2 Wire Ohms

[CalLabSolutions]

Can some one please tell me why Manufacturer's continue to put 2-Wire 0 Ohms test points in their test procedures.  Then put a statement that the meter must be zero-ed to remove lead resistance with a short before you can make an accurate measurement. 

You connect the short, zero the Meter, then write down zero on the test report.  Has no one in the industry came to the conclusion that 0-0=0.

I am not saying this test is completly point less, if anything you are checking the Meter ability to hold a stable Zero Ref. So the test should read something like: Connect a short, press Zero, wait 2 minutes and verify the Zero Ref has not changed more that x Ohms. 

Am I missing something here?

Mike

[CalibratorJ]

Mike,

Not sure what meter you are talking about, but I have noticed similar things. But, it does make sense when you think about it.

For example, if I am doing a 34420A, I am using a shorting plug for the 0 ohms verification and for the adjustment (if it is needed). And, it seems to me, the internal whizzits need that 0 ohm reference to base the other values off of. I have seen the 0 drift some, or else it was 'adjusted' by someone previously that did not recognize the meaning of allowing the plug to mate thermally with the meter (I love calibration, we get to make WAY too many uhm, 'references', that are perfectly acceptable).

Now, I might be totally off kilter here, I'm not usually a DC/Low guy. but unfortunately, sometimes I end up dabbling in that arena.......

Oh, and Joe Snuffy needs to zero out his test leads when he is measuring his whatzit because 9/10 times, he is using 30-50 foot leads......

[CalLabSolutions]

J.. I agree with you on an absolute 2-wire zero test.  With a calibrated shorting plug.  Those procedures do not have a little note in them saying you must zero the meter before you can make a measurement.

Those procedures say connect a shorting plug (and specify shorting Plug) then measure the 2 wire zero without pressing the set reference. 

But if they only way you can get the UUT to pass 2-Wire Ohms zero is to press the Ref/Zero button.  And there are not Adjustment Points for 2 Wire Ohms zero.. Then the test points should be dropped.

And Yes.. Agilent have very good Metrology Practices, it is kind of like they know what they are doing.   

[RFCAL]

I am surprised to hear that. Agilent makes their share of Metrology mistakes.

[CalibratorJ]

Ah, I see. You are talking about the moron mfrs that have you zero it then check the zero. Yeah, think that is mostly a check to see if the meter can even zero itself...... lemme guess, it's a little $5 meter from Harbor Freight? (which I have one at home, lil thing is great, but yeah, have to zero ohms....)

[CalLabSolutions]

J, No It is not a $5 dollar meter. 

RF-Cal.. Yes they do.  And I have caught every manufacturer in a what the F#@k do you think you are doing.  But I am an Agilent Partner..  So I have to point out they are much better than the rest of the manufacturer's.  Product for product they are less mistakes. 

Mike

[CalLabSolutions]

As I think about this.. My problem is I have to write the steps in the automated procedure exactly how the written procedure calls them..  Well as close as possible..

I make is an absolute measurement and fail units, the customer complains about the software.. If I set the Ref and Read 0.0000000, I think hmmm I could shave 30 seconds for each test point off the total calibration procedure by skipping the test that are not really testing anything.

Mike..

[measure]

But I am an Agilent Partner..  So I have to point out they are much better than the rest of the manufacturer's.  Product for product they are less mistakes. 

Mike

Thanks for pointing out that you are an Agilent partner, Mike. While I agree that their metrology practices have generally been sound, tell me how they can specify a Fluke 5520A calibrator as being an adequate reference to calibrate a 34410A/34411A DMM with TARs, in some cases, less than 1:1? Better yet, I'd like to hear Agilent's rationale for it!

There are, however, many manufacturers, other than Agilent, that I believe also have credible metrology practices, but anyone can make a mistake.. even you Mike 

[CalLabSolutions]

But I am an Agilent Partner..  So I have to point out they are much better than the rest of the manufacturer's.  Product for product they are less mistakes. 

Mike

Where are you getting

Thanks for pointing out that you are an Agilent partner, Mike. While I agree that their metrology practices have generally been sound, tell me how they can specify a Fluke 5520A calibrator as being an adequate reference to calibrate a 34410A/34411A DMM with TARs, in some cases, less than 1:1? Better yet, I'd like to hear Agilent's rationale for it!

There are, however, many manufacturers, other than Agilent, that I believe also have credible metrology practices, but anyone can make a mistake.. even you Mike 

I am not going to say I never make mistakes.  I will say I have learned from everyone of them. 

However, no one is saying or implying we should be using a Fluke 5520 to calibrate Agilent 34410A/11A.  I don't recall ever seeing an Agilent Procedure calling for the Fluke 5520A.  So I am not sure where you are trying to go with this?

Yes, yes I do were my Agilent Channel Partnership like a badge of honor. I don't have deep pockets, a million dollar a year marketing budget or a world-wide sales force. I compete on service and quality, so becoming an Agilent Solution Partner because Agilent hears good things about my company.   

[measure]

I don't recall ever seeing an Agilent Procedure calling for the Fluke 5520A. 

Look in the Service Guide for the 34410A/34411A located on the Agilent website...

So I am not sure where you are trying to go with this?

Only to reinforce the fact that, no matter how good ANY source might be, NONE are infallible. I'd still like to hear Agilent's rationale for this...

[CalLabSolutions]

34410A/11A Recomended Standards
Agilent 34172B
Fluke 5720A
Agilent 33220A
IET SCA–1μF

Page 60 of service manual Part Number "34410-90010"

[Bryan]

34410-90010, 34410/11 service manual jan 2006 2d edition
34410-90010, 34410/11 service manual apr 2006 3d edition
34410-90010, 34410/11 service manual feb 2007 4th edition (this is the service manual on line at present) call for 5720A.
Please link the manual you are referring to.

[Hawaii596]

Speaking of slightly off topic... Ever heard of the Ohm Labs zero ohm standard.  It is certified to less than 50 nano Ohms in any configuration.  At that point, lead balancing is essentially the sum total of resistance.

[Bryan]

Not familiar with it (or what for).  I hope you & yours are safe from the fires.   I don't think that I've ever seen it this bad in my time in TX (since 85).

[michthai]

Just taking a WAG to answer the original question, I'd say the reason that 2-wire tests are still valid is that more than half the users have their meters configured and use them that way.