Spider DSA User’s Manual
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clipping and may damage the input circuitry. Signals with a non-zero mean (DC
component) can be measured in this mode.
DC-Single End
In single-ended mode, one of the input terminals is grounded and the input is
taken as the potential difference of the center terminal with respect to this
ground. Use this mode when the input needs to be grounded to reduce EMI noise
or static buildup. Do not use this mode when the signal source is ground
referenced or ground loop interference may result (see the Grounding section
below). This mode also allows signals with a non-zero mean to be measured.
AC-Differential
AC-Differential is a differential input mode that applies a low frequency high-pass
(DC-blocking) analog filter to the input. It rejects common mode signals and DC
components in the input signal. Use this when DC and low frequency AC voltage
measurements are not required or when a DC bias voltage is present. The analog
high-pass filter has a cutoff frequency of -3dB at 0.3 Hz, and -0.1dB at 0.7 Hz.
Figure 23 shows the shape of the filter.
AC-Single End
AC-Single End grounds one of the input terminals and enables the DC-blocking
analogue filter. Use this mode for non-ground referenced sources where
measuring the DC or low-frequency components is not required. AC-Single End
shares the same high-pass filter as AC-Differential.
When either of the AC input modes is used, there is also a digital high-pass filter,
implemented in the DSP, with a user-definable cutoff frequency. Note that the
analog high-pass filter is always active, even if 0 is set as the cut-off frequency for
the digital filter.
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