SOLARTRON 7150 Replace mains filter now ? and calibration - Page 1
Forum section: electronics / testgear

author: dimlow
author_rank: Frequent Contributor
timestamp: February 15, 2013, 10:47:58 am
content: Just got a Solartron 7150 from ebay, i read that these can have problems with mains filters spilling their guts. I have had it powered up now for two days straight and there have been no signs of any problem with it so far. Should i be replacing the mains filter as a preventative measure now ? or should i take the risk and leave it as is ?In my view it needs new LEDS, new banana jacks to take shrouded probe jacks, plus this filter.I have done basic checks on resistance, current and voltage and they are all pretty close to my other meters so i think its OK. I'm kind of a perfectionist and i want at least one meter i can rely on. My other meters all give me various different readings and i was looking for a meter i could rely on to give me accuracy. I got the 7150 because its quoted DC accuracy was 0.002% far better than any of my other meters (0.8%) and because i cant afford anything better. I know it's old but have read that many of these meters are still within their 90 day calibration after all these years. I hope i made the right choice.I was thinking, i should get it calibrated first to check it out? Then if all is well, spend time and money updating it, Or should i spend the time and effort getting it updated then, calibrated ? Should i even bother to get it calibrated ?EDIT: It was last calibrated 2 Jan 2003, Its an Ex MOD unit ( not sure if they look after these things or if they abuse them )

author: SeanB
author_rank: Super Contributor
timestamp: February 15, 2013, 03:34:03 pm
content: Bench meters tend to get the kid glove treatment. Best to replace the filter caps now, and do the LEd's if needed ( you probably are wanting more brightness from them ) and the sockets, then send it in for certification. That will tell you if there are any issues, and will show that most probably there has been little drift since last cal.Handheld meters tend to have a hard life, often dropped and often going swimming in assorted fluids.

author: Bored@Work
author_rank: Super Contributor
timestamp: February 15, 2013, 05:13:51 pm
content: Replace the filter. I neglected doing this with the last 7150plus I got. I knew the mains filter could blow up, but this time I was to lazy. A few weeks later I had to pay the price, the magic smoke escaped, making a real mess.

author: Unknown
author_rank: Unknown
timestamp: February 15, 2013, 05:26:01 pm
content: I have a 7150 which I bought on Ebay last year; the seller mentioned that dc volts was slightly out but the others were pretty good. I had heard about the mains filter but my thinking was there was no point spending time replacing things until it had been through calibration. I took it to be calibrated late December; and it turned out they had to do a small repair as the error was too much for the offset to make good; maybe someone had been hammering it with large dc voltages over the years; anyway, it all turned out ok; I posted a pic of the cal results in one of these forum posts somewhere. Mine now is my "gold transfer standard" ;-) to use as reference for my other meters.If you're asking the question though "Should i even bother to get it calibrated ?" my view is it's the electronic project that dictates the level of accuracy you need, but it sounds like a great meter though! ;-)

author: ecat
author_rank: Frequent Contributor
timestamp: February 15, 2013, 07:15:05 pm
content: Quote from: jucole on February 15, 2013, 05:26:01 pmSo you did many thanks, I had totally forgotten.https://www.eevblog.com/forum/chat/calibration/msg178924/#msg178924Looking good.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: February 15, 2013, 07:42:08 pm
content: Quote from: dimlow on February 15, 2013, 10:47:58 amThis is correct, however the problem is not limited to Solartron DMMs but any device which uses mains filters made by the Swiss company Schaffner and which is 20 or more years old. After all these years, one of the capacitors dries out and blows, which results in a very nasty mess.QuoteReplace it, better sooner than later. These old filters are ticking time bombs. Also be careful when buying a replacement. Quite often you can find cheap 'old stock' but these filters are usually as old as the one in your DMM and not much better. Make sure you actually get a brand new one (can be checked on the label, if the filter is Made in Thailand its new, older filters are Made in Switzerland).QuoteRegarding the LEDs, I guess you want a brighter display? Well, there is not too much you can do. I have replaced the LEDs in my 7150 Plus with bright white LEDs, it's an improvement but you won't get the same brightness as other LEDs have.

author: dimlow
author_rank: Frequent Contributor
timestamp: February 15, 2013, 09:36:59 pm
content: I opened the meter up today, its a beauty inside, so clean,looking like new after all these years. So took your advice's and I decided to do the mods before getting it calibrated. I wont be using it again until i have changed the filters. I ordered a new IEC filter from RShttp://export.rsdelivers.com/product/schaffner/fn372-2-21/fn372-2fuse-inlet-filter-2a-5x20mm/4655193.aspxI hope this is not new old stock , i have no way of checking until it arrives.The Images below inspired me to want to change the back light LEDS in the LCD. I have some super bright blue LEDS i want to try in it. You will also notice in the image with the blue LEDs that the guy also changed the banana plug jacks. I ordered some replacements for them today as all my test leads are shrouded and will not insert into the meter unless i cut off the shrouding. Parts will arrive early next week i hope, I will post some pictures of the inside for electronics pron fans out there when i open it up again.

author: dimlow
author_rank: Frequent Contributor
timestamp: February 15, 2013, 09:51:49 pm
content: Just noticed that RS claim RoHS Status Compliant, So will this mean its new stock ? As RoHS Status Compliance dates from 2002 on-wards.

author: dimlow
author_rank: Frequent Contributor
timestamp: February 18, 2013, 06:51:55 pm
content: Changed the mains filter today, i got a replacement from RS. If anyone is interested the filter is a FN327-2-21 RS 4655193.It was a direct drop in replacement. The only thing i had to do was remove a resistor from the old filter and solder it onto the new. (not in any photo's) I also had to swap out the fuses.Whilst i had the unit open, i changed the LEDs to bright blue. The old LEDs were quite difficult to get out initially, but once i had learnt the method for one, the rest got easier.I posted full pictures on my Picasa Webhere.Below are a small amount of the pictures i took for the hardware porn junkies.Getting StartedTop Cover OffBottom Cover OffFirst Glimpse of some partsA Closer LookThe Bottom PCBOpen wideThe Problem Mains FilterMains Filters Side By Side, Note the new filter is made in Thailand (I got the right one)Installed and Ready to TestWorking Yay!LEDs RemovedNew LEDs InstalledBack at home waiting for the next upgrade, the new banana jacks. Still waiting on the delivery from china.

author: Unknown
author_rank: Unknown
timestamp: February 18, 2013, 09:21:32 pm
content: Great pictures!!

author: ecat
author_rank: Frequent Contributor
timestamp: February 19, 2013, 12:52:56 am
content: Very nice pictures indeed. While I'm not a fan of blue displays yours tends more to the funky side of purple so I'll let you offI've had my 7150+ for about six months now and I've not so much as waved a screwdriver in its direction let alone taken it apart. I decided to wait until I had some sort of reference to compare it against to see how well it has held up since its last calibration in December 1997 and to ensure any opening and twiddling were not detrimental.Just last week I got hold of a unused Vishay RCK02 0.01% resistor (http://www.vishaypg.com/foil-resistors/list/product-63214/), not ideal as 5k0000 is near the bottom end of the 7150s 20k range but the price was right. How does the little 7150 with a 15 year old calibration hold up? How does 5.00000k sound ? lol.Okay, there is some noise in the least significant digit of up to +5/-3 counts but, I think that's pretty good going. For those curious, the Vishay checks out on my Datron 1061 at 4.9999.

author: dimlow
author_rank: Frequent Contributor
timestamp: February 19, 2013, 01:38:36 am
content: Yep, my old Nikon Coolpix 995, take quite nice pictures.The back-light is in fact blue, but because i took the photo with the flash on, the color is off purple in the images.I have a couple of 1 ohm resistors and checked them and got 0.00101k on the display that was nice to see. My calibration is only ten years out of date. I was thinking of getting it done until i found out its going to cost more than the meter. So have come up with an idea, not sure if it will work.https://www.eevblog.com/forum/testgear/is-this-simple-ohms-law-test-for-calibration-of-multimeter-useful/

author: dimlow
author_rank: Frequent Contributor
timestamp: February 20, 2013, 12:59:34 pm
content: Today the meter is going off for calibrationhereThey will do ukas for £40 and non ukas testing for £30. So going for the non ukas unless they convince me otherwise. They will Also adjust if its out of calibration.

author: Unknown
author_rank: Unknown
timestamp: February 20, 2013, 01:48:29 pm
content: Quote from: dimlow on February 20, 2013, 12:59:34 pmGreat stuff! and sounds like a good price as well!

author: dimlow
author_rank: Frequent Contributor
timestamp: February 20, 2013, 03:34:24 pm
content: Not So Great stuff, i just got back from the lab, there was some confusion as to what meter they thought they were getting, the sales man i spoke to on the phone ( i thought he was the service manager) quoted me the price for a standard handheld multimeter. In the end full calibration is going to cost me £65. That includes adjustment if needed, also if the meter is faulty in anyway, they will not charge if they cant get it into calibration. So in the end i elected to go for the full calibration. Didn't really want to spend that amount but i guess it will give me confidence in the meter.On the plus side, My son and i also got a nice guided tour around the Lab. Well in fact we saw three labs in total, a repair lab, a standard calibration lab, and their ukas Lab, they sure had spent some cash on the ukas lab. lots of shiny new equipment with flashing lights and screens, it looked the business. I'm confident that they will do a good job.Could have the meter back by Friday if all goes well.

author: ecat
author_rank: Frequent Contributor
timestamp: February 20, 2013, 11:28:58 pm
content: That's still not a bad price is it? And a free tourEven if you were to attempt a diy job the standard 7150 can only be calibrated via the IEEE interface, IIRC, so that would be another outlay. Good luck to father and beastie.

author: dimlow
author_rank: Frequent Contributor
timestamp: February 21, 2013, 12:00:05 pm
content: Got a call this morning. "Hello, we tried to calibrate the meter this morning. Unfortunately it would not switch on, the meter is completely dead", " OK, i will come and collect it then"Shock horror! WTF!Grabbed the keys for the car, went to say good bye to the kids, picked up the phone and as walking to the car, got another call from them. As a final check the service manager tried the meter again and found it to be fully working so they are going to run some tests to see what the problem might be and if all is OK they will calibrate. I explained to them i had changed the mains filter and connector. I believe that they simply didn't push the mains cord in correctly it being a new connector and a little stiff. Service manager agreed with me and said they will call back if there are any more problems. Its been two hour now and no call, so i expect it will be fine.This is getting to be quite a journey. I really hope this all turns out ok

author: dimlow
author_rank: Frequent Contributor
timestamp: February 21, 2013, 06:31:19 pm
content: The meter is back from calibration but, i need some help evaluating the results. Basically i believe they have calibrated it on a machine that does not have the accuracy needed to test it.Attached are the Calibration results.Here is a link to the Calibrators Data sheet.Here is a link to the manual of the 7150 with the specs.It passed all the tests they did on it.When i first looked at the Calibration certificate the first thing i see it the wide Tolerances in DC voltage. Now from the specs of the meter it has in 0.2 DC volts range, a specification of 0.002% of the reading +5 counts in 6.5 digit mode.If i calculate that to a voltage tolerance i get +/- 4uV + 5 Counts, So that's a max Tolerance of +1uV to +9uV. The tolerance on the sheet is 24.7uV and thier uncertainties are +/- 30ppm, so is this right ? I dont think so. How could they possible reach the accuracy of the meter if the meter is more accurate than the calibrator they used.I hope I'm wrong and someone can help my figure this out as i have not done this beforeEdit: removed Cal certificate, because it had personal information on it

author: Unknown
author_rank: Unknown
timestamp: February 21, 2013, 09:05:24 pm
content: ok, this is the way I think it works but I could be wrong. Taking the dc 0.2v range as an example; on your results, the "tolerance" shows how close the reading has to be to "PASS"; the "gotcha" for old meters is the age; if you look at the 7150 manual, section 10.2, and "limits of error"; you have to factor in not the 0.002+5 counts but 0.01+5 counts for every 2 years since it was made + the temp co + the wind direction etc.Now in your results the 190.000mV applied voltage seems odd but when you think about it, but if they applied the full-scale of the meter which is 199.999mV, and say your error was +1uV or more it would probably return OL (overload) so you would never conveniently know your error; so the test voltage of 190.000mV is a good fixed value to set the GPIB software to use as a final result for a nice printout.

author: dimlow
author_rank: Frequent Contributor
timestamp: February 21, 2013, 10:02:52 pm
content: I agree mostly with what you are saying, but the point i was trying to make is that the uncertainties they have are +/- 30 ppm where as the solartron is accurate to +/- 4 ppm plus ten counts.Lets put that into real numbers.Calibrator voltage output is set to 0.190 000V but it could give values of 0.189 970 to 0.190 030Solartron when supplied with 0.190 000V could read values of 0.189 996 to 0.190 014The Solartons accuracy is inside the accuracy of the uncertainties they used.The 200 mV, 2V and 20V ranges are all effected because their error in these ranges is larger than the Solartrons accuracy, shouldn't Calibrations be done with a machine that is 10 time more accurate than the machine they are calibrating ?But still im not 100% sure im doing it right, that's why i need someone in the know to come and look at the data sheet and the calibrations to see if i need to go back to the Calibrators and talk about this to them. I did talk on the phone to them and the guy immediately offered my money back. Now should i take it ?

author: dimlow
author_rank: Frequent Contributor
timestamp: February 21, 2013, 11:43:46 pm
content: Just made a little spread sheet comparing the Calibrated Tolerances from Alpha Electronic to the Tolerances in the manual. looks interestingAs you can see the Meter would have failed calibration, but if you take Alpha's 30 ppm of their test equipment uncertainty into account the meter could be in calibration. if you look at the 2V range ( 1.99999 ) the reading is 1.900071 if you subtract the 30 ppm it would be a pass not a fail.Alpha Electronics Tolerances are way out at the lower ranges , but as they get higher they get closer to the Stated tolerances in the manual.

author: robrenz
author_rank: Super Contributor
timestamp: February 21, 2013, 11:54:35 pm
content: AFAIK you are not calculating your meter spec properly. The plus X counts is added to the % of reading inbothdirections. Your lowest range shown above would be +/- 9µV not -4µV + 9µV.This does not change the validity of you questioning the quality of this calibration, AFAIK the TUR should be at least 4:1

author: dimlow
author_rank: Frequent Contributor
timestamp: February 22, 2013, 12:11:00 am
content: Ah, thank you! I will change the spread sheet and see if it makes me Happier , But i think what its come down to is they have calibrated a 20ppm meter with a 30ppm Calibrator, Am i right in thinking that ?Edit: Just had a look at the spead sheet again and my error still would have made no difference to to results, its has still failed according to the specs in the manual, and i think its because of their test equipment.

author: Chasm
author_rank: Regular Contributor
timestamp: February 22, 2013, 12:50:41 am
content: Without looking at the actual specs and using a bad analogy as starting point...Trying to check the dimensional stability of a vernier caliper with a tape measure will only find gross errors. Very gross errors.You obviously can't actually calibrate an instrumentto it's full specificationswith an calibrator of lower accuracy.You can do a sanity check to find gross errors.Or you could throw the initial specs of the device under test out of the window and calibrate to a different,lowerstandard.-> This question isthepoint of an often repeated sentence in the Aligent cal lab videos: "Your cal lab is NIST certified. Nice. But what exactly is you cal lab actually NIST certifed for?"[Chasm says: 10V DC, +/-1% ?]

author: dimlow
author_rank: Frequent Contributor
timestamp: February 22, 2013, 01:26:10 am
content: Quote from: Chasm on February 22, 2013, 12:50:41 amI love this analogy, i think i may use it when i email them tomorrowJust for completeness here is the new sheet

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: February 22, 2013, 05:51:24 am
content: Quote from: dimlow on February 22, 2013, 01:26:10 amCouldn't you just quietly, on official looking letterhead, just invoice them for the rental of your solartron "transfer standard", which they used to calibrate their calibrator ?. just to see what happens.

author: dimlow
author_rank: Frequent Contributor
timestamp: February 22, 2013, 06:07:18 am
content: LOL! I liked that

author: mzzj
author_rank: Super Contributor
timestamp: February 22, 2013, 07:58:24 am
content: Quote from: dimlow on February 22, 2013, 12:11:00 amI think you are comparing eggs with apples. Your solartron is specified for 20ppm FOR 24 hours. More relevant specification is the 2-year spec: 100ppm + 10 counts.Gosh, I will always get headache from these "traceable" calibration certificates. At least your calibration is so called "with data"ANSI Z540-1 Compliant calibration = someone puts on sticker to your metercalibration with data = someone puts sticker to your meter and gives you some resultstraceable calibration with data =someone puts sticker to your meter and thinks that results are traceable to national standards17025 Accredited Calibration = you might actually get something trustworthy

author: Unknown
author_rank: Unknown
timestamp: February 22, 2013, 12:58:31 pm
content: I would ask the cal lab to state the ppm for the 202mV range of their cal meter on the day, then state the calculated ppm of an "ideal" 7150 on the 200mV range. If the TUR is worse than 4:1, I would ask for my money back!

author: dimlow
author_rank: Frequent Contributor
timestamp: February 22, 2013, 01:22:23 pm
content: ok, going to give then a call

author: robrenz
author_rank: Super Contributor
timestamp: February 22, 2013, 01:23:52 pm
content: Quote from: mzzj on February 22, 2013, 07:58:24 amNot so. IMO If they say they can calibrate that specific meter, the lab should be able to calibrate and adjust to the 24hr values with at least a 4:1 TUR on a 6.5 digit meter.

author: Unknown
author_rank: Unknown
timestamp: February 22, 2013, 01:59:41 pm
content: I emailed the makers of the actual cal meter this morning who replied: "Model 3010A (8ppm) would provide the necessary capabilities appropriate for your Solarton 7150"I then asked about their suggested TUR ratio, they replied:"The Solartron 7150 specifications are :70ppm in 5 1/2 digit mode (Best DCV spec)35ppm in 6 1/2 digit mode (Best DCV spec)So @ 8ppm accuracy (best DCV accuracy) the 3010A offers 4:1 ratioI worked out the 7150 to be 22 ppm - but I didn't factor-in anything else, so 35ppm sounds perhaps right.The moral of the story is, if you have to measure apples with oranges - just don't forget to juice them first!

author: ecat
author_rank: Frequent Contributor
timestamp: February 22, 2013, 02:01:32 pm
content: On the other hand, their UKAS accreditation ( from bottom ofhttp://www.alpha-electronics.com/StaticPage/256/ElectricalTestEquipmentUKASCalibration.html, pdf link onhttp://www.ukas.org/calibration/lab_detail.asp?lab_id=1443&vMenuOption=3) states they are only good for 32ppm on DC volts (2V to 20V @ 26ppm). Also, as we now know their unit was calibrated in March 2012 (see dimlow's test cirtificate attached to Reply #17) we have to assume the 12 month figure of 30 + 3 applies ( 30 + 3 = 33, where do UKAS get the 32 from ? I guess 11 months does not equal 12 months)So, yes, I think they should have said something before accepting the job, but they are not hiding anything as the information is there for anyone to read. The problem, as always, is knowing the questions to ask in advance.

author: robrenz
author_rank: Super Contributor
timestamp: February 22, 2013, 02:22:56 pm
content: Quote from: jucole on February 22, 2013, 01:59:41 pmAFAIK Transmille shows thier specs for the calibrator accuracy only. you have to add the uncertainty of the standards the calibrator was calibrated to to their values. All thier specs say (Accuracy relative to calibration Standards).

author: mzzj
author_rank: Super Contributor
timestamp: February 22, 2013, 03:03:09 pm
content: Quote from: robrenz on February 22, 2013, 01:23:52 pmWrong. If I send our 3458A 8½ digit meter with high stability option to any calibration lab I am pretty sure NONE of them are going to (or are able to) calibrate it with 24hr values with TUR 4:1

author: mzzj
author_rank: Super Contributor
timestamp: February 22, 2013, 03:17:06 pm
content: Quote from: ecat on February 22, 2013, 02:01:32 pmFor UKAS accredited uncertainties you have to actually calculate pretty much everything. And if your calibrator has good history(many years of calibration history with much lower drift than manufacturer specifies) you can also use better stability estimate than manufacturer's spec sheet.Dimlow's (thread starter) calibration certificate is NOT UKAS accredited calibration so Alpha Electronics is free to put any sort of uncertainties to their certificate.UKAS-accredited ISO/IEC 17025 calibration certificate would look quite different and probably cost 5-10 times more.

author: robrenz
author_rank: Super Contributor
timestamp: February 22, 2013, 03:39:40 pm
content: Quote from: mzzj on February 22, 2013, 03:03:09 pmYou are correct about the 3458A the TUR starts to shrink at that level.I am correct when I specifically said6.5 digitmeter.The calibration of my Fluke 8846A:1.0 V scale at 1.0 V Measurement 0.999999 Uncertainty 3.1 µV 24 hour spec 24 µVgreater than 4:1

author: mzzj
author_rank: Super Contributor
timestamp: February 22, 2013, 04:17:55 pm
content: Quote from: robrenz on February 22, 2013, 03:39:40 pm"Shrink" to put it slightly.I would say it's diminished. For example our local National Measurent Laboratory can calibrate 3458A with 2 ppm uncertainty and manufacturer 24h specification is 0.6ppmWhat is that, 0.6:1 TUR? And I had to pay approx 1500 usd for this level of calibrationAgilent UK cal lab seem to be able to do 0.8ppm according to their accreditation scope BMC (best measurement capability)My guess would be that is already against their josephson-standard. Must be bloody expensive, ie several thousand dollars.My point? I guess my point was that not that much point looking at 24h stabilities.

author: dimlow
author_rank: Frequent Contributor
timestamp: February 22, 2013, 04:54:04 pm
content: I contacted Alpha electronics today and spoke to the guy that calibrated the meter. He said he was not aware of the accuracy of the meter and calibrated it to the ukas spec set out by the ukas manager of the company as they calibrate all meters that way. He was just simply following his procedure. He again offered my money back. I think i will accept, but before i do i will talk to the ukas manager on Monday, he had last week off. They do apparently have something that can calibrate the meter. He mentioned a 1710A or 710A or something like that. I tried looking it up but could not find any details, so don't know what this instrument is.How exactly do you calculate the ppm of a meter? I see above the jucole contacted Transmile and got a value of 35 ppm for the solartron, but says he worked it out at 22 ppm. I thought it was 20ppm. I want to be sure about this before a speak to the ukas manager. ( Transmile is about 40 mins from here, they offered to calibrate and adjust the meter for £150 )This calibration business has taken far to much of my time now, i was stupid to think it was as simple as just taking the meter to be calibrated and the company would sort it all out for me. Then hand me back a fully calibrated meter. I now have no confidence in the calibration and im £65 + VAT down. All i really know is that the meter works. Lets hope the ukas manager can put my mind at rest.

author: mzzj
author_rank: Super Contributor
timestamp: February 22, 2013, 05:16:55 pm
content: Quote from: dimlow on February 22, 2013, 04:54:04 pmBe happy with your current calibration certificate and stop worrying nonsense.Are you planning to use your meter for something super-accurate within first 24 hours or what?Just my 2 cents as a Calibration Engineer who spends far too much time with these things.

author: jpb
author_rank: Super Contributor
timestamp: February 22, 2013, 05:30:51 pm
content: I've been following this thread with interest as I'm in a similar position. I've just bought a ADCMT 7451A 5 1/2 digit meter on e-bay and would like to get it calibrated and adjusted if need be as a standard but it seems this calibration business can be very expensive involve shipping the instrument and may very well not include any adjustment at all.Looking at different websites (eg RS calibration services) there is no clear statement as to whether or not they will adjust the instrument or whether this counts as a 'repair' and cost extra.Do they calibrate it to the 24 hr spec, the 90 day spec or the 1 year spec?What is the proper spec anyway - eg on most DC Volts ranges it is listed at 0.0020% + 2 digits which should be 20ppm + something like 2/300,000 if the reference is near the top of the 320,000 count display which I guess is around 27 ppm for the 24 hour spec (+/- 1C) but for 90 days it is 60 ppm + 3 which is around 70 ppm (+/- 5C), the yearly spec is up at 140ppm+3 or say 150ppm.I too thought it would be very simple - especially as the meter is closed box calibration just requiring the pressing of buttons to adjust the readings rather than any trimming of pots etc.Given the yearly spec is outside 0.01% perhaps a DIY approach with something like the Geller labs voltage source and a home made voltage divider is a better route.

author: mzzj
author_rank: Super Contributor
timestamp: February 22, 2013, 06:45:34 pm
content: Quote from: jpb on February 22, 2013, 05:30:51 pmJust to mess your head more: There is no universal standard how meter manufacturers specify meter accuracy. Some use k=2 confidence interval (95% probability) for their specifications, on the other hand for example Agilent uses k=4 or 99,994 confidence level for 34401A specifications...Manufacturer X may specify 20ppm/year with k=2 confidence. Means that there is 5% probability that meter X doesn't meet the 20ppm specification.30 ppm Agilent specification for 34401A is on the other hand with k=4 confidence level and it means that there is 0.006% probability that Agilent 34401A doesnt meet the 30ppm specification.30ppm from Agilent is better than 20ppm from manufacturer XI am going to say this for last time: Using 24 hour specs for TUR calculation is nonsense unless you are planning to calibrate your meter every 24 hours!

author: jpb
author_rank: Super Contributor
timestamp: February 22, 2013, 07:00:16 pm
content: Quote from: mzzj on February 22, 2013, 06:45:34 pmI agree when it is a case of checking the meter (i.e. not adjusting it if it is in spec) but if the meter is to be adjusted as a starting point perhaps after a new purchase or if the calibration has been lost then the 24 hour spec seems to be a good target for the adjustment. I would guess that it represents the tightest region that you can realistically expect to be able to adjust the instrument into.

author: Unknown
author_rank: Unknown
timestamp: February 22, 2013, 07:45:04 pm
content: Quote from: mzzj on February 22, 2013, 06:45:34 pmI'm confused; why would calibrating your 7150 meter with one 4x better require you to calibrate your meter every 24 hours?

author: Unknown
author_rank: Unknown
timestamp: February 22, 2013, 09:17:13 pm
content: Quote from: jpb on February 22, 2013, 05:30:51 pmYou might be lucky enough to find one close to where you live then you could perhaps take it in yourself to save on shipping cost.Regarding adjustment, you have to read the service manual to understand how it is done for any particular meter; with the 7150 in say the 200mV dc range, you apply 199.999 v, then read back the value, then tell the meter what the REAL value is; the meter then stores the result; The meter now knows the offsets and will apply them thereafter to hopefully give you the correct result; So you could say the "adjustments" are already done by the calibration software running over GPIB.Tell them that if the meter needs any additional work (repair) then to let you know before proceeding.QuoteFor hobby use; just ask them to calibrate it to as close to the "as new" as they can; If it's done properly when you compare the result to the manufacturers spec. it will tell you the real age of the meter!QuoteThe spec you describe is an indication by the manufacturer of the "best accuracy" after you have bought it; and how you might expect your "best accuracy" to change over time.

author: dimlow
author_rank: Frequent Contributor
timestamp: March 11, 2013, 05:34:51 pm
content: Looks like i didn't give the forum an update on this. I hate unresolved posts, you read all the way to the end and there is no final solution.I spoke to Alpha electronics and they gave me my money back. That was ok but i still have an un-calibrated meter, or at least a calibration that i cannot be certain of. As mentioned above Transmile state that the meter should be calibrated with uncertainties of 8 ppm not 20 ppm as Alpha electronics did.Over atMjlortons Forumi detail a phone conversation i have with Calibrate.co.uk Martins Sponsor. When i phoned i didn't get the expected answers to some questions i had about Ukas and ISO 17025. Later in the thread the MD of Calibrate.co.uk replied and also said they were getting in the 8 ppm Calibrator and i could have my meter calibrated on this. I have now since spoken to the MD, Barry and will be sending the meter in for calibration with them. Within 1 hour of arranging the calibration i was presented with a UPS label via email. All i have to do now is pack up the meter and call UPS to collect it when I'm ready.Will let you know how it goes.

author: ober
author_rank: Contributor
timestamp: February 02, 2019, 10:27:16 pm
content: Does anyone have dimlow's great set of images saved?Picasa is no more.