Instrumentation Amplifier; Valves - GE Corometrics 126 Service Manual

Instrumentation Amplifier

Valves

4-38
Theory of Operation: NBP Board
Compensated pressure transducer U16, produces an output voltage that is
proportional to the cuff pressure; the output is input to the instrumentation amplifier
section. Amplifiers U14 and U15 amplify the pressure transducer's output and
separate it into two channels. One channel has relatively low gain and represents the
static pressure in the cuff. The other channel has higher gain and represents the cuff
pressure changes caused by arterial volume changes. The outputs of the
instrumentation amplifier are sent to the processor. The processor can disable the
high gain channel during cuff deflation to prevent signal distortion.
Valves V1 and V2 vent the cuff's pressure to atmosphere. Two valves are required
to permit safe depressurization in the event of a defective valve; valve V1 has a
restricted orifice. The processor selects the appropriate valve to quickly and
accurately deflate the cuff based on the cuff's volume and pressure.
120 Series Maternal/Fetal Monitor
2015590-001
Revision B