There are many indicators of instrument safety: electrical, thermal, chemical and radiological safety: that is, to prevent the occurrence of electric shock accidents accidents.
Leakage current definition: the current that passes through the insulation of the instrument has nothing to do with the function of the instrument.
1. Master the panel layout of the electrical safety tester QA-90
2. Familiarize yourself with the use of QA-9'0 control interface
3. Learn to set the menu of the QA-90 and the function selection
4. Master the insulation resistance composition of the multi-parameter monitor
5. Positive gross connection between the monitor and the QA-90 test line
6. Master the insulation resistance test of the charged parts of the equipment to the shell
7. Master the insulation impedance of the applied parts to the shell
Physiological effects of electric current
◇The human body itself is an electric conductor, and when the human body becomes a part of the electric circuit, there is an electric current passing through the human body, which causes physiological effects.
◇The direct factor that causes physiological effects and injuries to the human body is current rather than voltage!
◇Example: A power supply with 107V voltage and 1A current may be harmless to the human body, while a power supply with 22,Ov voltage and 30A current is enough to kill the human body.
Factors affecting the physiological effects of electric current on the human body
I: the greater the current, the greater the effect, and vice versa, the smaller
The duration of energization: the longer the duration of energization, the more serious the damage to the human body
The higher the frequency, the lower the human body's impedance, and the greater the current flowing into the human body
After a frequency of more than 10,OHz, the effect of the stimulus with the increase in frequency and The stimulation effect is weakened with the increase of frequency. At 1MHz, there will be no stimulation effect, only thermal effect.
◇Current pathways: macro electric shock, micro electric shock and human adaptability
Measures to prevent electric shock
◇Basic principle of electric shock
◇Protection principle of electric circuits
◇Concept of "double protection," additional protection
◇Four kinds of additional protection measures to prevent electric shock measures a circuit to insulate (insulators). Circuit insulation (insuliation)
A. Insulation and housing
B. Equivalent circuit
C. Equivalent circuit of zj
Note: Zi is required to be sufficiently large, generally more than 20M (i.e., just, Ci impedance is greater than 20M) in order to ensure that leakage current is less than lOuA.
Testing to realize
Before the test, to ensure that the bedside AC power supply 220V is connected correctly, multi-parameter simulator for the inner turn-eye power supply, the application of the power switch is turned on, the use of the finished immediately turn off the power.
Pre-test preparation
①Press Ecluipment Classcfication (F6) and select the classification; (Fluorine press MORE (F1);
③Press Test according to (F7) and select the test standard:
④Press Test Type (F6) and select the rapid Press Test Type (F6) to select Rapid or Normal;
⑤ Press Test Mode (F5) and select Manual;
⑥ Press START (F4) to start the test.
Insulation resistance test from live parts of the equipment to the enclosure: Connect one end of the QA-90 to the ground terminal of the instrument under test. The other end and the instrument under test of the fire wire and zero wire connected together, and then insulation resistance measurement of insulation resistance of the application part to the shell: the power plug of the equipment under test into the socket on the front panel of the QA- 90, and then connect the calibration side of the test lead between the shell of the equipment under test and the ENCI_ jack on the front panel of the QA-90, if there is an application part of the part of the corresponding part of the test must be carried out, that is to say, the The patient lead is connected between the device under test and the lead jack on the QA. 90 front panel and then measured.