User manual

Front Panel Operation
3-124 2001-900-01 Rev. K/ August 2010
• Reduced multiplexer effects on high-impedance mea-
surements.
NOTE
With auto zero disabled, internal calibra-
tion and zero are affected by changes in in-
put level. Whenever the applied input
signal changes, press the selected function
key to perform an auto zero routine; other-
wise, substantial measurement errors will
result. Zero and calibration may also drift
with time; thus, it is recommended that the
selected function key be pressed periodi-
cally to attain optimum accuracy while
auto zero is disabled. An auto zero is also
performed whenever the range or function
is changed, or when an auto zero bus com-
mand is issued.
The correlation between auto zero and measurement speed
follows:
• Auto zero off is the fastest.
• Auto zero synchronous is the slowest and most
accurate. An auto zero routine is performed for every
reading.
• The speed of auto zero normal (default) is between auto
zero off and synchronous. An auto zero routine is per-
formed whenever necessary to achieve specified accu-
racy.
The burst data acquisition mode disables auto zero. This type
of measurement requires an auto zero refresh once every 24
hours by performing one of the following:
• Change the display resolution.
• Change the measurement function.
Perform the following steps to display the AUTOZERO
menu:
1. Display the GENERAL MENU as described in para-
graph 3.12.7.
2. Use the cursor keys ( and ) to highlight
AUTOZERO and press ENTER to access the following
menu:
SET AUTOZERO
DISABLE NORMAL SYNCHRONOUS
The cursor position indicates the present auto zero mode. To
retain the presently selected sense, press ENTER or EXIT.
The display returns to the SET AUTOZERO menu.
To change sense, place the cursor on the alternate selection,
using the cursor keys ( or ) and press ENTER. Any
change halts triggers and puts the instrument into the idle
state. Use the TRIG key to re-arm triggers. The instrument
returns to the SET AUTOZERO menu.
When finished, press EXIT to return to the GENERAL
MENU.
LINE-SYNC
Synchronizing A/D conversions with the power line
frequency increases common mode and normal mode noise
rejection. When line cycle synchronization is enabled, the
measurement is initiated at the first positive-going zero-
crossing of the power line cycle after the trigger. (See Figure
3-49.)
Perform the following steps to enable or disable power line
cycle synchronization of measurements:
1. Display the GENERAL MENU as described in para-
graph 3.12.7.
2. Use the cursor keys ( and ) to place the cursor on
LINE-SYNC and press ENTER to access the following
menu:
LINE SYNCHRONIZATION
ENABLED DISABLED
The cursor indicates the present selection. If no change is
needed, press EXIT to return to the GENERAL MENU. To
change the selection, move the cursor, then press ENTER.
Note that this action halts triggers and puts the instrument
into the idle state. Use the TRIG key to re-arm triggers.
DECIMAL
This menu item lets you select between periods and commas
to signify decimal points on the front panel display. To
change the selection from the GENERAL MENU, place the
cursor on DECIMAL and press ENTER. The following
menu is shown:
CHOOSE DECIMAL CHAR
PERIOD COMMA
Selection of one or the other returns you to the GENERAL
MENU. Exit completely from the main menu to view either
a period or comma in the normal display of triggered
readings.