Extech Instruments 7470 Operation Manual page 38

Use the Numeric keys to enter the Audible Alarm level, then press the ENTER key.
The program will provide a sample sound for checking immediately when the ENTER
key is pressed.
Change the Volume again or press the SETUP key to forward to the Smart GFI
selection. Press the EXIT key to return to the operation mode. The program will
store the Volume setting automatically.
4.1.5. Smart GFI
Press the SETUP key to advance the menu to the Smart GFI parameter. The display
will show:
Smart GFI
ENTER to Select
Use the ENTER key to toggle the Smart GFI ON and OFF.
The High Voltage power supply of the instrument is internally referenced to earth
ground. The leakage current measuring circuits monitor only currents that flow
through the Return lead. Therefore, the possibility exists for current to flow directly
from the High Voltage output to earth ground that typically would not be monitored.
GFI is a circuit that monitors the current between the High Voltage output and earth
ground. The GFI's main purpose is to protect the operator from prolonged exposure
to High Voltage in the case of an accidental contact with the High Voltage lead and
earth ground. If the operator accidentally touches the High Voltage lead and earth
ground, the High Voltage will be shut off immediately and the test will be aborted. If
the GFI threshold is exceeded, the display will indicate a GFI Fail.
Smart GFI allows the user to automatically configure the instruments return
configuration. When the Return lead is earth grounded, the GFI circuit is disabled and
the instrument operates in a grounded return mode of operation. Grounded Return
allows the user to perform tests on devices that have their chassis earth grounded by
the test fixture or test environment. The standard configuration of High Withstand
Voltage Tester is a floating return connection that is not directly connected to Earth
ground. The standard configuration allows monitoring of very low-level leakage
current without internal or external stray earth ground leakage currents being measured
and thereby causing errors in the reading. Grounding the return will create some
amount of leakage current that is proportional to the High Voltage output and can cause
small amounts of error depending on the test voltage and physical environment.
Toggle the Smart GFI function or press the SETUP key to forward to the GPIB address
selection. Press the EXIT key to return to the operation mode. The program will
store the Smart GFI setting automatically.
4.1.6. GPIB Address
Only appears if the GPIB option 01 is installed
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= ON or Smart GFI
ENTER to Select
= OFF