User`s guide
M3000A/M3046A/M3015A/M3016A Service Guide
Introduction to the Instrument 1-29
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The following components carry out the major signal processing functions within the
measurement.
3UHVVXUH3XPS—Inflates the cuff to preset limits, once or repeatedly, depending on the
measurement method used.
3UHVVXUH6HQVRU—Measures cuff pressure using solid-state technology.
2YHUSUHVVXUH6DIHW\6\VWHP²Triggers alerts at given pressures and time limits, and
deflates the cuff.
%DQGSDVV)LOWHU—Extracts arterial pressure oscillations from the cuff pressure.
'HIODWLRQ6\VWHP—Automatically deflates the cuff at steps of a given magnitude.
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As NBP signals pass from the patient to the Monitor, they progress through stages
corresponding to logical sections of the circuit, as shown in the block diagram. Circuit-
related faults can generally be isolated to one of the stages.
$FTXLVLWLRQ²Signals from the patient are received by the pressure sensor through the
cuff, which is connected to the circuit by a single tube. The cuff is inflated, deflated, and
monitored by a pump, deflation system, and safety system controlled by a microproces-
sor.
a. &XII,QIODWLRQ²During the initial cuff inflation, the cuff is inflated by the pressure
pump to a set pressure which is determined by the patient size. Thereafter the cuff is
inflated by the pressure pump to a cuff pressure above the patient’s systolic pressure.
Depending on the measurement method used, inflation occurs once or repeatedly.
When the cuff pressure is greater than the systolic pressure, the artery is occluded;
the pressure sensor then detects only the cuff pressure.
b. &XII'HIODWLRQ²Cuff pressure is automatically released by the deflation system in
steps until the artery is only partially occluded. At that point, measurement and
processing of arterial pressure oscillations begin and continue as the cuff pressure is
progressively released.
'HWHFWLRQ²The arterial pressure oscillations are superimposed on the cuff pressure.
They are extracted from the cuff pressure by a digital bandpass filter in the microcontrol-
ler.
0HDVXUHPHQW²As the cuff is deflated, the magnitude of the oscillations as a function of
cuff pressure increases until the mean arterial pressure is reached. When cuff pressure
falls below the mean arterial pressure, oscillation magnitude begins to decrease.
The systolic and diastolic blood pressure values are deduced from the oscillometric sig-
nal by extrapolation. Differences in the results with the standard stethoscope method can
be expected. The NBP accuracy complies with AAMI SP-10.