Patents by Inventor Thomas B. DeWitt

Thomas B. DeWitt has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Two-wire 4-20 mA electronics for a fiber optic vortex shedding flowmeter
    Patent number: 4742574
    Abstract: A method and apparatus for processing optically generated signals to form a two-wire 4-20 mA signal comprises generating a control signal having pulses at a selected frequency to drive a light emitter which generates light pulses, transmitting the light pulses to a light detector over a transmission line having variable attenuation to form a sensor signal and amplifying the sensor signal in an operational amplifier. The variations and attentuations follow a process variable to be measured. To save power the operational amplifier has a low-current mode into which it is switched whenever no pulse is present in the sensor signal. The amplifier is switched into its high-current mode only when a pulse is present in the sensor signal. Switching is controlled by the control signal for the light emitter. Peaks in the signal from the operations amplifier are sampled and held and then subject to low pass filtering to remove the selected frequency componnent and leave a cyclic filtered signal.
    Type: Grant
    Filed: February 3, 1986
    Date of Patent: May 3, 1988
    Assignee: The Babcock & Wilcox Company
    Inventors: Jane E. Smith, Thomas B. DeWitt