Theory Of Operation; The Saecg Patient Module - HP PageWriter XL M1705B Service Manual

Theory of Operation
The SAECG Patient
In standard mode, the SAECG patient module operates as described
Module
in "The Standard Patient Module," to acquire "classical" ECGs. In
SAECG mode, the SAECG patient module operates as in standard
mode except for the following:
n
The module collects data from 6 electrodes.
n
The multiplexors sample the data twice in each sampling period,
giving a functional sample rate of 8 kHz instead of 4 kHz.
n
SAECG mode increases amplifier gain and analog-to-digital
conversion resolution by a factor of approximately 4.1. This
provides better signal resolution and reduces system noise.
You
can use SAECG mode with all four limbwires (RA, LA, RL, LL)
attached. However, you will get better results if you attach only RA
and RL, and insert shorting plugs in LA and LL. This is because
the common mode rejection performance is enhanced if the LL and
LA inputs have shorting plugs installed. The SAECG software does
not include line frequency rejection; since the signals of interest are
smaller than in standard mode, common mode rejection becomes
critical.
Figure B-4 shows a block diagram of the SAECG patient module's
circuitry.
M1754A Signal Averaged ECG (SAECG) System B-13