7 Carrying out a measurement
13
•
Check that the instrument is functioning perfectly (for example at a
known voltage source) before and after every test.
•
If the safety of the user cannot be guaranteed, the instrument must be
switched off and secured to prevent unintentional usage.
When connecting the test leads to the test object, always connect
the common test lead (
COM
) to the test object first of all. When
disconnecting the test leads, always disconnect the +/- phase test
lead first of all.
7.2.
Current measurement
WARNING
Serious risk of injury to the user and/or destruction of the instrument
while measuring current.
> Measuring circuit must be de-energized.
The measuring instrument may only be used in circuits up to a
maximum voltage of 600V. The nominal cross-section of the
connection cable must be taken into account in order to ensure
safe connection (e.g. via crocodile clips).
Strong RFinterference and / or open leadswhen measuring A AC
may result in unstable display readings.
7.2.1.
Measuring A AC or A DC
Automatic measuring mode
1. Switch instrument on: set rotary switch to
.
-
The instrument switches on.
-
The instrument is in
AUTO A
mode.
2. Enclose the live conductor and centre it in the jaws.
-
The instrument automatically detects the
A AC
or
A DC
mode.
-
The measured value is shown on the LC display.
For measurements below 3.0 A AC, the automatic AC/DC
detection might not work. If that happens, set AC/DC manually.
Manual measuring mode
✓
Instrument is in automatic measuring mode
AUTO A
1.
Exit
AUTO A
measuring mode: press
[
]
<1 s.
2.
Switch
between
A AC
and
A DC
: press
[
]
<1 s.
-
The measured value is shown on the LC display.
Switch to automatic measuring mode: press
[
]
>1 s.
-
The instrument is in automatic measuring mode when
AUTO
is
illuminated on the LC display.
7.2.2.
Measuring µA AC or µA DC (testo 770/-2/-3 only)
Automatic measuring mode
1.
Switch instrument on: set rotary switch to
.
-
The instrument switches on.
