In this section:
Introduction .............................................................................. 9-1
Filters ....................................................................................... 9-1
Math ......................................................................................... 9-7
Introduction
This section discusses the digital and median filters, as well as the available math functions, such as
polynomial and ratio.
Filters
Filtering stabilizes noisy measurements caused by noisy input signals.
The Keithley Instruments Model 6517B Electrometer uses two types of filters: digital and median. The
displayed, stored, or transmitted reading is simply the result of the filtering processes. Note that both
the digital and median filters can be in effect at the same time.
When FILTER is enabled, the selected filter configuration for that measurement function is in effect.
Filtering is enabled by pressing the FILTER key (FILT annunciator turns on). Pressing FILTER a
second time disables filter.
When FILTER is enabled, the status of the two filters is briefly displayed. For example,
Filter Enabled
Digital = ADV(10) Median ON
The above display message indicates that the advanced filter (average 10 readings) is in effect and
the median filter is on. If no digital filter is selected (NONE) and the median filter is off, the message
"No Filters Selected" is displayed. In this case, enabling FILTER has no effect on the input signal.
Filtering is performed only on primary display measurements; it has no effect on multiple displays.
When the median filter is enabled, readings from the analog to digital converter have the median
filter applied first, then the results of the median filter are fed into the digital filter.
Section 9
Filters and math
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