Mindray Passport 5-Lead, Руководство по обслуживанию

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Block Diagrams Theory of Operation
2 - 18 0070-00-0420 Passport 5-Lead, 5L, LT, XG Service Manual
The P1 channel output is used for generating a systolic trigger, for heart rate measurement
purposes. The P1 pressure signal is fed through a Bandpass Filter, comprised of U21 and
associated components, to remove the mean pressure level and noise, and to set the
appropriate amplitude detection scaling. The signal is then measured by the Pulse Detect
comparator, U21, which has a minimum threshold of 189 mmHg, set by the hysteresis
created by R133 and R148. Its output, P-Trigger, is a variable duty cycle square wave whose
rise and fall is coincident with the systolic and diastolic portions of the pressure waveform.
This systolic trigger “logic” is detected by the microcontroller and communicated to the
Control Module.
Temperature
The temperature channel is designed to measure temperatures from 15°C to 45°C using
Yellow Springs series 400 or series 700 thermistor probes. The probes exhibit temperature/
resistance characteristics described by the relation 1/T = a+b(Ln R) + (Ln R)3 where T is
given in degrees Kelvin. The constants a, b and c are unique for each probe series. The
channel measures the probe resistance by a ratiometric method described below. The CPU
then determines the temperature by evaluating the given equation.
FIGURE 2-10
Temperature PreAmp Block Diagram
Ring
Tip
Sleeve
TA
TB
TC
TD
Comparator
Temp
Amplifier
Amplifier
Current Summing
Voltage
Temperature
Pre Amp
Q3
Q2
Q1
R68
R66
U8A
Programmable
Current Source
U9B
Q4,U9A
U8B
T flag