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30 October 2013

Oscilloscope Basics: Controlling an Oscilloscope (Part II)

An example of a touch screen-equipped oscilloscope.
Figure 1: An example of a
touch screen-equipped
In a recent post, we discussed how to control a modern digital oscilloscope using the front-panel controls. That was a natural place to begin, given that it's the "traditional" means of controlling the instrument and the one that most seasoned users cut their teeth on. But there's more than one way to skin this cat these days. Many of today's oscilloscopes carry touch screens that do everything the front-panel controls can do, plus some things they cannot do.

In fact, in this age of smartphones and tablets, we've become conditioned to expect display screens to have touch capability. So why shouldn't your oscilloscope? For me, one cool thing about the touch screen on, say, a Teledyne LeCroy HDO, is that you don't have to take your eyes off the display to adjust parameters and so on (Figure 1). Sometimes, after a lengthy session of using an HDO, I find myself stabbing my finger at my laptop's screen. No such luck, though!

Figure 2: Shown are the constituent parts of the touch
screen on a Teledyne LeCroy HDO oscilloscope.
On an HDO, the entire display is touch-enabled, and by the way, a single press of the Touch Screen button on the front panel will disable the touch screen functionality if desired. HDOs come with a stylus that lives in a slot just below the front panel, but the touch screen works just fine with a fingertip. The display supports touch, double-touch, touch-and-drag, touch-and-hold (equivalent to a right mouse click), and drawing of selection boxes. If touching isn't your thing, you can use a mouse, and you can jump back and forth from touch screen to front panel if you feel the need to.

Let's have a look at the various sections of the touch screen on an HDO (Figure 2). Across the top of the display is the menu bar of drop-down menus, providing access to setup dialog boxes. All of the instrument's functionality is accessible through the menu bar or through other shortcuts. One handy item on the menu bar is an Undo button at top right, which appears whenever the user performs an action that can be undone.

Figure 3: The HDO's channel descriptor box
The business area of the display is the grid area, in which waveforms are displayed. The Display drop-down menu allows dividing the grid area into as many as 16 separate grids for display of multiple waveforms. Feel free to drag and drop waveforms from one grid to another for a quick eyeball comparison.

Trigger level (vertical axis) and trigger position (horizontal axis) indicators appear at the right side and bottom of the grid area, respectively. They'll show up when you set a trigger and are color-coded to match the input.

Cursors show where measurement points have been set. You can touch and drag cursors to reposition the measurement point at any time.

Figure 4: The HDO's timebase descriptor box
Channel (C1-C4), Zoom (Z1-Z4), Math (F1-F8), or Memory (M1-M4) descriptor boxes appear immediately below the grid and summarize current settings for each open trace (Figure 3). Timebase and Trigger descriptor boxes appear at the right of the display (Figure 4). Timebase and Trigger settings only apply to channel traces. Touching any descriptor box opens the corresponding setup dialog.

Dialogs appear at the bottom of the display for entering set up data. The top dialog will be the main entry point for the selected function. For convenience, related dialogs appear as a series of tabs behind the main dialog. Touching tabs opens the relevant dialog boxes.

That concludes our brief tour around the touch screen of a modern digital scope, in this case, the HDO. All of the major manufacturers of test equipment approach their user interfaces a little differently, but much of what's been covered here will apply to other brands' touch screens. In the next installment of this series, we'll take a look at how the touch screen functions in practice.

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