| 摘要 |
<p>Blood pressure measuring equipment comprises a sleeve provided with an inflatable air chamber and a microphone, an appliance connected with the sleeve for measuring and indicating systolic and diastolic blood pressure, and an automatic zero setting device (75) to cause pressure signals indicating fluid pressure in the chamber to be set to zero before any measurement is carried out. A pressure sensor (39) is connected to the air chamber to measure fluid pressure therein and comprises a piezo-resistive bridge circuit (91), which is connected with an amplifier (101). The zero setting device (75) comprises a differential amplifier (113) which is provided with a capacitive feedback and one input of which is connected via a transistor (117), which is switchable under the control of a pulse generator (81), with the output of the amplifier (101) following the bridge circuit (91). The output of the amplifier (113) with the capacitive feedback is connected with an input (91d) of the bridge circuit. When the appliance is switched on, the pulse generator (81) temporarily closes the transistor (117). The zero setting device (75) then operates as an integral regulator and automatically balances the bridge circuit while the air chamber is free of pressure and before actual pressure measurement is carried out. <IMAGE></p> |
