ULTRASONIC TRANSMITTER CIRCUIT WITH MATCHED IMPEDANCE
A transmitter circuit and method for an ultrasonic thickness measurement system having an ultrasonic transducer and a cable with known cable impedance, the cable connecting at least the transmitter circuit to the ultrasonic transducer, the transmitter circuit comprising: an electrical pulse voltage signal emitter for producing an electrical pulse voltage signal to be propagated over the cable to the ultrasonic transducer, the electrical pulse voltage signal having a pulse nominal voltage value; a matched impedance circuit for matching a cable impedance of the cable at the transmitter circuit for an electrical parasitic reflection signal of the electrical pulse voltage signal, the electrical parasitic reflection signal being caused by an impedance mismatch between the cable and the ultrasonic transducer, a parasitic nominal voltage value of the electrical parasitic reflection signal being at most the pulse nominal voltage value.
1 . A transmitter circuit for an ultrasonic thickness measurement system having an ultrasonic transducer and a cable with known cable impedance, said cable connecting at least said transmitter circuit to said ultrasonic transducer, said transmitter circuit comprising:
an electrical pulse voltage signal emitter for producing an electrical pulse voltage signal to be propagated over said cable to said ultrasonic transducer, said electrical pulse voltage signal having a pulse nominal voltage value;
a matched impedance circuit for matching a cable impedance of said cable at said transmitter circuit for an electrical parasitic reflection signal of said electrical pulse voltage signal, said electrical parasitic reflection signal being caused by an impedance mismatch between said cable and said ultrasonic transducer, a parasitic nominal voltage value of said electrical parasitic reflection signal being at most said pulse nominal voltage value.
2 . The transmitter circuit as claimed in claim 1 , wherein a shape of said electrical parasitic reflection signal has at least one of a positive component and a negative component.
3 . The transmitter circuit as claimed in claim 1 , wherein said cable impedance of said cable is one of 50, 75, 93 and 95 ohms.
4 . The transmitter circuit as claimed in claim 1 , wherein said pulse nominal voltage value is between −50 V and −400 V.
5 . The transmitter circuit as claimed in claim 1 , wherein said matched impedance circuit is at least one resistance provided in said transmitter circuit to impact a circuit impedance of said transmitter circuit for said electrical parasitic reflection signal, said circuit impedance matching said cable impedance.
6 . The transmitter circuit as claimed in claim 5 , wherein said matched impedance circuit further includes at least one diode, said at least one diode controlling an effect of said at least one resistance on said circuit impedance.
7 . The transmitter circuit as claimed in claim 6 , wherein said matched impedance circuit is one resistance in series with a diode in which current circulates during transmission of said electrical pulse voltage signal.
8 . The transmitter circuit as claimed in claim 7 , wherein said matched impedance circuit is one resistance in series with a diode in which current circulates after said transmission of said electrical pulse voltage signal has ended.
9 . A method for reducing an impact of an electrical parasitic reflection signal in an ultrasonic measurement system having a transmitter circuit, an ultrasonic transducer and a cable with known cable impedance, said cable connecting at least said transmitter circuit to said ultrasonic transducer, comprising:
emitting an electrical pulse voltage signal at said transmitter circuit;
propagating said electrical pulse voltage signal having a pulse nominal voltage value over said cable to said ultrasonic transducer;
receiving, at said transmitter circuit, an electrical parasitic reflection signal caused by an impedance mismatch between said cable and said ultrasonic transducer, a parasitic nominal voltage value of said electrical parasitic reflection signal being at most said pulse nominal voltage value;
matching an impedance of said cable at said transmitter circuit for said electrical parasitic reflection signal.
10 . The method as claimed in claim 9 , wherein a shape of said electrical parasitic reflection signal has at least one of a positive component and a negative component.
11 . The method as claimed in claim 9 , wherein said cable impedance of said cable is one of 50, 75, 93 and 95 ohms.
12 . The method as claimed in claim 9 , wherein said pulse nominal voltage value is between −50 V and −400 V.
13 . The method as claimed in claim 9 , wherein said matching comprises providing at least one resistance in said transmitter circuit to impact a circuit impedance of said transmitter circuit for said electrical parasitic reflection signal, said circuit impedance matching said cable impedance.
14 . The method as claimed in claim 13 , wherein said matching further comprises providing at least one diode, said at least one diode controlling an effect of said at least one resistance on said circuit impedance.
15 . The method as claimed in claim 14 , wherein matching comprises providing one resistance in series with a diode in which current circulates during transmission of said electrical pulse voltage signal.
16 . The method as claimed in claim 15 , wherein said matching comprises providing one resistance in series with a diode in which current circulates after said transmission of said electrical pulse voltage signal has ended.