GW Instek GDM-398 - Manual (Page 42)

MEASUREMENT OPERATION
40
To use the EF function, connect the Meter as follows:
1. Set the rotary switch to EF and remove the test lead from the input terminals.
2. Place the front part of the housing with the
marking towards the object
being measured.
3. There will be three types of displays:
 LCD displays different size of digits to represent the strength of
detected signal.
 When the LCD displays OL, the buzzer beeps and the red LED blinks.