Theory Of Operation; Operational Overview; Ecg Data Path - HP PageWriter XL M1705B Service Manual

5
Theory of Operation
This chapter contains an overview of the cardiograph operation, and
circuit descriptions of the major subassemblies. Except as noted, the
information in this chapter applies to the M1700A PageWriter XLi,
the M1701A PageWriter XLs, and the M1702A PageWriter XLe.
Operational
Overview
This overview covers two areas of cardiograph operation: the
path that ECG data follows from collection to display, and the
cardiograph's power-on/power-off sequence.
ECG Data Path
ECG data is collected at the patient module. There, the data from
as many as 13 patieut electrodes is sampled after the multiplexors
at a 4 kIIz rate. The cardiograph software determines the number
of electrodes sampled and the order in which they are sampled.
Following the multiplexors is the analog-to-digital converter (ADC).
The ADC, by the process of successive approximation, converts the
multiplexed analog signals to digital words. The patient module
controller performs a parallel-to-serial conversion, then sends the data
to the cardiograph. In the cardiograph, the digital signal processor
(DSP) receives the ECG data, processes it, and sends it to the
system RAM where it is stored.
The data stored in memory is then ava.ilable for analysis (M1700A
only), printing, display, or storage to disk (M1700A and Ml701A
only).
Theory of Operation 5-l