Best scope for 5-6k

[Performa01]

One thing that makes it feel smaller too is that the trigger doesn't seem to fire when the waveform is zoomed out too much. With a 1.4Vpp sine wave at 10V/div with a DC rising edge trigger at 0V it doesn't fire. The same settings to fire the trigger on the Tek scope we're evaluating. Any ideas what's going on here?

First let us get the facts right: Trigger sensitivity is universally specified as divisions. A 1.4 Vpp signal at 10 V/div fills just 0.14 div.

Now let's see,what Tektronix has to say on that matter:

https://www.tek.com/en/support/faqs/what-are-reasonable-trigger-thresholds-how-small-signal-will-trigger-oscilloscope

Here we learn, that "Most Tektronix oscilloscopes will trigger on a signal of 0.35 divisions at up to 50 or 100 MHz". This is a pretty high sensitivity indeed, yet it's only guaranteed at lower frequencies, up to 100 MHz. Most importantly, that minimum level is still 3.5 Vpp, hence 2.5 times the 1.4 Vpp signal.

By contrast, the Siglent SDS3000X HD has a trigger sensitivity of 0.52 div over the full bandwidth. So yes, it is a bit less sensitive, but at the same time also more noise tolerant and not bandwidth limited. The special "Noise Reject" setting increases the trigger threshold to even higher 0.66 div.

The question remains, why someone would want to dsiplay a signal trace with such a tiny amplitude - and then trigger on it, on top of that?

In general, vertical sensitivity should be chosen to maximize the signal without clipping. Just like an analog meter, where you try to get the measurement in the upper third of the scale.

With 0.14 div, only ~1.7 % of the ADC range is used. In an 8-bit system, this reduces the acquisition to 2 bit resolution - it's still 6 bits in a 12-bit system. Either way, such a tiny signal is not a good trigger source, especially nowadays, where fully digital trigger systems are almost universally used.

A trigger signal should always be as much full scale as possible. If the signal is of no interest otherwise, then making it tiny by reducing the vertical gain is the wrong approach. One can just hide the trace or use the external trigger input instead.

[resonant_frequency]

Thanks for clarifying the trigger sensitivity. I wasn't aware that was a documented spec, but that makes sense.

My reason for wanting to do that is I frequently want to measure 4 signals at once. Sometimes the channel that makes the most sense to trigger off of I care about the least visually. With relatively limited vertical space on the display, it's nice to make the signal as small as possible, but still be able to glance at it and see the general shape. Another reason is to include all the waveforms in a screenshot

For example: recently I was looking into a power amp performance and was measuring the input signal, the output signal and the post transformer voltage and current. My trigger made most sense as the input signal as it had sharp edges and a constant magnitude, but after my primary evaluations I didn't care much about the shape, but still wanted to see when it started and ended relatively to the other signals.

There's not a way to set the V/div at a certain number and then digitally zoom out is there?

[Performa01]

There's not a way to set the V/div at a certain number and then digitally zoom out is there?

Why not pick up my suggestion: display the trigger signal full screen for a quality trigger with minimal jitter, but hide it?

If you still want to watch the signal, you can indeed rescale it by means of a math function. See attached screenshots for an example.

SDS2504X_HD_Trig_C4
A proper trigger setup for a 1.4 Vpp signal on C4.

SDS2504X_HD_Trig_Mon_C4_F1
Math channel F1 configured as a copy of C4 and scaled to 10 V/div.

SDS2504X_HD_Trig_Mon_F1
Same as before, but now C4 trace has been hidden.

[resonant_frequency]

Why not pick up my suggestion: display the trigger signal full screen for a quality trigger with minimal jitter, but hide it?

If you still want to watch the signal, you can indeed rescale it by means of a math function. See attached screenshots for an example.

This worked great!