S/5 Hemodynamic modules
Document No. 800 1008-2
13
Signal processing
Two signals from the pressure transducers are amplified and sent to A/D converter. After the
converter, digitized signals are sent to microprocessor for data processing. Before the converter,
one of the signals is used to adjust the offset to the pressure safety level.
The NIBP board is controlled with 80C51FA microprocessor at 16 MHz oscillator frequency.
Memory
NIBP program memory (EPROM) size is 128k
×
8. RAM size is 32k
×
8 bit and it stores variable
values in NIBP measurement. EEPROM is size 64
×
16 bit and is used to store the calibration
values for the pressure transducers, the pulse valve constants gained during measurements, the
PC board identification, and module serial number.
Software control
Software controls valves and pump. In addition to the individual on/off signals for each component
there is a common power switch for the valves and the pump that can be used at pump/valve
failures.
In addition to external RS485 reset line the microprocessor system is equipped with its own power-
up reset. See the section in ECG board’s description:
Watchdog timer
The NIBP board is equipped with software independent safety circuit to disconnect supply voltages
from the pump and the valves if the cuff has been pressurized longer than preset time. As soon as
the cuff pressure rises over a specifiedpressure limit, timer starts counting. The timer is adjusted to
stop the pump and open the valves in 2 minutes 10 seconds in adult/child mode and in 1 minute
5 seconds in infant mode.
Valves
Exhaust valves are used for emptying the cuff and the joining chamber after the measurement.
Exhaust valve 1 is also used as safety valve in infant mode. Valve opens at 165 mmHg. Exhaust
valve 2 is also used as safety valve in adult mode and opens at 320 mmHg.
Bleed valve is used for emptying the cuff during measurement. Zero valve is used for connecting
the pressure transducer B1 to open air.
Power supply section
All connections are established via 25-pin connector (D-type, female). The module needs +5 V,
±
15 V, and +15 VD (dirty) power supply to operate. The pump and the valves use se15 VD
power line. The supply voltages are generated in the power supply section of the S/5 monitor. The
reference voltages
±
5 V
ref
and +10 V
ref
are generated on the NIBP board.
Summary of Contents for S/5 M-ESTPR
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