Analog Oscilloscope XY Mode for a Phase Check
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Quick answer: XY mode plots one signal against another, not against time. For two sine waves of the same frequency, a Lissajous figure on the screen can be used to estimate phase. On the V-212, XY mode is listed and the X-axis bandwidth and phase difference are not published (shown as — below). V-5040D figures marked † in the table are covered by the confirmation note under that table. Keep the instrument earthed; do not remove a safety earth.
What XY mode is, and what it is not
An analog oscilloscope in a normal sweep mode plots voltage against time. In XY mode, one input drives the vertical deflection and the other drives the horizontal deflection, so the trace is one signal against the other. Tektronix’s primer XYZs of Oscilloscopes (03W-8605-6) describes XY mode and phase-shift measurements, including the intercept method for two sine waves of the same frequency: phase = arcsin(A/B), where A and B are distances read from the figure. That formula is a general method from the primer. It is not a specification of either instrument on this page, and it is not a substitute for a published phase-difference figure.
Both current analog models list XY (or X-Y) operation. The product handle for the V-212 includes the word “digital,” but the instrument itself is an analog CRT oscilloscope.
Compare the two analog models on published XY facts
| Model | Vertical bandwidth | XY / X-Y mode | X-axis bandwidth | Phase difference | Listed price (USD) |
|---|---|---|---|---|---|
| V-212 | 20 MHz (DC–20 MHz) | Listed (X-Y mode) | — | — | 548.20 (110 V or 220 V) |
| V-5040D | 40 MHz (DC–40 MHz) | Listed (X-Y operation) | † | † | 1180.00 (110 V or 220 V) |
— = not listed on the product page. † For the V-5040D, confirm the channel count, X-axis bandwidth, and phase with us before ordering.
The V-212 listing also includes two channels, a 6-inch CRT, dimensions 310 × 130 × 370 mm, weight 8.5 kg, 1 mV/grid sensitivity, CH1 / CH2 / alternate / chop / add vertical modes, and separate 110 V and 220 V options (they are not an automatic dual-voltage input). The packing list is the host, a power cord, two probes and a manual.
The V-5040D listing includes a 6-inch rectangular CRT with an 8 × 10 div internal graticule (1 div = 1 cm), CH1 or CH2 sensitivity of 5 mV/div to 5 V/div ±3% in 11 ranges, a maximum input of 400 V (DC + AC peak) at or below 1 kHz, A sweep 50 ns/div to 5 s/div, dimensions 310 × 130 × 370 mm, and weight 9.5 kg. 110 V and 220 V are again separate options. The feature list groups channel count with delayed sweep as items to confirm; those items are included in the confirmation already stated, and this table does not treat a channel count as a published fact.
Do not use older bandwidth or phase figures from earlier store copy. The current product page is the source for this table.
Worked example: two 1 kHz sine waves
A technician wants a rough phase check between a 1 kHz reference and a second 1 kHz sine taken after a filter. Both amplitudes are comfortable within the V-212’s vertical ranges. Select XY mode, apply one signal to the horizontal input and the other to the vertical input, and adjust the amplitudes so the figure is readable. If the result is an ellipse, the intercept method from the Tektronix primer can be used to estimate the phase. That estimate is only as good as the figure on the screen and the method itself. The V-212 page does not publish an X-axis bandwidth or a phase-difference specification, so the result should be recorded as a screen-based estimate, not as a numbered instrument accuracy.
If the same check is planned on a V-5040D, settle the channel count, the X-axis bandwidth and the phase figure before the instrument is ordered, using the confirmation already stated. Vertical bandwidth on that listing is 40 MHz, which is a different fact from the unpublished X-axis bandwidth.
Keep each instrument earthed through its supplied power connection. Do not remove a safety earth to view a signal.
Vertical bandwidth and X-axis bandwidth are different specifications. The 20 MHz figure on the V-212, and the 40 MHz figure on the V-5040D, describe the vertical deflection system. They do not stand in for an X-axis bandwidth, and they do not create a phase-difference rating. If a phase check will be made at a frequency where the horizontal channel may be rolling off, you need the X-axis figure, not only the vertical one.
The Tektronix primer’s intercept method also assumes two sine waves of the same frequency and a readable figure. If the frequencies differ, the trace is no longer a stable ellipse of the kind that method describes. If the amplitudes are badly mismatched, the figure is hard to read and the intercepts become a poor basis for an estimate. Record the frequencies, the amplitudes, the input coupling and the fact that the result is a screen-based estimate.
Use the probes that ship with the instrument, or probes that match the work, and keep the earth connection in place. For bandwidth and probe context, see the oscilloscope bandwidth and probe guide. Current instruments are in the oscilloscope collection.
A short checklist before you use XY mode
- Confirm that both signals are sine waves of the same frequency if you will use the Tektronix intercept method.
- Choose the instrument from published facts. V-212 lists XY mode; its X-axis bandwidth and phase difference are unpublished (—). V-5040D figures marked † follow the confirmation note under the table.
- Select the supply option (110 V or 220 V) that matches the site; they are not interchangeable on one unit.
- Keep the instrument earthed. Do not remove a safety earth.
- Record frequencies, amplitudes, coupling and the fact that the phase figure is a screen-based estimate, not a numbered instrument accuracy.
Worked example: when the intercept method does not apply
A technician compares a 1 kHz sine reference with a 2 kHz square wave from a different node. Those traces will not form the stable, same-frequency ellipse that the Tektronix primer’s intercept method describes. Switching to XY mode will still plot one input against the other, but phase = arcsin(A/B) is the wrong reduction for that pair. Return to a time-base display if you need to inspect period and timing, or use a method that matches those waveforms. The same caution applies if the two sines drift apart in frequency: the figure will move, and a single intercept pair is a poor basis for a reported phase.
Mistakes that show up on real jobs
Using the vertical bandwidth as if it were the X-axis bandwidth. 20 MHz on the V-212 and 40 MHz on the V-5040D describe the vertical system. They do not replace an X-axis figure, and they do not create a phase-difference rating.
Applying the intercept formula to mixed frequencies or to non-sine waveforms. The primer method is described for two sine waves of the same frequency.
Writing a screen estimate as a calibrated phase accuracy. The V-212 page does not publish an X-axis bandwidth or a phase-difference specification. On the V-5040D, those items belong to the confirmation already stated.
Treating the V-212 as a digital storage oscilloscope because the URL handle contains “digital.” The listing is an analog CRT instrument.
Selecting the wrong mains option, or removing the safety earth to view a signal. 110 V and 220 V are separate options on both models. Keep each instrument earthed through its supplied power connection.
An analog CRT does not keep a stored copy of the Lissajous figure after the inputs change or the instrument is switched off. If the phase estimate has to go into a report, record it at the time — frequencies, amplitudes, coupling, the intercepts you read, and a photograph or a sketch of the figure — rather than expecting a saved waveform as on a digital storage oscilloscope.
FAQ
Is XY mode the same as a normal time-base display?
No. A normal sweep plots voltage against time. XY mode plots one input against the other.
Can I read phase from a Lissajous figure on any waveform?
The intercept method in the Tektronix primer is described for two sine waves of the same frequency. Other waveforms need a method that matches those waveforms.
Does the V-212 handle mean the instrument is a digital storage oscilloscope?
No. The product is listed as an analog oscilloscope with a CRT, even though the URL handle contains the word “digital.”
Are 110 V and 220 V interchangeable on the same unit?
No. They are separate options on both models. Choose the supply that matches the site.
Sources
Specifications and prices are from the linked product pages and manufacturer documents and may change. Follow the supplied manual and the procedures that apply to your work.