True rms to dc converters

Claim 3

An apparatus for converting an unknown complex AC voltage wave to its true root mean square value according to claim 1 wherein said first coupling means comprises a capacitor, a fixed resistor and a variable impedance coupled in series.

Claim 4

An apparatus for converting an unknown complEx AC voltage wave to its true root mean square value according to claim 1 wherein said means for varying said first coupling means comprises: a. a variable impedance coupled from said comparison point to a reference terminal, said variable impedance being light responsive; b. first and second thermal converters having a pair of input and a pair of output terminals, said input terminals being connected in series and said output terminals being connected in series opposition, said input and output terminals having a common junction point coupled to said reference terminal, one of said input terminals being coupled to said DC reference voltage; c. means for amplifying an AC signal coupled between said comparison point and the other of said thermal converter input terminals; d. a light emitting device coupled in close proximity to said variable impedance and having one end coupled to said reference terminal; and e. a first differential amplifier having two input terminals and an output terminal, one of said input terminals being coupled to each end of said serially opposed thermal converter output terminals, said differential amplifier output terminal being coupled to said light emitting device varying the light output from said light emitting device in a manner to insure that the root mean square value of the AC voltage between said comparison point and said reference terminal is substantially equal to the DC reference voltage.

Claim 5

An apparatus according to claim 3 wherein said second coupling means comprises: a. a second differential amplifier having two input terminals and an output terminal, said amplifier providing said DC output voltage at said output terminal, one of said input terminals being DC coupled to said reference voltage, the other of said input terminals being DC coupled to said comparison point maintaining said DC voltage between said comparison point and said reference terminal substantially equal to said DC reference voltage, whereby said DC output voltage is substantially equal to the root mean square value of said unknown complex AC voltage wave.

Claim 6

An apparatus according to claim 4 wherein said variable impedance is a photoresistor and said light emitting device is a light emitting diode (LED).

Claim 7

An apparatus for converting an unknown complex AC voltage wave to its true root mean square value according to claim 1 wherein said first coupling means comprises: a. means for amplifying an AC and DC voltage having an input terminal and an output terminal, said output terminal being coupled to said comparison point; b. a variable impedance coupled from said output terminal to said input terminal of said AC and DC amplifying means, said variable impedance being light responsive; c. a capacitor; and d. a fixed resistor connected in series with said capacitor, and coupled to the input terminal of said AC and DC amplifying means.

Claim 8

An apparatus for converting an unknown complex AC voltage wave to its true root mean square value according to claim 6 wherein said variable impedance is a photoresistor and said light emitting device is a light emitting diode (LED), and said AC and DC amplifying means is an operational amplifier.

Claim 9

An apparatus for converting an unknown complex AC voltage wave to its true root mean square value according to claim 6 wherein said means for varying said first coupling means comprises: a. first and second thermal converters having a pair of input terminals and a pair of output terminals, said input terminals being connected in series and said output terminals being connected in series opposition, said input and output terminals having a common junction coupled to said reference terminal, one of said input terminals being coupled to said DC reference voltage, the other of said input terminals being AC coupled to said comparison point; b. a light emitting device coupled in close proximity to said variable impedance aNd having one end coupled to said reference terminal; and c. a first differential amplifier having two input terminals and an output terminal, one of said input terminals being coupled to each end of said serially opposed thermal converter output terminals, said differential amplifier output terminal being coupled to said light emitting device varying the light from said light emitting device in a manner insuring the root mean square of the AC voltage between said comparison point and said reference terminal is substantially equal to the DC reference voltage.

Claim 10

An apparatus according to claim 8 wherein said second coupling means comprises: a. a second differential amplifier, having two input terminals and an output terminal, said output terminal providing said variable DC output voltage, one of said input terminals being DC coupled to said reference voltage, the other of said input terminals being coupled to said comparison point; and b. third means for amplifying and inverting a DC voltage having an input terminal and an output terminal, said input terminal being DC coupled to the output terminal of said second differential amplifier, said output terminal being DC coupled to the input terminal of said means for amplifying an AC and DC voltage maintaining said DC voltage between said comparison point and said reference terminal substantially equal to said DC reference voltage, whereby, said DC output voltage is substantially equal to the true root mean square value of said unknown AC voltage.

Claim 11

An apparatus according to claim 9 wherein said output terminal of said third means is coupled to said input terminal of said means for amplifying an AC and DC voltage, by a second resistor, said second resistor being substantially equal to said fixed resistor.

Claim 12

An apparatus according to claim 9 wherein said output terminal of said third means is coupled to said input terminal of said means for amplifying an AC and DC voltage by a second resistor, said second resistor being proportional to said fixed resistor, whereby said DC output voltage is proportional to the true root mean square value of said unknown complex AC voltage.

Claim 13

An apparatus according to claim 8 wherein said second means comprises a second differential amplifier having two input terminals and an output terminal, said output terminal providing said variable DC output voltage and being DC coupled to the input terminal of said means for amplifying an AC and DC voltage, one of said input terminals being DC coupled to said DC reference voltage, the other of said input terminals being coupled to said comparison point maintaining said DC voltage between said comparison point and said reference terminal substantially equal to said DC reference voltage, whereby said DC output voltage is proportional to the true root mean square value of said unknown complex AC voltage wave.

Claim 16

An apparatus for obtaining the true R.M.S. value of a complex AC voltage wAve according to claim 13 wherein said first current path further includes an AC operational amplifier having input and output terminals, said output terminal being coupled to said first thermal converter, and a second capacitor, said second capacitor coupling said input terminal of said AC operational amplifier to a comparison point.

Claim 17

An apparatus for obtaining the true R.M.S. value of a complex AC voltage wave according to claim 14 wherein said first means comprises: a. a photoresistor coupled from said comparison point to a reference terminal; b. a light emitting diode coupled in close proximity to said photoresistor, said photoresistor having one end coupled to said reference terminal; c. first and second terminal converters having a pair of input and a pair of output terminals, said input terminals being connected in series and said output terminals being connected in series opposition, said input and output terminals having a common junction point coupled to said reference terminal, one of said input terminals being coupled to said DC reference voltage; d. a first differential amplifier having two input terminals and an output terminal, one of said input terminals being coupled to each end of said serially opposed thermal converter output terminals, said differential amplifier output terminal being coupled to said light emitting diode varying the light output from said light emitting diode in a manner to insure the R.M.S. value of the AC voltage between, said comparison point and said reference terminal is substantially equal to the DC reference voltage.

Claim 18

An apparatus according to claim 15 wherein said second means further includes: a. a second differential amplifier having two input terminals and an output terminal, said differential amplifier providing said variable DC output voltage at said output terminal, one of said input terminals being coupled to said DC reference voltage, the other of said input terminals being coupled to said comparison point maintaining said portion of said DC output voltage between said comparison point and said reference terminal substantially equal to said DC reference voltage, whereby said DC output voltage is proportional to the R.M.S. value of said unknown AC voltage.

Claim 19

An apparatus for obtaining the true R.M.S. value of a complex AC voltage wave according to claim 13 wherein said first current path further includes: a. an AC-DC operational amplifier, having input and output terminals, said input terminal being coupled through said first resistor and said first capacitor connected in series to said complex AC voltage wave, said output terminal being coupled to a comparison point; b. a photoresistor coupled from said output terminal to said input terminal of said AC-DC operational amplifier for controlling the gain of said AC-DC amplifier; and c. a second capacitor coupled between said output terminal of said AC-DC operational amplifier and an input terminal of said first thermal converter, said AC-DC operational amplifier being a common impedance in said first and second current paths.

Claim 20

an apparatus according to claim 17 wherein said first means comprises: a. a light emitting diode coupled in close proximity to said photoresistor, said photoresistor having one end coupled to a reference terminal; b. first and second thermal converters having a pair of input terminals and a pair of output terminals, said input terminals being connected in series and said output terminals being connected in series opposition, said input and output terminals having a common junction point coupled to said reference terminal, the other of said input terminals being coupled to said DC reference voltage; and c. a first differential amplifier having two input terminals and an output terminal, one of said input terminals being coupled to each end of said serially opposed thermal converter output terminals, said differential Amplifier output terminal being coupled to said light emitting diode varying the light output from said light emitting diode in a manner to insure the true R.M.S. value of the AC voltage between said comparison point and said reference terminal is proportional to the DC reference voltage.

Claim 21

An apparatus according to claim 18 wherein said second means comprises a second differential amplifier having two input terminals and an output terminal, said second differential amplifier providing said variable DC output voltage at said output terminal and being DC coupled to said input terminal of said AC-DC operational amplifier, one of said input terminals being coupled to said DC reference voltage, the other of said input terminals being coupled to said comparison point and said reference terminal substantially equal to said DC reference voltage, whereby said DC output voltage is proportional to the true R.M.S. value of said complex AC voltage wave.

Claim 22

An apparatus according to claim 19 wherein said output terminal of said second differential amplifier is coupled to the input terminals of said AC-DC operational amplifier by a second resistor, said second resistor being proportional to said first resistor, whereby said DC output voltage is proportional to the true R.M.S. value of said complex AC voltage wave.