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4-4
Range, Units, Digits, Rate, and Filters
Rate
The RATE key selects the integration time of the A/D converter, which is the period of
time the input signal is measured. The integration time affects the amount of reading
noise, as well as the ultimate reading rate of the instrument. The integration time is speci-
fied in parameters based on a number of power line cycles (NPLC), where 1 PLC for 60Hz
is 16.67msec (1/60) and 1 PLC for 50Hz (and 400Hz) is 20msec (1/50). The rate setting is
global for all ranges. Therefore, it does not matter what range is presently selected when
you set rate.
To select the rate, either press the RATE key to select SLOW (6 PLC, 60Hz; 5 PLC,
50Hz), MED (1 PLC), or FAST (0.1 PLC), or press CONFIG and then RATE, and then
enter the desired number of PLCs (0.01 to 60, 60Hz; 0.01 to 50, 50Hz).
To set the rate by remote, send :NPLC <plc> with an allowable range or 0.01 to 60 (60Hz),
or 0.01 to 50 (50Hz).
Damping
High capacitance seen at the input will increase reading noise. This capacitance can be
attributed to a long input cable, or to the capacitance of the source, or a combination of both.
Enabling damping (analog filtering) will reduce noise caused by high capacitance for current
measurements. However, damping will also slow down the response of the measurement.
To enable or disable damping from the front panel, simply press the DAMP key. Note that
the FILT annunciator will be on when damping is enabled. Via remote, send DAMP ON or
DAMP OFF. Note that the FILT annunciator is used for both the analog damping filter and
the two types of digital filters.
Filters
Filtering stabilizes noisy measurements caused by noisy input signals. The Model 6487
uses two types of filters: median and digital. The displayed, stored or transmitted reading
is simply the result of the filtering processes. Note that both the median and digital filters
can be in effect at the same time.
With both filters enabled, the median filter operation is performed first. After the median
filter yields a reading, it is sent to the stack of the digital filter. Therefore, a filtered reading
will not be displayed until both filter operations are completed.
The settings for the filter are global and both are controlled with the FILT key. When either
the median or digital filter is enabled, the FILT annunciator is on. Note that the FILT
annunciator is used for both the digital filters and the analog damping filter.
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Страница 35: ...1 20 Getting Started Model 6487 User s Manual...
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Страница 86: ...A Specifications...
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