Dielectric loss measuring apparatus employing plural tuned circuits

Claim 1

An apparatus for the precise measurement of very low dielectric losses of a dielectric specimen at high frequencies comprising: a stabilized high frequency oscillator; a tank circuit connected to said oscillator; a resonant circuit electromagnetically coupled to said tank circuit, and having an inductor and two variable air capacitors of equal capacity all connected in series, said capacitors being grounded at their common connected ends; first and second parallel tuned circuits having the same construction and circuit constants each having one end grounded and each being electrostatically coupled to said resonant circuit at the opposite ends of said grounded capacitors through very small capacitances of equal value; a secondary detecting circuit coupled to said first and second parallel tuned circuits; indicator means responsive to the vectorial addition of voltages of opposite phase in said detecting circuit for providing a manifestation of the resonance of said first and second tuned circuits; and circuit means for connecting said specimen in parallel wiTh said first parallel tuned circuit.

Claim 2

An apparatus for the precise measurement of very low dielectric losses of a dielectric specimen at high frequencies comprising: a stabilized high frequency oscillator; a tank circuit connected to said oscillator; a resonant circuit electromagnetically coupled to said tank circuit, and having an inductor and two variable air capacitors of equal capacity all connected in series, said capacitors being grounded at their common connected ends; first and second parallel tuned circuits having the same construction and circuit constants each having one end grounded and each being electrostatically coupled to said resonant circuit at the opposite ends of said grounded capacitors through very small capacitances of equal value; a secondary detecting circuit coupled to said first and second parallel tuned circuits; indicator means responsive to the vectorial addition of voltages of opposite phase in said detecting circuit for providing a manifestation of the resonance of said first and second tuned circuits; and circuit means for connecting said specimen in parallel wiTh said first parallel tuned circuit.

Claim 6

An apparatus for the precise measurement of very low dielectric losses of a dielectric specimen at high frequencies comprising: a stabilized high frequency oscillator; a tank circuit connected to said oscillator; a resonant circuit having an inductor coupled to the coil of said tank circuit and first and second variable capacitors all connected in series, said first and second capacitors being grounded at their one ends and being of equal capacity; first and second coils having the same construction and circuit constants connected in parallel with said first and second capacitors, the capacitances C1 and C1'' of said first and second capacitors and the inductances L1 and L1'' of said first and second coils having the relations of omega 2L1C1> 1 and omega 2L1''C1'' > 1, where omega represents angle frequency, with said first and second variable capacitors being adjusted to maintain said series tuning circuit at resonance; first and second tuned circuits each having the same construction and circuit constants, said first and second tuned circuits having third and fourth coils respectively, said third and fourth coils being electromagnetically coupled to said first and second coils with the same coupling respectively; an indicating circuit having inductors electromagnetically coupled to said third and fourth coils and an indicating meter whose deflection is set at zero under normal conditions so that the output voltages from said first and second circuits in their tuned state are equal to each other; and circuit means having test electrodes coupled to said first tuned circuit for connecting one specimen in parallel with the former; whereby the loss and capacitance components of the specimen under test are derivable from a minute change in at least one of the series-connected capacitors when the output of said dectecting input due to the presence of the specimen is made zero.

Claim 7

An apparatus for the precise measurement of very low dielectric losses of a dielectric specimen at high frequencies comprising: a stabilized high frequency oscillator; a tank circuit connected to said oscillator; a resonant circuit having an inductor coupled to the coil of said tank circuit and first and second variable capacitors all connected in series, said first and second capacitors being grounded at their one ends and being of equal capacity; first and second coils having the same construction and circuit constants connected in parallel with said first and second capacitors, the capacitances C1 and C1'' of said first and second capacitors and the inductances L1 and L1'' of said first and second coils having the relations of omega 2L1C1> 1 and omega 2L1''C1'' > 1, where omega represents angle frequency, with said first and second variable capacitors being adjusted to maintain said series tuning circuit at resonance; first and second tuned circuits each having the same construction and circuit constants, said first and second tuned circuits having third and fourth coils respectively, said third and fourth coils being electromagnetically coupled to said first and second coils with the same coupling respectively; an indicating circuit having inductors electromagnetically coupled to said third and fourth coils and an indicating meter whose deflection is set at zero under normal conditions so that the output voltages from said first and second circuits in their tuned state are equal to each other; and circuit means having test electrodes coupled to said first tuned circuit for connecting one specimen in parallel with the former; whereby the loss and capacitance components of the specimen under test are derivable from a minute change in at least one of the series-connected capacitors when the output of said dectecting input due to the presence of the specimen is made zero.