| Products > Test Equipment |
| Easy way to test the calibration of a DMM (Fluke 45)? |
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| Fried Chicken:
Hah. So now I have the slightest stupidest insight into what makes pushing the boundaries of metrology difficult. I have three or four multimeters or multimeter-like devices capable of reading voltages, but I'm not sure the accuracy of any of them. So what around the house options to I have to verify/test what's accurate and what's not? Fresh alkaline batteries? Stick the probes in an outlet and compare with what the power company is reporting? USB power from computers? I have two relatively nice DMMs (Fluke 45 and a Hioki handheld), along with other DMM-like devices (o-scope, chinese LCR meter with DMM capabilities, a chinese function generator that let's me dial in a voltage, the mtester thing)... Resistance notwithstanding. Are there any reliable around-the-house ways I can test these multimeters? Reliable resistors? Pencil lead? The nicest resistor I have laying around? |
| bdunham7:
Do the Hioki and the Fluke 45 disagree on anything you've measured? |
| Fungus:
I imagine the Fluke/Hioki won't drift much from spec. Simple check: Do they agree with each other on things? eg. A battery? USB power? A resistor? |
| adinsen:
Been there... I texted a friend who had gotten himsels an almost new bench meter, we had coffee, discussed life, work and other stuff, and I got my meters checked against his. Recently I got myself one of those small TL431 based voltage references with hand written values on the pcb which are available on eBay, but it drifts a little with temperature and it doesn't say what temperature it was calibrated on, so I can't trust it. |
| J-R:
My first thought was this: https://dmmcheckplus.com/shop/ols/products/dmm-check-plus-fully-loaded-with-all-options-lc-board-enclosure-and-dual-frequency But given the cost and the equipment you have, I am not sure if it makes a ton of sense to spend that kind of money. If not, maybe an option could be to go the route of sanity cross-checking combined with multiple DMMs and other test equipment. Different ranges and functions use different paths/configurations. Different resistor dividers, offset and gain calibrations for each individual range/function, etc. So apply 3V to the Fluke 45 and Hioki, then manually range up to 30V, 300V, 1000V, and see if everything is consistent. In some devices it's worth reversing the leads. The Fluke 45 seems to have multiple negative DC V performance tests but only a single -90mV calibration point. If you look at the theory of operation of some DMMs, this method isn't always overly useful if the same passives are used in multiple ranges and they've drifted. But if things align, then that provides some level of confidence I'd think. You could get some 0.1% resistors from DigiKey/Mouser and use them with Ohm's law. I picked up a pile some time ago and perhaps since they are designed to hold that spec through various temperature ranges, I found that at room temperature they were typically far better than spec. So a 1K 0.1% resistor is probably going to easily be between 999.5K and 1000.5K. Cross check the voltage drop with the current flow and resistor value and see if it all lines up. If it DOESN'T line up, then you have more work to do, but I suspect things will come out pretty good given your test equipment's pedigree. |
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