Specifications

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1820/1822 Operator’s Manual
Model 1820 Operation
The performance and operation of the 1820 Differential
Amplifier is identical to that of the 1822 except as
follows:
The 1822 EFFECTIVE GAIN indicator is not
included in the 1820. The 1820 operator will need to
keep track of the various attenuator and gain settings
to accurately account for the proper deflection factor
on the oscilloscope.
Front Panel Settings Effective Full Scale Range
GAIN ATTEN
VCOMP VDIFF
XI +10 +155V +lOOV
XI0, xl00,
+1o +155v +lOV
xl000
XI
+1 +15.5V +lOV
Xi0, xl00, +! +15.5V
+lV
xl000
Front Panel Effective Full Scale Range
Settings
with +100 Probe
GAIN ATTEN
VCOMP VDIFF
X1 +10 +15.5kV
+lOkV
XI0 +!0 ±15.5kV
41000V
X!
+!
+ 1550V + ! 000V
Xl0 +1 +1550V +iOOV
.
The VcoMe and WHIFF functions operate the same as
in the 1822. The 1820 does not contain the Precision
Voltage Generator, but the voltages required for the
operation of VCOMP and VDIFF can be provided
from an external source. This voltage source is
applied to the 1820 through the OFFSET
VOLTAGE connector on the rear panel. By using a
stable voltage source and monitoring the level with a
DVM, operation and accuracy similar to that of the
1822 can be achieved. The maximum input voltage
that can be applied depends on whether the 1820 is
operated in VCOMP or VDIFF.
The following charts will help the operator stay within the
maximum input voltage limits and understand the
relationship between the actual voltage applied and the
effective voltage. Effective voltage is always referred to
the input of the 1820 or the probe tip if a probe is used.
When using probes, the maximum effective voltage range
may be limited by the maximum voltage rating of the
probe.
When operating the 1820 with an external voltage source,
the applied voltage should not exceed 15.5 volts in
Comparison mode and 10.0 volts in Differential Offset
mode.
When these maximum external voltages are applied, the
effective voltage as seen by the amplifier is as follows:
2-6
Note that the effective voltage is always increased by the
attenuator. It therefore follows that any probe will
increase the effective voltage of both VCOMP and VDIFF
by its attenuation factor. In other words, a probe with a
+100 attenuation factor will increase the effective full
scale range by 100.
Although the full scale range may be 10kV or 15.5kV,
most probes have a much lower maximum input voltage
rating which must not be exceeded.