Principles of Operation
2-11
The NIBP is measured based on the pulse vibration principle. Inflate the cuff which is on the
forearm till the cuff pressure blocks the arterial blood, and then deflate the cuff according to a
specified algorithm. While the cuff pressure is decreasing, the arterial blood has pulses, which
are sensed by the pressure transducer in the cuff. Consequently, the pressure transducer,
connected with the windpipe of the cuff, generates a pulsation signal, which is then processed
by the NIBP module to get the NIBP value.
2.2.5.2.1 Valve Drive Circuit
This circuit controls the status (ON/OFF) of valves. It, together with the Motor Drive Circuit,
implements the inflation and deflation of the cuff.
2.2.5.2.2 Motor Drive Circuit
This circuit controls the action of the air pump. It, together with the Valve Drive Circuit,
implements the inflation and deflation of the cuff. Besides, it provides the status signal of the
motor for the A/D conversion part.
2.2.5.2.3 NIBP Signal Process Network
The NIBP signal is the differential input signal. The difference amplifying circuit amplifies the
dual-end difference signal and converts it to the single-end signal; meanwhile, this circuit
sends a channel of signal to the A/D conversion part, and the other to the DC isolating and
amplifying circuit.
The DC isolating and amplifying circuit removes DC components from the signal, amplifies the
signal, and then sends it to the A/D conversion part.
2.2.5.2.4 A/D
The A/D conversion part converts the analog signal to the digital signal, and sends it to the
CPU System for further processing.
2.2.5.2.5 Over Pressure Detect
The circuit detects the NIBP pressure signal. Once the pressure value exceeds the protected
pressure value, it will send a message to the CPU System, which asks the Valve Drive Circuit
to open the valve to deflate the cuff.
2.2.5.2.6 CPU System
Implementing the logical control of all the circuits;
Implementing the data processing for the NIBP parameter;
Implementing the communication with the main board.
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