Products > Test Equipment

Siglent SDS800X HD Review & Demonstration Thread

(1/87) > >>

Performa01:
A revised summary of this thread together with some new content in a PDF can be found here:

SDS800X HD Review Part 1

SDS800X HD Review Part 2

----------

I have decided to evaluate the SDS824X HD and will post the results here.

Why the 800 and not the 1000X HD?

Well, I suppose the SDS800X HD to be the most popular offer for hobbyists and small businesses in Siglent’s lineup, eventually replacing the successful SDS1000X-E series.
Even though there are some differences, most of that are comfort features (except for the 50 ohm inputs), hence the SDS800X HD test results should be largely valid for the SDS1000X HD as well.

I’ve once listed the obvious differences between SDS800X HD and SDS1000X HD here (reply #45):

https://www.eevblog.com/forum/testgear/siglent-just-drop-its-mic-new-sds800hd-12bit-scope-crazy-price-leaked/msg5212773/#msg5212773

In the meantime I have a confirmed list of differences:

-SDS800X HD has no external trigger input.
-Only the 200 MHz SDS800X HD have 100 Mpts memory, the lower models have only 50 Mpts.
-SDS800X HD has no 50 ohm inputs.
-SDS800X HD doesn’t have the higher quality encoders with indents
-SDS800X HD has less serial protocols: CAN-FD and FlexRay are missing.
-SDS800X HD has only 2 USB host ports.
-SDS800X HD has only 7” capacitive touch screen, but at the same resolution 1024 x 600.
-SDS800X HD doesn’t support probe factor detection.
-SDS800X HD doesn’t support Tektronix Mode.
-SDS800X HD doesn’t support Advanced Measurements Display Mode M2.
-SDS800X HD doesn’t support Measurement Histograms Secondary Zoom.
-SDS800X HD has no RTC.

+SDS800X HD supports NTP.

The first impression was very positive. The instrument feels solid, the display appears a bit small, especially for someone used to the 10.1” screens of the 2000 series, yet the resolution is the same and it’s bright and crisp.

Operation feels snappy, it appears to be (at least) on par with the SDS2000X Plus/HD series in this regard.

The fan noise is about the same as in the SDS1104X-E, thus it can be slightly annoying and users will have something to optimize 😉

Boot time is less than 40 seconds.

And sorry, no, I haven’t tried to install a web browser or PDF reader or play doom on it, even though I know that these might be the most important features for some 😉

Now that these trivialities are out of the way, let’s have a look at the performance – and I have to state in advance that there is a lot of progress when compared to the trusty 1000X-E series – it’s almost a completely different world.


Table of Content

This posting
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/

1.   Bandwidth
2.   Pulse Response

Reply #1
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293744/#msg5293744

1.   Noise & Spurs
2.   Vertical Zoom Demo

Reply #2
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293747/#msg5293747

1.   History & Sequence Mode
2.   Counting Pulses
3.   Trigger Jitter

Reply #3
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293750/#msg5293750

1.   Measurements
2.   Measurement Histograms
3.   Vertical Axis Labels
4.   DC Check
5.   Counter

Reply #4
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293753/#msg5293753

1.   AC Trigger Coupling
2.   Triggering noisy signals

Reply #5
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293756/#msg5293756

1.   Deep Measurements
2.   Probe Bandwidth

Reply #6
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293759/#msg5293759

1.   Poor Men’s Differential Probing
2.   Distortion measurements

Reply #7
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293762/#msg5293762

1.   Digital Channels

Reply #8
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293765/#msg5293765

1.   Measurements 2 (Trend/Track)
2.   FFT Dynamic range

Reply #9
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5293771/#msg5293771

1.   True Vertical Sensitivity
2.   Peak Detect
3.   Bode Plot at a glance

Reply #58
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5332358/#msg5332358

1.   Bode Plot Example

Reply #63
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5335604/#msg5335604

1.   SPI Speed Test

Reply #65
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5335802/#msg5335802

1.   The 200 Mbps SPI challenge

Reply #67
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5338655/#msg5338655

1.   Mask Test

Reply #68
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5341157/#msg5341157

1.   Zoom Expectations

Reply #72
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5343827/#msg5343827

1.   Serial Decoders

Reply #73
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5346977/#msg5346977

1.   Cursors

Reply #74
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5351024/#msg5351024

1.   System Performance with SP5050A Probe

Reply #80
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5354024/#msg5354024

1.   Custom Probe Factors

Reply #82
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5357321/#msg5357321

1.   Dots Mode

Reply #90
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5360858/#msg5360858

1.   X-Y

Reply #150
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5373095/#msg5373095

1.   Identity

Reply #155
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5373974/#msg5373974

1.   Noise Density

Reply #160
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5377403/#msg5377403

1.   Noise density 2

Reply #167
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5380811/#msg5380811

1.   Granular Noise

Reply #180
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5384846/#msg5384846

1.   HAM Test

Reply #199
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5389646/#msg5389646

1.   Fun with Square Waves

Reply #214
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5392730/#msg5392730

1.   Zoom Challenge

Reply #234
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5396741/#msg5396741

1.   FFT-Setup
2.   FFT Window Functions


Bandwidth

Let’s start with the bandwidth. We would like to get the specified bandwidth even with all channels active, yet we do not want to deal with excessive aliasing. 

At first, one single channel at 2 GSa/s:


SDS824X_HD_FR_2GSa_log

Amplitude drop at 200 MHz is less than 2 dB and actual -3 dB bandwidth is 244 MHz. Frequency response is even a tad better when two channels are in use at 1 GSa/s:


SDS824X_HD_FR_1GSa_log

Amplitude drop at 200 MHz is <1.8 dB and actual -3 dB bandwidth is 245 MHz. Finally we look at all four channels in use at only 500 MSa/s:


SDS824X_HD_FR_500MSa_log

Now the bandwidth is actually limited to the advertised 200 MHz.


Pulse Response

For all these tests, a 10 MHz square wave with 1 ns rise time has been fed into cannel 4.

Lets start with single channel mode and 2 GSa/s:


SDS824X_HD_PR_2GSa_Zoom_Stop

In stop mode, we get a clear picture of the imperfections of the pulse top even when zoomed in 20x (main window: 100 mV/div, zoom: 5 mV/div). The rise time measurements yield the expected result of ~1.8 ns, which corresponds to 1.5 ns rise time for the SDS824X HD. This is well below the specified 1.8 ns for the 200 MHz model.

In Run mode we can see some modulation because of noise, yet nothing that could not be cured by averaging using a math trace:


SDS824X_HD_PR_2GSa_Zoom_Avg16

In case you wonder why the imperfections of the pulse top are so pronounced in the previous screenshot, this is simply the price we pay for less than perfect impedance matching when using a scope that lacks 50 ohm inputs. External termination is always a compromise working reasonably well up to 70 MHz at best. Fast edges like the 1 ns rise time in this example occupy 600 MHz bandwidth. The output impedance of the pulse generator isn’t perfect 50 ohms either, and both phenomena combined lead to reflections showing up in the first ~16 ns of the pulse.

Of course it can be demonstrated, how better impedance matching improves things. For this I’ve used a quality 18 GHz cable with two 10 dB 18 GHz Narda in-line attenuators (one at each end) to ensure sufficient attenuation for any reflections between generator and DSO. Because of the 20 dB attenuation in total, I had to increase the generator output level by 20 dB as well. This would have been 6 V amplitude, but at that level, it’s rise time is limited to min. 1.2 ns, hence I made do with just 3 V and increased the DSO sensitivity to 50 mV/div, in order to still get the 1 ns rise time:


SDS824X_HD_PR_2GSa_Zoom_Avg16_Match

With two active channels, the sample rate drops to 1 GSa/s:


SDS824X_HD_PR_1GSa

The overshoot is more pronounced now (probably because of additional AA-filtering), yet rise time measurements haven’t changed.

With four active channels, the sample rate drops to only 500 MSa/s:


SDS824X_HD_PR_500MSa

We can see hints on slight reconstruction errors together with rather pronounced Gibbs ears. Rise time measurement is off by hefty 27%, so we can safely state that this configuration is not fit for characterizing pulses with <2 ns rise time.

With a signal rise time of 2ns we can measure 2.6 ns: assuming 1.5 ns rise time for the SDS824X HD, this measurement now is only ~5% off and should be acceptable already. Furthermore, we can use Dots mode to get rid of any reconstruction errors:


SDS824X_HD_PR_500MSa_2ns_Dots

Performa01:
Noise & Spurs

This is a demonstration of the noise with all channels active, where the bandwidth is limited to true 200 MHz.

The noise is shown for various conditions:

Ch.1: input open, 200 MHz bandwidth;
Ch.2: input open, 20 MHz bandwidth;
Ch.3: input 50 ohm terminated, 200 MHz bandwidth;
Ch.4: input 50 ohm terminated, 20 MHz bandwidth;

Because of the pronounced 1/f characteristic of the frontend noise below about 300 kHz, the results strongly depend on the lower bandwidth limit. Let’s start with 100 kHz:


SDS824X_HD_Noise_100kHz-200MHz_4Ch

Compare this with 10 kHz lower bandwidth limit:


SDS824X_HD_Noise_10kHz-200MHz_4Ch

1 kHz lower bandwidth limit:


SDS824X_HD_Noise_1kHz-200MHz_4Ch

Finally 200 Hz lower bandwidth limit:


SDS824X_HD_Noise_200Hz-200MHz_4Ch

Here you can see the noise characteristic up to 25 MHz at a RBW of ~90 Hz. In order to prevent aliasing taking effect, the noise measurement has been done of a 20 MHz bandwidth limited input channel. Since this bandwidth limiter is only first order, a digital 30 MHz lowpass filter has been added.


SDS824X_HD_Noise_20Hz-25MHz_4Ch_F30M

The Noise characteristic is a combination of the 1/f noise of the MOSFET input buffer in the HF path and the FET OpAmp in the LF path, which is fed with a heavily attenuated signal that has to be amplified again before the recombination of both paths.

We can clearly see this in the previous screenshot:
At 300 kHz, the measured noise level is -150.894 dBV, this corresponds to a noise density of just 3 nV/√Hz at a RBW of 89 Hz. The following table shows the complete measurements:

300 kHz:   -150.894 dBV    3.0 nV/√Hz
100 kHz:   -144.227 dBV    6.5 nV/√Hz
 30 kHz:   -135.927 dBV   16.9 nV/√Hz
 10 kHz:   -125.303 dBV   57.5 nV/√Hz
  3 kHz:   -116.034 dBV  167.2 nV/√Hz
  1 kHz:   -111.083 dBV  295.6 nV/√Hz
300 Hz:    -111.665 dBV  276.5 nV/√Hz
100 Hz:    -108.281 dBV  408.2 nV/√Hz

At 10 MHz, the noise density has dropped to about 2.4 nV/√Hz.

Finally let’s have a look at the spurious signals (CH.4, 50 ohm termination, 20 MHz bandwidth limit):


SDS824X_HD_Spurs_200Hz-200MHz_4Ch

The Peaks List shows the 10 strongest spurious signals, where all are at or below 1 µVrms, except for a single spur at 1.14155 MHz, which is 3.85 µVrms. This is exceptionally good, especially in this class.


Vertical Zoom Demo

Vertical zoom can suffer from noise, if high zoom factors are used. Some demonstrations use bandwidth limits to reduce noise when zooming in. It is in the responsibility of the user then to make sure that no relevant high frequency detail gets lost by this.

In general, the question remains: what if we need to look at higher frequencies? A 200 MHz 12-bit DSO should be able to demonstrate a resolution advantage with 200 MHz bandwidth signals just as well…

Here is the signal mix: a 1 MHz 600 mVpp sine with a 200 MHz 10 mVpp sine riding on it:


SDS824X_HD_VZ10x_Run

I’ve chosen straight 10 mV/div for the zoom window, i.e. a ten times magnification. The superimposed waveform is a little noisy, yet clearly visible.

This is run mode. In stop mode, we can see that all the noise is just modulation and lowering the bandwidth wouldn’t help anyway:


SDS824X_HD_VZ10x_Stop

In stop mode we basically get a clean waveform with some distortion. Yet this is just 12 bits without any additional tricks.

We can use the average math function to get rid of the modulation:


SDS824X_HD_VZ10x_Avg16

16 times average (Math trace F1) is enough to get the waveform pretty clean even in run mode. The implicit resolution enhancement of this measure is 4 bits, so that the DSO is effectively working with 16 bit data now.

Performa01:
History & Sequence Mode

Inspired by the complaint here:

https://www.eevblog.com/forum/testgear/rigol-hdo1000-and-hdo4000-12bit-oscilloscopes-launched-in-china/msg5269170/#msg5269170

I’ve tried to replicate the test scenario described by forum member Egonotto, which is a fairly moderate one. For this, the SDS800X HD doesn’t need any special mode; the always active background history can handle that:


SDS824X_HD_5ms_Hist

The test signal is a burst packet, 20 µs long, consisting of 100 pulses. The repetition interval (burst period) was 5 ms for this test.

At 5 µs/div, the SDS824X HD takes an average of 650 µs/frame and a maximum of <2 ms/frame. The screenshot shows the History List displaying the time delta between the packets. It is 5 ms throughout, with the occasional 4.999 ms because of the not so accurate timebase of the SDS800 (25 ppm vs. 1 ppm in the SDS2000X Plus/HD series).

For event recording, we’d rather use the dedicated Sequence mode. This provides a constant 52 µs/trigger @ 5 µs/div, hence can capture a burst period of 100 µs without a single missing frame:


SDS824X_HD_100us_Seq

The screenshot shows the History List displaying the time delta between the packets. It is 100 µs throughout, with the occasional 99 µs because of the not so accurate timebase of the SDS800.

For complete information, here are my measurements for the trigger rates during normal use with vector and dots display mode as well as sequence recording from the fastest timebase of 1 ns/div up to 100 µs/div.


SDS824X HD Trigger rate


Counting Pulses

This is a demonstration of the pulse count function. As further refinement, gated measurements can be used in order to ignore unwanted portions of the record.

First the basic pulse measurement without any bells and whistles; a 100 MHz pulse packet with 1 ns rise time and 1000000 pulses is fed into Ch.4


SDS824X_HD_Pulsecount

The scope registers the correct number of one million positive pulses. The negative pulse count naturally delivers the same number minus one. Together with the peak to peak deviation of zero over >100 acquisitions it is obvious that the pulse count is spot on.

Let’s add a measurement gate. We define it to start 1.0 ms after the trigger point and to be 5 ms wide:


SDS824X_HD_Pulsecnt_Gate

We now get a count of ~500k (100 MHz x 0.005 sec.) as expected. The count is a little higher because of the limited accuracy of the timebase in the SDS800.

We can engage the zoom view for a closer inspection of the waveform:


SDS824X_HD_Pulsecnt_Gate_Zoom

We can still see the gating cursors in the main window, but the detailed view with time data is in the zoom window now. Since the “B” cursor exceeds the size of the zoom window, it is drawn at the right border and the time specification of 6.00 ms is another hint that it is outside the zoom window, which is only 100 ns wide.

The gating cursors are fully independent, consequently we can still add regular cursors (manual/tracking/measurement):


SDS824X_HD_Pulsecnt_Gate_Zoom_Cursors

With all these information, screen gets a bit busy, but we could also use the traditional info block for the regular cursors and place it at the least disturbing spot:


SDS824X_HD_Pulsecnt_Gate_Zoom_Cursors2


Trigger Jitter

The datasheet specifies the trigger jitter as <100 ps. This doesn’t sound great, considering the SDS2000X HD, where the specification is <10 ps RMS (and it has been measured as 2.02 ps actually).

Now let’s measure this using a 200 MHz sine signal from an OCXO-driven AWG (SDG7102A), fed into channels 2 and 4 of the SDS824X HD via a 12.4 GHz resistive power splitter. This way we can observe the jitter in the trigger channel as well as a not triggered channel.

The high quality 200 MHz sine signal has been chosen for its fast edges and low inherent jitter – after all we want to characterize the DSO and not the signal source.

We need to utilize a measurement gate, because for some unknown reason the T@M measurement considers all rising edges in the record, whereas we only want to measure the first one.


SDS824X_HD_Trigger Jitter

At a timebase of 1 ns/div, we cannot see any jitter in the triggered as well as the non-triggered channel after more than 10 minutes at infinite persistence.

The jitter measurements are as follows:
Triggered channel: 28.6 ps pk-pk, 4.852 ps rms;
Un-triggered channel: 28.9 ps pk-pk, 4.652 ps rms;
Skew Ch.2-Ch.4: 20.9 ps pk-pk, 3.39 ps rms;

While this is about twice as much as the SDS2000X HD, it is still very respectable and miles ahead of older designs with analog trigger system (none of Siglent’s X and A series).

Performa01:
Measurements

There are the simple measurements, where we can define an arbitrary set of up to all 52 measurements that are related to a single channel. This set can subsequently be applied to any Input-, Zoom-, Math- or Reference-Channel. That’s also one disadvantage of the simple measurements – it’s restricted to a single channel. The other drawback is the total lack of statistics in this mode.


SDS824X_HD_Measure_Simple_Embedded

A high number of measurements might be desirable at times, yet it takes up a lot of screen space. Siglent has now introduced a new display option for measurements; “Floating”:


SDS824X_HD_Measure_Simple_Floating

This is a transparent overlay which might help to better utilize the screen space in certain situations.

We also got the Advanced Measurements., but unfortunately only mode A; mode B is available only in its bigger (and more expensive) siblings:


SDS824X_HD_Measure_Advanced_Embedded

We can have statistics and also enable the little Histicons (History Icons) as in the screenshot above, we can also mix various channels, yet we are restricted to only 5 measurements at a time.

We can have floating measurements in this mode as well, yet it might be a good idea to turn the axis labels off to avoid text collisions:


SDS824X_HD_Measure_Advanced_Floating


Measurement Histograms

The small Histicons in the advanced measurements statistics can be enlarged by simply clicking or tapping on them. This opens a separate window with a more detailed version of the histogram. The last measurement result is marked by a small red dot in the histogram, so one can watch the build up of the histogram even when there is already a lot of data collected and histogram bars don’t visibly change anymore.


SDS824X_HD_Measure_Advanced_Histogram


Vertical axis labels

The new kids in town like the SDS800X HD also bring new features: apart from the logarithmic frequency axis for the FFT, as demonstrated in the noise measurements, we also got a selectable vertical label position.


SDS824X_HD_VLabel_left


SDS824X_HD_VLabel_right


SDS824X_HD_VLabel_center


DC Check

One of the advantages of a 12 bit DSO should be not only high resolution, but also good accuracy. The SDS800X HD has a typical error of 0.5% at vertical gain settings from 5 mV/div up to 10 V/div, thus entering 3.5 digit DMM territory.

Here is a quick check with a 300 mV DC “signal”:


SDS824X_HD_DC_300mV

The error in this measurement is <0.13%. Mean and RMS measurements show pretty much the same result, as expected.


Counter

The SDS800X HD does not provide a DMM, but it has at least the Counter application. It can be used as a frequency counter or totalizer. I don’t see much use in the frequency counting function, chiefly because the automatic measurements can do exactly the same – and even on more than one channel at a time – and then we have the always visible 7 digit trigger frequency counter on top of that (I wouldn’t ever want a scope without that feature!).

But the Counter is still not totally useless, as it can also be configured as gated totalizer:


SDS824X_HD_Totalizer_Gated

Channel 3 is fed with a 1 ms wide pulse as a gating signal, channel 4 is connected to a 10 MHz sine source. Consequently, a single shot acquisition results in 10000 hits = 10 khits. This is deadly accurate because both signals come from the same AWG, hence both signals are derived from the same OCXO (whose accuracy is irrelevant in this application, yet is specified <100 ppb)

Other than the pulse counts in the measurements, the counting process can be controlled by an external signal.

EDIT: Section "Measurement Histograms" added.

Performa01:
AC Trigger Coupling

Most of us use DC coupling for the trigger almost all the time, and there is not much to talk about it, other than that it works just as it should. We rather want to examine AC trigger coupling now.

Why and when would we need AC coupling for the trigger at all? Usually, we make that choice for the channel input and if we select AC coupling there, the trigger will inevitably be AC coupled as well. So there we already have the answer – we have the opportunity to force the trigger into AC coupling, even when the corresponding input channel is DC coupled. This can be useful for AC signals that have a DC offset that we want to watch on the screen. The offset might change with time and we still don’t want to lose triggering.

AC trigger coupling does not display a trigger level indicator, simply because it would need to closely follow even a fast-changing signal offset, thus might be rather distracting instead of beneficial.

The following test uses a 200 mVpp 100 ns wide pulse at 1 MHz repetition frequency that is superimposed on a 600mVpp sine wave at 100mHz, which acts as a variable DC offset here. As if this weren’t enough, this signal has a fixed DC offset of -6V on top of that, which needs to be removed by means of the vertical position control and the trigger level adjusted accordingly. Infinite persistence is used to give a hint what is going on.


With DC trigger coupling, triggering would only occur about 1/3 of the total time in this scenario and even then, the horizontal position would only be reasonably stable because of the short 1 ns rise time of the pulse edges. A signal with slower edges would move horizontally as well, because of the permanently changing trigger level (relative to the AC portion of the input signal). 


SDS824X_HD_Trigger_DC_VarOffset

It’s totally different if we use AC trigger coupling. When using Auto-Set by pushing the trigger level control, the trigger level is set to 50% of the signal amplitude. With this, triggering occurs always at the same point on the X-axis, no matter what the DC offset or low frequency instantaneous signal level is. The waveform constantly changes its vertical position on the screen, but remains stable on the time axis – and even more important, the signal is triggered continuously.


SDS824X_HD_Trigger_AC_VarOffset

We’ve heard complaints about DSOs that prove unable to maintain an AC- or LFRJ-trigger without some additional jitter. So here’s a test with AC trigger coupling and a 6 ns wide pulse with 1 MHz repetition frequency. The screenshot has been taken after several minutes with infinite persistence.


SDS824X_HD_Trigger_AC_Jitter

Jitter can be measured as 36.0 ps peak to peak and 6.84 ps RMS; not quite as good as the former test with the 200 MHz sine signal, yet certainly not bad either – and also reveals that my pulse generator (SDG7102A) produces quite stable signals, even when fast edges are involved.


Triggering noisy signals

Of course, for serious measurements our goal should be to find a reliable, stable and noise-free trigger source with sufficient amplitude. Sometimes this is not available and we need to try the next best thing by getting a stable triggering also from less ideal sources.

Let’s assume a low frequency signal with high frequency spikes (maybe from fast logic cicuits nearby) superimposed. To simulate this, a 600 mVpp 1 kHz sine wave has a 10 mVpp 3.254 MHz pulse train (10 ns wide pulses) riding on it. Standard DC trigger doesn’t work with such a signal, but HF-reject coupling does:


SDS824X_HD_Trig_Spikes_HFRJ

Just for fun, we can do the opposite thing and use LF-reject trigger coupling. This triggers stably on the pulses, yet because of the high waveform update rate the screen is full of traces from the 1 kHz sine.


SDS824X_HD_Trig_Spikes_LFRJ

After stopping the acquisition, we can closely inspect the last record. Even better, we can look up all the previous acquisitions in the history:


SDS824X_HD_Trig_Spikes_LFRJ_Hist1


SDS824X_HD_Trig_Spikes_LFRJ_Hist2

Another common situation is just a noisy signal like this:


SDS824X_HD_Trig_Noise_DC

Infinite persistence has been used to visualize the unstable signal phase.

We can still trigger on such a signal by simply lowering the trigger bandwidth, i.e. using HFRJ:


SDS824X_HD_Trig_Noise_HFRJ

Alternatively, the Noise Reject switch in the trigger settings will increase the trigger hysteresis, thus making it immune to noise (within reason).


SDS824X_HD_Trig_Noise_DC_NRJ
 

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod