Products > Test Equipment
New Rigol DS1054Z oscilloscope
JohnPen:
Out of curiosity I rechecked the bandwidth of my hacked DS1054Z over an extended range. The -3db point is between 130-140 Mhz. At 200 Mhz I measured -4.8 dB. 250Mhz was -7.1 dB and 300 Mhz was -9.3 dB. The signal source was accurate at -7.7 dB at 10M and within +- 0.1 dB over the frequency range measured. Directly connected to the scope with a through 50 ohm termination. I also checked the triggering which worked fine to 500 Mhz. The display frequency measurement was by then jumping around all over the place around 500 Mhz. Above 100 Mhz don't expect reliable measurements on your own scope unless you can calibrate it yourself and it may well vary with the vertical sensitivity settings. However you can certainly view signals up to 300 Mhz with some confidence that they are real. The triggering, as has been mentioned before, far exceeds the usable viewing bandwidth of the scope.
2N3055:
--- Quote from: David Hess on August 03, 2019, 10:59:34 am ---
--- Quote from: Fungus on August 02, 2019, 09:57:09 am ---
--- Quote from: David Hess on August 01, 2019, 11:02:06 pm ---It also varies with signal level and volts/div setting which indicates that something uncouth is going on.
--- End quote ---
I think the problem is due to not zooming to maximum zoom. The DS1054Z does all calculations using "on-screen" pixels so for most accuracy in things like rise times you need to zoom in on the area of interest.
--- End quote ---
That has an effect on accuracy but reports of bandwidth vary over more than a 2:1 range. Some are more than 3:1. The DSOs I have used have no problem making accurate edge measurements over a 10:1 range in displayed signal amplitudes. The shape of the waveform should not vary with amplitude.
Like we have discussed in the past, I suspect one of the amplifier stages suffers from slew rate limiting causing saturation or cutoff which also explains the odd 10 nanosecond recovery time under certain conditions.
--- End quote ---
-3dB point is between 130 and 140 MHz. Period. Measured with frequency sweep from a siggen, 50 OHm pass trough terminator scope side .
The only way.
Outrageous claims are coming from people that either don't understand -3dB part , or people who keep calculating bandwidth from impulse response, ignoring the fact that DS1000Z input freq response has an odd shape that favors edge sharpness and not nice frequency response..
Like JohnPen very nicely wrote (my measurements are very similar to his), you can use to see if your 250MHz clock works without problem.
That doesn't make it 250MHz scope. -3dB point does...
TurboTom:
Actually, that doesn't reflect the complete situation: The DS1000Z has two physical, relay-switched sensitivity ranges in the input voltage divider. Further sensitivity adjustments are arranged via the internal digital gain modules in the HMCAD1511 ADC.
As long as the high sensitivity range is selected (this means a less than 330mV/div true input sensitivity), the mentioned figures are correct. But if you change the sensitivity to 335mV/div or above and thus select the low gain input configuration, the 3dB bandwidth increases to somewhere around 220MHz. Of course, this test requires a generator that's capable of some decent output amplitude since the use of a terminator at the scope input is mandatory at these frequencies.
If this behavior is something that's useful in any way may be discussed controversely, I prefer a scope with an input configuration that wouldn't (substantially) change bandwidth when selecting a different sensitivity, especially if it isn't documented anywhere. Anyway, I guess it is what it is and the user's the one who's got to make best use of it. If it helps in some situations -- good, if it doesn't never mind ;) .
I hope this helps to enlighten the situation a little.
Cheers,
Thomas
xrunner:
--- Quote from: 2N3055 on August 04, 2019, 10:16:03 am ----3dB point is between 130 and 140 MHz. Period. Measured with frequency sweep from a siggen, 50 OHm pass trough terminator scope side .
The only way.
--- End quote ---
Here's my data. I measured 130 MHz for the -3 dB point.
https://www.eevblog.com/forum/beginners/rogol-1054z-actual-bandwidth/msg1380072/#msg1380072
David Hess:
--- Quote from: TurboTom on August 04, 2019, 11:52:27 am ---Actually, that doesn't reflect the complete situation: The DS1000Z has two physical, relay-switched sensitivity ranges in the input voltage divider. Further sensitivity adjustments are arranged via the internal digital gain modules in the HMCAD1511 ADC.
As long as the high sensitivity range is selected (this means a less than 330mV/div true input sensitivity), the mentioned figures are correct. But if you change the sensitivity to 335mV/div or above and thus select the low gain input configuration, the 3dB bandwidth increases to somewhere around 220MHz. Of course, this test requires a generator that's capable of some decent output amplitude since the use of a terminator at the scope input is mandatory at these frequencies.
--- End quote ---
Besides the inconsistent reports, three things make me think that the bandwidth varies with amplitude:
1. The DS1054Z only has *one* switchable input attenuator which so the input buffer has to operate over a range 10 times larger than many oscilloscopes. This means the input slew rate is 10 times higher for a given frequency.
2. Per Dave's reverse engineering, the differential amplifier uses 3904s which are only marginally fast enough for a 100 MHz front end even at a lower signal level. The equalization networks at the emitters show that the designers were pushing the transistors to their limits.
3. The screenshot below shows a non-linearity in the transient response which should not exist. If this is a 100 MHz 3.5 nanosecond oscilloscope, then at most there should be signs of recovery rather than that flat slope for more than 5 nanoseconds. To me that looks like a transistor was driven into saturation or cutoff. The preshoot at 1 GS/s is also questionable.
What that all adds up to is that I suspect large signals applied to the input buffer result in slew rate limiting and besides the transient response issue, this results in a variation of bandwidth with signal level.
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