GE S5 Owners Manual

							Patient Side Module, E-PSM, E-PSMP (Rev. 01) 15
Document no. M1215098-002
2.2.3 ECG board in 12-lead measurement
The 12-lead ECG measurement consists of the  functions shown in Figure 7 on page 15. All 
functions are located in the ECG board except the ECG input unit.
Figure 7 12-lead ECG measurement block diagram
ECG input unit
The ECG input unit consists of the front panel connector and the ECG input connector board 
with the high voltage protection resistors. Th e connector for the 12-lead ECG cable is a green 
11-pin rectangle shaped connector.
Input protection and filtering
The input protection is implemented with high voltage protection resistors in the ECG input unit 
and with protection diodes in the ECG board.  The input filtering for ECG measurement is done 
with passive RC filtering.
PATIENT AND ECG ELECTRODES
ECG CABLE - ECG LEAD SET
- ECG TRUNK CABLE
ECG INPUT UNIT- ECG CONNECTOR
- INPUT PROTECTION RESISTORS
INPUT PROTECTION DIODES FOR ECG & RESPIRATION MEASUREMENT
INPUT FILTERING FOR ECG & RESPIRATION MEASUREMENTS
RESPIRATION
MEASUREMENT AMPLIFIERS
BASELINE
RESTORATION
ECG CPU
RESPIRATION
MEASUREMENT
CURRENT SUPPLYECG
PREAMPLIFIERS &
RLD CIRCUITLEADS OFF &PACER &
DEFIBRILLATION DETECTION
RS 485
COMMUNICATIONPOWER SUPPLYNV
MEMORY
ISOLATION                                 ISOLATION
MODULE BUS CONNECTORECG BLOCK DIAGRAM12_lead_ECG_meas_blck_dgrm.vsd 
						

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ECG preamplifiers
The buffer amplifiers are used for each lead. The “Leads off” detection is implemented by 
measuring the output level of the input buffer amplifiers with the A/D converter of the CPU. The 
ECG signals are measured using differential amplifiers.
ECG amplifiers and baseline restoration
The function of the ECG amplifiers and baseline restoration is to amplify the signal and to 
restore the baseline of the signal in the middle of the display after the change of the signal 
level, e.g. after the change of the DC offset voltage.
Pacer detection
Pacer detection has been made by using four slew rate detector circuits. The pacer detection 
amplifiers have been realized at the front of th e slew rate detectors independently of the ECG 
measuring channels.
Respiration impedance supply
The 31.25 kHz sine wave generator is used as the respiration measurement signal supply. 
Analog switches are used for connecting the sine wave to the ECG leads to be measured.
Respiration impedance amplifiers
Buffer amplifiers are used in respiration measurement. Analog switches are used for selecting 
the measurement leads. There are also additional amplifiers for increasing the respiration 
signal gain. When ECG measurement is 5/12-lead, the respiration measurement is always done 
between R and F, independently on the ECG lead selection. When ECG measurement is 3-lead, 
then the respiration measurement happens at the same lead as the ECG measurement (I, II or 
III).
ECG CPU
The CPU is a 16 bit H8/3052 single-chip microcompu ter. It contains 128 kbytes of flash memory 
and 4 kbytes of RAM. The clock frequency is 16 MHz.
RS485 communication
The communication to the CPU board of the mo nitor uses RS485 protocol. The RS485 driver 
circuits are optically isolated from the processor of the module. 
Power supply
The ECG board has a driver-controlled half-bridge  switching power supply with 5 kV isolation. 
The supply voltages have been regulated with linear regulators.
2.2.4 ECG filtering
Datex-Ohmeda S/5 monitors have three ECG filtering modes:
MONITORING 0.5 to 30 Hz (with 50 Hz reject filter)
0.5 to 40 Hz (with 60  Hz reject filter)
DIAGNOSTIC 12-lead ECG 0.05 to 150 Hz
ST FILTER 0.05 to 30 Hz (with 50 Hz reject filter)
0.05 to 40 Hz (with 60 Hz reject filter)
The purpose of filtering is to reduce high frequency noise and low frequency (e.g. respiratory) 
movement artifacts.
The monitor filter is used in normal monitoring.  The diagnostic filter is used if more accurate 
diagnostic information is needed. The ST filter  gives more accurate information of ST segment, 
but reduces high frequency noise. 
						

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Document no. M1215098-002
The high-pass filters 0.5 Hz and 0.05 Hz are done with software. The monitor sends a command 
to the hemodynamic module determining which of  the corner frequencies 0.5 Hz or 0.05 Hz is 
to be used.
The 50 Hz and 60 Hz reject filters are both lo w-pass filters with zero at 50 Hz or 60 Hz 
correspondingly. They are software based filters used for the mains supply filtering. With these 
filters the 3 dB value for low-pass filter is 30 Hz or 40 Hz.
In diagnostic mode the upper frequency is 150 Hz and it is limited by software.
2.2.5 STP board
Figure 8 STP board block diagram
Microprocessor unit
The CPU is a 16 bit H8/3052 single-chip microcompu ter. It contains 128 kbytes of flash memory 
and 4 kbytes of RAM. The clock frequency is 16 MHz.
High speed I/O is used to obtain a pulse control sequence necessary for pulse oximetry 
measurement. Timing for the clock is from the oscillator.
STP_brd_blck_dgrm.vsd
PATIENT AND SpO2 PROBE
SpO2 TRUNK CABLE
SpO2 CONNECTOR
A/D CONVERSION
STP CPU
STP BLOCK DIAGRAM
PATIENT AND TEMPERATURE SENSOR
TEMPERATURE CONNECTOR
PATIENT AND INVASIVE CANNULA OR CATHETER
FLUSHING KIT & INVASIVE PRESSURE
SENSOR WITH DOME
INV.PRESSURE CONNECTORINPUT PROTECTION CIRCUITRY
SpO2 PROBE RECOGNITION & LEDDRIVE SELECTION MATRIX
TEMPERATURE
MEASUREMENT
AMPLIFIER
SpO2
AMPLIFIERSpO2 LED
DRIVE
 SENSOR SIGNAL CURRENT
SOURCESENSOR SIGNAL VOLTAGE
SOURCEINV: PRESSURE
MEASURE MENT
AMPLIFIER
RS 485
COMMUNICATIONPOWER SUPPLYNV
MEMORY
ISOLATION                                 ISOLATION
MODULE BUS CONNECTOR 
						

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Document no. M1215098-002
Temperature measurement unit
The NTC-resistor value in the probe depends on the patient’s temperature. It is measured with 
the following principle described below.
The constant current source is supplied about 38 μA current through the temperature sensor 
(YSI 400-series NTC resistor). The constant current is caused a voltage over the temperature 
sensor (NTC resistor). The voltage over the temperature sensor is amplified in a differential 
amplifier stage. The amplified voltage is transfe rred to a controller of the STP board through an 
A/D converter.
Figure 9 Temperature measurement principle
Invasive blood pressure measurement unit
An isolated +5 V voltage is supplied to the pressure  transducer. The differential voltage, which 
depends on the pressure and the supplied voltage, is calculated from the bridge connection 
(see the formula below).
U
out = Uin  ×  pressure  × 5  μV, where Uin is 5 V
⇒  U
out = 25  μV  × pressure [mmHg]
d/dt
0
0
0 0
R
R
R
R
Temperature
sensors T1, T2 constant
currentsource
Differential amplifier
Defibrillation/ESD protection
resistors and diodes
To A/D
converter
0C:7k36
15C:3k54
25C:2k53
38C:1k30 45C: 984
PSM_temp_meas_principle.vsd
Ref2
Ref1
T2T1
RR 
						

							Patient Side Module, E-PSM, E-PSMP (Rev. 01) 19
Document no. M1215098-002
Pressure amplification is realized in the instrumentation amplifier. The gain of the amplifier is 
set to keep the level of the signal transferred to the A/D converter within the measurement 
range even when there are circumstantial offsets or offsets caused by the transducer. There is 
a filter before the amplifier to attenuate high frequency disturbances.
Figure 10 Pressure measurement principle
Pulse oximetry measurement section
LED control signals
The D/A converters of the microcontroller on the STP board set the LED intensity adjustment 
values for the infrared and red LEDs of the SpO
2 probe. The microcontroller on the STP board 
switches ON (to the adjusted intensity) and OFF the SpO
2 probe LEDs according to the 
predetermined sequence.
LED driving circuit
Differential amplifiers measure the LED currents (LED current indication) of the SpO2 probe over 
the shunt resistors placed in the LED current paths. The LED driving voltages (LED voltage 
indication) are measured from the driver circuitr y. The LED driving circuits also have MOSFET 
transistor matrix to enable the use  of different probe configurations.
Measured signal preamplification
The preamplifier is a bipolar/single-ended current-to-voltage converter with adjustable gain. A 
higher gain is used for measuring thin tissue.  The preamplification stage has also ambient light 
reduction and a second amplifier stage.
Input filter
Instrum entation
amplifier
to AD converter
Vout
G
PSM_pressure_meas_principle.vsd
Current
measurementG
to AD converter
Vin
Pressure
transducer 
						

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Figure 11 Pulse oximetry measurement block diagram
Red and infrared channel separation
It is possible to multiplex the detector signal to four different channels depending on the 
content of the signal. The detector signal must at least multiplex into infrared and red signals. 
Other channels are e.g. for diagnostic purposes.
Serial communication
An RS485 type bus driver makes the serial communication between the module and the frame. 
The data transmission rate is 500kbps.
LED Intensity adjustment 1
LED Intensity adjustment 2
LED ON/OFF control 1
LED ON/OFF control 2
LED Driving circuit 1
LED Driving circuit 2
LED voltage indication 1
LED current indication 1
LED voltage indication 2
LED current  indication 2
Preamplifier:
Current-to-voltage type
Bipolar/single-ended modes
Adjustable gain
Ambient reduction
Amplifier:
Gain = 2
DE-MUX
LP
LP
LP
LP
Gain=7.5
Gain=7.5
Gain=7.5
Amplifiers
DC-
suppression
DC-
suppression
DC-
suppression
Oximeter channel 1
Oximeter channel 2
Oximeter channel 3
Oximeter channel 4
SpO2
Probe
AnalogDigitalSpo2_measurement_blck_diagr.vsd 
						

							Patient Side Module, E-PSM, E-PSMP (Rev. 01) 21
Document no. M1215098-002
Figure 12 Serial communication of E-PSM(P) module
Signals and isolation barrier
The communication signals transfer over the isol ation barrier by using high isolation voltage 
(6kV) opto isolators. 
Power supply section
The power for the electronics on the floating pa rt of the STP and the ECG boards is made on 
each board with the switching power supplie s connected to a high voltage isolated 
transformer. The switching power supplies on the STP and ECG boards are synchronized to the 
frequency, about 340kHz of the switching power  supply on the NIBP board. The NIBP board 
supplies non-isolated 5 V to the ECG and STP boards. The module uses only Vmod 13.8 - 16 V 
voltage of the frame. The other voltages of th e measuring boards are made by the switching 
power supplies and regulators or the linear regulators. Each measuring board is protected 
against overloading with PTC type automatic fuses.
RS 485
DRIVER
NIBP BOARD CONNECTOR
DATA
NDATARECEIVE DATA SEND DATA
SEND/RECEIVE
NIBP BOARD CONTROLLERS
NIBP BOARD
RS 485
DRIVER
STP BOARD CONNECTOR
RECEIVE DATA
SEND DATA
SEND/RECEIVE
STP BOARD CONTROLLER
STP BOARD
PATIENT ISOLATION
RS 485
DRIVER
ECG BOARD CONNECTOR
DATA
NDATA
ECG BOARD CONTROLLER
ECG BOARD
PATIENT ISOLATION
DIRECT ECG (PW M)
PSM_serial_communication.vsd
Module bus connector
DATA
NDATA
synchronization signal
+5 V
+5 V
+5 V
RECEIVE DATA SEND DATA
SEND/RECEIVE 
						

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2.3 Connectors and signals
2.3.1 Module bus connector
Table 8 Module bus connector description
2.3.2 Front panel connectors
Table 9 ECG connector
5 pin connectorPin No.Signal
1
2
3
4
5 GND
Vmod 13.8 - 16 V
Data +
Data -
Shield
ECG Connector Pin No. Signal Name
1
2
3
4
5
6
7
8
9
10
11 R/RA; Right arm electrode
C2/V2; Chest electrode
C3/V3; Chest electrode
L/LA; Left arm electrode
N/RL; Neutral/Right Leg Drive electrode
C1/V1; Chest electrode
C4/V4; Chest electrode
F/LL; Left Leg electrode
C6/V6; Chest electrode
C5/V5; Chest electrode
Cable Shield 
						

							Patient Side Module, E-PSM, E-PSMP (Rev. 01) 23
Document no. M1215098-002
Table 10 SpO2 connector
Table 11 Invasive blood pressure connectors (P1, P2)
SpO2 connector  Pin No. Signal Description
1 DET_A Photodiode anode
2 DET_C Photodiode cathode
3DATA-
4Wire 1/3LED connection
5 IR_C IR LED cathode
6OUTER SHIELD
7 DET_SHIELD
8 PRB_ID Bin/ID Resistor+
9 Wire 3/5 LED Connection
10 RED_C RED LED cathode
11 DATA+
Invasive blood pressure 
connectors (Dual BP) Pin 
No.Signal Description
1BP_+V
REFBP transducer excitation voltage, channel 1
2 BP SIG+ BP transducer signal positive (+), channel 1
3BP_+V
REFBP transducer excitation voltage, channel 2
4 AGND Analog ground
5 BP SIG+ BP transducer signal positive (+), channel 2
6 SHIELD BP cable shield
7 AGND Analog ground
8 BP SIG1 BP transducer signal negative (-), channel 1
9 BP SIG2 BP transducer signal negative (-), channel 2
10 BP1_ID BP1 probe identification
11 NC Not connected 
						

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Document no. M1215098-002
Table 12 Temp connector (T1, T2)
Temp connector Pin No Signal
1 Sensor drive current
2 Input from temperature sensor, channel 1
3Not connected
4Not connected
5 Thermistor ID (LOW= Temperature error,  HIGH=YSI 400 series)
6 Cable shield
7 Analog ground
8 Input from temperature sensor, channel 2
9Not connected
10 Not connected
11 Digital ground