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Front Panel Operation
2-43
2.8.1 Basic measurement procedure
NOTE
After measuring high voltage in the volts
function, it may take a number of minutes
for input current to drop to within speci-
fied limits. Input current can be verified by
placing the protection cap on the INPUT
triax connector and then connecting a
jumper between COMMON and chassis
ground. With the instrument on the 20pA
range and zero check disabled, allow the
reading to settle until the input bias current
is within specifications.
Auto Discharge —
The Model 6517A has an auto discharge
feature for the coulombs function. When enabled, auto dis-
charge resets the charge reading to zero when the charge
reading reaches the specified level.
After the integrator resets, the charge measurement process
simply restarts at zero. For more details and the procedure to
configure auto discharge, see paragraph 2.8.2.
Use the following basic procedure to make charge measure-
ments:
NOTE
To ensure proper operation, always enable
zero check ("ZeroCheck" displayed) be-
fore changing functions (V, I, R, or Q).
The Z-CHK key controls zero check.
1. Enable zero check by pressing Z-CHK.
2. Select the coulombs function and select the desired
manual measurement range or auto range.
3. Auto discharge is configured from the Coulombs Con-
figuration menu. Refer to paragraph 2.8.2 to check or
change its configuration.
4. Connect the test cable to the Model 6517A. With the in-
put open, disable zero check and enable REL to zero the
instrument.
5. Connect the circuit to the INPUT of the Model 6517A
as shown in Figure 2-37.
NOTE
Do not connect the circuit to the instru-
ment with zero check enabled.
6. Take the charge reading from the display.
2.8.2 Coulombs configuration
The following information explains the various configura-
tion options for the coulombs function. The configuration
menu is summarized in Table 2-13. This menu is accessed by
pressing CONFIG and then Q. Paragraph 2.3.5 summarizes
the rules for navigating through the menu structure.
Note that a function does not have to be selected in order to
be configured. When the function is selected, it will assume
the programmed status.
SPEED
The SPEED parameter sets the integration time of the A/D
converter, the period of time the input signal is measure (also
known as aperture). It is discussed in paragraph 2.5.2.
FILTER
Use this menu item to configure the two basic filter types; av-
eraging and median. Note that you can use either the averag-
ing filter, the median filter, or both.
The filter menu is available from the function configuration
menus (i.e., press CONFIG V) or by pressing CONFIG FIL-
TER with the desired function already selected. All of the pa-
rameters (menu items) for FILTER are explained in
paragraph 2.17.
RESOLUTION
The RESOLUTION parameter sets the display resolution. It
is discussed in paragraph 2.5.2.
AUTO-DISCHARGE
The AUTO-DISCHARGE option is used to enable or disable
auto discharge. When enabled, auto discharge resets the
charge reading to zero at the specified level. After the inte-
grator resets, the charge measurement process simply re-
starts at zero.
The AUTO-DISCHARGE selections are as follows:
OFF: Use this selection to disable auto discharge. With auto
discharge disabled, you can use zero check to reset the inte-
grator.
ON: Use this selection to enable auto discharge. After select-
ing ON, you will be prompted to enter the discharge level.
The charge reading will reset every time the specified charge
level is reached. Note that if you specify a level that exceeds
the measurement range, the display will overflow before the
integrator resets.