Author Topic: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain  (Read 1124 times)

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Offline EEVblog

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EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« on: March 13, 2019, 09:23:47 am »
Dave bought a 6.5 digit Phillips PM2534 on Ebay for $140 delivered. Did it even survive the shipping?

 
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Online 0culus

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #1 on: March 13, 2019, 10:12:53 am »
WOW on the packaging. I have an HP 8569B spectrum analyzer I bought very cheap. It weighs about 75 lbs I'd say. It arrived similarly packed. Amazingly, it survived and is fully functional.
 

Offline edpalmer42

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #2 on: March 13, 2019, 10:50:04 am »
I bought this meter a few years ago, but I consider the 6.5 digit function to be rather worthless.  The problem is that the meter's input impedance is only 10M!  This means that when measuring anything but a power supply, the meter loading will turn the last digit or two into trash.  I hacked it to give me a high impedance on the lower scale, but ......

You should inspect the front panel buttons.  All the buttons should stick out about the same amount.  The top row has been pushed in.

Ed
 

Offline pylo

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #3 on: March 13, 2019, 11:23:33 am »
Congrats for the nice catch! If you know what you're looking for ebay can be a real goldmine.

About 4 years ago I bought a Fluke 87 for 50$ there, it was cheap because most of its screen segments weren't working. Well, after delivery I disassembled it, cleaned its screen's contact tabs, put it back together, screen is good as new ever since then :)

 

Online bd139

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #4 on: March 13, 2019, 11:29:44 am »
I’m surprised that survived. Everything Philips I’ve bought got smashed to buggery even if it was packaged properly.
 

Offline GigaJoe

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #5 on: March 13, 2019, 01:26:58 pm »
same thing ... heavy drifter on temperature, not really 6.5. not stable ....
 

Offline johnlsenchak

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #6 on: March 13, 2019, 01:44:25 pm »
A good video   idea   would be is to  send   that  test meter out for  calibration  and  see  what if any  difference  their  is  in the accuracy
John Senchak "Daytona  Beach  Florida "
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Offline Tony_G

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #7 on: March 13, 2019, 02:07:43 pm »
Pulled from a working environment my arse. I hate that phrase with the passion of a thousand blazing suns.....

TonyG

Offline EEVblog

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #8 on: March 13, 2019, 02:07:48 pm »
I bought this meter a few years ago, but I consider the 6.5 digit function to be rather worthless.  The problem is that the meter's input impedance is only 10M!  This means that when measuring anything but a power supply, the meter loading will turn the last digit or two into trash.

But it gives you the resolution to see changes.
 

Offline Rutger

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #9 on: March 13, 2019, 03:00:18 pm »
It looks like the lcd display and the buttons are pushed in at the top, maybe the LCD got damaged during transport.
 

Offline edpalmer42

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #10 on: March 13, 2019, 03:10:13 pm »
I bought this meter a few years ago, but I consider the 6.5 digit function to be rather worthless.  The problem is that the meter's input impedance is only 10M!  This means that when measuring anything but a power supply, the meter loading will turn the last digit or two into trash.

But it gives you the resolution to see changes.

Yes, that's true and that could be very useful.  But due to the low input impedance and depending on what it's measuring, it might have only 5.5 digits or less of accuracy.

I measured the output voltage of a Fluke 731B DC Reference Standard with a Fluke 8375A DMM (Nixies!!).  Input Impedance is spec'ed as 1G for the 1V scale.  The reading was 1V00013.  I bridged the PM2534 across the connection and the reading dropped to 1V00004, a change of 90 uV.  That's due to the ~900R output impedance of the 731B.  So, in this case, the effect was noticeable at the LSD of a 5.5 digit* measurement.  As the source impedance of your device under test increases, the effect will get worse.

Ed

*  For the OCD members of the audience, the 8375A can't actually be described as 5.5 digits because it counts to 119999 instead of 199999.  Still, not too shabby performance for a meter from the early '70's!
 

Offline David Hess

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #11 on: March 13, 2019, 07:30:23 pm »
I bought this meter a few years ago, but I consider the 6.5 digit function to be rather worthless.  The problem is that the meter's input impedance is only 10M!  This means that when measuring anything but a power supply, the meter loading will turn the last digit or two into trash.  I hacked it to give me a high impedance on the lower scale, but ......

This is why Bob Pease only recommended high resolution multimeters which support high input impedance up to at least their 10 to 20 volt range.  Unfortunately this usually (always?) requires considerable added complexity to the high impedance input buffer because it must be bootstrapped to support the wider voltage range and acceptable common mode rejection.  Many instruments like the popular HP3468/HP3478 only achieve this up to their 2 volts (3 volt for the HP3468/HP3478) range.
 

Offline johnlsenchak

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #12 on: March 13, 2019, 09:56:01 pm »


That  packaging  box  needs a little  Graphene   Wu  Wu to hold  it together  :)
John Senchak "Daytona  Beach  Florida "
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Offline LapTop006

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #13 on: March 13, 2019, 11:02:57 pm »
Looks like the contrast was set so it worked well on a shelf from above, makes a nice change.
 

Offline HalFET

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #14 on: March 14, 2019, 12:59:39 am »
WOW on the packaging. I have an HP 8569B spectrum analyzer I bought very cheap. It weighs about 75 lbs I'd say. It arrived similarly packed. Amazingly, it survived and is fully functional.

If it still has an HP badge on it you can also put  "tank armour panel" in the description field when shipping it... Only real risk is CRT damage. Then again UPS managed to bend the chassis on a Fluke 5200A, so maybe you do need some luck...

But I'm kind of curious how noisy everyone else's Philips meters are? I'll plug a GPIB card in my computer tomorrow and measure it actually. Because I can say without a doubt that my Philips PM 2535 is absolutely rubbish for absolute measurements because of the noise. Running it for long times doesn't really seem to improve it by much. I suppose it might be ok for spotting small relative changes though. What's a real turn off though is the measurement speed in 6.5 digit mode.

But one thing that Philips was good at was producing ok service manuals:
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/pm2534_PM2535.pdf
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/pm2534.pdf (user manual)

Looking at the service manual once more, it'd be pretty easy to convert one of these to run of a large lipo pack, and there's plenty of space in the case to integrate all of that as well. Since I'll still be at home for a while (quit work a few weeks ago, yaaaaaaaay  >:D ) I might actually give it a go.
 

Online thm_w

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #15 on: March 14, 2019, 05:44:06 am »
WOW on the packaging. I have an HP 8569B spectrum analyzer I bought very cheap. It weighs about 75 lbs I'd say. It arrived similarly packed. Amazingly, it survived and is fully functional.

The seller noted in the youtube comments that it was well packed and then Ebay GSP repacked the item. That is ridiculous that they can do this.
I could see if it was poorly packaged, or had a massive empty box, but it sounds like they are just taking out packaging to save money.

There are more comments if you dig through for his name.

"Greg Vioral
17 hours ago
Wasn’t us. It was the eBay global program."
 

Offline gnavigator1007

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #16 on: March 15, 2019, 08:12:44 am »
Bought one of these from the same seller and it was actually packaged worse, but arrived working and in surprisingly good cosmetic condition.
 

Offline Deodand2014

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #17 on: March 16, 2019, 02:30:27 am »
Enjoyed the video, I'm now wondering what the cheapest 8.5 digit DMM is like... 
 

Online Kleinstein

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #18 on: March 16, 2019, 03:02:43 am »
For 8.5 digit meters the choice is much more limited. There are not that many types available. The cheaper ones are likely the Solartron, Prema and ADTV6581T.  Especially the old Solartron are really slow - so by todays standard one may not specify it as 8.5 digits.  As there are fewer such meters are offered one might have to wait somewhat longer to get a cheap offer, especially if one does not like shipping from the US.  The 8.5 digit meters also tend to be quite a bit heavier than the old Phillips.

The Meter Dave got is also one of the really low end 6 digit meters -  more like comparable to newer 5.5. digit meters in many aspects. There is more than just the number of digits to set the quality of a meter. The more relevant numbers are usually the accuracy, noise and ranges.
In many aspects I would prefer the HP3478 - though only 5.5 digits, but with a 30 mV range and thus the same resolution for small voltages.
 

Offline Tony_G

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #19 on: March 16, 2019, 04:57:25 am »
Enjoyed the video, I'm now wondering what the cheapest 8.5 digit DMM is like...

You could do what TiN does and carve a 3458A from a block of rust...

TonyG

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Re: EEVblog #1189 - Ebay $140 6.5 digit DMM Bargain
« Reply #20 on: March 16, 2019, 06:48:23 am »
Enjoyed the video, I'm now wondering what the cheapest 8.5 digit DMM is like...

You could do what TiN does and carve a 3458A from a block of rust...

TonyG
It is not so much carve out of block of rust. More like buy a beaten up case with broken parts inside and buy the rest from keysight as expensive replacement parts. With broken units there is quite some risk. With a 8 digit meter is about one more digits in the dollars.
 


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