Multimeter questions

[Axtman]

Is there any reason for and electronics hobbyist / repair person to own the following multimeters?

Bench multimeter

Averaging multimeter

Manual range multimeter

Analog multimeter

Vacuum tube voltmeter

Thanks!

[olddawg]

It’s more important to know how to use the meter and it’s limitations. Nowadays you can do 90% of what you need to do with a $15 multimeter. I personally do not like auto ranging meters. People tend to not think when they use one.

[The Dude]

......I personally do not like auto ranging meters. People tend to not think when they use one.

+1 to that! And, a lot of them take too long to figure out which range to use.

[Enzo]

COntrasting view: I love my autoranging meter. I can push the range hold button any time I need to take a bunch of readings on the same scale. Some meters flip ranges slow, others several times a second. As to not thinking, most any tool will fool you if you don't pay attention. Try reading 400v B+ with your manual meter set for 20v. A novice will report "No reading" to us.

Bench meter: Most nice hand meters are more than accurate enough. A bench meter is laid out to sit on a shelf, a hand meter is laid out to hold while taking readings. Prop my hand meter against a book or a box, et voila, bench meter. Fancier meters tend to be in bench format. Ones with four wire measurements for example. Ones with fifteen digit readouts will be bench types. Until you are doing real lab work, you don't need that amount of precision.

FOur wire readings may have uses, but I can make equivalent readings with my hand meter. There are tricks of the trade. You know how to weigh your cat? Weigh yourself, then step on the scale with your cat in your arms. Now subtract the first reading. I can do similar things reading fractional ohms or tiny currents.

Autoranging versus manual range selection. Look, you can find good meters either way. Use the one you are most comfortable with.

Averaging? This is an advanced feature, the meter has a memory, you can take a number of readings at the same point, then the meter averages them out. Not a feature I have ever needed.

Analog meter. You mean a meter with a moving needle? Sure, I used one for decades, then digital meters came along, and I switched over. I measure voltages a lot. Analog meters won't autorange, so I cannot move from B+ to +5 without switching Also, my digital will measure either polarity as it sits. If I measure +400 on my analog, then probe the -70v bias supply, I will slam my needle against the peg. Analog means you have to select polarity or reverse your probe leads.

Modern multimeters are digital circuits made of solid state. In the old days, the equivalent unit was based on vacuum tubes (and would be analog). Nothing wrong with those. Many old timers still use their VTVM, they are used to them. I see no reason anyone would grow up on digital meters and then change to VTVMs, unless just a sense of retro fun.

You left out VOMs - volt-ohms-milliamps meters. Like the venerable Simpson 260. COmpletely analog, set any range by the switch. High quality piece. Nice mirrored scale for the meter needle. I have the Triplett version of the same thing. I never use it, but it is a nice meter. If I had been using it all along, there would be no reason to stop. But the versatility on a DMM - digiital multi-meter - is built in, it doesn't depend upon experience.

[The Dude]

One spot an analog meter comes in handy is if your doing peaking adjustments for instance in radio adjustments (not applicable much on an amp forum). It's nice to watch a needle instead of numbers in that case. I still have the Heathkit I built in tech school for that, but it rarely, if ever, comes out any more. It's one of these.



An advantage of the DVM over one of these is the diode check function, which I use probably more than any function when troubleshooting solid state circuits.

[Enzo]

Needles are great for peaking yep, but most digital meters have analog bars along the bottom for that purpose. On the bench, I'd probably use a scope for peaking anyway.


I do have several VTVMs here.

[Axtman]

Okay I will answer my own questions.

Bench multimeter: I would love to have one, if I had shelves. I just use a table and don't need more clutter. I would love to have a super accurate meter, maybe for amateur calibration, but can't see a use.

Averaging multimeter: I don't see an advantage other than they are cheaper for someone getting into the hobby. I don't really measure irregular wave forms but have a True RMS meter anyway.

Manual range multimeter: I have heard a few people talk about manual ranging meters measuring faster. I can see the advantage there, but my Fluke can be set to manual range so I have the best of both worlds. (As a side note, my father used to love slide rules over calculators because you had to figure out the degree of magnitude first then get the answer.)

Analog multimeter: I have seen that there is an advantage to seen how a capacitor charges or discharges or how a signal acts. It is a lot more intuitive to see a needle swing than a bunch of flickering numbers.

Vacuum tube voltmeter: I have heard that this is the way to go for repairing vacuum tube gear since they can measure high high voltage.

Volt Ohm Meter: I have an old Simpson 260 but never drag them out of the closet.

The reason for this post is that I see different multimeters and get and am eager to buy but have to ask myself, "What will I do with it?" So I guess for now I am stuck with my Fluke 87v.

[nevetslab]

Long Live Analog Meters!

While my normal maintenance work seldom involves more than a signal source and a Fluke 8060A 4.5 digit DMM, which I'm still in love with for all of its' features, I also work with SPL meters. I still prefer an analog meter movement with a wide range linear db increments, which is accomplished with a log converter behind the panel. My favorite analog meter....for AC use, is the Bruel & Kjaer 2607 Measuring Amplifier. It has interchangeable meter scales, is both True RMS with a wide range of averaging times (Fast, Slow, 0.1S, 0.3S, 1S, 3S, 10S, 30S, 100S, 300S) so you can take a wildly fluctuating signal and average it down to a steady state reading. It also provides impulse (35mS rise time), impulse hold, +Peak, -Peak & Max Peak (50uS rise time). You can capture the full transient peak level of snare drum hits, gun shots, you name it. You can select a 50dB Linear scale, which while watching & listening to music or speech, you find the min/max range easily spanning 30dB or greater meter readings. B & K provides a small notebook full of various meter scales to insert into the meter, so you can optimize the instrument for reading SPL with a 1" mic, a 1/2" mic, a 1/4" mic, accelerometers of various sensitivities (vibration pickups), basic Linear Voltage scales (1V & 3V ranges, with a log db scale), Lin/Log scale, etc. The meter has a mirror window so you can get the accuracy (minimize parallax), it's illuminated. Sensitivity range on the instrument is 10uV thru 300V Full Scale, has a basic bandwidth of 2Hz-200kHz, plus HP/LP and weighting filters....22.4Hz HP, 22.4kHz LP, A, B, C & D weighting filters, as well as being able to insert Octave, 1/3 Octave & narrow band tunable BP/BR filters. I have a collection of different B & K condenser measuring mics for my acoustical work, that interface with it, besides being able to plug in BNC cables into the screened inputs (special adapters). It's noise floor is very quiet, and they work nice as a mic preamp, for that matter.



The photos above were pulled off the internet, as I don't have all my files here at home to draw from.

[Axtman]

One advantage to a portable (as opposed to bench) multimeter is that I can put it near or on the piece of equipment that I am testing. That way I avoid having to look up and away from the piece of gear I am testing and thus avoiding a probe slip short.

Another advantage to portable multimeters is that you can take it with you to test something away from the bench, for example test car fuses and light bulbs outside in the driveway.

One disadvantage is the multimeters get temporarily lost or buried on the bench. I would be nice to always have a meter handy rather than have to go look for it or remember where I put it last.

[nickb]

I really think you are asking the wrong question. It's not a question of format or technology but functionality of performance. I would start by asking what is it is need to measure, do a have spare shelf space, does it need to be portable, what is my budget and so on?

For tube amp stuff, you need DC & AC Volts 600V min, DC & AC current to 10A and able to resolve 0.5mA. Resistance 10Meg and able to resolve 1 ohm. A diode test is highly desirable. True RMS is a bonus but I hardly ever use it.

Then there are performance questions such as, how accurate and what input impedance. 3% is probably good enough. Get the input impedance over 10Meg.

Then there is durability. Many of the cheep meters fail in that department.

Once you have answered these kinds of questions you have narrowed your choice enormously

[nevetslab]

One advantage to a portable (as opposed to bench) multimeter is that I can put it near or on the piece of equipment that I am testing. That way I avoid having to look up and away from the piece of gear I am testing and thus avoiding a probe slip short.

Another advantage to portable multimeters is that you can take it with you to test something away from the bench, for example test car fuses and light bulbs outside in the driveway.

One disadvantage is the multimeters get temporarily lost or buried on the bench. I would be nice to always have a meter handy rather than have to go look for it or remember where I put it last.

With the cost of today's instruments, you can find very suitable & affordable battery-powered portables. As for bench meters, I have a couple Multimeters, one that IS auto-ranging. An HP 3467A 4-Ch logging Multimeter, something I picked up when I was in manufacturing, and used it with four Fluke Thermocouple Adapters for monitoring specific temperature points on a power amp, or power transformer during temperature rise measurements (besides doing the delta-R for change in copper resistance on the lead wires before and after equilibrium was reached). The other is a Philips PM2535 System Multimeter, which has a lot of extra features that come in handy over the years. But, interestingly, neither of these bench meters will read over 300VDC! There are portables that also will NOT read high voltages as we encounter in tube amps, so it pays to review what you're buying.

An additional bench meter I've come across used (an ebay purchase) is an Amber 3501a Audio Analyzer. This is the military version, which uses a conventional power supply (nice Toroid, solid voltage regulators to run the circuits, instead of the switching supply in the standard 3501). This has a built in low distortion oscillator (10Hz-100kHz, Thd residual around -106dB down <20kHz), uses the log converter of the AD636 True RMS meter IC to give you linear dB steps on the meter...though they chose to limit the range to 12dB meter range. It does have wider dynamic range than that, as I use it as a front end on for a Vellman PCSGU250 USB scope/meter for bode plots. The Meter is true differential with internal protection, can be set to read Input or Osc Output, distortion, noise, as well as make it a manually tuned spectrum analyzer (constant percentage 1/3 Oct tuning), or a tunable Low Pass filter. As an Audio Meter, it's bandwidth is +/- 1dB @ 300kHz, though greater thru the Distortion Monitor connector, as seen in the response curves.

I think I paid $150 for it at the TRW Radio Ameteur's Technical Swap Meet in the mid-90's, then had to trouble-shoot it to find the shorted dip-tantalum power supply bypass caps and got it running. I later modified it by installing a mute switch (instead of having to turn the Output Attenuator fully CCW to the OFF position), a meter damping switch for Slow/Fast meter response (it has Slow damping as stock), installed an oscillator sync output (one feature they left off), and installed a pink noise generator that can be patched in on the rear panel jacks. Also added LED illumination to see the meter in subdued lighting.

[olddawg]

Yeah Enzo.. I know a lot of techs that like auto ranging. I did say it’s more important to know how to use whatever meter you have. I’m absolutely sure it isn’t a issue with you. I think I may have told this story before. I was brought in as a consultant for a large scale electrophoresis lab a while back. Their machines were 10 years old and replacements were no longer available. Their PHD Chemist in charge of everything had a lot of expensive theories and excuses about why their yields had fallen 60-70%. The VP asked me to take a look at it. There’s not much to this tech.... an anode plate, a cathode plate, and a power supply pretty much. and the wires and plugs connecting them. Turned out the lead connections to the plates were corroded, resistive, and intermittent. I asked them how they were testing the connections? Anything more than 200 ohms was bad. I said show me. Their lead tech brought out an EXPENSIVE Fluke lab spec auto ranging meter and measured continuity.. He said “See.. it says 20! 20 is less than 200!” I said, “What’s that little M mean?” Turns out it was 20 meg resistance from the lead to the plate. They never could figure out how to use that meter in a week. I told the VP to put it and others in his desk drawer. I went to Frys and bought a couple of $14 meters on sale that had a “continuity” beep function. Problem solved. PHD Chemist was fired. And I rebuilt the defective “unavailable” units with a drill press, instrument wire, new banana plugs, solder, and 5 minute epoxy. As far as I know they are still working. But they lost hundreds of thousand of dollars if not millions because no one in the lab knew how that particular auto ranging unit really worked... that and a stubborn PHD that refused to listen to the crusty old bench tech...

[Dave H]

Nowadays you can do 90% of what you need to do with a $15 multimeter.

I agree a $15 DMM is all you need for a meter.

[g1]

I agree a $15 DMM is all you need for a meter.

As long as it can read AC properly. (shows zero volts on AC range when DC applied)

[Dave H]

As long as it can read AC properly. (shows zero volts on AC range when DC applied)

Good point, I have one that reads DC as zero on the AC range and another that reads 10V DC as about 22V on AC which is a bit unsettling when you measure B+ with it set to AC and it shows over 1000V