I just bought a Data Precision 2480R Bench DMM

[c4757p]

:/ that isn't what they taught me in school

They oversimplified it because in all of the example problems they would ever give you it would work, and they wanted to treat you like a moron, which is fun. They don't give a shit if it leaves you unprepared to deal with real problems.

This is, at least, my experience.

[IonizedGears]

Could you point me towards the direction in which I could look up more on this method?

[c4757p]

It really is just common sense! If you pick a point and go around a full circle back to that point, you have to get back where you started, right? So for every volt you gain, you must lose one somewhere else in the same circle.

[IonizedGears]

Okay, that sentence is really all I needed.

[c4757p]

Likewise, short of the "something" being a magical electron eater, every charge unit into something must exit it, since you can't create or destroy them. This is Kirchhoff's current law. What goes in must come out, or in other words, the sum of all currents entering a point (where positive currents leaving are equivalent to negative currents entering) is zero.

I've found that students often see this as unintuitive in the case of a charging capacitor, where they think that charge should enter one side, but not exit the other, because they imagine it like a "charge tank". The symmetry between "positive currents leaving" and "negative currents entering" shows why even this case will be symmetric, with charge moving in one side and out the other: the positive side charging to become more positive is the exact same thing as the negative side charging to become more negative.

[EpicIntelGamer]

  Think I'm more confused than ever now lol

Anyways, I put in a best offer to try to get a second identical meter from the same seller for the same price as before ($20) hopefully I can get it!!

[EpicIntelGamer]

I did not get the second but I might later.

I did however receive the one I did order!

The faceplate was held on from the factory with two little strips of 30some year old double sided tape and was almost fallen off so I hot glued it back on.

Other than that I only powered it up and tested out the 10VDC range with my REF02 .3% 5VDC Voltage Reference (here's a thread about it: https://www.eevblog.com/forum/projects/simple-voltage-reference-idea/ ) and it tells me that it is 5.009VDC which is probably correct (but I have nothing more accurate to check it against).

I'll check some of the other functions and ranges tomorrow if I get a chance, but for now at least we know it works and its readings are reasonable.

[MatCat]

How has it been treating you?  I just picked one up on ebay for $0.99 + $15 shipping, hopefully it comes out good

[MatCat]

Got mine in today, and I am pretty happy!  The only thing accurate I had access to was a good resistor box, I tested between 0.01% to 0.5% of the value, which I am sure is down to the resistors in the box.

[FlyingHacker]

Sorry to dig up an old thread, especially one that went crazy off topic to begin with, but I will bring it back to the initial topic:

I got one of these Data Precision 2480R meters recently. It has an issue where DCV at the 100v setting shows the wrong value. Interestingly (since the attenuator resistors for the different scales seem to be in series with one another), the other ranges work fine. I believe all the kOhm ranges work correctly too.

Does anyone have a schematic for this? I only find them for sale on eBay for the usual Tucker Electronics high prices.... More than the cost of the meter.

In trying to diagnose this I find a TP by the attenuator resistors that measures around 91k ohms on all other ranges, but 62k ohms when you push the 100v switch. This is pretty proportional to the increase in displayed voltage. I can measure the voltage on the switch (which is one of those mult-contact push buttons with the physical lockout of other switches) and it is equal to the voltage displayed. It is just wrong.

I am wondering if perhaps it is the switch itself. I sprayed contact cleaner in there as well as I could. I may try shorting the contacts on the switch manually. However, I am thinking the issue may be further up the line, as this is a decrease in resistance to ground, which makes me think it is more of a mild short, or failed part. Without the schematic it is hard to trace where things go, especially since I don't know precisely how those switches work in the first place (what contacts are being opened and close by the switch).

Any help would be appreciated... Thanks!