Ectron 560H, Инструкция по эксплуатации

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Applications Model 560H
The wire should be copper to minimize thermal
effects, and the shielding should be 100% coverage
to minimize degradation in common-mode rejec-
tion. The shield should be continued as close as
possible to the connector termination. The input
signal leads should neither be routed near conduc-
tors which carry high ac currents nor be near
equipment producing magnetic fields.
Output wiring should be two-conductor twisted
pair with or without shield. If shielded, the shield
should be tied to output common at the amplifier,
not the load. The pin assignments for the card-edge
connector are listed in Table 4-1.
COMMON-MODE EFFECTS
The common-mode potential of an input signal is
that floating potential common to both input leads
with respect to output common. For example, if the
amplifier is measuring the voltage drop across a
shunt located in the

5 V lead of a power supply,
the common-mode voltage is the 5 V supply
voltage and the desired signal is the millivolt drop
across the shunt. (This assumes that the common
of the 5 V supply is tied to output common of the
amplifier.) The common-mode rejection of the
amplifier is the ability of the amplifier to reject the
5 V signal and amplify only the millivolt shunt
signal.
The Model 560H has the ability to reject common-
mode signals by 50 dB plus gain in dB for voltages
from dc to 60 Hz having an amplitude up to
±10 V dc or peak ac and with an unbalanced resist-
ance of up to 350

. In the power supply example,
operating with a gain of 100 (40 dB), the Model
560H would reduce the effects of the 5 V
common-mode signal by at least 90 dB or to an
equivalent 160 µV or less. Multiplied by the gain
of 100, this would produce an output offset of no
more than 16 mV. Note that this offset can be
canceled by zeroing the amplifier with no load on
the power supply.
The unbalanced-resistance part of the specification
would be the resistance of the shunt, or the differ-
ence in resistance present in the two inputs to the
amplifier. Unbalanced resistance is only significant
for ac common-mode signals.
In order to maximize common-mode rejection,
several precautions must be observed when wiring
the input to the amplifier. Shielding should be as
complete as possible; and, for ac-common-mode
signals, unbalanced resistance should be mini-
mized. If the signal leads are coupled through
connectors, the shells of the connectors should be
connected to the common-mode signal the same as
the cable shield.
COMMON-MODE VOLTAGE
The maximum operating common-mode voltage
rating of this amplifier is ±10 V dc or peak ac. For
signals over a few tenths of a volt, the maximum
common-mode voltage must be reduced so that the
sum of common-mode and signal (normal-mode)
voltages does not exceed the 10 V rating. When the
100:1 divider is used, the common-mode voltage
rating of the amplifier is ±300 V dc or peak ac.
ENCLOSURES
WARNING
When using an enclosure, make sure that its
chassis is connected to earth ground, preferably
through third-wire ground.
Three enclosures are available for use with the
Model 560H amplifier. The Model R513-16
accepts 16 amplifiers and is designed to fit a
standard 19-inch EIA rack enclosure. The Model
E513-6A is a bench-mounting enclosure that
accepts up to six amplifiers. The Model E513-2A,
also a bench-mounting enclosure, holds two
amplifiers. Each of these enclosures includes an
integral ac power supply which provides all
necessary amplifier power.
MODEL R513-16 (DRAWING 513-622)
This sixteen-channel enclosure provides all neces-
sary power for the amplifiers. It operates from
100 V ac to 240 V ac.
MODEL E513-6A ENCLOSURE (DRAWING
513-613)
This six-unit enclosure, designed for bench use,
includes two 115/230 V ac power supplies and
rear-panel connectors with mates for all inputs and
outputs. The power supplies generate the necessary
voltages for the amplifiers. The zero-detector
switch S2, located on the front panel, allows the
user to turn off the null-indicating LED’s on the
amplifiers. The output connectors P7-P18 contain
5-2