You need to test, we're here to help.

You need to test, we're here to help.

06 December 2017

Probing Techniques and Tradeoffs (Part IV)

Applying bandwidth filters to a 2.5-GHz clock signal clearly shows the effect of bandwidth on rise time
Figure 1: Applying bandwidth filters to a 2.5-GHz clock
signal clearly shows the effect of bandwidth on rise time
The topic of probe bandwidth is a broad and deep one. We began our discussion of bandwidth in an earlier post with some basic information about what bandwidth means and the importance of the -3 dB point. Next, we looked at a Fourier deconstruction of a square wave into its fundamental and the lower-order harmonics, and covered the importance of bandwidth in capturing enough harmonic content to understand the signal's overall shape.

27 November 2017

Probing Techniques and Tradeoffs (Part III)

Bandwidth is defined as the frequency at which the ratio of the displayed amplitude to the input amplitude is -3 dB (or 0.707)
Figure 1: Bandwidth is defined as the frequency at which
the ratio of the displayed amplitude to the input amplitude
is -3 dB (or 0.707)
Any discussion of oscilloscopes and/or probes must include the topic of analog bandwidth. Bandwidth is one of a short list of key specifications for a testbench setup. All oscilloscopes and probes come to market with a bandwidth specification, which is defined as:

The frequency at which the ratio of the displayed amplitude to the input amplitude is -3 dB (or 0.707).

This is known as the "-3 dB point," or the half-power point (Figure 1). At this frequency, a sine-wave input signal is attenuated to 70.7% of its true amplitude. Any higher frequencies will likely be distorted on the display, making accurate measurements and calibration impossible.

20 November 2017

Probing Techniques and Tradeoffs (Part II)

A snapshot of available probes from Teledyne LeCroy
Figure 1: A snapshot of available probes from
Teledyne LeCroy
Our first post in this series concentrated on connectivity and various means by which one might apply an oscilloscope probe to a circuit or device under test. Now, we'll look at an "ideal" probe vs. a real-world probe, and then begin a discussion of probe specifications.

15 November 2017

Probing Techniques and Tradeoffs (Part I)

Probes are the signal's gateway to the oscilloscope
Figure 1: Probes are the signal's gateway to the oscilloscope
As any oscilloscope user (hopefully) knows, probing is perhaps the most critical element of getting good measurement results (Figure 1). We must understand our probes' specifications to ensure that we obtain the best possible signal fidelity, and thereby accurately characterize our signal under test. In this series of posts, we'll take you through probing tradeoffs and techniques and help you choose the right probe for the task at hand.

30 October 2017

The Power Integrity Measurement Mindset

Figure 1:  The holistic view
of power integrity
In kicking off a series of posts on power integrity measurements, it might be helpful to start with some thoughts on the mindset, or approach, that one should take in the endeavor. Power integrity is best approached holistically, with an eye toward each of the paths energy may take throughout a system.

24 October 2017

Automotive Ethernet Compliance: Test Equipment Requirements

The TF-ENET-B Ethernet test fixture offers all necessary interconnects for compliance test
Figure 1: The TF-ENET-B Ethernet
test fixture offers all necessary
interconnects for compliance test
Having completed an exhaustive tour of the Automotive Ethernet compliance tests, we would be remiss if we didn't offer our take on the test equipment required for the job. Let's look at what the needs would be in terms of the oscilloscope itself as well as the necessary ancillary equipment, test fixture, probes, and cables. We'll conclude with a short discussion of automated compliance software.

17 October 2017

Automotive Ethernet Compliance: Tests in Detail (Part IV)

The specified pass/fail mask for the  transmitter power spectral density test
Figure 1: The specified pass/fail mask for the
transmitter power spectral density test
We've been making our way through a detailed accounting of the compliance tests for Automotive Ethernet, and in our last post, we covered the distortion test. Now we'll wrap up the tour of the compliance test suite with the test of transmitter power spectral density.