Block Diagram; Theory Of Operation - Philips M3001A Service Manual

Temperature and Invasive Blood Pressure (Temp/Press) measurement
Temp Mode
Measurement Range: -1 to 45
Safety
To ensure the safety of the patient, the patient-applied part is isolated from ground by opto-
couplers and a transformer. The circuit is also encapsulated in plastic.

Block Diagram

This illustration shows the block diagram of the Temp/Press circuit.

Theory of Operation

The signals progress through the circuit as follows:
Excitation Voltage
This supplies 5V
CPU switches the voltage source off (to reduce power consumption).
Input Protection Network
This provides protection for the rest of the circuit against defibrillator voltage, electrostatic
discharge, and any electromagnetic interference. The signal is passed on to the analog to
digital converter, and to the transducer detection circuit.
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Excitation
Voltage
Transducer
Detection
Input Protection
Network
Resistor
To and from Array
Temperature
Sensor
Current
Source
to a connected transducer. If a short circuit is detected by this circuit, the
DC
o o
C (30 to 113 F)
A/D
Converter
To and from
System CPU
CPU
ROM/RAM
Introduction to the Instrument