| Products > Test Equipment |
| Easy way to test the calibration of a DMM (Fluke 45)? |
| << < (9/29) > >> |
| alm:
--- Quote from: robert.rozee on March 31, 2024, 01:28:15 pm ---one could probably go a long way with just a DIY hamon divider http://conradhoffman.com/HamonResistor.html and the raw output from a simple LM399 reference. first send the LM399 off to someone with a good 6.5 digit meter to measure it, then use the LM399 and hamon divider to calibrate low DC voltage ranges at 7v, 700mv, 70mv. if desired, 70v and 700v points can be calibrated using the same gear plus an adjustable HV supply and a little creativity. i dare say resistance ranges can similarly be calibrated using similar methods to scale up/down and just a single precision resistor that has been measured with a good 6.5 digit meter. sending off a small PCB (containing LM399 + CC source) and a single resistor through the post should be relatively cheap, and the time expended by the recipient making measurements relatively short. --- End quote --- Yes, that could certainly work. That's how metrology labs did it before instruments like the HP 3458A and Fluke 5700A automated it. They would have 1.018V standard cells and 1 Ohm standard resistors and derive everything from those. There's no reason why you couldn't do the same artifact calibration by hand if you had ways of scaling voltage and resistance (note that the ratio of the voltage across two resistors in series is proportional to the resistance ratio). ACV and ACI is more tricky, though maybe there you could use a trick like ratio transformers. Solutions like the cal club could be useful for importing the cardinal points like 10V and 10k that you can scale to any other value. |
| J-R:
Of course the calibration service I'm proposing is not going to be making the owner rich, and I'm confident Doug/Russ/Ian are not doing what they do for the money. As long as you're close to breaking even then you are doing fine because you're investing in yourself and probably having some fun at the same time. And I would suggest this basic service would be just a verification of the calibration points listed in the service manual. There is no need to get carried away with the more mundane metrology aspects. If you need that then go with an accredited lab. $5k or even $10k plus hundreds per year for an external cal is really nothing for a dedicated hobbyist. It just comes down to what you choose to spend your money on. |
| BILLPOD:
Shamelessly self-promoting my products..... :-DMM https://www.ebay.com/itm/285781907875 Plus, I have precision resistors, etc.... [/quote] Good Morning Majorassburn, when I went to E-Bay to look at your module, it indicates it is sold and no others are available??? :wtf: |
| Majorassburn:
Removed listings: Deleted BTW, you can always do an advanced search on eBay for SQWARREL to see my listings. |
| EEVblog:
--- Quote from: Majorassburn on April 01, 2024, 07:33:46 pm ---Here are a few of today's listings: --- End quote --- Please do not spam these in existing threads, use the Buy/Sell section. |
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