Ectron 560H, Инструкция по эксплуатации

Страница: 17 / 36

SECTION V
5
APPLICATIONS
SAFETY
When using the Model 560H in an ac-powered
enclosure, ensure that the chassis is connected to
“earth” ground. This is normally accomplished
using the ac-line cord that accompanies the
enclosure.
MODEL 560H OPERATING CONTROLS
A number of controls are available on the front
panel of all Model 560H amplifiers. In addition,
two operating controls, RTO offset and the 100:1
divider, are located on the circuit card. The switch-
able filter control is available only on those ampli-
fiers having Option L, M, or N.
GAIN CONTROLS
The step-gain control provides an accuracy of
±0.1% of the indicated step-gain position when the
VERNier IN/OUT switch is OUT. The VERNier
control increases the fixed gain step by more than
2.5 times, so the overall gain range without divider
is from 1 to more than 2500.
The 100:1 gain divider IN/OUT switch is located
at the connector end of the main circuit card of the
Model 560H. This control reduces the front-panel
gain settings by a factor of 100 thereby affording a
total gain range from 0.01 to more than 2500. With
the divider in use, input impedance drops from the
nominal 50 M

to 1 M

.
ZERO CONTROLS
The 560H has two controls that affect amplifier
zero: RTI zero and RTO zero with its associated
three-step range switch. (RTI stands for referred-
to-input and RTO stands for referred-to-output.)
The RTO-zero potentiometer, located on the front
panel, produces an offset at the output of the
amplifier that has a range determined by a three-
position switch located at the connector end of the
circuit card. The range switch is labeled with its
full-scale ranges of ±0.1 V, ±1 V, and ±10 V. That
is, the front-panel RTO-zero potentiometer can
offset the output by ±0.1 V, ±1 V, or ±10 V. Note
that the resolution of the RTO-zero control
diminishes as range increases.
The RTI-zero potentiometer, also located on the
front panel, affects the input zero of the amplifier
ahead of the gain-multiplying circuits. Thus the
effect at the output of the amplifier of the RTI-zero
control increases with increasing gain (whereas the
RTO-zero control setting is independent of gain).
For example, if the amplifier’s input is shorted and
the RTI-zero control is set such that there is an
input offset of 20 µV, assuming the RTO-zero
control is set for zero output at low gain; as gain
increases, output zero will become increasingly
further from zero by an amount equal to the gain
times the 20 µV offset. Although amplifier opera-
tion will be normal with the zero controls set off
zero, the proper method of setting zero controls is
to set RTO zero at low gain and RTI zero at high
gain. By repeating this procedure a few times the
output will remain at zero when gain is varied
throughout its total range.
ZERO INDICATORS, OUTPUT MONITOR
JACKS
The amplifier’s output signal is available on the
front-panel monitor jacks labeled HI and LO.
These jacks can be connected to a meter to deter-
mine the output level or to set zeros. Also located
on the front panel are two LED indicators that
show the output condition of the amplifier. One
LED, labeled

, is energized when the offset is
plus and the other LED, labeled

, is energized for
minus. When both LED’s are extinguished, the
amplifier output is within approximately 2 mV of
zero. (The range is from 2 mV to 20 mV
depending on the setting of R84.) Noise will cause
both LED’s to turn on and if it is sufficient may
mask a null condition.
SIGNAL WIRING
Two-conductor, twisted-pair shielded cable is rec-
ommended for wiring to the inputs of the ampli-
fier. A dc return path from input to output low is
not required unless it is needed for noise reduction.
5-1