Method and apparatus for decreasing the interference and noise sensitivity of a ratiometric converter type of circuit

A converter which receives an input sense signal and an input reference signal from a remote transducer and which provides an output signal proportional to said input sense signal and inversely proportional to said input reference signal, said converter comprising;

• (a) a first analog-to-digital converter which receives said input sense signal from said remote transducer and converts said input sense signal to a digital sense signal using a conversion reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal;
• (b) a second analog-to-digital converter which receives said input reference signal from said remote transducer and converts said input reference signal to a digital reference signal using said conversion reference signal;
• (c) a first digital filter coupled to said first analog-to-digital converter which filters said digital sense signal to provide a filtered digital sense signal;
• (d) a second digital filter which filters said digital reference signal to provide a filtered digital reference signal;
• and
• (e) a divider circuit coupled to said first and second digital filters which divides said filtered digital sense signal by said filtered digital reference signal to provide said output signal.

A converter which receives an input sense signal and an input reference signal from a remote transducer and which provides an output signal proportional to said input sense signal and inversely proportional to said input reference signal, said converter comprising;

• (a) a time multiplexed analog-to-digital converter which receives said input sense signal from said remote transducer and converts said input sense signal to a digital sense signal using a conversion reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal, and which receives said input reference signal from said remote transducer and converts said input reference signal to a digital reference signal using said conversion reference signal;
• (b) a time multiplexed digital filter coupled to said time multiplexed analog-to-digital converter which filters said digital sense signal to provide a filtered digital sense signal, and which filters said digital reference signal to provide a filtered digital reference signal;
• and
• (c) a divider circuit coupled to said time multiplexed digital filter which divides said filtered digital sense signal by said filtered digital reference signal to provide said output signal.

A converter which receives an input sense signal and an input reference signal from a remote transducer and which provides an output signal proportional to said input sense signal and inversely proportional to said input reference signal, said converter comprising;

• (a) a first analog-to-digital converter which receives said input sense signal from said remote transducer and converts said input sense signal to a digital sense signal using a conversion reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal;
• (b) a second analog-to-digital converter which receives said input reference signal from said remote transducer and converts said input reference signal to a digital reference signal using said conversion reference signal;
• (c) a time multiplexed digital filter coupled to said first and second analog-to-digital converters which filters said digital sense signal to provide a filtered digital sense signal, and which filters said digital reference signal to provide a filtered digital reference signal;
• and
• (d) a divider circuit coupled to said time multiplexed digital filter which divides said filtered digital sense signal by said filtered digital reference signal to provide said output signal.

A method for converting two output signals from a remote transducer of a ratiometric measurement system to a single output signal, said ratiometric measurement system having said two output signals from said remote transducer of a sense signal and a reference signal, such conversion method comprising the steps of:

• (a) converting said sense signal from said remote transducer to a digital sense signal based on an internal reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal;
• (b) converting said reference signal from said remote transducer to a digital reference signal based on said internal reference signal;
• (c) filtering said digital sense signal through a low pass digital filter to provide a filtered digital sense signal;
• (d) filtering said digital reference signal through a low pass digital filter to provide a filtered digital reference signal;
• and
• (d) dividing said filtered digital sense signal by said filtered digital reference signal to provide said single output signal which is proportional to said sense signal and inversely proportional to said reference signal.

A ratiometric converter for receiving an input sense signal and an input reference signal from a remote transducer of a ratiometric measurement system and for providing an output signal proportional to said input sense signal and inversely proportional to said input reference signal, said ratiometric converter comprising;

• (a) a first analog-to-digital converter for receiving said input sense signal from said remote transducer and for converting said input sense signal to a digital sense signal based on an internal reference signal of said ratiometric converter such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal;
• (b) a second analog-to-digital converter for receiving said input reference signal from said remote transducer and for converting said input reference signal to a digital reference signal based on said internal reference signal of said ratiometric converter;
• (c) a first low pass digital filter coupled to said first analog-to-digital converter for filtering said digital sense signal to provide a filtered digital sense signal;
• (d) a second low pass digital filter coupled to said second analog-to-digital converter for filtering said digital reference signal to provide a filtered digital reference signal;
• and
• (e) a divider circuit coupled to said first and second digital filters for dividing said filtered digital sense signal by said filtered digital reference signal to provide said output signal.

A method for converting a sense signal and a reference signal from a remote transducer to an output signal, said output signal being proportional to the magnitude of said sense signal within a predetermined frequency range and inversely proportional to the magnitude of said reference signal within said predetermined frequency range, such conversion method comprising the steps of:

• (a) converting said sense signal from said remote transducer to a digital sense signal using a conversion reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal;
• (b) converting said reference signal from said remote transducer to a digital reference signal using said conversion reference signal;
• (c) filtering said digital sense signal to provide a filtered digital sense signal;
• (d) filtering said digital reference signal to provide a filtered digital reference signal;
• and
• (e) dividing said filtered digital sense signal by said filtered digital reference signal to provide said output signal.

A converter which receives an input sense signal and an input reference signal from a remote transducer and which provides an output signal proportional to the magnitude of said input sense signal within a predetermined frequency range and inversely proportional to the magnitude of said input reference signal within said predetermined frequency range, said converter comprising;

• (a) a first analog-to-digital converter which receives said input sense signal from said remote transducer and converts said input sense signal to a digital sense signal using a conversion reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal;
• (b) a second analog-to-digital converter which receives said input reference signal from said remote transducer and converts said input reference signal to a digital reference signal using said conversion reference signal;
• (c) a first digital filter coupled to said first analog-to-digital converter which filters said digital sense signal to provide a filtered digital sense signal;
• (d) a second digital filter which filters said digital reference signal to provide a filtered digital reference signal;
• and
• (e) a divider circuit coupled to said first and second digital filters which divides said filtered digital sense signal by said filtered digital reference signal to provide said output signal.

A method for converting a sense signal and a reference signal from a ratiometric DC measurement system to an output signal, said output signal being proportional to said sense signal and inversely proportional to said reference signal, such conversion method comprising the steps of:

• (a) converting said sense signal from said ratiometric DC measurement system to a digital sense signal using a conversion reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal;
• (b) converting said reference signal from said ratiometric DC measurement system to a digital reference signal using said conversion reference signal;
• (c) filtering said digital sense signal to provide a filtered digital sense signal;
• (d) filtering said digital reference signal to provide a filtered digital reference signal;
• and
• (e) dividing said filtered digital sense signal by said filtered digital reference signal to provide said output signal.

A method for converting a sense signal and a reference signal from a transducer to an output signal, said output signal being proportional to said sense signal and inversely proportional to said reference signal, such conversion method comprising the steps of:

• (a) converting said sense signal from said transducer to a digital sense signal using a conversion reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said conversion reference signal being independent of both of said sense signal and said reference signal;
• (b) converting said reference signal from said transducer to a digital reference signal using said conversion reference signal;
• (c) filtering said digital sense signal to provide a filtered digital sense signal;
• (d) filtering said digital reference signal to provide a filtered digital reference signal;
• and
• (e) dividing said filtered digital sense signal by said filtered digital reference signal to provide said output signal.

A method for converting a sense signal and a reference signal to an output signal, said output signal being proportional to said sense signal and inversely proportional to said reference signal, such conversion method comprising the steps of:

• (a) converting said sense signal to a digital sense signal using a conversion reference signal such that said digital sense signal is inversely proportional to the amplitude of said conversion reference signal, said amplitude of said conversion reference signal being independent of both of said sense signal and said reference signal and having a range of variation due to factors other than said input sense and reference signals which is greater than the range of variation due to factors other than said input sense and reference signals of the amplitude represented by said output signal;
• (b) converting said reference signal to a digital reference signal using said conversion reference signal;
• (c) filtering said digital sense signal to provide a filtered digital sense signal;
• (d) filtering said digital reference signal to provide a filtered digital reference signal;
• and
• (e) dividing said filtered digital sense signal by said filtered digital reference signal to provide said output signal.