Electrical Impedance

Impedance definitions 47

Figure 2.10

Example of an 1P impedance, a General Radio 1406-D 100 pF gas-dielectric

capacitor.

2.2.3 Two-terminal pair

In two terminal-pair,ortwo-port (2P) impedance definition, Fig. 2.11(a), the

impedance standard is provided with two separate ports, labeled H and L.

V

I

Z

H

L

(a) 2P definition.

HL

M

LH

VI

Z

(b) 2P connection.

Figure 2.11

(a) Two-terminal pair (2P) definition of impedance. (b) The connection of a

2P impedance standard to a meter M.

Voltage is measured at port H, current at port L. Impedance is defined as

Z

2P

=

V

H

I

L

, with the defining condition V

L

≡ 0.

Two terminal-pair definition is widely employed in low-frequency impedance

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