PMEL Forum

K Sections => K3/4 - Waveform Analysis & RF Generation => Topic started by: briansalomon on 04-17-2018 -- 19:00:03

Title: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: briansalomon on 04-17-2018 -- 19:00:03
My lab need to replace our old scope calibrators.

What do you like to cover scopes up to 1Ghz?
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 04-17-2018 -- 19:37:02
You can pick up an HP 8648 for cheap and it will more than cover that frequency.  If you convert the dB leveling error to linearity then compare the TARs you will see it is more than accurate enough that you don't need a power meter..

If you are looking for new.  The Keysight MXG's are pretty impressive.  We have sold a couple to some of our customers to support the Tektronix MDO-3000 and MDO-4000 Scope / Spectrum Analyzers.

Mike.
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: silv3rstr3 on 04-17-2018 -- 19:41:47
The Fluke 9500B with scope heads is my favorite.  There is a 600MHz, 1.1GHz, and 3.2GHz option and if you get the 9560 active head it can output 6GHz.  The 9500 with all the heads makes automating oscilloscopes in Met/Cal very efficient.  The Fluke 5520A and 5522A scope options are very similar and easy to use. 

We still occasionally get some of those old Tektronix SG504's in for calibration and surprisingly they still work good.  The newer standards + automation allows me to run multiple stations at the same time while calibrating something else manually.
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: griff61 on 04-17-2018 -- 21:26:29
I'm begging for a few Fluke 5522As with the 1.1GHz scope package. Our experience with the 9500 is that the heads are prone to failure by design and Fluke won't cough up the schematics etc to repair them.
The same design flaw is in the 9640 source head as well.
Almost seems...intentional
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: briansalomon on 04-17-2018 -- 22:31:44
My boss is looking at the Fluke 5820A.

Any thoughts?
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 04-18-2018 -- 01:09:19
The problem with the Fluke 552xA Scope output is that it is not accurate enough to calibrate today's scopes.  And the normal output is noisy as hell.

Also.. Check out the new Transmille 401x.  We built drivers for it in Metrology.NET.  I think it is going to give the 5522A a run for its money.

Mike
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 04-18-2018 -- 01:10:58
My boss is looking at the Fluke 5820A.

Any thoughts?
It has the same DC Volts accuracy problem as the scope output on the Fluke 552xA.

Mike
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: griff61 on 04-18-2018 -- 01:51:27
The problem with the Fluke 552xA Scope output is that it is not accurate enough to calibrate today's scopes.  And the normal output is noisy as hell.

Mike
What DC volts accuracy problem?
I've never seen either of those problems with the 5500 series. The 5820 had a design flaw with the switches. If you didn't exercise them regularly, it would fail. It was sort of half the bang for your buck as calibrators go and low reliability due to design error.
I haven't run across any oscilloscope in the 1.1 Ghz range and below that a 5522A wasn't accurate enough to calibrate. Certainly not anything that Tektronix, HP or Lecroy puts out, as we've calibrated lots of those. Both here and at commercial labs. Most of today's newer scopes are essentially calibrated with DC levels, because they're essentially digital signals referenced to DC, the 5522 is very capable for that, the frequencies over 1.1 GHz we provide with signal generators.
Not clear on what noise problem you're referring to, as we don't use calibrators for low noise applications
But to each their own I suppose, I'm always willing to learn something new
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: Hawaii596 on 04-18-2018 -- 15:01:31
We use 5520A with 1100 MHz Scope option. We also have a couple of Wavetek 9500/3200 with 9530 (3.2 GHz) heads. Between all of those, they seem to handle all of the scopes we support (large and diverse customer base) up to 3.2 GHz.  For scopes above that BW, we use microwave generators externally monitored with RF Power meter/splitter.

I have also seen in a previous life when calibrating scopes (at an HF radio manufacturing facility) there was sporadic EMI that made a mess of measurements. When one of those radios got keyed, even though it was shielded coax into a load, it made a messy adder to my otherwise clean waveforms.  This can be an issue in many forms.  Mine was a nice "clean" HF band (0.5 to 32 MHz) sine riding on my sine signal.  In other environments, it can be other EMI mitigants.
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: silv3rstr3 on 04-18-2018 -- 15:59:41
I'm begging for a few Fluke 5522As with the 1.1GHz scope package. Our experience with the 9500 is that the heads are prone to failure by design and Fluke won't cough up the schematics etc to repair them.
The same design flaw is in the 9640 source head as well.
Almost seems...intentional

Luckily I haven't had any problems with the active heads.  I calibrate a lot of them for our company every year.  What's weird though is the last 2 years in a row the 9500 base unit intermittently fails self test.  We had to have it repaired twice now and as a result we had to shorten the calibration interval this year.  I didn't know that about the LPNX.  I'm still using the 3335A and trying to push to get the newer generator.  I am tired of doing spectrum analyzers manually.  Automating those would save a lot of time. 


Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 04-19-2018 -- 16:11:25
The problem with the Fluke 552xA Scope output is that it is not accurate enough to calibrate today's scopes.  And the normal output is noisy as hell.

Mike
What DC volts accuracy problem?
I haven't run across any oscilloscope in the 1.1 Ghz range and below that a 5522A wasn't accurate enough to calibrate. Certainly not anything that Tektronix, HP or Lecroy puts out, as we've calibrated lots of those. Both here and at commercial labs. Most of today's newer scopes are essentially calibrated with DC levels, because they're essentially digital signals referenced to DC, the 5522 is very capable for that, the frequencies over 1.1 GHz we provide with signal generators.
Exactly.  Look at the TURs of the DC Voltage output of the Fluke 552x and 582x.  Many of today's scopes are better than the 1% and 2% scopes of yesteryear. 
We have helped one of our customers move from the 9500 to 5820 only to discover the TURs are not as good with the 5820.  But in the end, they did the switch anyway because it was less paperwork for TUR issues than recall issues when a head failed calibration on the 9500.

The noise is out of the Normal Output.  Connect it to a scope, turn off averaging then watch it bounce ever second or so..

Mike
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: griff61 on 04-19-2018 -- 20:42:56
Exactly.  Look at the TURs of the DC Voltage output of the Fluke 552x and 582x.  Many of today's scopes are better than the 1% and 2% scopes of yesteryear. 
The noise is out of the Normal Output.  Connect it to a scope, turn off averaging then watch it bounce ever second or so..

Mike
DC is bouncing on the Normal output of a 552X?
That sounds like a problem with your instrument, not every instrument. I have never seen DC bounce on a 55XX series calibrator.
The 5522A has a One Year absolute accuracy of 12ppm + 20uV from 0 to 32.999VDC,
As far as DC gain goes, which ones have better than 1% gain? The Tek DPO7000 series are 1%, MDO4000 series are 1.5%, DPO/MSO5000 series are 1.5% and the MSO54/6/8 are 1%
Those are the baseline best ratings according to Tektronix
Keysight specifications are: InfiniiVision 1000 X-Series, 2000 X-Series are 3%FS
InfiniiVision 3000T X-Series, 4000 X-Series, Infiniium S-Series, V-Series Oscilloscopes, Z-Series Oscilloscopes are 2%FS

Myself, Im looking forward to three brand new 5522A/1GHz calibrators
If my CERB survives, that is
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: silv3rstr3 on 04-19-2018 -- 22:28:04
Exactly.  I haven't seen a oscilloscope come through here that had an accuracy of less that 1%.  And this place has a lot of the newer Keysight and Rhode & Schwarz.  The other good thing about the 5522A verses the 5520A is that they put a fuse on the bottom of it so that you can't blow up the input.  I saw people do that a few times at my previous employer and it was like $7,000ish to fix it!!  The fuse on the 5522A is just one of those blue Fluke fuse's which are a hell of a lot cheaper.  One of those guys was using it to measure temperature in an oven (Don't know why because we had a bunch of the handheld process calibrators) and hit the heating coil.  It traveled down the thermocouple and blew the input! 
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 04-20-2018 -- 04:19:19
The DC Output of the Fluke 5522A's scope output is not in the ppm range like the normal output. 
50 Ohms is -- 0.25% + 40 uV
1M Ohm is -- 0.05% +40 uV

When you do your Uncertainty budgets those numbers go up!
When you are testing the scope at lower voltages that 40 uV is more of a problem and so do your Type A uncertainties. (40 uV is a rectangular distribution!) 

Keep in mind, we are TUR's not TAR's.  And 17025 Accredited calibrations, these little things will kill you with a good auditor.

It was an eye-opening event for me when I discovered the 5520A was not accurate enough to calibrate the Fluke 87's on capacitance. 

Same thing when we compared the Uncertainties of the 55xx Scope Output to the 9500.

That said... I miss the old Milstandard days!

Mike
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: ck454ss on 04-20-2018 -- 13:55:01
The DC Output of the Fluke 5522A's scope output is not in the ppm range like the normal output. 
50 Ohms is -- 0.25% + 40 uV
1M Ohm is -- 0.05% +40 uV

When you do your Uncertainty budgets those numbers go up!
When you are testing the scope at lower voltages that 40 uV is more of a problem and so do your Type A uncertainties. (40 uV is a rectangular distribution!) 

Keep in mind, we are TUR's not TAR's.  And 17025 Accredited calibrations, these little things will kill you with a good auditor.


Mike

So I may be missing something but why not just use the normal DC output on your 5520?  Nothing says you have to use the scope output for all measurements.  Most 33k and 17-20 procedures use a standard DC Voltage calibrator anyway for DC measurements? 
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: silv3rstr3 on 04-20-2018 -- 14:16:46
You definitely can use the normal calibrator outputs for doing gain and offset.  Keep in mind not everyone works in a A2LA accredited lab.  And a lot of companies that are don't even follow A2LA guidelines.  At a previous lab I worked in they made everyone list the best case scenario off the scope of accreditation.  Even when most of the time you weren't even using the specific standard listed on it.  I knew it was wrong but all they cared about is increasing the amount of money billed by the lab each month. 

I run the majority of our oscilloscope calibrations here in Met/Cal using the 9500+9530 heads.  When looking at the calibration data there isn't any TAR's < 4:1.  I'm not seeing an issue with using any of the standards we have been talking about.  Unfortunately my current employer is starting to push to get all our labs 17025 accredited.  I can foresee headaches in the future.... 
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: griff61 on 04-20-2018 -- 14:29:54
The DC Output of the Fluke 5522A's scope output is not in the ppm range like the normal output. 
50 Ohms is -- 0.25% + 40 uV
1M Ohm is -- 0.05% +40 uV

Why would you use the scope output to perform a DC check?
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: silv3rstr3 on 04-20-2018 -- 14:41:56
The Met/Cal procedure does those checks with the scope output like the 9500 does it straight through the active head. 
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 04-20-2018 -- 16:15:17
The DC Output of the Fluke 5522A's scope output is not in the ppm range like the normal output. 
50 Ohms is -- 0.25% + 40 uV
1M Ohm is -- 0.05% +40 uV

Why would you use the scope output to perform a DC check?

Because the Normal output on the 5520A is noisy.
Connect it to a scope.  Turn the averaging on the scope off.  And you will see what I am talking about.

Mike!
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: silv3rstr3 on 04-20-2018 -- 17:26:41
Explains why military procedures tell you to set the averaging to a sufficient number of samples.  I've never had an issue using these standards for calibrating oscilloscopes.
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: griff61 on 04-20-2018 -- 20:49:59
Because the Normal output on the 5520A is noisy.
Connect it to a scope.  Turn the averaging on the scope off.  And you will see what I am talking about.

Mike!

I've never seen noisy DC on a 5500 series that I have used since 2000 when I started in commercial cal after the Army.
Of course, you could just leave the averaging on, on your noisy one, but I would investigate what malfunction is occurring in your equipment.
Or just use a 57xx?
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 04-21-2018 -- 04:05:25
It's not a malfunction.  All of them do it.  It's like a chirp, if you play with the trigger and set the scope to wait for the trigger you can capture the signal.
Note... I haven't checked the 5522A.
And the Fluke 57xx as I know don't have this issue.

Mike
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: griff61 on 04-21-2018 -- 05:06:20
It's not a malfunction.  All of them do it.  It's like a chirp, if you play with the trigger and set the scope to wait for the trigger you can capture the signal.
Note... I haven't checked the 5522A.
And the Fluke 57xx as I know don't have this issue.

Mike

Again, my 5520 doesn't do that nor did my 5500 at Goodrich, or the ones at National, Simco and Sypris. I would call it a malfunction and have a talk with Fluke.
But I am getting 5522As, that's what I recommended.
It must be one helluva "chirp" to change the normal DC into something worse than .25%
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 04-22-2018 -- 01:48:23
Griff,
When you write automation software, you leave an audit trail.  When there is a problem with a test, I have to figure out why.  Is it software or is it hardware.  I know a ton of little issues with equipment.

If you look at the 55xx's out with anything that averages the voltage you will not see it.  If you connect the Normal DC voltage out to a scope set to no averaging, no free run and set the trigger level just about or below the voltage you will see a small chip.

If I have time the next couple of weeks I will try to grab a scope and a calibrator and give you guys some specific settings!

Mike
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: DaveRodda on 11-21-2018 -- 18:38:26
Hello...If you convert the dB leveling error to linearity then compare the TARs you will see it is more than accurate enough that you don't need a power meter.The Keysight MXG's are pretty impressive.  We have sold a couple to some of our customers to support the Tektronix MDO-3000 and MDO-4000 Scope / Spectrum Analyzers.

pcb assembly process (https://www.7pcb.com/PCB-Assembly-Process.php)
Title: Re: 50Khz to 1Ghz Oscilloscope Calibrator
Post by: CalLabSolutions on 11-22-2018 -- 15:47:05
I am going to add to DaveRodda's comment and say those older HP 8648A/B/C/D can also do the test without the Power Meter.