Specifications

First, the linear portion of the 1820/1822’s +5V output
range is around zero volts. As the 1820/1822
approaches its limits, the output signal will be distorted.
Moving the oscilloscope position control way from
center screen can allow these distortions to appear on the
oscilloscope’s screen where they may be mistaken for
part of the displayed signal.
Second, proper operation of the 1822’s Precision Voltage
Generator (PVG) depends on the operator knowing the
location of zero volts on the display. The readout in the
PVG is designed to display the voltage of the signal as it
crosses the center line of the oscilloscope screen. If the
oscilloscope position or offset control has been moved,
incorrect readings could result.
Using Oscilloscope V/Div Settings Greater than
500 mV/Div
"I know the input to the 1820/1822 is a sinewave, but I
am seeing a square wave on the oscilloscope." This
comment is the result of the operator setting the
oscilloscope sensitivity to something less than 1V/div. If
the oscilloscope sensitivity is set to 2V/div, the
1820/1822 will limit at 2-1/2 divisions above and below
center screen (zero volt point if the oscilloscope’s
position control is properly set). Thus, a sinewave large
enough to overdrive the 1820/1822 will appear as a
square wave on the oscilloscope.
The 1820/1822 is designed to cleanly limit the output
signal to +5V. Keeping the oscilloscope’s position at
center screen and using oscilloscope sensitivities between
500mV/div and I mV/div (or the oscilloscope’s most
sensitive setting) will insure good signal integrity. When
the displayed signal contains mostly low frequency
components, the operator can use the oscilloscope’s
1V/div setting to allow large signals to be completely
shown on screen.
182011822 Operator’s Manual
Failure to Terminate the Amplifier into 50 f2
"All the signals displayed on my oscilloscope seem to be twice
as large as they should be." This comment results from not
having the output of the 1820/1822 properly terminated into 50
if2. The 1820/1822 output impedance is 50 f). The cable
connecting the 1820/1822 to the oscilloscope or spectrum
analyzer should be 50 f2 and be terminated with a 50 ~ load.
If the termination at the end of the connecting coaxial cable
is missing, the amplifier will not be properly terminated.
The gain of the amplifier will be twice that indicated by the
front panel settings and the 1822’s EFFECTIVE GAIN
indicator will be offby a factor of two.
In some measurements, the operator can take advantage of this
increased gain if the problems caused by not terminating the
output are fully understood and taken into account.
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