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S/5 M-PRESTN Modules
19
Document No. 8005571-1
Microprocessor unit
The CPU is a 16 bit H8/3052 single-chip microcomputer. 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 pulse control sequence necessary for pulse oximetry
measurement. Timing for the clock is from the oscillator.
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 7
µ
A 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 transferred to a controller of the STP board through an A/D converter.
d/dt
0
0
0
0
10k
10k
100k
100k
Temperature
sensor
constant
current
source
Differential
amplifier
Defibrillation/ESD protection
resistors and diodes
To A/D
converter
0C:7k36
15C:3k54
25C:2k53
38C:1k30
45C: 984
te
mp_meas_pr
inc
iple.
vs
d
Figure 8
Temperature measurement principle
Summary of Contents for S/5 PRESTN
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