rat shack or fluke

[lowell]

Never been able to cough up the dough for a fluke meter. I've been having issues as far as I can remember with measuring ripple on power supplies... My rat shack meter moves all over the place. Is this normal and because there isn't much ripple and the meter is confused? Who owns a fluke? And are u able to accurately measure AC voltage? Thinking of the Fluke 115. If i have a scope, is there any reason to upgrade to the 117 for frequency setting?

[Amp Kat]

Well lets be honest here that the Fluke isn't the best for nothing and that's just the price tag that comes with it but as far as measuring AC ripple all meters will fluctuate because you are measuring a modulating signal which is why it's called Alternating Current. You are seeing the amplitude vs frequency modulation at a value of RMS. So to answer your question the answer is yes but how much could be the difference between a Fluke and RS.

[Jazz P Bass]

I have three of the Fluke 77 (the older style) meters.
I simply love them.
The only issue I have with them is the $25.00 for the test leads
Time to time you can find them on EBay for $30-$40.

[booj]

Old saying where I used to work. "If it works, it must be a Fluke". They build good stuff.

[Enzo]

If I measure AC voltage on simple AC voltage, my meter is stable. The mains are shaking at 60 times a second, or crossing zero at 120 times a second. That is way too fast to see a meter swaying. Now every time some motor starts up and some other load shifts on the mains, my voltage can bump or sag. That is normal. Monitor your mains to see how stable it is. A cheap meter might be inaccurate, but it won;t likely sit there changing its reading all the time if the voltage is actually stable. It will just be wrong - stable but wrong.

Now putting a meter on AC to read ripple on a DC voltage is no big for most meters, unless they are real low end ones that get confused by that. But the ones that get confused get REALLY confused, so if you want to read the ripple on your bias supply and the meter reads 400v, then your meter is confused. But if your meter is checking ripple on B+ and likes to sway a lot, then put the meter baack on DC and see if THAT is also swaying around.

Remember, if you have 120v mains and 480v B+, then every volt the mains moves, your B+ moves 4 volts. A 5 volt mains move results in a 20v B+ shift. Now a simple step up of say 5v can appear as AC to an AC meter. You might have a real stable DC voltage that is clean. Your AC meter will settle down to about zero volts AC on the meter. But turn the voltage up and for a moment, the AC meter swings up as the change goes by, then settles back down. Try it on your bench DC supply. Read the AC on a nice clean 10v setting, then spin the knob up to 15v and see if the AC indicates for a moment. When the DC voltage of a B+ supply goes bobbing around, that will also affect AC readings.


One other aspect of "moving all over the place" is how much is all over the place? If a meter reads 4 or 5 digits, we can read something like 2.1034v and those last three digits will indeed usually bob all over the place, so we read it as 2.1v I know if I have 2.1v of ripple on something, I surely do not care it it has or has not got an additional 0.0034v on there.

[lowell]

Very detailed informative post, thanks. I think my meter is confused. I'm measuring B+ in a tube amp on AC with the meter. It moves tens of volts, and never reads a number for more than 1 second, if even. What does your high-end meter read when you measure for AC ripple on B+? Assuming your typical tube amp supply ripple? Is it accurate and stable?

All I have for a DC supply on my bench is a Dunlop 9v adapter. Sad, I know. What do you use for a DC bench supply? Did you purchase or build it?

[imaradiostar]

The Fluke 115 is an excellent meter. The voltage limit of 600 volts could be a limiting factor for some tube circuits but it should rarely be a problem. I bought mine at a pawn shop in Nashville for $40. If you're near Chicago maybe you could find something in a pawn shop there?

I don't feel like a Fluke is really necessary. I have a lot of cheap meters and all of them measure within a small percentage of the Fluke meter.

IIRC Enzo mentioned using Electrophoresis power supplies in the past. They're all over ebay and they can be quite cheap. The key is to find one with voltages that are right for you.

Jamie

[imaradiostar]

as an example, check this link:

Isco 494 - Page 2 - diyAudio

That's an amazing bench supply!

Jamie

[Enzo]

Did you flip your meter back to DC volts to see if the B+ was hopping around even on DC?. My mains bounces all the time.

If the mains settle dowwn, I can read AC on top of DC readily.

Low volts bench suplies? I have a pile of them. The main one in front of me is a Heath Educational Systems unit, with a pair of 0-20VDC half-amp independent supplies. A switch lets you link them. Also there is a separate +5v 2A supply. I have three of them. I have a similar B&K which I think goes 0-30v on the two supplies, and +5. Plus a bunch of open frame linear and SMPS power supplies I can wire up when I need them.

[nickb]

Never been able to cough up the dough for a fluke meter. I've been having issues as far as I can remember with measuring ripple on power supplies... My rat shack meter moves all over the place. Is this normal and because there isn't much ripple and the meter is confused? Who owns a fluke? And are u able to accurately measure AC voltage? Thinking of the Fluke 115. If i have a scope, is there any reason to upgrade to the 117 for frequency setting?

Well you made me look...
I have a Radio Shack 22-163 and a Fluke 179 so did a face off on some simple tests.

Measurement	Fluke	RS	Notes
ACV on top of 48V DC	1.2mV	8mV	Signal is small to be meaningful
48.4 DCV	48.38	47.6	RS is lower by 1.6%
ACV 2V pk-pk @ 60Hz no DC offset	0.712	0.701	RMS value expected is 0.707
ACV for 2V pk-pk @ 1KHz on top of 4VDC offset	0.705	0.693	RMS value expected is 0.707
ACV for 2V pk-pk @ 60Hz on top of 4VDC offset	0.713	0.702	RMS value expected is 0.707
DCV for 2V pk @ 60Hz on top of 4VDC offset	3.992	3.988

BTW, there is not much difference in the fundamental accuracy of the two meters from the spec sheets. I was surprised how accurate the RS was at 1KHz, I expected it to fail miserably. The Fluke does have a big protective plastic body and the controls are more rugged and easy to use. I never seen a dead Fluke either. I This particular RS has little buttons and is not as rugged, still for bench use it's OK.

[lowell]

Awesome Nick thanks for the shoot out! Yah I've replaced many a rat shack meter. I'm sold on the Fluke, if they are less prone to failure, and potentially more accurate (at least on the ripple test)

[Chuck H]

When I was 20yo I bought my first meter for $70 US. A B+K 2704 (no suffix letter). It has to be the most reliable meter I've ever owned. I say this because I'm still using it and have never upgraded! I'm 44yo now! I cut my teeth using this meter and it's never failed to take the abuse. Incorrect settings (no auto range), over voltage, setting amps on it, dropping it repeatedly and anything else a novice to intermediate tech can do to a meter, accidentally or otherwise, hasn't compromised it one bit. Tough as a nail. None of the jumpy flailings you get from cheap meters either. Not as nice as the Fluke but it's still getting the job done. My only complaint is that there is no zero calibrate. Low ohm, voltage and capacitance measurements need to be figured out by subtracting the probe touch reading. But other than that it's golden. I'm on my second set of probes and I've had to install exactly three 9V batteries. It's about ready for a fourth. In twenty four years I'd say that's acceptible economy and performance.

JM2C

EDIT: The current incarnation of the B+K 2704 (now with suffix letter only) costs $60 to $80 US. So, same price as a quarter century ago! I wouldn't buy one. Looks like a turd by modern standards and couldn't possibly be the equal of the one I have. Inflation figures $70 US in 1988 to be about $135 today. That's about the cost of a Fluke 117. The B+K 388 or 389 is about that price too... But the Fluke features look more workman like and easier to use.

[big_teee]

I worked Tele Comm for 40+ years, I have used most Digital and Analog meters.
If your not doing Calibrated voltage reading, and just doing general VOM type stuff, most will do fine.
I own a Fluke 89.
I keep it in my Desk Drawer.
I have At least 6 of the small Harbor Freight DVOMs, and they work great.
I have them in various places. Never have too many.
They are like Dial Calipers, You need several, so they are handy!
Biggest complaint, they don't turn off automatically, and the cords could be longer.
I like a meter that you manually choose the range, they usually work faster, and your not waiting for it to pick the right range.
The Rat Shack meter that I used at a local guitar shop seemed very slow.
I was giving up, and the local tech, said be patient, and sure enough it would eventually read something.
T

[Prairie Dawg]

It helps to have a selection of multimeters for any occasion. Most of the time absolute precision is not necessary for troubleshooting

In no particular order I have on or nearby a couple of Harbor Freight DMMs, the twenty dollar kind for measuring bias, a Craftsman autoranging DMM, A B&K 290 FET multimeter, a Triplett VTVM and a Valhalla Scientific multimeter-counter. On the back bench is a Fluke 8000 with nixie tube display, a Weston digital bench model and a B&K bench model. The Valhalla is an interesting piece of equipment. I bought it on fleabay brand new AF surplus for $15 with leads and wall wart. I know how much these things cost when they were in current production and that is about $2,400. I know this because my boss had to buy one to do in flight computer calibrations on some Garrett equipped airplanes. That was back in 1988.

[Bruce / Mission Amps]

Awesome Nick thanks for the shoot out! Yah I've replaced many a rat shack meter. I'm sold on the Fluke, if they are less prone to failure, and potentially more accurate (at least on the ripple test)

Don't know if this will work but, when trying to measure AC riding on a high potential DC node, maybe you can try using a high voltage plastic capacitor to couple the AC to your meter.
Maybe a .1uF-630v or .22uF-630v etc...