Re: Getting calibration equipment calibrated


Harvey White
 

There's a lot of stuff you don't need to do unless you want to.

Remember that the analog scopes you're checking, unless they have digital counters (7D15, et al), you're deciding whether or not you read to the edge of the trace, the middle of the trace, or the other edge of the trace.  Check the specs on the scopes to see what accuracy you *can* read them to.  3%?  You don't need a six figures accurate counter or DMM to set that.

For frequency, you can easily take any available counter and check it to a packaged oscillator.  Then find one that's calibrated (you do have access to that) and see what it reads on that one.  Or if you don't, you're getting close.  Ditto with the voltmeters.

Rise time, well, that is a possible problem, and if you're going after that, you do need bandwidth.

Harmonic Distortion?  Either a good distortion meter at that frequency, or a spectrum analyzer, or a scope with an FFT.

Flatness?  bring on the high bandwidth scope.

However, how much do you need those particular measurements? Most people calibrate the timebases, vertical and horizontal sensitivity, look at the risetime, look at the bandwidth, and let it go at that.

For digital scopes, I'm not even sure you *can* adjust any of the timing.

Harvey

On 5/24/2021 12:31 AM, Dave Peterson via groups.io wrote:
Hmm,

Seems kind of a mixed bag then. I would love to get my own level and time references setup. I have only superficially heard about using GPS based clocks/timing. Seems this might be my opportunity to learn up on that. And thanks for the level reference link Sean. I'll follow up on that too.

The spectral requirements of the SG503/504 sounds out of my league. When opening up my wallet for a place like Keysight, are we talking 100s? It certainly can't be more than, say, $500 for calibrating one plug-in? Can it? But paying for professional services does get expensive fast.



On Sunday, May 23, 2021, 9:24:27 PM PDT, Eric <ericsp@gmail.com> wrote:
For timing a good (lots of digits) frequency counter hooked to a GPSDO will get you where you need to know then you time reference Is based on the GPS clocks which are HIGHLY accurate. At least WAY more accurate then a 400 series scope at 3%. I did a TG501 and a 184 in my lab with a DMM, Frequency counter, and 100 Mhz scope. There is one adjustment in the 184 that you have to balance 2 trigger points these are the 2 bright spots the should be level.  But the SG503 and 504 need spectral purity characterized as well as the SG503 needs that odd 50 Ohm cable. I have to tare in to my 503 it kind of went nuts on me when I was working on a 465. Sorry for the 2 replies I started this on the small screen and moved to the large one.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dave Peterson via groups.io
Sent: Monday, May 24, 2021 12:06 AM
To: TekScopes@groups.io
Subject: [TekScopes] Getting calibration equipment calibrated

Hi All,

How much does it cost to get PG506s, SG503/SG504s, and TG501s calibrated?

I can certainly search for local calibration facilities, but having no experience at all: do they tend to be amenable to DIYer's, is the cost in the realm of reasonable, is it worth it?

I have a PG506 that's working beautifully, but I can't be certain that the voltage levels are in spec.

The SG503 seems to work, and I can tell pretty well that it's level above 100MHz, but only on an un-calibrated 7854 scope. So while I feel good about the 100MHz scopes I'm testing with it, no one could call that calibrated.

The TG501 is dead, the SG504 blew a fuse when pressed the "ref" button. So those will need some repair. If I can get them working it would be nice to add them to the calibration set.

It'd be really nice to have all four of these officially calibrated. That'd give me assurance that the scopes I'm repairing are properly tuned up. I don't have any means at hand otherwise to verify level or timing. I could keep working on finding means of establishing standards for level and time. But would it just be more cost effective to pay for calibration?



Thanks,
Dave















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