Electrothermal conversion elements, apparatus and methods for use in comparing, calibrating and measuring electrical signals
OwnerFred L. Katzmanninventor
Life of this patent
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Abstract
Electrothermal conversion elements, apparatus and methods for use in comparing, calibrating and measuring electrical signals utilizing a thin film heater on a thin, low mass, low thermal conductivity substrate and low mass thermoresistive or PN junction thermal radiation sensors. The element emits IR radiation in response to electrical input. The radiation is collected and converted to an electrical signal proportional to the RMS value of the input signal. Isothermal operation enhances both IR and electrical operation.
Claims33
An electrothermal conversion element for use in conversion of a first signal of unknown RMS amplitude to another electrical signal having an amplitude representative of the RMS amplitude of the first signal, said conversion element comprising
- a thin, low mass, low thermal conductivity substrate,
- a first low mass, thin film heater of relatively low temperature coefficient of electrical resistivity on a surface of said substrate, and
- a low mass, thermoresistive sensor element of relatively high temperature coefficient of electrical resistivity positioned to receive IR radiation from said heater.
An electrothermal conversion element for use in conversion of a first signal of unknown RMS amplitude to another electrical signal having an amplitude representative of the RMS amplitude of the first signal, said conversion element comprising
- a thin, low mass substrate having low thermal conductivity and high electrical resistivity,
- two low mass, thin film heaters of relatively low temperature coefficient of electrical resistivity on a surface of said substrate, and
- a low mass thermal sensor element arranged to receive only radiant thermal radiation from said heaters.
An electrical signal conversion apparatus for receiving a first electrical signal of unknown RMS amplitude and for producing an electrical output signal having an amplitude representative of the RMS amplitude of the first electrical signal, said apparatus comprising
- a thin, low mass, low thermal conductivity substrate,
- a first, low mass, thin film heater on a surface of said substrate, said heater powered by the first electrical signal, and
- a thermal sensor arranged to receive only radiant thermal energy from said first heater and producing the representative signal.
An electrical signal conversion apparatus for receiving a first electrical signal of unknown RMS amplitude and for producing an electrical output signal having an amplitude representative of the RMS amplitude of the first electrical signal, said apparatus comprising
- a first, low mass heater connected to receive and be heated by said first electrical signal,
- a second, low mass heater,
- first and second thermal sensors arranged to sense radiant heat from said heaters, said thermal sensors being electrically connected on opposite sides of a bridge circuit,
- an amplifier connected to the output of the bridge circuit, said amplifier being arranged and connected to provide a negative feedback electrical signal to heat said second heater.
A method for conversion from a first electrical signal to a second electrical signal of proportional RMS amplitude comprising the steps of heating a first heater by the first electrical signal which is the signal to be converted, concurrently heating a second heater by the second electrical signal, transmitting radiant heat from the first and second heaters to two thermal sensors which are electrically connected on opposite sides of a bridge circuit, and utilizing the output of the thermal sensor to maintain the summed detected temperature of the two heaters relatively constant at the desired nominal temperature by controlling the amplitude of the second signal.
Dependencies are inferred from the claim text.