Bridge sensor with collocated electronics and two-wire interface
A transducer, including: a housing; a bridge sensor circuit disposed within the housing and including at least one micro electro-mechanical systems (MEMS) sensing elements and first and second output ports; circuitry disposed within the housing; and an input/output (I/O) line electrically connected to the circuitry, accessible at an exterior of the housing, and adapted for receipt of input voltage or current. The circuitry is for generating a single data signal that combines respective outputs of the first and second output ports, and transmitting the DC-coupled single data signal on the I/O line. The circuitry is for generating and transmitting to the bridge sensor circuit an excitation current or voltage using the input voltage or current.
1. A method of generating a two-wire output for a bridge sensor transducer, comprising the steps of:
accepting a first constant current from an internal electronic piezoelectric (IEPE) compatible two-wire current source on a two-wire line accessible at the exterior of a housing for the transducer; and,
within the housing for the transducer:
converting said constant current to an excitation voltage or current using said constant current on said two-wire through a conversion circuit line;
supplying said excitation voltage or current to a bridge sensor circuit, said bridge sensor circuit including at least one micro electro-mechanical systems (MEMS) sensing element;
outputting, from said bridge sensor circuit and responsive to said excitation voltage or current, first and second bridge sensor output signals;
generating through a conversion circuit a data signal combining said first and second bridge sensor output signals; and,
outputting, on said two-wire line, said data signal.
2. The method of claim 1 wherein said data signal includes a DC component.
3. The method of claim 1 wherein said excitation voltage or current is thermally compensated.
4. A bridge sensor transducer for use with an internal electronic piezoelectric (IEPE) compatible two-wire circuit, comprising:
a resistive bridge sensor circuit having a plurality of bridge sensor input/output (I/O) ports;
a differential amplifier electrically connected to said resistive bridge sensor circuit, said differential amplifier configured to generate a differential amplifier output;
a conversion circuit electrically connected at least one of said bridge sensor I/O ports and electrically connected to said differential amplifier, said conversion circuit configured to convert a constant current supply from an IEPE compatible two-wire current source to an excitation voltage or current for input into said resistive bridge sensor circuit, and said conversion circuit further configured to convert said differential amplifier output to a single-ended DC-coupled output; and
two transducer I/O ports electrically connected to said conversion circuit, said transducer I/O ports configured and arranged for electrical connection to said IEPE compatible two-wire current source.
5. The bridge sensor transducer of claim 4 wherein said bridge sensor circuit, said differential amplifier and said conversion circuit are disposed within a single housing.
6. The bridge sensor transducer of claim 5 wherein said transducer I/O ports are accessible at the exterior of said housing.
7. The bridge sensor transducer of claim 4 wherein said bridge sensor circuit comprises a micro-electro-mechanical systems (MEMS) sensing element.
8. The bridge sensor transducer of claim 4 wherein said bridge sensor circuit comprises a plurality of strain gauges.
9. The bridge sensor transducer of claim 4 wherein said excitation voltage or current is thermally compensated.
10. The bridge sensor transducer of claim 4 , further comprising a filter circuit electrically connected to said differential amplifier and electrically connected to said conversion circuit, said filter circuit configured and arranged to filter a signal from said differential amplifier.