Electrical test and measurement equipment reviews.

  Digital Multimeter, Clamp on meter, Oscilloscope, Electronic component testing tools, all measuring equipment for demanding applications of our times:  Switching or Uninterruptible power supply, PV Inverters, VFD motor controllers, industrial electronics repair & HVAC.

Written by Kiriakos A. Triantafillou, Industrial maintenance electrician, Hellas.

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Table No 1

GDS-2102A Basic wfms/s  Measurement at

500 ns/div Time base

Input frequency

Average

Max

Min

20 MHz

84,507

85,774

81,475

10 MHz

84,525

85,355

81,497

1 MHz

81,330

81,893

79,383

Table No 2

GDS-2102A Extended wfms/s Measurement

20MHz  1 ns - 200 ns/div

Time base

Average

Max

Min

1 ns/div

154,870

160,700

149,670

2 ns/div

141,900

147,400

135,960

5 ns/div

136,750

141,890

131,610

10 ns/div

135,320

140,370

130,250

20 ns/div

138,100

143,000

132,220

50 ns/div

58,460

59,217

56,903

100 ns/div

58,410

59,041

57,006

200 ns/div

58,373

59,318

56,614

Table No 3

GDS-2102A Extended wfms/s Measurement

1MHz 50 ns - 50 ms ns/div

Time base

Average

Max

Min

50 ns/div

55,936

56,399

54,675

100 ns/div

55,860

56,455

54,976

200 ns/div

55,600

56,395

54,230

500 us/div

81,330

81,893

79,283

1 μs/div

42,159

42,455

41,021

2 μs/div

25,704

25,930

25,292

5 μs/div

13,284

13,408

13,101

10 μs/div

7,953

8,032

7,842

20 μs/div

4,138

4,195

4,050

50 μs/div

1,640

1,685

1,495

100 μs/div

696

746

585

200 μs/div

313

346

253

500 μs/div

114

132

79

1 ms/div

53

68

32

2 ms/div

26

34

13

5 ms/div

~11

~16

~5

10 ms/div

~5

~14

~1

20 ms/div

~3

4

~1

50 ms/div

~1

~2

~0

GDS-2102A &  wfms/s  measurements.  

GDS-2000A Waveform Update Rate.

By Kiriakos Triantafillou ©2013 5 April

Intro

Wfms/s or waveform update rate per second, is today one among the most important specifications of the latest entry level professional oscilloscopes.

Why it matters that much?

Thanks to my latest Webinar’s which Agilent organizes for free, today I am capable to answer this question too.

And the all story is about the visualization of the called glitches or Ghost waveforms, which looks like random and fast occurring events, and in a way as instant pollution of the expected and basic waveform.

Due the fact that I own one old but tremendously features reach function generator, I did manage to create my own local Ghost waveforms by playing around with the Burst Mode & MOD Sweep Period,  now imagine that with a Period control knob and five ranges starting from 0.05 - 1 ms and as last 5-100 Seconds , I did manage to bring the GDS-2102A in a thought spot, but the scope it did prove it value when their mentioned specifications came's in to play.

While the GDS-2102A is my personal selection, which was made after serious , in depth, and long term research, so to be fully capable to handle with extreme performance and detail the maximum of 20MHz that is the maximum output of my Function generator, it has a specified Rise time (100 MHz bandwidth) of 3,5 ns and when this model will be upgraded to 300 MHz it will inherit the lowest possible Rise time of 1,17 ns.

I am making this introduction because in my measurements below I did not resist my self from taking Wfms/s measurements even at such fast timings ( Time base settings ) which I believe that the hardware it can not currently follow with the expected accuracy.

While the most detailed Wfms/s data as comparison point, are currently offered by measurements that Agilent did regarding their 2000-X series, what their documentation does not mention is the bandwidth of their tested scope, their 200 MHz model comes with Calculated rise time at 1,7 ns.

Now just think for a minute that if the GDS-2102A at just 100 MHz bandwidth and 3,5 ns Rise Time offers improved performance as is … I am coming to ask what it will do at 300 MHz ? It would take off as jet plane and have a flight?   

My advice to you, that you plan to use my measurements as comparison point is to ignore the time base settings that your Oscilloscope are not specified to handle due bandwidth & rise time limitations.         

How - to & Measurements repeatability.  

In the document which GW Instek documented the method or better said … The steps to follow regarding Wfms/s verification on those GDS-2000A, their advise is to use another DSO (oscilloscope) so to measure the frequency of the GDS-2000A Trigger-Out, (Demo 1) Probes test point.

The reasons behind this suggestion is many:

a) GW Instek is an Oscilloscope manufacturer, and they have thousands DSO.

b) GW Instek would never think to use a multimeter !!

c) The Trigger-Out has an voltage range not higher than 200 mV AC, which varies significantly depending the time base of the scope and usually ranges from 120 mV to 5 mV and even less than that.

The only multimeter which had the proper sensitivity as frequency counter due their low mV range, plus the Min/Max/Average function, is the U1270A Series.

Agilent from the other hand, it clearly writes in their documentation regarding  Wfms/s (benchmarking) that what it matters is the average Wfms/s measurement.

In my case I did just that, by setting a minimum (Min/Max/Average) recording duration of 60 seconds for its one measurement, before writing down those numbers in my paper.

Regarding repeatability I did recheck them two times.


What it does worth to be aware if you try to make similar measurements with your Oscilloscope :

1) Always press the Auto-Set button once, so the scope to set the proper memory buffer size, which needed for the specific frequency range of the waveform.

2) Always test by moving the Time Base knob few increments above or below the Time Base which the scope will automatically select by the Auto-Set.

3) Avoid using a multimeter if possible, very few are capable for this task, if you have a sensitive and fast dedicated frequency counter capable for 4-5 measurements at the 100 KHz range … Use it.

4) Have Fun.   

Note :  I did made the bellow spreadsheets by spending a significant amount of time and energy, I made them easy to be copy ed as is, so to use them as reference for personal use only.   

You may share the link of this page, and reward in away the statistics counters of my site, which are important about bringing food in my table.

Thank you .

For questions, More tips, or just for a warm & friendly chat, post a message at the ITTSB Forum.

By Kiriakos Triantafillou ©2013 5 April

Regarding the Table No 2 and those 140,000 wfms/s in those low Time base settings, my measurements are all correct, and totally repeatable.

Those readings it can possibly cause some confusion when it comes to direct comparisons, mostly because this increase of wfms/s is totally undocumented in the specifications of the GDS-2102A.  

Even so in order to be in the safe side regarding assumptions, I did further measurements so to find out the default time-base settings which the scope selects automatically by the use of Autoset button, in a range of frequencies starting from 1 to 20 MHZ.   

The point of interest is the time base at 20 ns and lower, in which those 130,000 wfms/s or more starts to show up.

AutoSet (Time base selections) VS MHz

MHz

ns

1

500

2 up to 3

100

4 up to 10

50

11 up to 19

20

20 MHz

10 ns

Table No 2

GDS-2102A Extended wfms/s Measurement

20MHz  1 ns - 200 ns/div

Time base

Average

Max

Min

1 ns/div

154,870

160,700

149,670

2 ns/div

141,900

147,400

135,960

5 ns/div

136,750

141,890

131,610

10 ns/div

135,320

140,370

130,250

20 ns/div

138,100

143,000

132,220

50 ns/div

58,460

59,217

56,903

100 ns/div

58,410

59,041

57,006

200 ns/div

58,373

59,318

56,614

It clearly looks that is something that it happens by starting from 11 MHz up to 20 MHz (which is the end of the road regarding the frequency range of my function generator).

Bellow there is two pictures as proof of those specific measurements, which I did mostly as exploration of those unexpected readings.

I am also including one screen shot of something that I was expecting almost for a year to see, and this is the voltage output of my function generator at 20 MHz by my own Oscilloscope.

And further below there is two souvenirs regarding my  wfms/s exploration.

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