Display Readings; Input Connections To Common; Input Overload Protection - Fluke 8020A Instruction Manual

d. Extend the battery by sliding it toward the
connector end until it can be tilted out.
e. Carefully pull the battery clip free from the
battery terminals.
f. Press the battery clip onto the replacement
battery and return
compartment.
Make sure the battery and its leads are fully
g.
within the confines of the battery compartment
before sliding the cover into place.
WARNING
DO NOT OPERATE THE 8020A UNTIL THE
BATTERY COVER IS IN PLACE AND FULLY
CLOSED.
2-10. BATTERY ELIMINATOR
2-1 1. A line-powered battery eliminator (Model A8 1)
is available as an accessory, and is described in Section 6
of this manual. When the A81 is used, the battery is
automatically disconnected to conserve battery life. The
A81 connects to the 8020A through a recessed, side-panel
jack.
2-12.

Display Readings

NOTE
The liquid crystal display used in the8020A is
a rugged and reliable unit which will give
years of satisfactory service. Display life can
be extended by observing the following
practices:
I . Protect the display from extended
exposure to bright sunlight.
2. Keep the voltmeter out of high tempera-
ture, high humidity environments, such
as, the dash of a car on a hot sunny day,
turn black. Recovery occurs at normal
operating temperature. ( A l s o , t h e
numbers become sluggish at extremely
cold temperatures).
2-13. The front panel display provides a continuous
indication of the 8020A's operating status. That is, low
battery, overload, and normal operation. A " B Y is
displayed when approximately 80% of the battery's life is
exhausted (battery replacement is indicated). And,
followed by three blanked digits is displayed (decimal
point may be present) as an overrange indication. This
does not necessarily mean that the instrument is being
both to the battery
a
exposed t o a damaging input condition. For example,
when measuring resistance an open-input will cause an
overrange indication.
NOTE
When the 8020A is powered with the A81
Battery Eliminator the " BT' indicator may
come on due to low line voltage. However,
instrument operation will be normal.
Normal operation is indicated by an on-scale
2-14.
display complete with polarity and decimal point, when
required. The position of the decimal point is
determined by the selected range, and is not affected by
the measurement function. Polarity, on the other hand,
is only used for the dc voltage and current measure-
ment functions. A minus sign indicates that the input
signal is negative with respect to the COMMON input
terminal. Positive inputs are indicated by the absence of
the minus sign.
NOTE
The minus sign may flash momentarily as
(-)
the 8020A comes out of an overrange
condition. This will most likely be seen in the
ohms mode as the open circuit test leads are
applied to an in-range resistance value. Ifthe
minus sign remains on for in-range ohms
readings, the circuit is live (a negative voltage
is present at the input terminals due to
charged capacitors, etc.) and incorrect
resistance readings will be observed.

2-15. Input Connections to COMMON

WARNING
TO AVOID ELECTRICAL SHOCK AND/OR
I N S T R U M E N T D A M A G E D O N O T
C O N N E C T T H E
TERMINAL TO ANY SOURCE OF MORE
THAN 500 VOLTS ABOVE EARTH GROUND.
2-16. The 8020A may be operated with the COM-
MON input terminal at a potential of up to 500V dc or
V ac above earth ground. If this limit is exceeded,
instrument damage may occur. This, in turn, may result
in a safety hazard for the operator.
CAUTION
Exceeding the maximum input overload
C O M M O N I N P U T