Tektronix 1A5 Instruction Manual page 15

F i g. 2-5. S i m pli fied input circu i t and table to show the change in
×
CMRR (apparent) due to 10 probes that are within 1, 2, and 3%
of their attenuation values.
voltage divider reduces the output range to ±0.5 V to
keep the E qu i va lent Comparison Voltage R
with the maximum input voltage range. To determine the
actual voltage present in these three positions, read the
Vc AMPLITUDE dials as ins
by 10.
The Vc is applied directly to the input amplifier within
the Type 1A5. B e cause it by-passes the attenuator, it is
equivalent to an input signal which is the product of Vc
and the attenuator in use. In the 1, 2, 5, 10 and 20mV/CM
positions it is equivalent to a
because a ×1 attenuation factor is in effect.
attenuator in the 50 mV, .1 and .
equivalent to a ±50- V input voltage range, and the ×1 00
attenuator in the .5, 1 and 2 V
equivalent range of ±50 0 V. S
to ±0. 5 V in the 5, 10 and 2
the ×1 000 attenuator in use again provides an equivalent
range of ±50 0 V.
The equivalent voltage ranges just explained are indi ­
cated through color-coding on the front panel of the Type
1A5. This color coding is explained in conjunction with
the VOLT S/ CM control ass e
All Vc s et tings in this manual are writ
s epa rated by hyphens. S a mples of this method are illus ­
trated in F i g. 2-8B, C and D.
VOLTS/CM Control Ass
The s ett ing of the VOLT
mines the deflection factor, the Input S
E q u i v a lent Comparison Voltage R
input voltage of the Type 1A5.
R e f e r to F i g. 2-9A. The large gray knob is attached to
a s ha ft which controls the gain of the output stages of the
Type 1A5. A white dot on this knob indicates the deflec ­
a nge consistent
t ructed and divide the results
±5- V range of input signals
The × 10
2 V/ cm positions makes it
/ cm positions provides an
i nce the Vc range is reduced
0 V/ cm s e n s iti vi ty positions,
mbly.
t en as three digits
e mbly
S/ CM control ass emb ly deter ­
i gnal Range, the
a n ge and the maximum
Operating Instructions — Type 1A5
tion factor of the Type 1A5 and oscilloscope combination
at any instant.
The clear plastic flange between the gray knob and the
front panel of the Type 1A5 is connected to an intermittent
drive planetary gearing which
attenuators in the A and B INPUT circuits.
Fig. 2-6. Connecting a differential amplifier across a circuit.
ground shown in (C) is not essential to the measurement.
simultaneously switches
Attenuator
The
2-7