| US 7,543,508 B2 | ||
| Zero crossing detection of an ultrasonic signal with variable threshold value | ||
| Tobias Lang, Stuttgart (Germany) | ||
| Assigned to Robert Bosch GmbH, Stuttgart (Germany) | ||
| Appl. No. 10/585,049 PCT Filed Jan. 26, 2005, PCT No. PCT/EP2005/050319 § 371(c)(1), (2), (4) Date Jun. 29, 2006, PCT Pub. No. WO2005/093379, PCT Pub. Date Oct. 06, 2005. |
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| Claims priority of application No. 10 2004 014 674 (DE), filed on Mar. 25, 2004. | ||
| Prior Publication US 2008/0190213 A1, Aug. 14, 2008 | ||
| Int. Cl. G01F 1/66 (2006.01) | ||
| U.S. Cl. 73—861.28 | 7 Claims |
| 1. An ultrasonic flow sensor having
at least one ultrasonic converter (A, B) for transmitting and receiving ultrasonic signals (A0, B0) and
a receiver unit (4) that is connected to the ultrasonic converter (A, B), monitors when the ultrasonic signal (A0, B0) exceeds a predetermined threshold value (SW), and, depending on this event, determines a reception time (t0) of the ultrasonic signal (A0, B0), wherein the receiver unit (4) determines a piece of information about the amplitude (Amp) of the ultrasonic signal (A0, B0) and adapts the threshold value (SW) based on the information determined; wherein the receiver unit (4) has a first S/H stage (12), whose input (US) is supplied with a converter output signal (5), and a subsequent second S/H stage (13), which adopts and stores the maximum value (Ampmax) of the first S/H stage (12).
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