available. This forces the CPU to retrieve the data and to calculate the scaled pressure
waveform of temperature value.
Wave Processing and Filtering
Pressure measurement: Data from the A/D converter is sent to a single-pole digital filter
which generates the specified frequency response. Additionally, the transducer zero value is
subtracted from the signal.
Temperature measurement: This is referenced against a high-precision calibration resistor.
Each temperature value consists of 16 averaged samples and the test resistor verifies the
linearity of the measurement. With an offset resistor all offsets are eliminated.
Pressure & Temperature Mode Detector
The CPU switches between two different A/D converter controls and wave processing
algorithms depending on the connected transducer: Pressure or Temperature. To recognize
the presence of a pressure transducer, a coding within the transducer is checked. To recognize
the presence of a temperature transducer, the transducer's resistance is measured and must be
within specified limits. This is only done when no pressure transducer is present.
Invasive Pressure Software Module
The Invasive Blood Pressure Module derives three numerical pressure values (systolic,
diastolic, and mean), a blood pressure waveform and a pulse rate. The module is designed to
be used with DC pressure transducers (5 µV/V/mmHg) only. Alarm limits can be set for
pressure and pulse values. Alarm messages are issued if the calculated values are outside the
set range or outside the measurement range.
Block diagram of the Invasive Pressure Software Module
This module is responsible for the A/D conversion of the analog signal from the pressure
transducer. The Signal Acquisition module provides a raw pressure waveform to the Wave
Processing module. A special test mode and a zero procedure can be enabled and preformed
on request. The module also performs various self-tests and consistency checks to ensure
proper operation and reports errors and failures to the Acquisition Module.
Introduction to the Instrument
Temperature and Invasive Blood Pressure (Temp/Press) measurement
(systolic, diastolic, mean)