Tektronix 323, Instruction Manual

Page: 27 / 170

S
l-
Z
TABLE 2-1
Signal Transporting Methods, Passive
Method Advantages
Limitations
Equipment
Required1
Source
Loading1
Precautions
Unshielded Test Leads
Availability
Limited frequency re­
sponse; subject to stray
pickup and oscillation
B N C - 1 o-Binding Post
Adapter; two test leads
Oscilloscope input im­
pedance
Insert 47 £2 resistor in se­
ries with signal lead to
suppress oscillations. Place
leads strategically to re­
duce
shunt capacitance
and stray pickup
Unterminated c o a x i a l
cable or 1 X probe
Convenience
Limited frequency re­
sponse; high capacitance
of cable
Coaxial cable with BNC
connectors; or 1 X probe
Oscilloscope input im­
pedance plus cable ca­
pacitance High capacitive loading
Coaxial cable terminated
in characteristic impedance
at oscilloscope F u l l oscilloscope band­
width. Provides uniform re­
sponse while using long
cables
Loading effect due to
termination (typically 50
fl); power limit of termi­
nation
Coaxial cable with BNC
connectors and BNC ter­
mination (typically 50 Q)
Termination value (Typ­
ically 50 fl) in parallel
with oscilloscope input
impedance
Loading on test point;
power limit of termination;
Use DC-blocking capacitor
between source and termi­
nation;
reflections from
oscilloscope input imped­
ance
Terminated coaxial cable
with coaxial attenuator be­
tween source and termina­
tion
Less reflection from oscil­
loscope input impedance;
increased voltage range Reduces oscilloscope sen­
sitivity Coaxial cable with BNC
connectors; BNC coaxial
attenuator; BNC termi­
nation
Termination value (typ­
ically 50 Q) in parallel
with oscilloscope input
impedance
Loading on test point;
power limit of attenuator
and termination; use DC-
blocking
capacitor be­
tween source and termi­
nation
Tap into terminated co­
axial system with a BNC
T at oscilloscope input
Optimum signal transfer;
no termination required at
oscilloscope
BNC T; 2 signal cables
with BNC connectors
Oscilloscope input im­
pedance Signal size may require
use of attenuators
Attenuator probes Reduces oscilloscope load­
ing; increases v o l t a g e
r a n g e ; protects oscillo­
scope Oscilloscope sensitivity
reduced by attenuation
factor
10X, 100X or 1000X
probe
10X SS lOMfJ and 10
pF
100X SS 10 M fl and
2.5 pF
1000X 5S 100 MQ and
3 pF
Current probe Permits current evaluation
without interrupting circuit
Current Probe; Amplifier
(optional) increases range R <0.03
a
L < 3 [M
1See Tektronix catalog fo r specific equipment characteristics.
O
p
e
ra
ti
n
g
In
s
tr
u
c
tio
n
s
—
Ty
pe
3
2
3