Datex-Ohmeda S/5 monitors
Document No. 8001013-1
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FUNCTIONAL DESCRIPTION
2.1
Measurement principle
2.1.1
Invasive blood pressure
To measure invasive blood pressure, a catheter is inserted into an artery or vein. The invasive
pressure setup, consisting of connecting tubing, pressure transducer, an intravenous bag of normal
saline all connected together by stopcocks, is attached to the catheter. The transducer is placed at
the same level with the heart, and is electrically zeroed.
The transducer is a piezo-resistive device that converts the pressure signal to a voltage. The monitor
interprets the voltage signal so that pressure data and pressure waveforms can be displayed.
2.1.2
Temperature
The temperature is measured by a probe whose resistance varies when the temperature changes,
called Negative Temperature Coefficient (NTC) resistor.
The resistance can be measured by two complementary methods:
•
Applying a constant voltage across the resistor and measuring the current that flows through
it.
•
Applying a constant current to flow through the resistor and measuring the voltage that is
generated across it.
In S/5 module the two methods are combined in a form of a voltage divider. The NTC-resistor is
connected in series with a normal resistor and a constant voltage is applied across them. The
temperature dependent voltage can be detected at the junction of the resistors, thus producing the
temperature signal from the patient. The signal is amplified by analog amplifiers and further
processed by digital electronics.
2.2
Main components
The M-PT module consists of the following main parts:
•
PT board
•
Two connectors for YSI 400 series temperature probes; temperature channels T3 and T4.
•
Nicolay-type connector for an invasive blood pressure sensor; invasive blood pressure
channel P3.
•
Key for pressure zeroing.
•
DIN-type connector for two direct ECG output signals and pressure 3.
NOTE: These output-signals are non-floating
The M-P module consists of the following main parts:
•
PT board
•
Nicolay-type connector for an invasive blood pressure sensor; invasive blood pressure
channel P3.
