| Products > Test Equipment |
| Easy way to test the calibration of a DMM (Fluke 45)? |
| << < (21/29) > >> |
| CalibrationGuy:
--- Quote ---(I'm not sure why they'd do that, was it just so that people could have accurate clocks?) --- End quote --- In Ye Olden Days the 60Hz line was used for a whole lot of timing purposes. In cheaper devices, it eliminated an internal clock circuit. (Yes, I am that old.) TomG. |
| mawyatt:
--- Quote from: CalibrationGuy on April 04, 2024, 12:04:12 am --- --- Quote ---(I'm not sure why they'd do that, was it just so that people could have accurate clocks?) --- End quote --- In Ye Olden Days the 60Hz line was used for a whole lot of timing purposes. In cheaper devices, it eliminated an internal clock circuit. (Yes, I am that old.) TomG. --- End quote --- Ironically the 60Hz Power Grid was not that accurate short term, over the span of precisely a day it was dead on by design. As mentioned during the day the frequency would drop, this was caused by the on-line loads in the Grid (1/2 the US on each Grid, East and West coast). However during lighter loads late at night and early morning the grid would "Speed Up" to catch up time-wise (think of an old clock which was based upon a synchronous motor). Exactly 60 cycles/sec * 60 seconds/min * 60 minutes/hr * 24 hours/day or 5,184,000 cycles/day were created by the Grid and "tuned" to such every day. This was why old wall clocks were always in time from day to day, week to week, month to month and only needed setting when power was interrupted. In fact, we used the wall clock to discover if we had a power interruption and how long this was by simply comparing the wall clock to our wristwatch which we synched up every day. Back in ~1970 we made an instrument to monitor and plot the Grid Frequency. While giving a lecture on such the Nuclear Power Plant Turkey Point in South Florida tripped off-line and we all witnessed a large Dip in the Eastern US Grid Frequency, recall this Dip was something like ~30mHz!! You could see the Grid "Speed Up" at night/early morning and the "Dip" mid day when viewing the instruments chart recorder output over a 24 hours period. Best, |
| J-R:
--- Quote from: shabaz on April 03, 2024, 09:09:59 pm ---Trying quoting for the first time: --- Quote from: J-R on April 03, 2024, 08:26:43 am ---It's true that not everyone needs the same level of performance from their test equipment, but these random unknown references really are bad no matter how you look at it. The technical shortcomings have already been well discussed (and perhaps somewhat ignored), but a different point is that you are frequently contributing to people who would be totally fine scamming you wherever possible. --- End quote --- That works both ways. There's no innocence on either side, with Westerners openly scamming by unlocking functionality that they have not paid for on Eastern test equipment. I don't choose to automatically mistrust every seller based on the occasional bad experience here or there. --- End quote --- What about all the threads here for hacking the Agilent/Keysight scopes (one over 131 pages long)? No need for any West/East nonsense... People will hack equipment in their possession for various reasons and it has nothing to do with where they or the equipment came from. You're moving the goalposts now... Back on topic: how ELSE would you describe an online seller that prints out duplicate copies of a calibration sheet and applies them to all the "references" they ship out? That is an extremely solid definition of a scammer. --- Quote from: shabaz on April 03, 2024, 09:09:59 pm --- --- Quote from: J-R on April 03, 2024, 08:26:43 am ---Instead, send your money to individuals who are not really doing it for the money but for the love of the hobby. Win/win for everyone. --- End quote --- Not everyone thinks the same. It is possible to "buy local" as well as to help others across the world, who might actually need the money. --- End quote --- I don't know what you are arguing against here. I never said anything about not buying local. Support honest businesses. Local as well. --- Quote from: shabaz on April 03, 2024, 09:09:59 pm --- --- Quote from: J-R on April 03, 2024, 08:26:43 am ---And again my main point about why these cheap references are "dangerous" is that they have specific voltages printed on them and are sold as "references" so buyers apply additional weight to them. What ratio of buyers do we think have adjusted their DMM based on the "reference" compared to adjusting the "reference" based on their DMM? --- End quote --- Let's guess at an extreme 90% of buyers adjusting their DMMs based on that board. Even if they did, so what? They would have a DMM that was possibly inaccurate by tens of mV at the most? What are the implications: (a) For a hobbyist, if it affects their projects, it will be a great learning curve on what to trust. If something is worth doing, it's worth doing wrong. (b) On the other hand, if you're a professional: a qualified engineer may well rely on prototype or 'uncalibrated' equipment when developing products; there's nothing abnormal in that. But equally, that engineer is in every way liable for trusting a $10 device over a calibration if they ignored a process, or were supposed to be working to a standard, or if a body of other professionals would not have done the same for that specific task. --- End quote --- Quite an incredible stance. You are OK with people adjusting their previously factory calibrated test equipment with some random reference? I think you should reconsider your position. |
| shabaz:
--- Quote from: J-R on April 04, 2024, 03:56:56 am ---What about all the threads here for hacking the Agilent/Keysight scopes (one over 131 pages long)? No need for any West/East nonsense... People will hack equipment in their possession for various reasons and it has nothing to do with where they or the equipment came from. You're moving the goalposts now... --- End quote --- No I didn't, except perhaps in the most minor of ways. You were the one that stated that buying from AliExpress means frequently contributing to scammers. I merely responded. But, now you mention Keysight, you think it makes it any better that the scammers that I mentioned in return, are perfectly willing to do the same to fellow colleagues in our own countries too? --- Quote from: J-R on April 04, 2024, 03:56:56 am ---Quite an incredible stance. You are OK with people adjusting their previously factory calibrated test equipment with some random reference? I think you should reconsider your position. --- End quote --- I'm perfectly OK with what I stated. Not my problem if you misinterpret. The text is there forever, and anyone can read it to judge for themselves. |
| Finnaaah:
Not sure if it's that relevant or useful since it's only resistance, but I stumbled across this series of resistors when I last ordered from Mouser. RNCF0805TKW e.g. 1K would be RNCF0805TKW1K00 I definitely wouldn't use them to adjust calibration, but 2ppm/C and 0.01% for $4.50 AUD lets you pick up enough to check multiple ranges on a budget. I made a 4W measurement PCB for Vishay's hermetically sealed metal foil resistors and left a few SMD footprints on it, which I've attached. Not saying this is (remotely close to) the pinnacle of accuracy, but it's very handy to have a bunch laying around if you're buying second hand equipment or just want a quick n' dirty idea of your meters resistance accuracy :-+ :-DMM |
| Navigation |
| Message Index |
| Next page |
| Previous page |