Datex-Ohmeda S/5 M-NE12STPR, Technical Reference Manual Slot

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Datex-Ohmeda S/5 monitors
Document No. 800 1008-2
14
2.2.4 ECG board in 3-and 5-lead measurement
Patient signals are connected to overload protection circuits (resistors and gas-filled surge
arresters) and analog switches to instrumentation amplifiers. Then the signals are amplified by 480
and limited by slew rate. Then they are A/D-converted, analyzed and transferred to module bus in
digital form.
SLEW-
RATE
DETECTOR
SLEW-
RATE
DETECTOR
SLEW-
RATE
DETECTOR
ANTI-
ALIAS ANTI-
ALIAS ANTI-
ALIAS
A/D
MICRO-
PROCESSOR
(uP)
DIRECT
ECG
OPTO-
COUPLER
POWER
SOURCE
DIRECT
ECG
OPTO-
COUPLER
POWER
SOURCE
PATIENT
OVERLOAD PROTECTION
ANALOG SWITCHES
to STP Board
ISOLATION
uP uP uP
SUPPLY
VOLTAGES
HP
Filter
uP
HP
Filter
uP
HP
Filter
uP
SLEW-
RATE
DETECTOR
ANTI-
ALIAS
uP
HP
Filter
uP
R L
F C N
LEAD SELECTION LOGIC
Controlled by ECG lead
selection signals from uP
Resp
amplifier
Sync. Rectifier
Amplifier
DEFIBRILLA-
TION
DETECTOR
uP
31 kHz
from uP
Figure 6 3- and 5- lead ECG board block diagram
Analog ECG section
ECG cable is connected to connector pins E1 to E6 on the input board which contains an overload
protection circuit. Leads are connected to amplifiers via analog switches. States of the switches
depend on the cable type. Lead-off, noise and pacemaker are detected by a slew rate detector.