Test Equipment Anonymous (TEA) group therapy thread

[factory]

Maybe someone would like a meter with a few less digits. 
https://www.ebay.com/itm/402683624528



Or something that really shouldn't have ''Precision'' on the front panel. 
https://www.ebay.com/itm/265020418350



David

[tggzzz]

There is NO compensation for circuit loading in any of these meters. They measure what appears at the terminals regardless of the load they place on the external voltage. The meters are in parallel so differences in input impedance is irrelevent. The impedance should not matter with a modern Voltage standard anyway because it's imedance is tiny compared to the meter.

It is reasonable to expect that a 10Mohm load would load the output of a reference voltage source sufficiently to be detected by a decent meter, given a appropriate definition of "decent".

Disagree, if you connect a DMM with a 10Mohm loading in parallel with another DMM with say 10Gohm loading to a voltage source then its perfectly reasonable and logical to expect that both meters should (assuming identical calibration status) read the same, but they don't. If you do the same with a resistor, however then they will read differently as both DMM's are outputting a voltage which will differ and also both DMM's are also trying to measure the others impedance.

What do you mean by DMMs outputting a voltage?

Perfectly simple, even with a analogue meter, remove the battery, no resistance ranges, but it will still measure a voltage if one is applied to it. If a DMM does not output a voltage then it cannot measure the resistance that you wish to measure as there is zero current flowing though the circuit for the meter to derive a value of the unknown resistor from.

Oh, you are comparing one meter measuring voltage and another measuring resistance. I fail to see how that is relevant.

[med6753]

Maybe someone would like a meter with a few less digits. 
https://www.ebay.com/itm/402683624528



Or something that really shouldn't have ''Precision'' on the front panel. 
https://www.ebay.com/itm/265020418350



David

Already got one. 

(Psst...in case you didn't already know it's a Heathkit)

[Specmaster]

There is NO compensation for circuit loading in any of these meters. They measure what appears at the terminals regardless of the load they place on the external voltage. The meters are in parallel so differences in input impedance is irrelevent. The impedance should not matter with a modern Voltage standard anyway because it's imedance is tiny compared to the meter.

It is reasonable to expect that a 10Mohm load would load the output of a reference voltage source sufficiently to be detected by a decent meter, given a appropriate definition of "decent".

Disagree, if you connect a DMM with a 10Mohm loading in parallel with another DMM with say 10Gohm loading to a voltage source then its perfectly reasonable and logical to expect that both meters should (assuming identical calibration status) read the same, but they don't. If you do the same with a resistor, however then they will read differently as both DMM's are outputting a voltage which will differ and also both DMM's are also trying to measure the others impedance.

What do you mean by DMMs outputting a voltage?

Perfectly simple, even with a analogue meter, remove the battery, no resistance ranges, but it will still measure a voltage if one is applied to it. If a DMM does not output a voltage then it cannot measure the resistance that you wish to measure as there is zero current flowing though the circuit for the meter to derive a value of the unknown resistor from.

Oh, you are comparing one meter measuring voltage and another measuring resistance. I fail to see how that is relevant.

Now you're just yanking on my chain 

[Specmaster]

Maybe someone would like a meter with a few less digits. 
https://www.ebay.com/itm/402683624528



Or something that really shouldn't have ''Precision'' on the front panel. 
https://www.ebay.com/itm/265020418350



David

Already got one. 

(Psst...in case you didn't already know it's a Heathkit)

Its a give away styling, they used that same style for a few items in their range.

[mnementh]

Nope. Not gonna get sucked into another argument here. Bottom line is that for as long as we've been trying to measure angry pixies, different manufacturers' meters will give different readings from the same precision source.

Every meter is itself a series-parallel circuit, and as such will affect the measurement, and different designs affect it differently. Compounding that with modern meters is that they are subject to software flaws as well.

It is nothing to do with different manufacturers. Different meters of the same type will give different readings, within the limits specified.

Meters are modeled as a perfect voltmeter that takes no current in parallel with a resistor. A precision Meyer should have a resistance of many Gohms. For many handheld meters that resistance is nominally 10Mohm, and that is also the case for many precision meters on ranges >10V.

This is what I was getting at. You get 6 of the same meter at the same time from the same MFR, then it's reasonable to expect them all to come within a few ticks of each other at that resolution due to same design and cal'd on the same machinery in the same lab using the same process reasonably close time to each other. Otherwise, without cal'ing all your meters to the same standard, any coincidence between your meters at that resolution is just that... coincidence.

Jeez.

mnem
 

[alextwin007]

I have one of those 2 1/2 digit multimeters on my bench.  I find that it's a useful sanity checker when my primary meter is measuring something else.  Also it has the bonus of the extra cool factor of using nixies.   Ironically I essentially have 2 of those meters, one is the bell and howard, the other is the IM 1202 which have the same schematics although very different form factors.  Although I just got a IM-2212 delivered today that might replace it just for size reasons.

[mnementh]

I loved mine so much I gave it to med.

mnem
 

[med6753]

.......snip

the other is the IM 1202 which have the same schematics although very different form factors.  Although I just got a IM-2212 delivered today that might replace it just for size reasons.

Got one of them too. Notice how Heath deliberately packaged it to look like a VTVM so it would have better acceptance among the techs back then?

    

And this is the one Mnem gave me. 

[med6753]

Holy shit......a guy has just taken shots at the cops with an AR rifle. He's now barricaded in a camper and cops have temporarily retreated to the edge of the property.

Shit...they just called for radio silence. 


Update, they captured him unharmed.

[mnementh]

Oh for cryin' in the mud.

*tries to think of it in the best light possible*

No telling what a man will do in times of desperation... and there's a lot of that going around right now.

mnem
*sigh*

[med6753]

Oh for cryin' in the mud.

*tries to think of it in the best light possible*

No telling what a man will do in times of desperation... and there's a lot of that going around right now.

mnem
*sigh*

They got him in custody......unharmed.

[mnementh]

That's good.

Pivotal moments in a man's life... terrifying to peek in on...

mnem

[Specmaster]

Nope. Not gonna get sucked into another argument here. Bottom line is that for as long as we've been trying to measure angry pixies, different manufacturers' meters will give different readings from the same precision source.

Every meter is itself a series-parallel circuit, and as such will affect the measurement, and different designs affect it differently. Compounding that with modern meters is that they are subject to software flaws as well.

It is nothing to do with different manufacturers. Different meters of the same type will give different readings, within the limits specified.

Meters are modeled as a perfect voltmeter that takes no current in parallel with a resistor. A precision Meyer should have a resistance of many Gohms. For many handheld meters that resistance is nominally 10Mohm, and that is also the case for many precision meters on ranges >10V.

This is what I was getting at. You get 6 of the same meter at the same time from the same MFR, then it's reasonable to expect them all to come within a few ticks of each other at that resolution due to same design and cal'd on the same machinery in the same lab using the same process reasonably close time to each other. Otherwise, without cal'ing all your meters to the same standard, any coincidence between your meters at that resolution is just that... coincidence.

Jeez.

mnem
 

And now we come full circle, back to where I was earlier when I was saying that all Meds meters were only a few uV away from agreeing with each other and on that basis I would happily work with any one of them and have maximum confidence in it.  I personally would not consider spending possibly $100's getting any of re-calibrated. If I had to be able to measure safely and reliably down to the uV level then I'd invest in meter specially designed to just that. 

[cyclin_al]

And......I'm sick of this shit. 

It is not really that much !!!!  BUT, If it bothers you that much, please send it here.  The bases of the skis are getting all chewed up from hitting rocks here.

We have had so little snow here that I have yet to use the snowblower in the Great White North.   
Actually, the machine ran fine on pre-winter shake-down.  There was one snow that was borderline for needing the blower.  However, the machine would not start.  I just shovelled the snow by hand.  When I went troubleshooting later with the aid of daylight, it started and ran perfectly... 

[cyclin_al]

Maybe someone would like a meter with a few less digits. 
https://www.ebay.com/itm/402683624528



Or something that really shouldn't have ''Precision'' on the front panel. 
https://www.ebay.com/itm/265020418350



David

Already got one. 

(Psst...in case you didn't already know it's a Heathkit)

Who really cares what they are called, right?  They qualify as nixxie tube TE. 
I still have not been able to get the local seller of the HP nixxie counters to agree on a time to meet....    It has been numerous weeks now...

[mnementh]

Nixie tube I'll give ye; but the TE part... ehhhhhhh.

mnem
more like a people tester than actual TE...

[Kosmic]

Got lucky on ebay. I snipped 3 substitution boxes for 20$   


The IET RCS-502 are really nice. They combine resistance (0.1%) and capacitance (1%) decades. The CDE CDB-3 is a lot older and only has only capacitance. Its also less accurate at 3%.

When received the CDB-3 was a bit inconsistent. I decided to open it up to clean the switches. The internal construction is somehow rustic with the piece of wood glued in the middle 


Also I never seen those capacitors before. Look like they are in ceramic. If radiomuseum.org is accurate, they were selling for 16.35 in 1965 (https://www.radiomuseum.org/r/cornel_dub_decade_capacitor_cdb3.html) In pretty good shape for it's age.

They look a lot like the paper/oil capacitors that often leak or fail in the "Shango066" radio or TV resurrection videos, hopefully I'm wrong and yours are a bit newer. 


David

Ouch it's oil-paper then. Capacitance is fine. I will check ESR later today.

Dissipation factor and ESR are good. They all seem to be healthy. Maybe I should try to charge them with 500VDC or 120VAC ? 

I usually check the for leakage using an analogue Megger (BM8 MkII), if it doesn't go to maximum on the resistance scale (at nearest range to rated voltage) then it's probably a paper based capacitor, don't forgot to discharge afterwards.

David

I had the Megohm meter out today so I checked leakage on the old CDE decade capacitor. After waiting for a while for the cap to charge, I measured 9.2GOhms at 500V. I think they are pretty much alive 



I also found this interesting little guy in my box of used cap. I guess it's a sealed paper & oil capacitor ? Measured 650GOhms.

[mnementh]

This is what I was getting at. You get 6 of the same meter at the same time from the same MFR, then it's reasonable to expect them all to come within a few ticks of each other at that resolution due to same design and cal'd on the same machinery in the same lab using the same process reasonably close time to each other. Otherwise, without cal'ing all your meters to the same standard, any coincidence between your meters at that resolution is just that... coincidence.

Jeez.

mnem
 

And now we come full circle, back to where I was earlier when I was saying that all Meds meters were only a few uV away from agreeing with each other and on that basis I would happily work with any one of them and have maximum confidence in it.  I personally would not consider spending possibly $100's getting any of re-calibrated. If I had to be able to measure safely and reliably down to the uV level then I'd invest in meter specially designed to just that.

Nor would I; but I'm a confirmed volt-mutt. 

I was talking aboot med's case... where he bought the "one meter to rule them all". To go tinkering with it's cal oneself based on the results of any used meter of unknown provenance, or even a collection of them, which he has, is to admit utter failure in that endeavour. Don't ask that of the man. 

At least let him have the dignity of a proper, cert-carrying cal to salve that wound...

mnem
...or grind salt into it.

[med6753]

Gee whiz, you guys keep kicking this volt nut ball back and forth and you don't even stop and realize we are all on the same page and singing from the same choir. I said right from the get go that my little experiment pitching the 8505A and 3456A against each other proves nothing in a practical sense or is applicable in general everyday use. But it does demonstrate perils of venturing into 5.5 and 6.5 digit territory and getting your panties twisted up in microvolts and nanovolts. The only thing I'm trying to reconcile is that if I'm going to venture into the rabbit hole I want the equipment to at least be consistent and repeatable. I think I have demonstrated that it isn't but I would have no problem using either the 3456A, or the 8505A, or the 3055 to successfully fix any piece of equipment I have here and be confident that it's correct and accurate. But if I do notice, and prove beyond any doubt, that one of these units, like the 3055, is not meeting the expectations that I think it should I'm going to strive to correct it.

Hopefully I can put a cap and this "debate" by leaving you with this. Whenever I post pictures of my troubleshooting activities what DMM always appears? That's right....a lowly 3.5 digit Fluke 87.         

[Zucca]

is not meeting the expectations that I think it should I'm going to strive to correct it.

This is music to my hears.

[Specmaster]

Gee whiz, you guys keep kicking this volt nut ball back and forth and you don't even stop and realize we are all on the same page and singing from the same choir. I said right from the get go that my little experiment pitching the 8505A and 3456A against each other proves nothing in a practical sense or is applicable in general everyday use. But it does demonstrate perils of venturing into 5.5 and 6.5 digit territory and getting your panties twisted up in microvolts and nanovolts. The only thing I'm trying to reconcile is that if I'm going to venture into the rabbit hole I want the equipment to at least be consistent and repeatable. I think I have demonstrated that it isn't but I would have no problem using either the 3456A, or the 8505A, or the 3055 to successfully fix any piece of equipment I have here and be confident that it's correct and accurate. But if I do notice, and prove beyond any doubt, that one of these units, like the 3055, is not meeting the expectations that I think it should I'm going to strive to correct it.

Hopefully I can put a cap and this "debate" by leaving you with this. Whenever I post pictures of my troubleshooting activities what DMM always appears? That's right....a lowly 3.5 digit Fluke 87.         

I think we agree on that point, but here is an interesting thought, all three of your heavy hitting meters were calibrated by different people on different calibration devices, probably costing thousands of $ each. Therefore, it is highly likely that at the time they were originally calibrated, they all agreed with the calibration device used. It is also possible that if they were to be recalibrated on the self same machine used in the first setup, that they could very well still agree with them. Then mix up the meters, so they were tested on a device that one of the meters were done by, they would fail to meet their expectations by a few uV each. So if that is true, then why would they be expected to adhere to 2 different voltage references, costing considerably less than the originals did.

Send the Siglent back to be recalibrated at what cost, only to discover possibly upon its return that the discrepancies between, Siglent, Fluke, and HP are even wider and then even worse when compared to your 2 AD584's, where does futile pursuit of perfection end, when by your own admission when being used seriously in troubleshooting activities, you always rely on a 3.5 digit Fluke 87?

Personally I always one or more of my 5.5 digit meters for troubleshooting only because they are right there in front of me, rack mounted and thus taking up no bench space. I could get away very easily with 3.5 digit meters, but those extra digits are just so alluring, sexy even, in much the same way as a car that is capable of doing 200MPH.

That being said, there is one thing that we can all agree on is that if there was only 3.5 digit meters available that these topics of conversation would occur far less frequently   

[BU508A]

Just for the records:

calibration is not adjusting.

Calibration means: comparing the DUT to a reference and checking, if it is within specs.
If it is within specs, the differences will be documented.

If the DUT is out of specs, then an adjustment or repair of the DUT can be considered.

[Specmaster]

Just for the records:

calibration is not adjusting.

Calibration means: comparing the DUT to a reference and checking, if it is within specs.
If it is within specs, the differences will be documented.

If the DUT is out of specs, then an adjustment or repair of the DUT can be considered.

So if you send a meter away for calibration, it will come back to you with the same settings as you sent it with? I was under the distinct impression that if the meter was in need of an adjustment, it would be made and then returned to you, with a demonstrable calibration. When I read the service manual for my BlackStar 4503, it gives precise instructions on how to check each range.  Then how to enter the calibration mode and make the required corrections to its parameters and saving those corrections to memory, which is what I did after repairing the damage done by the leaking battery.

[beanflying]

The 6 1/2'th digit is more about 'drift' and minimizing those sources than a meaningful number on a 6 1/2 digit meter even if it is 'near spec' or 'properly calibrated' . What that sort of meter gives you in simplistic terms is however 'a reasonable certainty' of measurement at the 5 1/2 digit (depending on the specifications).

Looking at trends over time with a more stable reference than the meter uses or in particular against a range of real world environmental changes to measurements helps even if just a mental note as to a meters good or bad points. Using this and some long term data (weeks of logging) has lead me to the conclusion that my 34401A is a 'better' meter than the 34461A in the real world even though both are Keysight Calibrated and well within spec.

Much as I like the little AD584 for a quick check mine has settled quite a lot over the few years and it does drift more than the meters so it is not a good choice for looking at the last PPM's. For anything 4 1/2 toward maybe 5 1/2 digits they are fine in particular if you can get them tested against a known standard.

More than I need and yet I have a project 3458A to get into after Summer