Topics

TM 500 Digital Multimeter Recommendations


Göran Krusell
 

Hi, do not pick the DM501 or the DM502. If you are measuring voltage and without thinking, like I often do, would turn the switch into the current range your object will be shorted by the multimeter and perhaps damage your object. This has been pointed out by another member some time ago.
Göran


Stephen
 

On Thu, Aug 6, 2020 at 01:18 AM, Göran Krusell wrote:


Hi, do not pick the DM501 or the DM502. If you are measuring voltage and
without thinking, like I often do, would turn the switch into the current
range your object will be shorted by the multimeter and perhaps damage your
object. This has been pointed out by another member some time ago.
Göran
Yes, I know they’re not auto-ranging. But, on the other hand, they’re also easier to find.
I’m usually very careful with these things, but you’re right, a mistake is never to be ruled out.
And I have made many in the past too.


Colin Herbert
 

Is this such a big problem? Almost any multimeter, whether digital or analogue, will surely have the same problems. Just be careful. As I have heard before "A,B,C" - "Always Be Checking".
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Göran Krusell
Sent: 06 August 2020 13:19
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM 500 Digital Multimeter Recommendations

Hi, do not pick the DM501 or the DM502. If you are measuring voltage and without thinking, like I often do, would turn the switch into the current range your object will be shorted by the multimeter and perhaps damage your object. This has been pointed out by another member some time ago.
Göran


 

For a Tek TM500 DMM recommendation, I have to go with the *DM504A.*
it's 4 1/2 digit, auto-ranging, True RMS and has split connections for current, thus avoiding the
mis-selection trap of earlier models. plus, it supports temperature with the correct probe.
very simple user interface. spec says 0.07% DC accuracy, wow.  mine always tests better.

it also has the *best looking display Tek ever made in the TM500 series*. it's only detracting feature
is no dB, but I have learned to live with that. I now have one on every TM500 bench, and really
like them. it is also wickedly accurate, and holds the cal very well.  it is a much later design than other
units in the DM5xx series.

anyway, just my $0.02 worth on this topic. you can see info on this unit here:
http://w140.com/tekwiki/wiki/DM504
sadly, the pic does not show it illuminated, but it is outstanding.

all the best,
walter

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)


Stephen
 

On Thu, Aug 6, 2020 at 02:39 AM, Colin Herbert wrote:


Is this such a big problem? Almost any multimeter, whether digital or
analogue, will surely have the same problems. Just be careful. As I have heard
before "A,B,C" - "Always Be Checking".
Colin.
Yep. On both my analog/tube DMM and my digital one I have to select what I’m measuring.
The only difference is that the digital one detects the measured range automatically, whereas the tube one has to be set to the right range being measured.


Stephen
 

Ok so, of the 4 most easily available: 501, 501A, 502, 502A, which one would you recommend?


Colin Herbert
 

The first decent-looking one you see on eBay/other offer?
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 06 August 2020 15:21
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM 500 Digital Multimeter Recommendations

Ok so, of the 4 most easily available: 501, 501A, 502, 502A, which one would you recommend?


Stephen
 

On Thu, Aug 6, 2020 at 03:33 AM, Colin Herbert wrote:


The first decent-looking one you see on eBay/other offer?
Colin.
Yes, but the reason I’m asking in the first place is that The 501/A is, on paper, more precise and has 4.5 digits as opposed to the 3.5 digits on the 502/A.
So is there a not so obvious reason to get a 502/A instead of a 501/A? It would seem that the 502/A would be an improved version of the 501/A, but the specs seem to apparently indicate otherwise.


Andy Warner
 

There can be a myriad other reasons for an updated model including: cost
savings, customer requests, component EOL.
It doesn't always have to be monotonic progress towards ever improving
specs.

I will admit to not owning *a single* meter that has V & I on the same pair
of jacks.
I am surprised how prevalent they are among this group.

I have a couple of DM501A modules, they are fine workhorse meters - if you
can find one at a price you like, get it.

On Thu, Aug 6, 2020 at 10:21 AM Stephen <stephen.nabet@...> wrote:

On Thu, Aug 6, 2020 at 03:33 AM, Colin Herbert wrote:


The first decent-looking one you see on eBay/other offer?
Colin.
Yes, but the reason I’m asking in the first place is that The 501/A is, on
paper, more precise and has 4.5 digits as opposed to the 3.5 digits on the
502/A.
So is there a not so obvious reason to get a 502/A instead of a 501/A? It
would seem that the 502/A would be an improved version of the 501/A, but
the specs seem to apparently indicate otherwise.



--
Andy


Stephen
 

On Thu, Aug 6, 2020 at 04:54 AM, Andy Warner wrote:

Interleaved answer.

There can be a myriad other reasons for an updated model including: cost
savings, customer requests, component EOL.
It doesn't always have to be monotonic progress towards ever improving
specs.
Apparently...

I will admit to not owning *a single* meter that has V & I on the same pair
of jacks.
V & I???? I don’t understand what you mean.

I have a couple of DM501A modules, they are fine workhorse meters - if you
can find one at a price you like, get it.
That was my first impression, just a gut feeling. I just needed a confirmation.

Thanks


robeughaas@...
 

I would avoid the TM501. It is an object lesson in the difference between accuracy and precision. It is precise to 4 1/2 digits; it is not accurate to 4 1/2 digits. It has an A/D converter made of op amps and discretes which is not stable. It has a high-frequency isolated power supply which contributes noise. Every Tek DVM after the DM501 used IC A/D's and a quiet linear isolated supply using an on-board 60-Hz transformer.

Like Walter, I like the DM504A. I have one on my bench. But the problem with the DM504A is that it is self-calibrating. The calibration procedure is guided by the internal microprocessor but you must have the specified voltages, currents and resistances at the proper times. This requires a Fluke Meter Calibrator.

I had a DM504A with bad AC accuracy which was caused by a leaky C104 33uF Tantalum. I replaced it with an aluminum electrolytic. I had another DM504A go totallly nutzo, which appears to be unredeemable.

Bob

--
Bob Haas


 

Be careful with blindly selecting the DM501/a, 502/a DMMs. there's a LOT of switch contacts in there,
with MANY interacting poles. I have found every single one of these to need service on the switches, and
I am certainly not alone in that regard.  they just do not age so well, thanks to the switches.

the DM504A has a dramatically reduced and simplified switch count, and looks and works a lot better
than a long-in-the tooth DM501-502A.  just saying, if you are going to have only one, look for the really
good one.

again, only my $0.02 worth on this topic. sadly, I see none on ebay at the moment.

regards,
walter

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)


Stephen
 

On Thu, Aug 6, 2020 at 05:41 AM, walter shawlee wrote:


Be careful with blindly selecting the DM501/a, 502/a DMMs. there's a LOT
of switch contacts in there,
with MANY interacting poles. I have found every single one of these to
need service on the switches, and
I am certainly not alone in that regard.  they just do not age so well,
thanks to the switches.
I’m sure you’re right on that.

the DM504A has a dramatically reduced and simplified switch count, and
looks and works a lot better
than a long-in-the tooth DM501-502A.  just saying, if you are going to
have only one, look for the really
good one.
There’s no way to tell the condition of the switches though.

I see none on ebay at
the moment.
My point exactly.... If I find, I’ll buy it at the right price.


Andy Warner
 

Certainly true about the switches in the DM501A - and some of them are a
royal pain to reach with deoxit.

I will happily acknowledge the downsides of the DM501A, however they are
significantly more available and reasonably priced than DM504s on the open
market.

You can make some of them work without _too much_ pain (just buckets of
deoxit, which I'll admit does not come cheap.)

On Thu, Aug 6, 2020 at 11:41 AM walter shawlee <@walter2> wrote:

Be careful with blindly selecting the DM501/a, 502/a DMMs. there's a LOT
of switch contacts in there,
with MANY interacting poles. I have found every single one of these to
need service on the switches, and
I am certainly not alone in that regard. they just do not age so well,
thanks to the switches.

the DM504A has a dramatically reduced and simplified switch count, and
looks and works a lot better
than a long-in-the tooth DM501-502A. just saying, if you are going to
have only one, look for the really
good one.

again, only my $0.02 worth on this topic. sadly, I see none on ebay at
the moment.

regards,
walter

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend
on us.
We are not the only experiment. (R. Buckminster Fuller)




--
Andy


 

When I was young and didn't know much (60 years later that hasn't changed) I got my first "instrument". It was a VOM. At first I had fun measuring skin resistance, and batteries. Eventually I was brave enough to check the 120V AC by putting the leads into a wall outlet. As I grew more confident in my understanding of electricity I found more uses for my VOM. One day I realized the only thing I had not used it for was to measure current because batteries only put out volts. I looked everywhere before I realized there was a simple readily available source of current I could measure. So I turned the dial of my VOM to the highest current setting and plugged the two leads in to a wall outlet. Although I did not actually see what happened next (because it was over in an instant) I was smart enough to know that the smell of something burning is never a good thing. Also, the meter needle was badly bent and stuck way past the right side of the scale although it was fine a moment earlier. I never made that mistake again - at least that much has changed in 60 years.

I agree with Walter Shawlee that the DM504A is an excellent choice. It also uses actual pushbuttons instead of "soft" pushbuttons so you know what it will measure even if you power off the mainframe and turn it on later. I also like that you can disable the auto-ranging. Each time a multi-meter automatically changes ranges its impedance changes causing changes to the measurement it is making. This is most annoying when measuring small currents. As the current increases to the point where the meter switches ranges the series resistance of the meter changes and the current you are trying to measure jumps.

Tek has made a lot of different DMMs for their TM5xx mainframes. I have most of them at the present time. I think I have had all of them at one time or another. What my shelf of TM5xx DMMs tells me is Tek DMMs are not reliable. 3/4 of the 20+ TM5xx DMMs I own have at least one significant measurement problem that makes them untrustworthy.

Two more comments about Tek DMMs:
First: The WORST Tek DMM, by far, is the DM5010. I am impressed with the way they optically isolated the front end from the rest of the instrument. That is an extremely valuable feature to have in some situations. But once the battery dies and you lose the calibration constants it is virtually impossible to find a replacement battery and recalibrate the instrument. I know this because I had 4 of them once. The battery recharges itself from the mainframe and if the DM5010 sits on a shelf for too long the battery goes dead. Also, it is not a true DMM. It only measures voltage and resistance. It can't measure current.
Second: the BEST Tek DMM by far is the 3-wide TM5xxx DM5120 Programmable Digital Multi-Meter. It is a stunning, extremely accurate 5 1/2 digit DMM. I consider myself very lucky to own one. What most people don't know about the DM5120 is that someone at Tek finally realized they couldn't design a DMM with this level of accuracy. So they bought a Fluke OEM module and put into their TM5xxx plugin. It is a compliment to Tek that they did this. Because it is really a Fluke design I trust this DMM more that I would if Tek had designed it. This instrument is also very convenient to use and it has many smart features.

Dennis Tillman W7pF




--
Dennis Tillman W7pF
TekScopes Moderator


Stephen
 

Ooh, the DM501A has soft buttons? I didn’t realize that. I hate soft buttons.
From the 2 last responses, it appears that since no DM504 are currently available anywhere, and since I don’t own a TM500x, I’m either gonna get a DM501 with the waffle rotary switch, or no Tektronix DM at all...
Are these good at least?


Tom Norman
 

I'd like to second Dennis' comment on the DM5010. For my dabbling, it's overkill, but very enjoyable to own and use and has kelvin sensing inputs. I also have a DM5110, which is single-wide, 4-1/2 digit, and the same as a DM511 (I think) except it has GPIB capability. It sits next to a PS503 and often finds itself monitoring output voltages. For TM506, the DM511 wouldn't be a bad choice in my opinion.

Tom


 

As Dennis said, Fluke is the key to the good  DMM performance in the DM5120. The Tek DM5xx
conversion hardware was not so wonderful, and is certainly dated now.

While I have DM504A's in every TM506 at each bench, my usual go to meter while working is a
Fluke 87, 4.5 digits, true rms out to 10KHz and beyond, and holds cal accuracy like a rock.

I have used them since they came out, and still find them the best compromise between
cost and functionality. I think Fluke handhelds remain exceptional, although I lament the
shift offshore, and the steady cheapening of construction coupled with increasing prices.
I guess that's just the Dannaher way. What you really want is an older 87 in good condition.

all the best,
walter

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)


Andy Warner
 

Nope, the DM501A does not have soft buttons (at least neither of mine do.)

I'm coming over as a champion of the DM501A here, I'm far from that - but
they can be made to work well enough and are not made of unobtainium.

On Thu, Aug 6, 2020 at 12:52 PM Stephen <stephen.nabet@...> wrote:

Ooh, the DM501A has soft buttons? I didn’t realize that. I hate soft
buttons.
From the 2 last responses, it appears that since no DM504 are currently
available anywhere, and since I don’t own a TM500x, I’m either gonna get a
DM501 with the waffle rotary switch, or no Tektronix DM at all...
Are these good at least?



--
Andy


Stephen
 

On Thu, Aug 6, 2020 at 06:58 AM, Andy Warner wrote:


Nope, the DM501A does not have soft buttons (at least neither of mine do.)

I'm coming over as a champion of the DM501A here, I'm far from that - but
they can be made to work well enough and are not made of unobtainium.
Andy
That’s what I understood from Dennis’ reply...

Quote: “ I agree with Walter Shawlee that the DM504A is an excellent choice. It also uses actual pushbuttons instead of "soft" pushbuttons so you know what it will measure even if you power off the mainframe and turn it on later.”