A Survey of items appearing in the Tektronix 3000 Series oscilloscope time domain display
Greetings and welcome to our 61st Test and Measurement video. Today we’ll get into an area that is right at the heart of the users’ experience with the amazing Tektronix MDO31043 oscilloscope. It is of 19 items that appear in this instrument’s time domain display. These are separate and distinct, although there is some overlap, from items that appear in the frequency domain display and also items that appear in the arbitrary function generator display. Moreover, not all of these items appear all the time. Some of them come and go as different oscilloscope functions are invoked by means of the front panel controls and contextual soft keys.
For this demonstration, we need a signal, so we have connected a 120-volt, single-phase utility power circuit, accessed from a premises branch circuit, to a TPP1000 10:1 attenuating probe, and thence to the oscilloscope’s channel one analog input port. What is displayed, of course, is a 60-Hz sine wave.
In doing this type of hookup, it is worth repeating that care must be taken that the probe’s ground return lead is not connected to the black, hot conductor that is referenced to but floats above the premises electrical system ground potential. Instead, it should be connected to the white, neutral conductor. The first time this hookup is done it is a good idea to check the wiring to make sure the white and black conductors were terminated correctly all the way from the building’s electrical service to the final power plug. If the wiring has been crossed anywhere along the line, there will be heavy fault current, possible damage to the oscilloscope and circuit being measured, and a generally hazardous situation will be created.
As an interesting subtopic, I would like to point out that there is a completely hazard-free way that you can access one or more utility power waveforms without danger of crossing the probe leads. Just connect the probes to the end of a flexible cord, such as a short extension cord, without plugging into live power. Lay this cord segment parallel to an energized power cord, about an inch from it. This is essentially a very low inductance isolation transformer with small current and a phantom voltage on the secondary.
The price to pay for this safe hookup is a slight amount of distortion in the sine wave as displayed on the oscilloscope, but for this demonstration that is not an issue.
So now let’s take a look at the display and do a survey of all on-screen items. At the upper left corner of the screen next to the Tek logo is the current triggering status. Most of the time, when the Run/Stop button is green, it will say Run. If you press that button, it will turn red and the triggering status will change to Stop. Also, pressing the Single button stops the acquisition and changes the status to Stop until it is toggled back to Run.
To the right at the top is the trigger state. PrTrig indicates that the oscilloscope is acquiring pretrigger data. Trig? Means the instrument is waiting for trigger. Trig’s indicates that it is in the triggered state.
The rectangular bar at the top corresponds to the entire acquisition and in its center is an orange triangle that is the expansion point. It shows the location around which the horizontal scale expands and compresses. Turning the small inner Wave Inspector knob, the display goes to split-screen format and brackets are shown that enclose the corresponding zoomed view. Directly below the expansion point is another orange icon that is the triggering point.
The triggering level can be moved vertically using the level control in the triggering section, and horizontally using the position control in the horizontal section. When the triggering level is made higher or lower than a waveform peak, the trace goes out of synch and become unstable.
In the lower information bar below the display are shown some pertinent pieces of information. To the left is the active channel with its dedicated color, in this instance yellow for channel one. Adjacent to it the number of volts per division is shown. The remainder of this information bar shows other data such as the sampling rate and the triggering level, and also the date and time.
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