contact ?

Answer 12

50

Question 13

What current for patient leakage current in µA with direct contact to the heart ?

Answer 13

10

Question 14

what are the 3 protection classes ?

Answer 14

Techniques with earth conductor
without earth conductor
safety extralow voltage

Question 15

Cite the type of first failure

Answer 15

Interruption of the earth conductor
interruption of a conductor
occurence of a voltage at the signal in/output
Occurence of an external Voltage at signal in/output
Malfunctioning of a mechanical or electrical component
malfunctioning of a t° restrincting component

Question 16

How to test for protection class I ?

Answer 16

test current 10A-25A for 5s

low resistive connection between tangible parts of the housing

Question 17

Site main ways to protect (I,II and III as well)

Answer 17

1Adding a earth conductor
2measurement circuit of the current given to a person
3we have to ensure that in case of first failure, we are still over the limit of 1000 micrOhms
4protective insulation if not earth conductor. Insulator around voltage caring parts.
5-low voltage - you minimize risk to do something wring. U use special connectors.
6- Decoupling patient and application parts