Instruction manual

DC Input Amp Specifications
6-10
■ Filter Characteristics
The analog filter is a 2nd-order Butterworth filter, with a cutoff frequency that is about 1.2 times the aliasing
frequency (1/2Fs). The filter prevents 128-times delta-sigma A/D (analog to digital) high-order aliasing.
The digital filter is used when down-sampling 128-times delta-sigma A/D data. The attenuation
characteristics are about -6 dB at 1/2Fs. The aliasing component in -6 dB occurs at a sampling frequency of
1.1 times from 1 of the 1/2Fs. The attenuation is abrupt so attenuation occurs quickly up to the noise level.
■ Calibration
When the power is turned on, all channels and all ranges self-calibrate using a DSP. In this operation, when
the power is first turned on, the 2 basic signals of zero and + full scale are converted from analog to digital,
and the zero point error and gain error are calculated for each range, and then stored. During recording, the
data converted from analog to digital is adjusted by the calibration data for each range.
Block Diagram
-6 dB
Analog filter
(-12 dB/oct)
1/2 Fs
Digital filter
1.1 x 1/2 Fs
Input Amp
AD
PLD
FIFO
DSP
FIFO
RAM
Input Amp
AD
IN 1
IN
8