GE Medical Systems Solar 9500 Service Manual page 112

Ground Continuity Test
Impedance of Protective Earth Connection
6-12
Maintenance: Electrical Safety Tests
Completion of this test is checked by the following steps:
1. Disconnect the device under test from the power outlet.
2. Connect the negative(-) lead of the DMM to the protective earth
terminal (ground pin in power inlet connector) or the protective earth
pin in the Mains plug (ground pin in power cord). Refer to the US
120Vac power cord figure above.
3. Set the DMM to the milliohm (m Ω ) range.
4. Connect the positive (+) lead of the DMM to all exposed metal
surfaces on the device under test. If the metal surfaces are anodized
or painted scrape off a small area in a inconspicuous place for the
probe to make contact with the metal.
5. Resistance must read:
‹
0.1 ohm or less without power cord
‹
0.2 ohms or less with power cord
This test unlike a ground continuity test will also stress the ground
system by using special ground bond testers.
This test normally is only required as a manufacturing production test to
receive safety agency compliance (i.e. IEC601-1).
Some country agency's do require this test after field equipment repairs
(i.e. Germany's DIN VDE 0751 standards).
Consult your country/local safety agency if in question.
Compliance is checked by the following steps:
1. A current not less than 10A and not exceeding 25A from a current
source with a frequency of 50 or 60 Hz with a no-load voltage not
exceeding 6 V is passed for at least 5 s through the protective earth
terminal or the protective earth pin in the mains plug and each
accessible metal part which could become live in case of failure in
basic insulation.
2. The voltage drop between the parts described is measured and the
impedance determined from the current and voltage drop. It shall not
exceed the values indicated.
For equipment without a power supply cord the impedance between the
protective earth terminal and any accessible metal part which is
protectively earthed shall not exceed 0.1 ohms
For equipment with a power supply cord the impedance between the
protective earth pin in the mains plug and any accessible metal part
which is protectively earthed shall not exceed 0.2 ohms.
When taking this measurement, move the unit's power cord around.
There should be no fluctuations in resistance.
Solar 9500 Information Monitor
2001085-061
Revision A