Remote measuring transformer coupled impedance bridge for balanced and unbalanced circuits

Claim 2

For use in combination with a conventional bridge normally unsuited for measurements on balanced-to-ground impedance or admittance and in circuit with a signal generator and with a null signal detector, a balanced-to-ground impedance/admittance determining network comprising: a balancing transformer having its primary side connected to an impedance measuring input terminal of said conventional bridge; a first center tap connected to said primary side and to electrical ground; a secondary side of said transformer; a second center tap connected to said secondary side and to electrical ground; a variable capacitor coupled across said secondary side; a variable resistor coupled in parallel circuit with said capacitor and said secondary side; and a pair of terminals respectively coupled to opposite sides of said secondary side for receiving and connecting to an unknown impedance or admittance.

Claim 3

A network as in claim 1 further including a switch in circuit between said second center tap and electrical ground for enabling the determination of whether said unknown impedance or admittance is balanced to electrical ground.

Claim 4

An impedance/admittance bridge, comprising: a first balancing circuit for coupling to a source of electrical energy and having a signal detector integral therewith for sensing the presence or absence of a null signal condition, said first balanced circuit including; a first terminal for coupling to said electrical energy source; a first impedance coupled to said first terminal; a second impedance of equal value with respect to said first impedance and coupled to said first terminal; and a first transformer coupled between said first and second impedance, said detector being coupled to said secondary of said transformer; a calibrating circuit including variable impedances coupled to said first balanced circuit, said calibrating circuit including; a second, balancing transformer, the primary side of which is coupled to said first impedance, to said first transformer and to a point of common electrical ground potential, and the secondary side of said second balancing transformer being connected in circuit with said variable impedances, a test circuit for coupling to an unknown impedance/admittance, said test circuit being coupled to said first balanced circuit whereby the calibrating circuit impedances are adjustable to create a null signal condition at said detector when the value of said unknown impedance is equal to the value of said calibrating circuit impedances, said test circuit including; a third, balancing transformer, the primary side of which is coupled to said second impedance, to said first transformer and to a point of common electrical ground potential, a pair of electrical terminals for connecting to said unknown impedance; and the secondary side of said third balancing transformer being connected in circuit with said pair of terminals, a variable capacitor in circuit across the secondary side of said third balancing transformer, a blocking capacitor in series circuit between said second impedance and the primary side of said third balancIng transformer; a first relay coil in series circuit between said second impedance and electrical ground, two relay contacts respectively connected to said pair of electrical terminals for selectively connecting said pair of terminals to electrical ground or to the secondary side of said third balancing transformer, a second relay coil in series circuit between said second impedance and electrical ground, a center tap located on the secondary of said third balancing transformer, and a relay contact connected to said center tap for selectively coupling said center tap to electrical ground when said second relay coil is energized.

Claim 5

An impedance/admittance bridge, comprising: a first balancing circuit for coupling to a source of electrical energy and having a signal detector integral therewith for sensing the presence or absence of a null signal condition, said first balanced circuit including; a first terminal for coupling to said electrical energy source; a first impedance coupled to said first terminal; a second impedance of equal value with respect to said first impedance and coupled to said first terminal; and a first transformer coupled between said first and second impedance, said detector being coupled to said secondary of said transformer; a calibrating circuit including variable impedances coupled to said first balanced circuit, said calibrating circuit including; a second, balancing transformer, the primary side of which is coupled to said first impedance, to said first transformer and to a point of common electrical ground potential, and the secondary side of said second balancing transformer being connected in circuit with said variable impedances, a test circuit for coupling to an unknown impedance/admittance, said test circuit being coupled to said first balanced circuit whereby the calibrating circuit impedances are adjustable to create a null signal condition at said detector when the value of said unknown impedance is equal to the value of said calibrating circuit impedances, said test circuit including; a third, balancing transformer, the primary side of which is coupled to said second impedance, to said first transformer and to a point of common electrical ground potential, a pair of electrical terminals for connecting to said unknown impedance; and the secondary side of said third balancing transformer being connected in circuit with said pair of terminals, a variable capacitor in circuit across the secondary side of said third balancing transformer, a blocking capacitor in series circuit between said second impedance and the primary side of said third balancIng transformer; a first relay coil in series circuit between said second impedance and electrical ground, two relay contacts respectively connected to said pair of electrical terminals for selectively connecting said pair of terminals to electrical ground or to the secondary side of said third balancing transformer, a second relay coil in series circuit between said second impedance and electrical ground, a center tap located on the secondary of said third balancing transformer, and a relay contact connected to said center tap for selectively coupling said center tap to electrical ground when said second relay coil is energized.

Claim 6

A bridge as in claim 3 further including a rectifier in circuit between said second relay coil and said second impedance.

Claim 7

A bridge as in claim 3 further including a resistor in parallel circuit with respect to said secondary of said third balancing transformer and said variable capacitor.

Claim 8

A remote impedance measuring system for directly measuring the complex impedance of a remote load relatively inaccessibly located at a more conveniently located site, said system comprising: a test circuit including a first transformer having predetermined electrical characteristics located at the site of said remote load for transformer coupling of said load from input terminals to output terminals of said test circuit, a first length of transmission line having predetermined electrical characteristics and having one end electrically connected to the output terminals of said test circuit, and a conveniently located impedance measuring device comprising: two equal impedances connected together as two adjacent arms of a four arm bridge circuit, signal source means connected to the connected junction of said equal impedances for supplying electrical power to the bridge circuit, detector means connected across the other ends of said equal impedances for detecting a null condition of said bridge circuit, the other end of said transmission line being connected with a first of said equal impedances whereby the transformer coupled remote load impedance is connected via said first transmission line as a third arm of said bridge circuit, calibrated variable known impedance elements, a second length of transmission line having the same predetermined electrical characteristics as said first length of transmission line, and a second transformer having the same predetermined electrical characteristics as said first transformer connected for transformer coupling between said known impedance elements and one end of said second length of transmission line, the other end of said second length of transmission line being connected to a second of said equal impedances whereby the transformer coupled known impedances are connected via said second transmission line as a fourth arm of said bridge circuit.

Claim 9

A remote impedance measuring system for directly measuring the complex impedance of a remote load relatively inaccessibly located at a more conveniently located site, said system comprising: a test circuit including a first transformer having predetermined electrical characteristics located at the site of said remote load for transformer coupling of said load from input terminals to output terminals of said test circuit, a first length of transmission line having predetermined electrical characteristics and having one end electrically connected to the output terminals of said test circuit, and a conveniently located impedance measuring device comprising: two equal impedances connected together as two adjacent arms of a four arm bridge circuit, signal source means connected to the connected junction of said equal impedances for supplying electrical power to the bridge circuit, detector means connected across the other ends of said equal impedances for detecting a null condition of said bridge circuit, the other end of said transmission line being connected with a first of said equal impedances whereby the transformer coupled remote load impedance is connected via said first transmission line as a third arm of said bridge circuit, calibrated variable known impedance elements, a second length of transmission line having the same predetermined electrical characteristics as said first length of transmission line, and a second transformer having the same predetermined electrical characteristics as said first transformer connected for transformer coupling between said known impedance elements and one end of said second length of transmission line, the other end of said second length of transmission line being connected to a second of said equal impedances whereby the transformer coupled known impedances are connected via said second transmission line as a fourth arm of said bridge circuit.

Claim 10

A remote impedance measuring system as in claim 15 wherein said first transformer comprises a first center-tapped winding with opposite ends thereof being normally connected across a nominally balanced-to-ground remote load and with the center tap normally connected to ground potential, and means for selectively and remotely disconnecting said center tap from ground potential whereby an unbalanced condition of said load may be detected.

Claim 11

A remote impedance measuring system as in claim 16 further comprising means for selectively and remotely disconnecting said opposite ends of said first center-tapped winding from said remote load whereby reference impedance measurements may be taken that are not dependent upon the value of said remote load impedance.