Empathy List Archives

CE

Chris Erickson

Mon, Jan 3, 2011 7:14 PM

Charles has an excellent point, but as one of those eBay sellers and
hardcore volt-nut/time-nut, ask the pertinent questions regarding
traceability and procedures used to check out and calibrate the equipment in
question. Also keep in mind that "known and respected calibration lab[s]"
also charge HUNDREDS of dollars for calibration and I charge a fraction of
that in terms of markup, as I am a "secondary" source. I sell most of my
stuff calibrated to make a few extra dollars on "value added." All of my
calibrators are themselves calibrated annually by the local NIST traceable
cal lab, and I thoroughly test and run each piece of equipment I sell
through the complete calibration procedure in its manual. I also provide
full traceability data on my calibrators as well. If it doesn't work right,
won't calibrate, or I can't find the manual/don't have the equipment to
calibrate it, I won't state that it is in my auction.

Being a time/volt nut, I also have calibration equipment of ever increasing
accuracy - for example, I'm currently overhauling a Valhalla 2720GS DC
calibrator with accuracy of 1ppm and annual drift of 3ppm to replace my
still very good Valhalla 2700C, which the local cal lab got within 1.5ppm
when freshly cal'd, but it has a drift of about 30ppm annually.

"In one case, the seller responded and when I called the lab, they had no
record of the item." There are dishonest people everywhere, more so in this
economy. eBay is a virtual flea market and I've dealt with some real
shysters. Check out the seller and their feedback. Call the cal lab if
something doesn't seem quite right. I have 100% positive because I make good
on my promises as both a buyer and seller.

Point being: don't completely ignore the term "calibrated" if it is not from
a known cal lab - just be well informed and ASK QUESTIONS. ASK about
traceability. ASK about procedures. ASK about calibration equipment, cal
dates, and serial numbers (all my stuff comes with this data, as with any
"known and respected calibration lab.")

Just as a side note: I don't currently have any hp/Tek/Fluke equipment for
sale, so I'm not fishing for a sale here, merely stating my case as someone
who calibrates equipment I sell and am not myself a certified lab.

Chris

Be very, very careful about "calibrated" equipment you find

on-line. Ebay is full of sellers who sell "calibrated" equipment

that hasn't been tested, much less adjusted, in three decades. Some

"calibrated" equipment I've bought has been nonfunctional. Now, I

ask the seller what lab calibrated the equipment, and on what

date. Rarely will sellers answer such a question. In one case, the

seller responded and when I called the lab, they had no record of the

item.

So, unless the seller is prepared to show you a calibration

certificate from a known and respected calibration lab, I'd suggest

ignoring any such claim when you value the item.

Best regards,

Charles

Charles has an excellent point, but as one of those eBay sellers and hardcore volt-nut/time-nut, ask the pertinent questions regarding traceability and procedures used to check out and calibrate the equipment in question. Also keep in mind that "known and respected calibration lab[s]" also charge HUNDREDS of dollars for calibration and I charge a fraction of that in terms of markup, as I am a "secondary" source. I sell most of my stuff calibrated to make a few extra dollars on "value added." All of my calibrators are themselves calibrated annually by the local NIST traceable cal lab, and I thoroughly test and run each piece of equipment I sell through the complete calibration procedure in its manual. I also provide full traceability data on my calibrators as well. If it doesn't work right, won't calibrate, or I can't find the manual/don't have the equipment to calibrate it, I won't state that it is in my auction. Being a time/volt nut, I also have calibration equipment of ever increasing accuracy - for example, I'm currently overhauling a Valhalla 2720GS DC calibrator with accuracy of 1ppm and annual drift of 3ppm to replace my still very good Valhalla 2700C, which the local cal lab got within 1.5ppm when freshly cal'd, but it has a drift of about 30ppm annually. "In one case, the seller responded and when I called the lab, they had no record of the item." There are dishonest people everywhere, more so in this economy. eBay is a virtual flea market and I've dealt with some real shysters. Check out the seller and their feedback. Call the cal lab if something doesn't seem quite right. I have 100% positive because I make good on my promises as both a buyer and seller. Point being: don't completely ignore the term "calibrated" if it is not from a known cal lab - just be well informed and ASK QUESTIONS. ASK about traceability. ASK about procedures. ASK about calibration equipment, cal dates, and serial numbers (all my stuff comes with this data, as with any "known and respected calibration lab.") Just as a side note: I don't currently have any hp/Tek/Fluke equipment for sale, so I'm not fishing for a sale here, merely stating my case as someone who calibrates equipment I sell and am not myself a certified lab. Chris > Be very, very careful about "calibrated" equipment you find > on-line. Ebay is full of sellers who sell "calibrated" equipment > that hasn't been tested, much less adjusted, in three decades. Some > "calibrated" equipment I've bought has been nonfunctional. Now, I > ask the seller what lab calibrated the equipment, and on what > date. Rarely will sellers answer such a question. In one case, the > seller responded and when I called the lab, they had no record of the item. > So, unless the seller is prepared to show you a calibration > certificate from a known and respected calibration lab, I'd suggest > ignoring any such claim when you value the item. > Best regards, > Charles

JF

J. Forster

Mon, Jan 3, 2011 7:24 PM

A bunch of people on eBay sell knock-off Kelvin Klips. I'd like to get a
set for 4-terminal Ohms with my 3478A.

Does anybody have any experience on which are good and which are trash? I
do have a slight preference for made-up lead sets w/ Bananna Plugs on the
meter end.

I am not interested in 8 digit accuracy, just being able to measure low
ohms w/o contact issues.

Best,

-John

=================

A bunch of people on eBay sell knock-off Kelvin Klips. I'd like to get a set for 4-terminal Ohms with my 3478A. Does anybody have any experience on which are good and which are trash? I do have a slight preference for made-up lead sets w/ Bananna Plugs on the meter end. I am not interested in 8 digit accuracy, just being able to measure low ohms w/o contact issues. Best, -John =================

BC

Brooke Clarke

Mon, Jan 3, 2011 10:09 PM

Hi John:

A lot depends on how low. I did a lot of testing using the 34401A DMM
in 4-wire mode and determined that the DC method is not accurate below
50 milliohms because of voltage generation. This testing was done using
the HP 11059A Kelvin lead set.
http://www.prc68.com/I/Kelvin.shtml
Links to Kelvin clips and part numbers at the bottom of the above page.

For 100 milliohms and lower you need to use an AC method, like the 4328A
http://www.prc68.com/I/HP4328A.shtml

Have Fun,

Brooke Clarke
http://www.PRC68.com

J. Forster wrote:

A bunch of people on eBay sell knock-off Kelvin Klips. I'd like to get a
set for 4-terminal Ohms with my 3478A.

Does anybody have any experience on which are good and which are trash? I
do have a slight preference for made-up lead sets w/ Bananna Plugs on the
meter end.

I am not interested in 8 digit accuracy, just being able to measure low
ohms w/o contact issues.

Best,

-John

=================

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Hi John: A lot depends on how low. I did a lot of testing using the 34401A DMM in 4-wire mode and determined that the DC method is not accurate below 50 milliohms because of voltage generation. This testing was done using the HP 11059A Kelvin lead set. http://www.prc68.com/I/Kelvin.shtml Links to Kelvin clips and part numbers at the bottom of the above page. For 100 milliohms and lower you need to use an AC method, like the 4328A http://www.prc68.com/I/HP4328A.shtml Have Fun, Brooke Clarke http://www.PRC68.com J. Forster wrote: > A bunch of people on eBay sell knock-off Kelvin Klips. I'd like to get a > set for 4-terminal Ohms with my 3478A. > > Does anybody have any experience on which are good and which are trash? I > do have a slight preference for made-up lead sets w/ Bananna Plugs on the > meter end. > > I am not interested in 8 digit accuracy, just being able to measure low > ohms w/o contact issues. > > Best, > > -John > > ================= > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > >

S

shalimr9@gmail.com

Mon, Jan 3, 2011 10:19 PM

The HP 3456A has an offset compensation feature in the Ohm mode (2 and 4 wires) that compensates for DC voltages in series with the resistance to be measured.
This will null any thermocouple generated voltage.

This function is not selected by default, it is accessible via the appropriate function key (O.C. Ohms).

Didier

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Brooke Clarke brooke@pacific.net
Sender: volt-nuts-bounces@febo.com
Date: Mon, 03 Jan 2011 14:09:24
To: jfor@quik.com; Discussion of precise voltage measurementvolt-nuts@febo.com
Reply-To: Discussion of precise voltage measurement volt-nuts@febo.com
Subject: Re: [volt-nuts] 3478A - Kelvin Klips

Hi John:

A lot depends on how low. I did a lot of testing using the 34401A DMM
in 4-wire mode and determined that the DC method is not accurate below
50 milliohms because of voltage generation. This testing was done using
the HP 11059A Kelvin lead set.
http://www.prc68.com/I/Kelvin.shtml
Links to Kelvin clips and part numbers at the bottom of the above page.

For 100 milliohms and lower you need to use an AC method, like the 4328A
http://www.prc68.com/I/HP4328A.shtml

Have Fun,

Brooke Clarke
http://www.PRC68.com

J. Forster wrote:

A bunch of people on eBay sell knock-off Kelvin Klips. I'd like to get a
set for 4-terminal Ohms with my 3478A.

Does anybody have any experience on which are good and which are trash? I
do have a slight preference for made-up lead sets w/ Bananna Plugs on the
meter end.

I am not interested in 8 digit accuracy, just being able to measure low
ohms w/o contact issues.

Best,

-John

=================

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

The HP 3456A has an offset compensation feature in the Ohm mode (2 and 4 wires) that compensates for DC voltages in series with the resistance to be measured. This will null any thermocouple generated voltage. This function is not selected by default, it is accessible via the appropriate function key (O.C. Ohms). Didier Sent from my Verizon Wireless BlackBerry -----Original Message----- From: Brooke Clarke <brooke@pacific.net> Sender: volt-nuts-bounces@febo.com Date: Mon, 03 Jan 2011 14:09:24 To: <jfor@quik.com>; Discussion of precise voltage measurement<volt-nuts@febo.com> Reply-To: Discussion of precise voltage measurement <volt-nuts@febo.com> Subject: Re: [volt-nuts] 3478A - Kelvin Klips Hi John: A lot depends on how low. I did a lot of testing using the 34401A DMM in 4-wire mode and determined that the DC method is not accurate below 50 milliohms because of voltage generation. This testing was done using the HP 11059A Kelvin lead set. http://www.prc68.com/I/Kelvin.shtml Links to Kelvin clips and part numbers at the bottom of the above page. For 100 milliohms and lower you need to use an AC method, like the 4328A http://www.prc68.com/I/HP4328A.shtml Have Fun, Brooke Clarke http://www.PRC68.com J. Forster wrote: > A bunch of people on eBay sell knock-off Kelvin Klips. I'd like to get a > set for 4-terminal Ohms with my 3478A. > > Does anybody have any experience on which are good and which are trash? I > do have a slight preference for made-up lead sets w/ Bananna Plugs on the > meter end. > > I am not interested in 8 digit accuracy, just being able to measure low > ohms w/o contact issues. > > Best, > > -John > > ================= > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > > > _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.

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Re: [volt-nuts] HP 3478A - Value? Quirks? Opinion?