Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Patent
1995-06-27
1997-05-06
Regan, Maura K.
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
324649, 324691, 324713, G01R 2716
Patent
active
056274769
ABSTRACT:
An impedance probe circuit and method presents a balanced load to a DC or RF voltage source and to two voltage measurement nodes. The impedance probe circuit is accurate for measurement of an impedance device X which has a range always less than the value of a characteristic impedance C. A source terminal is coupled to a voltage source having a series impedance C. A test resistor T is connected between the source terminal and one terminal X1 the unknown impedance. A reference resistor R is connected between the source terminal and the other terminal X2 of the unknown impedance. The parallel combination of the test resistor T and the reference resistor R has an impedance substantially equal to C/3. A third impedance of value C/3 is connected to the node X1 and to a first voltage measurement terminal. A fourth impedance of value C/3 is connected to the node X2 and to a second voltage measurement terminal. The voltage measurement terminals are respectively connected to ground through respective LOAD1 and LOAD2 resistors having values C. When the value of the test resistor T and the reference resistor R are properly chosen, the ratio of the voltages across LOAD1 and LOAD2 provides a measurement of the value of the unknown impedance. The sensitivity of the probe circuit in db per ohm is set by predeterminedly choosing the values of the reference resistor R and of the test resistor T.
REFERENCES:
patent: 2800629 (1957-07-01), Tagg
patent: 4028507 (1977-06-01), Hoppough
patent: 5345182 (1994-09-01), Wakamatsu
patent: 5463323 (1995-10-01), Wakamatsu
patent: 5469071 (1995-11-01), Obata
Brown Glenn W.
Heller III Edward P.
King Patrick T.
Regan Maura K.
Seagate Technology Inc.
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