Page 104 - Electrical Engineering Dictionary

Brewster window transmission window ple of the so-called bridge circuit. This and
oriented at Brewster’s angle with respect to other similar circuits are characterized by the
an incident light beam; light polarized in the bridge balance condition, which represents
plane of incident experiences no reflection. a relationship between the bridge elements
when the current in the diagonal impedance
bridge a simple device that connects is absent (in the case shown this condition is
two or more physical local-area networks Z 1 Z 3 = Z 2 Z 4 ). The bridge circuits find ap-
(LANs). It forwards packets of data from plication in instrumentation and transducers.
one LAN segment to another without chang-
ing it, and the transfer is based on physical bridge linearization necessary design
addresses only. The separate LAN segments concern in transducer application of the
bridged this way must use the same protocol. bridge circuits. It is achieved by reduction
of the bridge sensitivity in the bridges where
bridge balance condition represents the only one arm is a transducer. Linearization
relationship between bridge circuit compo- can also be achieved with two transducers
nents when the current in the balance indica- providing the signals of opposite signs and
tor is absent. Most of the technically useful connected in the opposite arms of the bridge
bridges include a regular connection (series, or using a current source instead of the volt-
parallel, series-parallel, or parallel-series) of age source as a bridge power supply.
two two-ports. The condition of balance can
be reformulated in terms of two-port param- bridge rectifier a full-wave rectifier to
eters, so that depending on structure, the sum convert ac to dc, that contains four rectifying
of two forward transfer parameters or the sum elements for single phase, and six elements
ofoneforwardandanotherbackwardtransfer for three phase, connected as the arm of a
parameter is equal to zero. bridge circuit.

bridge calibration used in bridge trans- bridge sensitivity the ratio of the vari-
ducer applications. It is achieved connect- ation of the voltage or the current through
ing two auxiliary circuits to the bridge. One the detector to the variation of the compo-
circuit including two resistors and a poten- nent that causes the disbalance of the bridge
tiometer is connected in parallel to the bridge circuit.
power supply diagonal, and the potentiome-
ter tap and one end of detector are connected bridge-controlled multivibrators using
to the same bridge node. Sliding the tap, switches in a two-operational amplifier or in
one can eliminate the bridge offset. An- an amplifier-comparator multivibrator so that
other circuit, usually including a constant the bridge is “rotated” each half of the period,
and a variable resistor, is connected in series one can obtain control of the oscillation fre-
with power supply. This circuit allows one quency by detuning a resistive bridge. The
to change the voltage applied to the bridge, circuit can be applied in sensors with limited
and to establish the correspondence between number of access wires.
the maximal deflection of the detector and
maximum of the physical variable applied to bridging using bridges for local-area net-
the bridge resistors playing the role of active works.
gauges.
brightness the perceived luminance or ap-
bridge circuit the circuit that includes parent intensity of light. This is often differ-
four lateral impedances, Z 1 , Z 2 , Z 3 , Z 4 ,a ent from the actual (physical) luminance, as
diagonal impedance Z o , and a voltage source demonstrated by brightness constancy, Mach
E g of the output impedance Z g is an exam- band, and simultaneous contrast.

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