*Help!* Crazy Tailcap Readings...Excel XL830L

I am sure that's not ok -- Undecided. Now that's making no sense for sure... My $12-$15 DMM is going on a year now and works great, the UNI-T UT33D model, but I did buy a better model from FT: UNI-T UT50B. What's nice bout the 50B is it shuts off automatically because I constantly seem to leave things on...

I didn’t think so…wonder if there’s any way to calibrate it? We know about what a 2.8A driver should do, right?

I’ve got a tiny little pocket-sized meter that’s 20 years old and it seems to be spot on AFAIK, but it doesn’t do current.

With 2.8A's, I read really close to it, maybe 2.85 or 2.88A at tops. the 350 7135's can get higher readings, 380's usually lower. 3.3A is out there. Seem to recall someone seeing or talking about a similar issue... Dunno...

Hows the voltage reading from a known voltage. Is it off also?

Turning that little pot will change the voltage reading for calibration on a cheap harbor freight DMM.
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I have been told that all meters should contain the pot for calibration of voltage. I don’t know that the current can be calibrated on this model. What meter are you using?
Update: Well there it is in the thread title, how did I miss that? :~
http://www.petervis.com/meters/XIOLE_XL830L/XIOLE_XL830L_Inside_View.html
Should be that little yellow and white pot in the link.
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To calibrate the meter you will either need a known accurate meter to check against or a voltage standard.
http://www.voltagestandard.com/DMMCheck.html

Never seen a 2.8 driver read more than 2.98ish. The AMC7135’s typically allow more than 350ma each.

There was a thread about a DMM giving weird readings, and it ultimately was caused by a depleted DMM battery.

Yep, put a fresh battery in it.

I got caught out at work earlier this week - replaced a faulty alternator in a car, & the new one tested at ~17 volts. I thought it had a faulty regulator, replaced it with another unit, same reading…… turned out my work multimeter battery was getting flat…… :zipper_mouth_face:

New battery was the first thing I did if you read the OP.

My old Elenco meter is giving voltage readings about 0.10v too high (at least at around 4 to 6 volts) and gives too high of current readings. Thread I posted about current here. I never fixed it. I just replaced it (although I find myself using it and forgetting the voltage readings are a little high). There are quite a few pots inside mine.

My XL-830L has proven good though with thick leads (I posted my test in the original T-Mart deal thread dchomak linked).

I'd suggest always trying to test your meter / leads with a Nanjg driver and fresh battery since you know what you should be reading.

-Garry

Garry, what do you get when checking your Nanjg for current?

So, the way you calibrate these babies is…“throw it out and get a good meter?” I like it. :wink:

Post #65 in that thread. I was getting 2.05A on a 2.1A Nanjg (6x7135's) which matched my 2.051 on my "good meter", both with short thick 12ga leads.

-Garry

Ah, thanks. I think my meter might be a return…it had a battery already in it (plus another wrapped battery) and there was a crack in the protective cover. This was also the second one they sent out, first one didn’t make it here.

Great deal….“Two 9v batteries for $5.94!!”….comes with piece o’ plastic cr@p meter. :frowning:

I'd recommend taking a step up in meter quality, especially if this will be your only meter.

-Garry

I think that is good advice!

Really, my old pocket-sized Radio Shack meter has been rock-solid for over 20 years, but it doesn’t do current.

I’m going to poke around in the Excel and see about calibrating it with a known source…

Some very quick recommendations on another meter:

Equus 3320 (thinking it might even be at some Walmarts): $18.74 at Amazon.

Here's a Mastech MS8268 which seems identical to my "good one" but without the lux meter (not sure how good it is anyway) and without temp/humidty (who needs that anyway): $24 at Amazon. My Mastech has a bit of a cheap feel to it (and the probe sockets don't lock the probes in so tight), but it functions well (get what you pay for I guess).

-Garry

Thanks for the recommends!

After messing with the calibration pot inside this meter, I’m convinced this one is rubbish. I couldn’t even get it close to what it should read on a 2.8A Nanjg.

At least I got some good leads made for when a proper meter comes along!

I ordered the Mastech from Amazon as well as some helping hands.

“Back in the day” a VTVM was a rare item, not just anyone had one - but I did. Mid 60’s, this one cost $39.95 and it was a KIT. You had to put it together, all point to point wiring!

And note there is no Amp scale.
This next one also came in kit form and cost $69.95, a for real DMM - from the mid 70’s
Sabtronics Model 2000

Back in the 60’s, $39.95 was a LOT of money! It is because of that, I am happy to use a cheap Harbor Freight meter and not complain. Relatively speaking, a bargain, and more accurate than either of these 2. That is also why I can’t help buying meters, they all seem so inexpensive.

EDIT: I plan on restoring these 2 and get them up and running.
Speaking of calibration, in the directions for the EICO VTVM, the calibration procedure was to plug the probes into a US AC outlet and adjust for 117V. The DC calibration was connect to a fresh Carbon-Zinc D cell and adjust to 1.65V!
And that was it!
The ohms adjust was just under the meter face, you can see it in the pic, and had to be constantly adjusted as the Vacuum Tubes heated up.
God I feel old!