Instrument Layout; Power Button; Measurement Theory - IDEAL 61-920 Mode D'emploi

4. Instrument Layout

• Feature callouts
1 Transformer jaw
Lever
2
Backlight button
3
Switches on/off the backlight
Function button
4
Switches ACA/Earth
resistance function
5 Memory mode button
Records the measured value
with a data number
6 Data hold button
Holds the indicated value.
Release the held value

Power button

7
Turns the meter on/off
Display unit (LCD)
8
Cursor button (UP)
9
Selects data number to save the
measured value or to view the
measured data in memory
Cursor button (DOWN)
10
Selects data number to save the
measured value or to view the
measured data in memory.
Save button
11
Saves the measured value.
• Marks to be displayed on the LCD
Displayed when saving the measured value
MEM
or when instrument is in memory mode
Displayed when batteries are exhausted
Displayed in Earth resistance function
when Transformer jaws are not properly
closed.
Displayed in Earth resistance function
with current or noise which affects the
measured value.
Displayed when data hold functions
activated
Displayed when ACA function is selected
Displayed when instrument is in continuity
mode at Earth resistance function
3
4
5
11
Data number
1 to 100
Measured value Unit
8

5. Measurement Theory

This instrument can measure the earth resistance to earth in a multi-earthed system. Let's
regard earth resistance under test as Rx, and the other earth resistances as R1, R2, ...Rn.
1
2
Of these earth resistances, R1, R2, ...Rn can be considered connected in parallel and can
6
be regarded as a combined resistance Rs. The Rs can be regarded small enough against Rx
7
since combined resistance consists of several resistances. Following is an equivalent circuit
diagram of this scenario.
8
9
10
9