Magnetic flowmeter with isolation amplifier and ranging circuit therefor and method
AssigneeEmerson Electric Co.
InventorMax H. Gaertner
Life of this patent
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Abstract
An isolation amplifier especially suited for magnetic flowmeters includes circuitry for converting an analog input signal to a duty cycle imposed upon a digital waveform, including generating clock pulses for synchronizing the digital waveform. Low-cost opto-couplers are provided for optically transmitting the digital waveform and information representative of the clock pulses across a barrier which would degrade the analog input signal and for receiving the optically transmitted digital waveform and clock pulse information and recreating the digital waveform with imposed duty cycle therefrom. Circuitry for digitally ranging the duty-cycle signal before the analog signal is reconstructed is also disclosed.
Claims49
An isolation amplifier for analog input signals comprising:
- means for converting an analog input signal to a duty cycle imposed upon a digital waveform, said means including means for generating clock pulses for synchronizing the digital waveform;
- means for optically transmitting the digital waveform and information representative of the clock pulses across a barrier which would degrade the analog input signal;
- and
- means for receiving the optically transmitted digital waveform and clock pulse information and recreating the digital waveform with imposed duty cycle therefrom.
A method of providing isolation for analog input signals comprising the steps of:
- converting an analog input signal to a duty cycle imposed upon a digital waveform, said converting step including generating clock pulses for synchronizing the digital waveform;
- optically transmitting the digital waveform and information representative of the clock pulses across a barrier which would degrade the analog input signal;
- and
- receiving the optically transmitted digital waveform and clock pulse information and recreating the digital waveform with imposed duty cycle therefrom.
In a magnetic flowmeter comprising a body adapted to be connected in a flow system for flow of liquid therethrough, coil means for generating a magnetic field in the path of the fluid flowing through the body, voltage means for applying a voltage waveform across the coil means to generate the magnetic field, electrode means disposed transverse to the path of the fluid for detecting an induced voltage caused by the flow of the fluid through the magnetic field, and flow sensing means responsive to the electrodes for measuring the flow of the fluid, the improvement comprising:
- means for converting an analog input signal from the electrodes to a duty cycle imposed upon a digital waveform, said means including means for generating clock pulses for synchronizing the digital waveform;
- means for optically transmitting the digital waveform and information representative of the clock pulses across an isolation barrier which would otherwise degrade the analog input signal from the electrodes;
- and
- means disposed across the isolation barrier from the transmitting means for receiving the optically transmitted digital waveform and clock pulse information and recreating the digital waveform with imposed duty cycle therefrom.
Dependencies are inferred from the claim text.