SECTION 3
Front Panel Operation
NOTES:
1.
2.
3.
4.
Do not use zero check while in V/I ohms. Doing so
will blank the display (i.e. ” KU’) and cause the
ZERO CHECK indicator to flash.
Placing the V-Source in standby while in V/I ohms
will result with zeroes being displayed (i.e.
0.00000
I6-U.
The minus (-1 sign is not disabled in V/I ohms. Po-
larity changes during a test could indicate charge/
discharge effects of the DUT. For example, a DUT
may behave as a capacitor. At a certain voltage the
capacitor will charge and display some positive re-
sistance reading. If the V-Source is decreased, the ca-
pa&or will discharge causing current to flow in the
opposite direction. A negative resistance reading
will then be displayed.
If a current Rel baseline exists (REL indicator on
while displaying current measurements) when V/I
Ohms is selected, resistance is calculated as follows:
R=&
where: I is the actual current.
IO is the current rel baseline level.
Optimiziig Accuracy
When using V/I ohms, the V-Source range and current
range should be set up to optimize accuracy. In most
cases, it is best to use the maximum voltage possible and
set the current range accordingly. The instrument should
be placed in the most sensitive range possible without
causing an overranged condition. Doing so will optimize
the measuement for resolution and accuracy.
Autoranging can facilitate range selection.
V/I ohms measurements tend to be more accurate when
current measured is close to full scale. Disadvantages of
operating with higher voltages include power dissipa-
tion in the DUT and voltage coefficient of high imped-
ance DUT.
Leakage Resistance
There ,are cases where leakage resistance could adversely
affect V/I ohms measurements. For example, test fixture
leakage paths may appear in parallel with the device be-
ing measured, introducing errors into the measurement.
These errors can be minimized by using proper insulat-
ing material (such as Teflon@) for terminal connections
in custom-built test fixtures.
The current Rel feature provides a way to compensate for
leakage resistance which cannot be eliminated from the
test fixture. If the DUT (device under test) is removed
from the test fixtwe and then the test voltage is applied to
the fixture, the resulting Current will be entirely due to
the leakage resistance. Using Rel (while in the current
function) will “eliminate” this leakage current. Then with
the DUT in the test fixture, the current used for the V/I
ohms calculation will be entirely due to the DUT.
NOTE
Paragraph 3.16 contains additional considera-
tions that must be addressed when making
current measurements.
3.8 MENU
The menu items are listed in Table 3-8. In general, each
press of the MENLJ key displays a menu item in the order
shown in the table. The available selections of the dis-
played menu item are selected and displayed with the ro-
tary knob or the4 and b keys. The selected option of the
displayed menu item is entered by again pressing
MENU. To exit the menu, press SHIFT and then EXIT.
The following information wiIl provide the detailed
steps for selecting the available options of the menu item
program.
3.8.1 Data Store
This menu item is used to arm the data store and select
the number of readings to store in the buffer. Details for
using the data store is contained in paragraph 3.11.
Data Store Selections:
NO Do nothing
YES Arm data store
BUl%ERSIZE
ODD RDGS
Wraparound
operation (cir-
cular buffer)
BUFFERSIZE 001512 RDGS Number of
readings to
store in buffer
3-16
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