EE 420L Engineering Electronics II Lab - Lab 2
Operation of a compensated scope probe
Pre-lab work
- Watch
the video scope_probe and review scope_probe.pdf (associated notes).
- Vary
the parameters in the simulations found in probe.zip to ensure you
understand the operation of a compensated 10:1 scope probe.
- From
lab 1 ensure that you understand the operation and analysis of simple
RC circuits (likely a quiz on this).
- Ensure
that you can read/create Bode plots and plot the corresponding
signals in the time-domain at a particular frequency.
- Read
the write-up seen below before coming to lab
Perform, and document in your html lab
report, the following:
- Show
scope waveforms of a 10:1 probe undercompensated, overcompensated, and
compensated correctly.
- Comment
on where the type of scope probe (i.e., 1:1, 10:1, 100:1, etc.) is set
on your scope (some scopes detect the type of probe used automatically).
- Draft
the schematic of a 10:1 scope probe showing: the 9 MEG resistor, 1 MEG
scope input resistance, capacitance of the cable, scope input
capacitance, and capacitance in the probe tip.
- Using
circuit analysis, and reasonable/correct values for the capacitances,
show using circuit analysis and alegbra (no approximations), that the
voltage on the input of the scope is 0.1 the voltage on
the probe tip.
- Devise
an experiment, using a scope, pulse generator, and a resistor, to
measure the capacitance of a length of cable. Compare your measurement
results to the value you obtain with a capacitance meter. Make sure you
show your hand calculations.
- Build
a voltage divider using two 100k resistors. Apply a 0 to 1 V pulse at 1
MHz to
the divider's input. Measure, and show in your report, the output of
the divider when probing with a cable (having a length greater than or
equal to 3 ft) and then a compensated
scope probe. Discuss and explain the differences.
- Finally,
briefly discuss how you would implement a test point on a printed
circuit board so that a known length of cable could be connected
directly to the board and not load the circuitry on the board.
Ensure
that your html lab report includes your name, the date, and your email
address at the beginning of the report (the top of the
webpage).
When
finished backup your work.