Topics

VOM Advice?

Mark M
 

Sorry if this is a bit off topic but it is related to uBitX hacking...

My ancient, el-cheapo VOMs (Radio Shack/Harbor Freight freebies) all have pretty much ceased working so I'm looking for some suggestions about suitable replacement units. I'm not looking for lab quality, just something for a hobbiest/amateur hardware hacker (like for modifying the uBitx). I'd like to find something that's reliable and reasonably accurate for a few 10's of dollars. I see many units on Amazon for around that but don't know which ones would be good buys. So, any advice from y'all?

Thanks & 73....     Mark    AA7TA

Arv Evans
 

Mark  AA7TA

It is relatively easy to build up an Arduino with LCD display to display voltages that are
presented to one, or more, of the ADC inputs.  This gives you a basic 5V range that can
be increased with dividers. 

Arv  K7HKL
_._


On Thu, Jun 14, 2018 at 8:11 PM Mark M <junquemaile@...> wrote:
Sorry if this is a bit off topic but it is related to uBitX hacking...

My ancient, el-cheapo VOMs (Radio Shack/Harbor Freight freebies) all have pretty much ceased working so I'm looking for some suggestions about suitable replacement units. I'm not looking for lab quality, just something for a hobbiest/amateur hardware hacker (like for modifying the uBitx). I'd like to find something that's reliable and reasonably accurate for a few 10's of dollars. I see many units on Amazon for around that but don't know which ones would be good buys. So, any advice from y'all?

Thanks & 73....     Mark    AA7TA

Jerry Gaffke
 

I picked up about a half dozen harbor freight DVM's when they were on sale for $1 or so.
Not auto ranging and pretty easy to blow, but well worth a buck.
Something I can knock around without worrying too much.

If you're willing to spend big money, $12 will get you an autoranging meter that shows capacitance:
I got one of these 5 or more years ago:
    https://www.amazon.com/GigaMax-Multimeter-Pocket-Size-Resistance-Capacitance/dp/B00RSQD6IW
I can't recommend it, as you can see how small the "V" indication is that shows it is reading Volts.
That can do an autoranging jump to "mV" to show millivolts, and it takes me awhile to figure my probe
isn't quite making contact with the battery or whatever.

But do consider getting one with a capacitance range, it's handy.
This UT10A generally shows about 100pf across the leads with my hands on the probes.
I put the cap down on the desk and hold the probes to it, take a reading.
Then gingerly pull the probes away a fraction of an inch, take a second reading.
Subtracting the second from the first I get the value of the cap to within about 10pf.

Jerry



On Thu, Jun 14, 2018 at 07:11 pm, Mark M wrote:
Sorry if this is a bit off topic but it is related to uBitX hacking...

My ancient, el-cheapo VOMs (Radio Shack/Harbor Freight freebies) all have pretty much ceased working so I'm looking for some suggestions about suitable replacement units. I'm not looking for lab quality, just something for a hobbiest/amateur hardware hacker (like for modifying the uBitx). I'd like to find something that's reliable and reasonably accurate for a few 10's of dollars. I see many units on Amazon for around that but don't know which ones would be good buys. So, any advice from y'all?

Tim Gorman
 

For most anything you'll do with the ubitx you don't need an expensive
desk meter.

this one:
www.ebay.com/itm/Digital-Voltmeter-Ammeter-Ohmmeter-Multimeter-Volt-AC-DC-Tester-Meter-US-Seller/271496690158?hash=item3f3676b9ee:g:qgUAAOSwHnFVkYPk

is representative of one that has lots of functions. It's a lot like
the one I use much of the time. PLEASE don't hook the test leads up the
way it is shown, it won't work!

There is a huge gap in its current measuring scales, from 200ma to
10amp in one big jump, but that will probably get you by.

tim ab0wr

On Thu, 14 Jun 2018 19:11:08 -0700
"Mark M" <junquemaile@...> wrote:

Sorry if this is a bit off topic but it is related to uBitX hacking...

My ancient, el-cheapo VOMs (Radio Shack/Harbor Freight freebies) all
have pretty much ceased working so I'm looking for some suggestions
about suitable replacement units. I'm not looking for lab quality,
just something for a hobbiest/amateur hardware hacker (like for
modifying the uBitx). I'd like to find something that's reliable and
reasonably accurate for a few 10's of dollars. I see many units on
Amazon for around that but don't know which ones would be good buys.
So, any advice from y'all?

Thanks & 73....     Mark    AA7TA


Ashhar Farhan
 

I too have three chinese voms of a make called mastek. They work pretty well for my needs. They cost me about two dollars each.
- f

On Fri, 15 Jun 2018, 08:41 Tim Gorman, <tgorman2@...> wrote:
For most anything you'll do with the ubitx you don't need an expensive
desk meter.

this one:
www.ebay.com/itm/Digital-Voltmeter-Ammeter-Ohmmeter-Multimeter-Volt-AC-DC-Tester-Meter-US-Seller/271496690158?hash=item3f3676b9ee:g:qgUAAOSwHnFVkYPk

is representative of one that has lots of functions. It's a lot like
the one I use much of the time. PLEASE don't hook the test leads up the
way it is shown, it won't work!

There is a huge gap in its current measuring scales, from 200ma to
10amp in one big jump, but that will probably get you by.

tim ab0wr

On Thu, 14 Jun 2018 19:11:08 -0700
"Mark M" <junquemaile@...> wrote:

> Sorry if this is a bit off topic but it is related to uBitX hacking...
>
> My ancient, el-cheapo VOMs (Radio Shack/Harbor Freight freebies) all
> have pretty much ceased working so I'm looking for some suggestions
> about suitable replacement units. I'm not looking for lab quality,
> just something for a hobbiest/amateur hardware hacker (like for
> modifying the uBitx). I'd like to find something that's reliable and
> reasonably accurate for a few 10's of dollars. I see many units on
> Amazon for around that but don't know which ones would be good buys.
> So, any advice from y'all?
>
> Thanks & 73....     Mark    AA7TA
>
>
>




Doug W
 

I'm another fan of the Harbor Freight cheep/free DVM.  I honestly don't know how many I have as they are so cheap and handy I keep them all over the place.  If the zombie apocalypse comes I will stay safe in a shelter made from all my harbor freight tarps lashed together with harbor freight dvm leads while I stab zombies with harbor freight screw drivers.



--
www.bitxmap.com

Howard Fidel
 

I pick one up whenever they have the "fee" coupon in the paper or email. Worth it just for the battery!.

On 6/14/2018 11:30 PM, Doug W wrote:
I'm another fan of the Harbor Freight cheep/free DVM.  I honestly don't know how many I have as they are so cheap and handy I keep them all over the place.  If the zombie apocalypse comes I will stay safe in a shelter made from all my harbor freight tarps lashed together with harbor freight dvm leads while I stab zombies with harbor freight screw drivers.



--
www.bitxmap.com


Jerry Gaffke
 

I'm not sure I would recommend trying to replicate all the ACV/DCV/Ohms/Amps/mAmps ranges 
of a $1 Centek DVM from Harbor Freight.
But instead of spending the extra $11 bucks on a DVM with a capacitance range, it might be worth
building this capacitance meter into your Raduino:
    http://wordpress.codewrite.co.uk/pic/2014/01/21/cap-meter-with-arduino-uno/

Select it with a menu option.

Jerry



On Thu, Jun 14, 2018 at 07:25 pm, Arv Evans wrote:
It is relatively easy to build up an Arduino with LCD display to display voltages that are
presented to one, or more, of the ADC inputs.  This gives you a basic 5V range that can
be increased with dividers. 

Jerry Gaffke
 

That's the same Centech brand as the red rectangular cheapies form Harbor Freight.
Pretty much the same functionality.  And I'd guess the same stuff inside.
The primary differences I see is that this ebay job has a continuity beeper  and a backlight. 

Jerry



On Thu, Jun 14, 2018 at 08:11 pm, Tim Gorman wrote:
For most anything you'll do with the ubitx you don't need an expensive
desk meter.

this one:
www.ebay.com/itm/Digital-Voltmeter-Ammeter-Ohmmeter-Multimeter-Volt-AC-DC-Tester-Meter-US-Seller/271496690158?hash=item3f3676b9ee:g:qgUAAOSwHnFVkYPk

is representative of one that has lots of functions. It's a lot like
the one I use much of the time. PLEASE don't hook the test leads up the
way it is shown, it won't work!

There is a huge gap in its current measuring scales, from 200ma to
10amp in one big jump, but that will probably get you by.

tim ab0wr

Jack, W8TEE
 

One feature I find really useful is the ability for the unit to "beep" when doing continuity checks. Without that feature, I seem to lose my test points when I go to look at the meter's display. With the beep feature, it can keep the leads where they belong rather than slipping off the part under test and releasing the magic white smoke from the most expensive part on the board.

Jack, W8TEE

On Thursday, June 14, 2018, 11:11:52 PM EDT, Tim Gorman <tgorman2@...> wrote:


For most anything you'll do with the ubitx you don't need an expensive
desk meter.

this one:
www.ebay.com/itm/Digital-Voltmeter-Ammeter-Ohmmeter-Multimeter-Volt-AC-DC-Tester-Meter-US-Seller/271496690158?hash=item3f3676b9ee:g:qgUAAOSwHnFVkYPk

is representative of one that has lots of functions. It's a lot like
the one I use much of the time. PLEASE don't hook the test leads up the
way it is shown, it won't work!

There is a huge gap in its current measuring scales, from 200ma to
10amp in one big jump, but that will probably get you by.

tim ab0wr

On Thu, 14 Jun 2018 19:11:08 -0700
"Mark M" <junquemaile@...> wrote:

> Sorry if this is a bit off topic but it is related to uBitX hacking...
>
> My ancient, el-cheapo VOMs (Radio Shack/Harbor Freight freebies) all
> have pretty much ceased working so I'm looking for some suggestions
> about suitable replacement units. I'm not looking for lab quality,
> just something for a hobbiest/amateur hardware hacker (like for
> modifying the uBitx). I'd like to find something that's reliable and
> reasonably accurate for a few 10's of dollars. I see many units on
> Amazon for around that but don't know which ones would be good buys.
> So, any advice from y'all?
>
> Thanks & 73....     Mark    AA7TA
>
>
>



bobolink
 

For the complex digital mode signals you might be interested in a “true rms” voltmeter. I paid a little extra for that (about $12) from banggood.
I haven’t tested it against my Fluke. That would be an interesting comparison.
true-rms

Karl Heinz Kremer, K5KHK
 

Jack is right, it should beep, and it should also beep right away, without any delay: I have to meters, one (actually a relatively cheap true RMS pocket meter from Banggood) beeps right away, my more expensive one has a small delay, and when you are testing for conductivity, you will wait until it beeps, but if you are testing for non-conductivity, the instant feedback is much better than to decide if you've waited long enough :) 
--
Karl Heinz - K5KHK

n5ib_2
 

An interesting tale about one of those inexpensive Harbor Freight DMMs...

A few years back I was working on a GPS tracker for our high altitude balloon project. It was outdoors on a bright sunny day. I was measuring the DC supply to the GPS and noticed the voltage reading bouncing around for no apparent reason. After a few minutes of bafflement I noticed that when I leaned over to read the meter, it was in my shadow, and the reading changed. Curiosity piqued, the meter (one of the early yellow ones) was promptly disassembled for inspection.

Turns out the chip that controls the whole thing was, as in most low-cost mass-produced stuff, not encapsulated in a package, but just die bonded to the PCB with a resin overcoating. The ground plane beneath the die was etched away on the other side of the PCB. The chip was located right underneath the LCD display. Strong sunlight would filter through the display, through the translucent PCB material, and fall on the silicon substrate of the chip. Can you say "phototransistor" ?! A bit of strategically placed black tape solved the problem. I've taken apart some later versions of that DMM and see that there now is an opaque strip underneath the display.

N5IB

Vince Vielhaber
 

Back when those meters were going for $6-$8 at trade shows and ham swaps, I was buying them in quantities of 96 or more (they came in boxes of 48, that's why the 96 price break) for a few pennies over $2. Still have a bunch of 'em left, batteries are dead tho.

Vince.

On 06/15/2018 12:52 AM, Jerry Gaffke via Groups.Io wrote:
That's the same Centech brand as the red rectangular cheapies form
Harbor Freight.
Pretty much the same functionality. And I'd guess the same stuff inside.
The primary differences I see is that this ebay job has a continuity
beeper and a backlight.

Jerry



On Thu, Jun 14, 2018 at 08:11 pm, Tim Gorman wrote:

For most anything you'll do with the ubitx you don't need an expensive
desk meter.

this one:
www.ebay.com/itm/Digital-Voltmeter-Ammeter-Ohmmeter-Multimeter-Volt-AC-DC-Tester-Meter-US-Seller/271496690158?hash=item3f3676b9ee:g:qgUAAOSwHnFVkYPk

is representative of one that has lots of functions. It's a lot like
the one I use much of the time. PLEASE don't hook the test leads up the
way it is shown, it won't work!

There is a huge gap in its current measuring scales, from 200ma to
10amp in one big jump, but that will probably get you by.

tim ab0wr

 

I have heard good things about this MM from several different sources. I don't think you can beat it for quality/features VS price.

https://www.ebay.com/itm/ANENG-AN8008-True-RMS-Wave-Output-Digital-Multimeter-9999-Counts-Backlight-AC-DC/222719150587?hash=item33db1889fb:m:mSCw_nrSk9gqavl1qMGdf8Q

Joel
N6ALT

Gwen Patton
 

I have a couple of older Radio Shack VOMs around here, mostly for field use (from back when I did computer field service), but I lucked out for my bench VOM. I got a Fluke 27/FM, the military model, on Ebay. If not for a song, it was at least for a couple of choruses and a jingle -- a small percentage of the original price of the civilian model. This one was of a large batch that had been purchased for the military and never deployed, but instead had been warehoused. They maintained them well, calibrating them before they sold them off. I paid about $80 plus a little shipping. It has served me more than adequately, and is a True RMS meter with a HUGE display and more features than I'll ever use. I love the thing to pieces.

Keep an eye out for sales of such on Ebay. If you spot such a deal, pounce on it. You won't regret having such a wonderful device on your bench.

Gwen NG3P

bobolink
 

it might be worth
building this capacitance meter into your Raduino:
lol. Of course. 
The VOM should be built into the radio! With the JackAl board ADC/DAC audio capabilities, it could talk to you. 
Audio Voltmeter  Arduino demo.

Mike Yancey
 

Well, I like to go both ways - vintage AND modern (heh).

Vintage - you can't go wrong with a Simpson 260. Older models sell for pretty cheap - shopgoodwill.com, (fl)ebay, sometimes an antique stores. They were built to last, and really the main thing that goes wrong is the case gets cracked or broken. I believe Micronta also had a swell model. Heathkit had a good VOM - but now you're competing with the Heathkit collectors, so...
 
Also: VTVMs (Vacuum Tube VoltMeters) are excellent for this type of work, particularly peak alignment - you watch the needle, not a series of flopping digits. Problem with VTVMs is - well, unless you find one from someone you KNOW who's restored it - they're usually out of spec, battery leakage internally (there's a battery for testing OHMs,  but - you can 'fix' that in going thru and repairing them - I usually add a 1.55 VDC supply off of the 6.3 VAC filament voltage - with a little bridge and LM317 regulator.

VTVM Brands: Heathkits V-7As, IM-11, IM-13... KnightKit - KG-620.

Modern - you CAN'T go wrong with Fluke - be sure & check for the 'cheap Chinese-made' Flukes - excellent quality, at Chinese prices - there's a 17B that's excellent and I think there's a model 12. A number of older model Flukes are great and reliable - desk model 8050A is one.

However, if you'd like to have a 'second' DVM - try ANENG - these are *definitely* cheap Chinese DVMs - I've found the 8002, 8008 and 8009 to be excellent build quality. Do NOT expect these to take (or be safe) for High Voltage (anything higher than mains, really - and be judicious and careful with mains...)

There's also an ANENG AN101 that's a pocket (cheap leads, but... eh, it's a pocket / keep in your car unit). Check EEVBLOG for some thorough reviews of these (and others).

Mark M
 

Thanks for all the input. I didn't expect to get so many replies! Looks like there are lots of alternatives out there. Now to chase them down & decide which way to go.

Thanks & 73...     Mark    AA7TA

Ryan Flowers
 

Mark,

I went through the same agony in making a decision, and have been VERY happy with mine. The Ammeter is wonderfully accurate too. The harbor freight meters are junk sorry guys. I don't trust them. 

I wrote about my search and why I chose the one I did on my blog. $20 was all that I needed to spend:

http://miscdotgeek.com/inexpensive-digital-multimeter/


--
Ryan Flowers - W7RLF
MiscDotGeek.com
Multi Band BITX40
The BITX40 FAQ