Calibration headache - Page 1
Forum section: electronics / general

author: IvoS
author_rank: Frequent Contributor
timestamp: April 02, 2013, 11:11:29 pm
content: Just received my HP3478A back from TEKTRONIX calibration lab and the unit says "UNCALIBRATED"??. I have doubts they properly calibrate this DMM. Calibration equipment used: FLUKE 5700A & FLUKE 5522A. Tektronix doesn't even have their own calibration instruments? I am disappointed.

author: free_electron
author_rank: Super Contributor
timestamp: April 03, 2013, 12:21:50 am
content: Tek never made any calibrators. Fluke and Wavetek.They may have forgotten to flick the CAL switch back ....

author: vk6zgo
author_rank: Super Contributor
timestamp: April 03, 2013, 01:51:13 am
content: Maybe not for DMMs,but they certainly made them for Oscilloscopes!

author: IvoS
author_rank: Frequent Contributor
timestamp: April 03, 2013, 07:24:09 pm
content: TEKTRONIX gave me a calibration certificate even though the ohm scale wasn't calibrated at all. I just lost 3 weeks of my time hoping for this unit to come back calibrated. This is a bad experience for me with Tektronix and I will never buy anything that says Tektronix. They suck. They have balls not even tell me that it couldn't be calibrated for some reason.They are probably hoping that I will never find out because I sent it there as a person, not a company.It was Tektronix in Mass, Billerica. They suck.

author: amspire
author_rank: Super Contributor
timestamp: April 03, 2013, 07:36:28 pm
content: What did Tek send you? Calibration usually does not include any adjustments (see Dave's video blogs on calibration).Did you get a report on the errors on each range?Are you saying they didn't test resistance ranges at all?Richard.

author: MetraCollector
author_rank: Regular Contributor
timestamp: April 03, 2013, 07:49:03 pm
content: What about writing a complaint ?Did DMM work before it was sent ? 3478A is pretty old, I could ever believe that it simply couldn't be calibrated due to fault.

author: IvoS
author_rank: Frequent Contributor
timestamp: April 03, 2013, 08:00:25 pm
content: I have certificate of calibration that doesn't basically say anything conclusive. It says: Tektronix certifies the performance of the above instrument has been verified using test equipment of known accuracy......Has been verified?? How? Did they compare the voltage scale to bananas?

author: Unknown
author_rank: Unknown
timestamp: April 03, 2013, 08:16:37 pm
content: QuoteAsk them for aCalibration Reportprint-out on your meter... if they have attempted to make any calibration andyou have paid for that service, then you have the right to see the report; all they have to do is e-mail it ?

author: staxquad
author_rank: Frequent Contributor
timestamp: April 03, 2013, 08:18:50 pm
content: Quote from: IvoS on April 03, 2013, 08:00:25 pmCalibration Lab or Pass Fail Lab?A few hundred bucks for nothin'; the plumbers of the electronics world

author: IvoS
author_rank: Frequent Contributor
timestamp: April 03, 2013, 08:42:29 pm
content: This should be calibration lab. This is amazing business!!! I send an instrument for calibration assuming they will work for the money and give me something I can verify the measured values, instead I get basically blank sheet that just says :Tektronix certifies.... like I wrote before. What did they do for the money? I can do this kind of business as well.There is Joe sitting on the chair, he puts my meter on the bench, drinks Dunkin Donut coffee....and how do I find out he did the job? Do you see something wrong with this?

author: IvoS
author_rank: Frequent Contributor
timestamp: April 03, 2013, 08:46:53 pm
content: Quote from: staxquad on April 03, 2013, 08:18:50 pmYeah, but if I bring plumber to my house, I will make damn sure he will get the job done.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: April 04, 2013, 06:23:03 am
content: You know the one about the doctor and the plumber? No?Doctor's faucet has a leak: drip, drip drip driving him nuts. So he calls a plumber.Plumber comes over, shuts off the water, takes the faucet apart and changes out a couple of washers. Puts it all back together, turns on the water and the drips are gone.Doctor is very happy with the work and asks for a bill right there. Plumber says gimmyasec, and produces a bill for $150.Poor old doctor becomes irate. "What?" he says, "$150 for 15 minutes work??" A pause. "Hell, that's more than even I charge!"Plumber says, ".... Yeah I know... I used to be a Doctor to."

author: amspire
author_rank: Super Contributor
timestamp: April 04, 2013, 06:49:00 am
content: I gather that Tek provide the test data via an Online Electronic Certificate (DATA). Is that the certificate you are talking about, or are you talking about a printed certificate?Do you have a login account, and have you checked it to see if you have any online data records?They do adjust to manufacturers specs if out of tolerance I gather.The Test Data Report is optional for a standard calibration. I don't know if it is optional after the event.

author: IvoS
author_rank: Frequent Contributor
timestamp: April 04, 2013, 08:12:11 pm
content: Well, I called Textronix today and they told me that I did the basic calibration without data log sheet compared to reference. Sure enough, I did. The unit came back with certificate that says "In Tolerance". Voltage scale is off like 1%. The ohm scale doesn't even work in manual range, and they say it's in tolerance. I tried to explain that dude that there is a likelihood that they could possibly let it sit in their warehouse for 2 weeks without touching it, and then they just print out the certificate saying" In Tolerance". That is not enough evidence for me to believe that the actual calibration was done. I would like to have a solid proof in my hands. He said that when they gave me the certificate saying "In Tolerance", the unit must be "In Tolerance", that's what they do. Give me a break... really? I just pay $129 plus shipping and got basically nothing in return. That's how I see it.What kind of support will I get, If I buy $3K Tektronix multimeter that may need adjustment after 5 years of use, and they give me this.........Not happy at all. I know most of you guys here are engineers and you are very familiar with calibration and the way it goes. I can see you laughing at me thinking what kind of idiot I am, I don't even know what I am doing. All I want is a solid proof of evidence. That is common sense to me.

author: ve7xen
author_rank: Super Contributor
timestamp: April 04, 2013, 10:38:19 pm
content: Calibration is for traceability, they don't do any adjustments or anything like that. For some customers it's enough simply to know that the meter is within spec, as that then validates their own accuracy claims / requirements. I think Dave's video on the mobile Agilent cal lab goes a bit into why customers get calibration done and that the calibration is basically just there to validate measurements made between two separate calibrations are within spec of the instrument. In large part it's just bureaucracy, as most of these instruments will stay in spec with no adjustment for far, far longer than their calibration interval. It serves an important purpose though - if an instrument does go out of spec (breaks, etc.) you'll know about it within a certain amount of time if you're doing regular calibration. You pay more if you want them to note down the actual values and provide them for you.I'm not clear on what the certificate you received says. In your OP you say the instrument wasn't calibrated at all, but now you say it says it's in tolerance? I'm confused, maybe if you scan the certificate we can help you interpret it?Another thing worth noting is that the cal lab is generally only going to care whether or not it's within its specified tolerance. Even if you ask them to adjust it to spec, they're not going to touch any ranges that are in spec, even if they're 'out' substantially. I don't know for sure, but it's probably difficult to get them to do so even at special request. As far as the lab is concerned, the instrument is only as good as its specifications and any error within that is entirely inconsequential.What testing have you done to determine the instrument is outside its specifications?

author: nanofrog
author_rank: Super Contributor
timestamp: April 05, 2013, 02:01:46 am
content: Take a look at this, and see if it helps (different types of calibrations).http://www.keithley.com/services/calibration

author: grenert
author_rank: Frequent Contributor
timestamp: April 05, 2013, 02:46:05 am
content: It sounds like there are two separate issues here: First, the OP got back his DMM with an "UNCALIBRATED" error. Second, it sounds like he didn't understand the different levels of calibration services available?On the first, I'd ask the lab to explain how they were able to calibrate with this error, or what they could have done that generated it.On the second, if the data is important to you, then you can see if it was recorded and you can pay the difference to get it.

author: Len
author_rank: Frequent Contributor
timestamp: April 05, 2013, 05:01:53 pm
content: Quote from: grenert on April 05, 2013, 02:46:05 amHe also said this:Quote from: IvoS on April 04, 2013, 08:12:11 pmIf the calibration was supposed to include the resistance scales, you have to wonder if they actually did anything.

author: codeboy2k
author_rank: Super Contributor
timestamp: April 05, 2013, 07:15:24 pm
content: Quote from: Len on April 05, 2013, 05:01:53 pmMost cal labs won't calibrate broken equipment; did the ohms scale work before it was sent for calibration, and is broken now??If it was broken before it was sent then they won't touch it. But they should have reported that back to you at least.

author: vk6zgo
author_rank: Super Contributor
timestamp: April 06, 2013, 02:45:24 am
content: Philips (Australia) used to do a fixed price repair/calibration on Fluke 77 meters & the like, back in the day.A good deal if your meter was faulty,& still reasonable if it just needed calibration.Probably too expensive for a calibration lab these days.