Author Topic: EEVblog #374 - DIY Multimeter Calibration  (Read 34178 times)

0 Members and 1 Guest are viewing this topic.

Offline ModernRonin

  • Contributor
  • Posts: 44
Re: EEVblog #374 - DIY Multimeter Calibration
« Reply #25 on: October 24, 2012, 10:22:12 am »
Quote from: Matje link=topic=11512.msg156693#msg156693
Well, a bit more probably. You need a case (cheap), some connector stuff (can be quite expensive), preferably a (pre-)-regulator, a diode to protect against input power connected the wrong way around, some random stuff.

I still think it can be done. Of course, BOM cost is not final product cost. But, assuming the usual BOM cost * 3, you could still maybe make something for ~$30. (I wish I had the time...)

Quote
I think I paid about 30 to 40 Euros for something using LT1021s with 5 and 10 Volts, 0.05% nominal. This is more than enough for the usual DMMs, and still enough to check that a 34401A is doing reasonably OK. The reason for having 5 and 10 Volts is that different DMMs have different ranges, checking near maximum range value is a good idea.

Yeah, mine has a 2V range and a 20V range. 2V is easy, of course. 20V... not so sure.

Quote
I don't think that is worth it for hobbyist use. Resistors with 0.01% cost real money. Precision OpAmps cost real money.

I dunno about precision resistors, but opamps with less than a mV of offset even in the worst case (typical = 200 uV) aren't that expensive. LT1013 for $1.95 in qty 100, and that's two opamps per chip.

Quote
As far as I know for affordable DMMs you don't get to adjust every range individually, the ratios are fixed. So why bother?

I think hobbiests will buy all sorts of crazy stuff that's overkill, just for the fun of it. ;]

Though, again, I don't have the time to do the market research to back that assertion up. (Alas...)
 

Offline all_repair

  • Frequent Contributor
  • **
  • Posts: 532
Re: EEVblog #374 - DIY Multimeter Calibration
« Reply #26 on: October 24, 2012, 07:11:23 pm »
I know someone that got one of these and claims that it's as the aussies say: ducks guts
http://www.voltagestandard.com/DMMCheck.html
I really have to wonder if any such device could be used as a standard for anything.

I suppose it's better than nothing but I would rather have the real deal like Dave does.

Got one to see some  light.  Problem is the bench space, there are more things to play than calibration.  What is lacking is I still cannot find a case to fit the DMM Check plus, and also the method, the equipment and the calibrations of voltagestandard.com for him to certify their products.

 

Offline ecat

  • Frequent Contributor
  • **
  • Posts: 296
  • Country: gb
Re: EEVblog #374 - DIY Multimeter Calibration
« Reply #27 on: October 26, 2012, 01:17:48 am »
I found this calibration service on ebay, I'm in no way affiliated, and was wondering if anyone had any comments or experience of them.

http://www.ebay.co.uk/itm/Electrical-test-equipment-calibration-service-collection-and-delivery-/230749957993?_trksid=p2047675.m1982&_trkparms=aid%3D555001%26algo%3DPW.CURRENT%26ao%3D1%26asc%3D29%26meid%3D2961668007543752372%26pid%3D100009%26prg%3D1013%26rk%3D1%26sd%3D321004372343%26

(that's pjoindustrial for the days after the ebay link dies)

Uk only I guess but £24 to calibrate a single device, a price which appears to include shipping both ways. Too cheap to be true? Or does this look about right?

 

Offline PA4TIM

  • Super Contributor
  • ***
  • Posts: 1115
  • Country: nl
  • instruments are like rabbits, they multiply fast
    • PA4TIMs shelter for orphan measurement stuff
Re: EEVblog #374 - DIY Multimeter Calibration
« Reply #28 on: October 26, 2012, 02:07:45 am »
http://www.pjoindustrial.co.uk/index.php?*p=about Seems like part of a rather big company.
But it is a bit strange if all calibration would be the same price, and be carefull, calibration is just testing if an instrument is still within specs, not adjusting it. There is no specification added so maybe it is the start price for a simple multimeter or a resistance standard. (transport is 15 pound and that is also strange, shipping a 30 kilo IET GR1620 would cost them more as the total price payed by the customer for postage and calibration) But if this is true I regret not living in England.
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
www.schneiderelectronicsrepair.nl  repair of test and calibration equipment
http://www.youtube.com/user/pa4tim my youtube channel
 

Offline scopeman

  • Regular Contributor
  • *
  • Posts: 159
Re: EEVblog #374 - DIY Multimeter Calibration
« Reply #29 on: October 26, 2012, 11:13:34 am »
Dave,

Great meter and standard. I have the same setup and they are both outstanding.

You might want to consider getting a spare lithium battery that is used for the backup battery for the calibration constants for the HP3478A. Just make sure that you have the meter powered on and use a butane powered soldering iron when you are replacing the battery.

Sam
W3OHM
 

Offline ecat

  • Frequent Contributor
  • **
  • Posts: 296
  • Country: gb
Re: EEVblog #374 - DIY Multimeter Calibration
« Reply #30 on: October 28, 2012, 09:29:11 am »
http://www.pjoindustrial.co.uk/index.php?*p=about Seems like part of a rather big company.
But it is a bit strange if all calibration would be the same price, and be carefull, calibration is just testing if an instrument is still within specs, not adjusting it. There is no specification added so maybe it is the start price for a simple multimeter or a resistance standard. (transport is 15 pound and that is also strange, shipping a 30 kilo IET GR1620 would cost them more as the total price payed by the customer for postage and calibration) But if this is true I regret not living in England.

I see.
So when they say calibrate they probably mean verify  and the cost of a true calibration would probably be a lot more than £24.

The reason I'm asking, I'm now the proud owner of a Solartron 7150 Plus which was last calibrated (or verified!!!) in 1997, and just wondering how best to whip it into shape.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf