Some Probing Tips - Tektronix PRIMER P6101B Manual

Figure 1.10. Probe compensation adjustments are done either at the probe head or at
a compensation box where the box attaches to the oscilloscope input.
For example, current probes are designed to sense the
current flowing through a wire. The probe converts the sensed
current to a corresponding voltage signal which is then
conveyed to the input of the oscilloscope. Similarly,
optical probes sense light power and convert it to a voltage
signal for measurement by an oscilloscope.
Additionally, oscilloscope voltage probes can be used with a
variety of other sensors or transducers to measure different
phenomena. A vibration transducer, for example, allows you
to view machinery vibration signatures on an oscilloscope
screen. The possibilities are as wide as the variety of available
transducers on the market.
In all cases, though, the transducer, probe, and
oscilloscope combination must be viewed as a measurement
system. Moreover, the realities of probes discussed above also
extend down to the transducer. Transducers have bandwidth
limits as well and can cause loading effects.

Some Probing Tips

Selecting probes that match your oscilloscope and application
needs gives you the capability for making the necessary
measurements. Actually making the measurements and
obtaining useful results also depends on how you use the
tools. The following probing tips will help you avoid some
common measurement pitfalls:
Compensate Your Probes
Most probes are designed to match the inputs of specific
oscilloscope models. However, there are slight variations from
oscilloscope to oscilloscope, and even between different input
channels in the same oscilloscope. To deal with this where
necessary, many probes, especially attenuating probes (10X
and 100X probes), have built-in compensation networks.
If your probe has a compensation network, you should adjust
this network to compensate the probe for the oscilloscope
channel that you are using. To do this, use the following
procedure:
1. Attach the probe to the oscilloscope.
2. Attach the probe tip to the probe compensation test point
on the oscilloscope's front panel (see Figure 1.10).
3. Use the adjustment tool provided with the probe or other
non-magnetic adjustment tool to adjust the compensation
network to obtain a calibration waveform display that has
flat tops with no overshoot or rounding (see Figure 1.11).
4. If the oscilloscope has a built-in calibration routine, run this
routine for increased accuracy.
An uncompensated probe can lead to various measurement
errors, especially in measuring pulse rise or fall times. To avoid
such errors, always compensate probes right after connecting
them to the oscilloscope and check compensation frequently.
ABCs of Probes
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