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Model 6517B Electrometer Reference Manual
Section 4: Basic measurements
EXT- FDBK
This option is used to enable or disable the external feedback mode. The following menu items are
used to control external feedback:
OFF: Disable external feedback
ON: Enable external feedback
SPEED
The speed parameter sets the integration time of the analog to digital (A/D) converter, the period of
time the input signal is measured (also known as aperture). The integration time affects the usable
resolution, the amount of reading noise, as well as the ultimate reading rate of the instrument. Any
triggers received while the instrument is processing a reading are ignored. From the front panel, the
integration time is specified in parameters based on a number of power line cycles (NPLC), where 1
PLC for 60 Hz is 16.67 ms and 1 PLC for 50 Hz and 400 Hz is 20 ms.
The SPEED parameters for all functions (except frequency) are explained as follows:
FAST: Sets integration time to 0.01 PLC. Use FAST if speed is of primary importance at the expense
of increased reading noise and less usable resolution.
MEDIUM: Sets integration time to 0.1 PLC. Use MEDIUM when a compromise between noise
performance and speed is acceptable.
NORMAL: Sets integration time to 1 PLC. A compromise like MEDIUM, but NORMAL provides better
noise performance at the expense of speed.
HIACCURACY: Sets integration time to 10 PLC. Use HIACCURACY when high common-mode and
normal-mode rejection is required.
SET-SPEED-EXACTLY: When this parameter is selected, the present PLC value is displayed. By
using the cursor keys and the RANGE keys, you can enter any PLC value from 0.01 to 10. Be sure to
press ENTER after keying in a new value. Note that an integer PLC value increases noise rejection.
SET-BY-RSLN: This parameter optimizes the integration time for the present resolution setting.
FILTER
Use this menu item to configure the two basic filter types: averaging and median. Note that you can
use either the averaging filter, the median filter, or both.
The filter menu is available from the function configuration menus (for example, press CONFIG V) or
by pressing CONFIG FILTER with the desired function already selected.
RESOLUTION
All functions can operate with 3.5 to 6.5-digit resolution, or they can default to a setting appropriate for
the selected integration time.
3.5 d, 4.5 d , 5.5 d, or 6.5 d: Sets resolution to the specified number of digits.
AUTO: Optimizes the resolution for the present integration time setting.
6517B-901-01 Rev. C / August 2015
4-5
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