Test Equipment Anonymous (TEA) group therapy thread

[Kosmic]

Totally agree, those Chinese AD584-M really are great little units and excellent value for money, if only they also did current and AC units like them, or could even build a unit with all three tests for a bit extra cash, it would be a great device to add into the toolkit.

Agree, as long as it is the one's with a legitimate label on the back indicating it's actual measured voltage. Both mine are. The one's with no label or "cookie cutter" label should be considered suspect.

I'm not sure how trustworthy the chinese devices are w.r.t. drift over time.

I'd look at Ian Johnson's devices https://www.ianjohnston.com/index.php/onlineshop He's on this forum He's evaluating whether his stock will allow him to offer more

We had some considerable conversation on this subject in here a year or three ago... I thought the consensus was that as long as the Vref was one of those obviously made using a reclaimed AD584x, they should be considered to be pretty well-aged and therefore pretty stable...?

mnem
 

Yes, we did indeed, and considering the huge price gulf between the Chinese AD584-M devices and those that Ian produces, I'd challenge anybody to get a better bang per buck performance ratio. Ian also has a Mastech MS7221 voltage and current calibrator in his arsenal which I also have, and he likes those as well. He paid £45 on eBay as a faulty unit and mended it, I also got mine on eBay but as a working unit and IIRC for a bit less as the seller had never used it and it was indeed like brand new in its case.

Ian devices use a LM399 voltage reference. You can't really compare them to a AD584 or Mastech MS7221.

I had mostly bad luck with cheap AD584 references. Ordered 3 and were all off from each other. Like I said previously they are probably ok to check 4.5 digits meters.

In all the discussions over these, I don't think anybody ever suggested they were suitable for anything more than 3.5-4.5 digits; I always considered them just a good reality check or value as a transfer standard, as long as you gave everything plenty of time to temp-stabilize and do your cal/adj all on the same bench at the same time, with immediate post-adjustment cal confirmation.

   https://www.tindie.com/products/circuitvalley/lm399-10v-precision-voltage-reference-calibrated/

Was it you that got one of the circuitvalley LM399 references? I can't remember if it was a bought thing or built from the GitHub project when we discussed it...

mnem
Oh dear... chiddlers are awake.

Nope. Got a Fluke 332a and 5101B.

[med6753]

Totally agree, those Chinese AD584-M really are great little units and excellent value for money, if only they also did current and AC units like them, or could even build a unit with all three tests for a bit extra cash, it would be a great device to add into the toolkit.

Agree, as long as it is the one's with a legitimate label on the back indicating it's actual measured voltage. Both mine are. The one's with no label or "cookie cutter" label should be considered suspect.

I'm not sure how trustworthy the chinese devices are w.r.t. drift over time.

I'd look at Ian Johnson's devices https://www.ianjohnston.com/index.php/onlineshop He's on this forum He's evaluating whether his stock will allow him to offer more

We had some considerable conversation on this subject in here a year or three ago... I thought the consensus was that as long as the Vref was one of those obviously made using a reclaimed AD584x, they should be considered to be pretty well-aged and therefore pretty stable...?

mnem
 

Yes, we did indeed, and considering the huge price gulf between the Chinese AD584-M devices and those that Ian produces, I'd challenge anybody to get a better bang per buck performance ratio. Ian also has a Mastech MS7221 voltage and current calibrator in his arsenal which I also have, and he likes those as well. He paid £45 on eBay as a faulty unit and mended it, I also got mine on eBay but as a working unit and IIRC for a bit less as the seller had never used it and it was indeed like brand new in its case.

Ian devices use a LM399 voltage reference. You can't really compare them to a AD584 or Mastech MS7221.

I had mostly bad luck with cheap AD584 references. Ordered 3 and were all off from each other. Like I said previously they are probably ok to check 4.5 digits meters.

In all the discussions over these, I don't think anybody ever suggested they were suitable for anything more than 3.5-4.5 digits; I always considered them just a good reality check or value as a transfer standard, as long as you gave everything plenty of time to temp-stabilize and do your cal/adj all on the same bench at the same time, with immediate post-adjustment cal confirmation.

   https://www.tindie.com/products/circuitvalley/lm399-10v-precision-voltage-reference-calibrated/

Was it you that got one of the circuitvalley LM399 references? I can't remember if it was a bought thing or built from the GitHub project when we discussed it...

mnem
Oh dear... chiddlers are awake.

Nope. Got a Fluke 332a and 5101B.

Why screw around? Get one of these and be set for life. 

[Kosmic]

Nice... 80 bucks, 70 Euros maybe, made in Germany so cheap shipping for me I guess.

A potential next step ./ upgrade from my cheap Chinese AD584...

The github is here if you feel like building your own: https://github.com/circuitvalley/LM399_Voltage_reference

For most of us, I still believe the DMMCheck/DMMCheck is the best bang/buck, as it comes with a variety of standards to check pretty much all the modes of a common DMM.

IIRC, the consensus was that it is adequate reference for up to 4.5-5.5 digits, or as a transfer standard for higher...?

https://dmmcheckplus.com/technical-information#

mnem
 

Oh yeah the DMMcheck of course, how could I forget about this one !

Hmm.. let me see the pros and cons of each product.

Circuit Valley :

- Half the price
- Open H/W.
- 10V output which is versatile, allows me to test all the digits all my DMM : 3,200 counts, 4,000 counts, and 50,000 counts.
- Super accurate.

It's unclear to me if the Circuit Valley ref is really accurate. I don't think the seller mention own it was calibrated and adjusted.

Just saw the listing on tindie:

Calibrated with Keithly DMM7510 7.5 Digit multimeter

There is no mention if the DMM7510 is regularly calibrated.

On the other hand, if I remember correctly, the DMMCheck Check Plus is calibrated and adjusted with a HP 3458a (8.5 digits).

[Kosmic]

Totally agree, those Chinese AD584-M really are great little units and excellent value for money, if only they also did current and AC units like them, or could even build a unit with all three tests for a bit extra cash, it would be a great device to add into the toolkit.

Agree, as long as it is the one's with a legitimate label on the back indicating it's actual measured voltage. Both mine are. The one's with no label or "cookie cutter" label should be considered suspect.

I'm not sure how trustworthy the chinese devices are w.r.t. drift over time.

I'd look at Ian Johnson's devices https://www.ianjohnston.com/index.php/onlineshop He's on this forum He's evaluating whether his stock will allow him to offer more

We had some considerable conversation on this subject in here a year or three ago... I thought the consensus was that as long as the Vref was one of those obviously made using a reclaimed AD584x, they should be considered to be pretty well-aged and therefore pretty stable...?

mnem
 

Yes, we did indeed, and considering the huge price gulf between the Chinese AD584-M devices and those that Ian produces, I'd challenge anybody to get a better bang per buck performance ratio. Ian also has a Mastech MS7221 voltage and current calibrator in his arsenal which I also have, and he likes those as well. He paid £45 on eBay as a faulty unit and mended it, I also got mine on eBay but as a working unit and IIRC for a bit less as the seller had never used it and it was indeed like brand new in its case.

Ian devices use a LM399 voltage reference. You can't really compare them to a AD584 or Mastech MS7221.

I had mostly bad luck with cheap AD584 references. Ordered 3 and were all off from each other. Like I said previously they are probably ok to check 4.5 digits meters.

In all the discussions over these, I don't think anybody ever suggested they were suitable for anything more than 3.5-4.5 digits; I always considered them just a good reality check or value as a transfer standard, as long as you gave everything plenty of time to temp-stabilize and do your cal/adj all on the same bench at the same time, with immediate post-adjustment cal confirmation.

   https://www.tindie.com/products/circuitvalley/lm399-10v-precision-voltage-reference-calibrated/

Was it you that got one of the circuitvalley LM399 references? I can't remember if it was a bought thing or built from the GitHub project when we discussed it...

mnem
Oh dear... chiddlers are awake.

Nope. Got a Fluke 332a and 5101B.

Why screw around? Get one of these and be set for life. 

Yep and open my own calibration lab 

Could be interesting as a retirement project.

[capt bullshot]

One short episode from the "No Fun with TEA" department:

https://www.eevblog.com/forum/testgear/keysight-edu36311a-(rant)/msg4113034/#msg4113034

[PA0PBZ]

One short episode from the "No Fun with TEA" department:

https://www.eevblog.com/forum/testgear/keysight-edu36311a-(rant)/msg4113034/#msg4113034

 

[ch_scr]

One short episode from the "No Fun with TEA" department:

https://www.eevblog.com/forum/testgear/keysight-edu36311a-(rant)/msg4113034/#msg4113034

Bug report rejected - works as specified 

[TERRA Operative]

Oof, Keysight too..... ouch.

[med6753]

D'OH 

[capt bullshot]

And another one from the "This is fun to work with TEA" department:

For a setup that I won't disclose any further, I need to measure the power consumption while some device operation.

One can use a current probe, a scope and your preferred calculator to roughly calculate Ws (or Joule) from a scope trace.

Or just set up some fancy math and cursor functions and read the result directly from the scope screen:



yellow trace: voltage
violet trace: current
thick blue: power
thin blue: integrated power

Cursor readout somewhere in the lower right corner: 1.27J

[tggzzz]

One short episode from the "No Fun with TEA" department:

https://www.eevblog.com/forum/testgear/keysight-edu36311a-(rant)/msg4113034/#msg4113034

Bug report rejected - works as specified 

Back in the day, that kind of response would have resulted in a terse polite note from Bill (Hewlett). Nowadays, who knows.

[med6753]

And another one from the "This is fun to work with TEA" department:

For a setup that I won't disclose any further, I need to measure the power consumption while some device operation.

One can use a current probe, a scope and your preferred calculator to roughly calculate Ws (or Joule) from a scope trace.

Or just set up some fancy math and cursor functions and read the result directly from the scope screen:



yellow trace: voltage
violet trace: current
thick blue: power
thin blue: integrated power

Cursor readout somewhere in the lower right corner: 1.27J

That's because digital will always lie to you, like an evil woman. Analog will just smack you in the face and call you stupid.

Speaking of analog. I don't get it. Why do nuvistors hate extended power off time? This Type 3A74 plug-in hasn't been used in perhaps 6 months or more. Upon first power up all 4 traces had all kinds of noise and hash on them. Then slowly one by one they cleared up and perfect. Didn't touch anything. And if I power it off and come back several hours later the traces will be clean right from the get go. I dunno. It's weird.

[Neomys Sapiens]

.
.

Why screw around? Get one of these and be set for life. 

Yep and open my own calibration lab 

Could be interesting as a retirement project.

Now let's be honest - the first one from this thread to aquire a fully fledged multimeter calibrator of this category will probably let this nobody know, because he would be the target of a veritable avalanche of calibration requests! 

[med6753]

.
.

Why screw around? Get one of these and be set for life. 

Yep and open my own calibration lab 

Could be interesting as a retirement project.

Now let's be honest - the first one from this thread to aquire a fully fledged multimeter calibrator of this category will probably let this nobody know, because he would be the target of a veritable avalanche of calibration requests! 

Aw shit, did I just let the cat out of the bag? 

I wish

[mnementh]

There is one problem in this kind of testing / situation, though, which often haunts me... you don't know how many cycles it would take for the thing to FAIL, I mean, due its normal life expectancy.

Say it's good for a 1,000 cycles before it needs fixing/servicing... then by testing it 500 times, you are happy thinking cool, it works but... you have now just significantly reduced the life of the thing and will need to fix it again much sooner than it would otherwise have needed to ! 

I'd say that a tool of this sort damned well better have a helluva lot higher than 1,000 cycle design life on the primary controls. Given that, 500 cycles should be statistically insignificant "wasted lifespan".



Not saying they DO; ISTR recently, bd139 saying that this family of TTi PSUs (TS3021 pictured) has a similar design and the same exact failure mode to the one THD has, often resulting in multiple pass elements failing CE short.

"Digital cancer..." he called them.

mnem
 

[Ice-Tea]

.
.

Why screw around? Get one of these and be set for life. 

Yep and open my own calibration lab 

Could be interesting as a retirement project.

Now let's be honest - the first one from this thread to aquire a fully fledged multimeter calibrator of this category will probably let this nobody know, because he would be the target of a veritable avalanche of calibration requests! 

Aw shit, did I just let the cat out of the bag? 

I wish

What now?

https://www.ebay.de/itm/144391578429

 

[Cubdriver]

Speaking of analog. I don't get it. Why do nuvistors hate extended power off time? This Type 3A74 plug-in hasn't been used in perhaps 6 months or more. Upon first power up all 4 traces had all kinds of noise and hash on them. Then slowly one by one they cleared up and perfect. Didn't touch anything. And if I power it off and come back several hours later the traces will be clean right from the get go. I dunno. It's weird.

It's peeved at you because it feels unloved after you ignored it for six months.  It's being petulant.

-Pat

[Kosmic]

.
.

Why screw around? Get one of these and be set for life. 

Yep and open my own calibration lab 

Could be interesting as a retirement project.

Now let's be honest - the first one from this thread to aquire a fully fledged multimeter calibrator of this category will probably let this nobody know, because he would be the target of a veritable avalanche of calibration requests! 

Aw shit, did I just let the cat out of the bag? 

I wish

What now?

https://www.ebay.de/itm/144391578429

 

I already got one of those 

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg3685504/#msg3685504

[Ice-Tea]

.
.

Why screw around? Get one of these and be set for life. 

Yep and open my own calibration lab 

Could be interesting as a retirement project.

Now let's be honest - the first one from this thread to aquire a fully fledged multimeter calibrator of this category will probably let this nobody know, because he would be the target of a veritable avalanche of calibration requests! 

Aw shit, did I just let the cat out of the bag? 

I wish

What now?

https://www.ebay.de/itm/144391578429

 

I already got one of those 

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg3685504/#msg3685504

Only one? 

[Kosmic]

.
.

Why screw around? Get one of these and be set for life. 

Yep and open my own calibration lab 

Could be interesting as a retirement project.

Now let's be honest - the first one from this thread to aquire a fully fledged multimeter calibrator of this category will probably let this nobody know, because he would be the target of a veritable avalanche of calibration requests! 

Aw shit, did I just let the cat out of the bag? 

I wish

What now?

https://www.ebay.de/itm/144391578429

 

I already got one of those 

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg3685504/#msg3685504

Only one? 

Well, if you sell it the same price I paid for the other one, I'll get that one too 

[mnementh]

Oh yeah the DMMcheck of course, how could I forget about this one !

Hmm.. let me see the pros and cons of each product.

Circuit Valley :

- Half the price
- Open H/W.
- 10V output which is versatile, allows me to test all the digits all my DMM : 3,200 counts, 4,000 counts, and 50,000 counts.
- Super accurate.


DMMCheck :

- 5V output won't let me test properly my 3,200 and 4,000 meters, I would lose a precious digit. Even my 50,000 count meters well... the ref could still make them overflow and again lose the MSD.
- Less accurate than the other one.
- Twice the price or maybe more, their site doesn't say how much it would cost, shipped, when buying from their German stock.
- Features I don't need/want : frequency and duty cycle and AC.
- Good : does current, and offers a few precision resistors.

So if I could be arsed, the best bang for buck for me only for meeee.. would be to mix both products.
That is, make my own PCB, using the CircuitValley one and add precision resistors to the board, and add current as well. I guess I could simply connect the on-board precision resistors to the Vref and call it a day. The shunt value of the DMM ammeter would be much less than the ref Resistor on the board so it would still be plenty accurate enough for a very decent sanity check.

Oh, does that mean I have just added yet another project to my pile of projects ?! 

I'd probably rather the DMMCheck+ with 100Hz & 10KHz AC standard, and add the LC board. I have a lot more trust in Doug Malone's entire process as he pre-ages all his units for 250 hours, he posts his traceable cal certs publicly, and he is well-regarded here on eevBlog. The bottom line is what you're paying for is the Cal Sheet; even at $170 the fully-loaded DMMCheck+ is a bargain compared against even the most basic services from any accredited Cal lab.

As for the lack of 10V output... once you've confirmed that your meter is accurate in the low ranges with the 5V reference, then you can just use your Cheap & Cheerful™ China-Direct Vref as a transfer standard up the rest of the ranges.

mnem
 

[med6753]

It has arrived.

My review: This is super cool. Get one! 

[Ice-Tea]

Well, if you sell it the same price I paid for the other one, I'll get that one too 

*Ice-Tea has left the chat*

[Cubdriver]

It has arrived.

My review: This is super cool. Get one! 

Ordered one on Saturday.  I blame you.   

-Pat

[med6753]

Ordered one on Saturday.  I blame you.   

-Pat

I accept full blame/responsibility.