Interface unit for use between analog sensors and a microprocessor
First Claim
1. An interface circuit of the type for use between variable voltage analog sensors measuring physical magnitudes and a microprocessor for digital processing of the latter, said interface circuit comprising:
- an analog multiplexer connected to said sensors to select the output signals of the latter, an analog-to-digital converter including a voltage/frequency converter responsive to the output signals of said analog multiplexer and a counter for converting said frequency into digital data, and a bus adapter being provided for delivering corresponding digital data to the microprocessor, wherein said analog multiplexer comprises a differential analog multiplexer having two differential voltage outputs, and having a sign detector connected to the differential voltage outputs of said multiplexer, a switching block is interconnected between said differential voltage outputs of said multiplexer and said voltage/frequency converter, said switching block being connected to the output of said sign detector so as to act as a selector circuit transmitting each voltage output signal of said multiplexer with a constant sign to the voltage/frequency converter, and said counter being an up/down counter resettable to an intermediate value, whose up/down counting input is connected to said sign detector output for counting up or down depending on said sign detector output.
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Abstract
An improved interface circuit for use between variable voltage analog sensors which are measuring physical parameters and a microprocessor which is processing the data relating to such parameters. The interface unit is of the type employing an analog multiplexer, an analog to digital converter, a voltage to frequency converter, a counter for converting frequency to digital data, and a bus adapter for connection to the microprocessor. The inventive improvement relates to providing the multiplexer as a differential multiplexer having two differential voltage outputs and having a sign detector connected thereto. A switching block is connected between the differential voltage outputs and the voltage to frequency converter and also to the sign detector thereby acting as a selector circuit. The selector circuit passes each voltage output signal of the multiplexer which has a constant sign to the voltage to frequency converter, wherein the counter is an up/down counter whose counting input is connected to the sign detector output.
37 Citations
9 Claims
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1. An interface circuit of the type for use between variable voltage analog sensors measuring physical magnitudes and a microprocessor for digital processing of the latter, said interface circuit comprising:
- an analog multiplexer connected to said sensors to select the output signals of the latter, an analog-to-digital converter including a voltage/frequency converter responsive to the output signals of said analog multiplexer and a counter for converting said frequency into digital data, and a bus adapter being provided for delivering corresponding digital data to the microprocessor, wherein said analog multiplexer comprises a differential analog multiplexer having two differential voltage outputs, and having a sign detector connected to the differential voltage outputs of said multiplexer, a switching block is interconnected between said differential voltage outputs of said multiplexer and said voltage/frequency converter, said switching block being connected to the output of said sign detector so as to act as a selector circuit transmitting each voltage output signal of said multiplexer with a constant sign to the voltage/frequency converter, and said counter being an up/down counter resettable to an intermediate value, whose up/down counting input is connected to said sign detector output for counting up or down depending on said sign detector output.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
Specification