| 摘要 |
<p>The invention relates to a transmitting and receiving circuit for ultrasonic flowmeters comprising: a) at least two ultrasonic measuring transducers (TR1, TR2) configured for the bidirectional transmission and reception of ultrasonic signals over a measuring distance; b) a signal generator for the controlled generation of electric signals to be transmitted to said ultrasonic measuring transducers (TR1, TR2); and c) detecting means (Z2) for parsing the measured values of the transmission time to be used in computing the flowrate to be measured; the transmitting and receiving circuit also comprises an amplifier (1) provided with: a first reversing input terminal for the connection to one of the ultrasonic measuring transducers (TR1, TR2); e) a second non-reversing input terminal for the connection to the signal generator; f) an output terminal for the connection to the detection means (Z2); g) a feed-back loop to connect the detection means between the output terminal and the first input terminal. By providing switching means (S1 and S2) for the alternative functional connection of one of the ultrasonic measuring transducers (TR1, TR2), to the first input terminal, a simplified circuit layout which is highly insensitive to the components tolerance and the various temperature coefficients is obtained.</p> |
