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

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

## 12 December 2018

### Squeezing More Bandwidth From a 10x Passive Probe

 Figure 1: Shown is a comparison of inherent oscilloscope noise and noise at the shorted tip of a 10x passive probe
Now that we have a better understanding of what's happening under the hood of a 10x passive oscilloscope probe, we can sum up its key characteristics. The first thing to know about such probes is that they offer relatively low bandwidth (<100 MHz). This is largely a result of the probe's tip inductance.

## 28 November 2018

### 10x Passive Probes and Cable Reflections

 Figure 1: With unequal impedances at either end of the coax, are cable reflections a concern in 10x passive probes?
We've been discussing the ubiquitous 10x passive probe here on Test Happens, beginning with an overview of the probe-oscilloscope system. We turned to the 10x passive probe itself and the issues posed by its constitutive circuitry. Then we covered what about that circuitry makes it usable at all, namely, its built-in equalization circuit.

## 08 November 2018

### How Tip Inductance Impacts a Probing System's Bandwidth

 Figure 1: Shown are FFT plots of a 10-MHz, fast-edge square wave reaching the oscilloscope via direct coax connection (orange-yellow plot) and 10x passive probe fitted with a coax tip adapter (straw-colored plot)
If you're using 10x passive probes with your oscilloscope, it's important to understand the bandwidth of your probing system and how it's affected by various methods of probing the signal of interest. There's a relatively easy way to determine this parameter by probing a fast-edge, 10-MHz signal from a square-wave generator. Doing so can also instruct us in the effects of tip inductance on the probe's bandwidth.

## 01 November 2018

### How Equalization Works in 10x Passive Probes

 Figure 1: The adjustable equalization circuit on the oscilloscope end of the coaxial cable compensates for the 10x passive probe's inherent low-pass filter characteristics
We've been discussing 10x passive probes and their inner workings; our last post covered all the ways in which a 10x passive probe is apt to be a liability. They'd be basically unusable for any measurements at all but for one attribute: their equalization circuit (Figure 1). Without it, the 10x passive probe makes a pretty good low-pass filter, but the equalization circuit counters that with a high-pass filter to balance things out.

## 24 October 2018

### Secrets of the 10x Passive Probe

 Figure 1: The 10x passive probe becomes a better measurement tool when we understand its limitations
We began this series of posts on oscilloscope probes by putting them in perspective: Probes have a number of different jobs to do, including serving effectively as both a mechanical and electrical interface. Despite having electrical attributes of their own, we want them to grab our signal of interest, but we don't want them to affect that signal in any way.

## 10 October 2018

### Putting Probes in Perspective

 Figure 1: Probe, cable, and oscilloscope form a system that makes or breaks the accuracy of signal acquisitions
Few aspects of using an oscilloscope are as important as the probe: after all, the probe forms both the mechanical and electrical interfaces between the device under test (DUT) and the oscilloscope itself. To feed a signal into an oscilloscope, we're limited to a coaxial connection. Thus, we need a geometry transformer that picks up the signal of interest from the DUT and transfers it to the oscilloscope's coaxial connection.

## 13 September 2018

### Decision Feedback Equalization

 Figure 1: DFE filter output is based ona linear combination of previous bitdecisions
In debugging high-speed serial links, one must be cognizant of various forms of equalization that might be used in the link to compensate for signal degradation in the channel. Inter-symbol interference (ISI), attenuation, impedance mismatches, and insertion losses can all contribute to this loss of signal quality. To combat these effects, designers implement techniques such as continuous time linear equalization and feed-forward equalization.