Metrology grade scanner card? - Page 1
Forum section: electronics / general

author: dr.diesel
author_rank: Super Contributor
timestamp: December 05, 2016, 01:31:59 pm
content: I don't have any experience with scanner cards. Does a suitable metrology scanner card exist when one wants to track/log numerous say 731Bs or better references?Any personal experiences with say a K2002 and 2000-Scan/2001-scan cards? Added noise, or readings offsets etc? Perhaps an external scanner card of some sort I could pair with my 7510 or future 3458A?Or should I just move in withTiNand hog all of his resources?

author: TiN
author_rank: Super Contributor
timestamp: December 05, 2016, 01:49:19 pm
content: Why me, I don't have ready scanner setup, still.2001-TCSCAN ain't good enough for 73x stuff. Need something like 706 scanner + 7168 card or Data Proof DP160/DP320

author: Theboel
author_rank: Frequent Contributor
timestamp: December 05, 2016, 02:04:03 pm
content: what about thishttps://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/msg610755/#msg610755

author: dr.diesel
author_rank: Super Contributor
timestamp: December 05, 2016, 02:14:37 pm
content: That thread has tons of info that I somehow missed, many thanks for digging it up for me.

author: branadic
author_rank: Super Contributor
timestamp: December 05, 2016, 07:38:56 pm
content: You could search for a Prema 2080.http://ohh.de/2080.htm

author: macboy
author_rank: Super Contributor
timestamp: December 06, 2016, 02:00:36 pm
content: The 2000-SCAN card used in the 2000, 2001, 2002 meters is rated for < 1 uV contact potential per relay contact pair. That's not bad but not great.I have a ... (ahem) few Keithley 7001 scanners that have model 7011-S scanner cards in them. They are rated for < 500 nV contact potential per relay contact pair, quite good performance for relays. Each card is actually four 1x10 scanners that can be used independently or combined (into 1x40, two 2x20, a 20x20 matrix, etc). If you are looking at switching a 10 V reference voltage to multiple meters, or multiple 10 V references into one meter, then you are only disturbing the voltage by less than 0.05 ppm.Those relay based cards use latching relays to help avoid effects caused by coil heating.Keithley also makes a nanovolt scanner card for the 7001/7002 systems that uses FETs instead of relays. It is an order of magnitude better but is very limited in voltage and current switching (10 V, 50 mA - and those are peak ratings, not average). That card will set you back about $3600.(p.s. if you are interested in acquiring a 7001 scanner as described above let me know by PM)

author: Echo88
author_rank: Frequent Contributor
timestamp: December 06, 2016, 04:43:59 pm
content: Could you let us know which FETs are used in the 7011-S-card? pretty please

author: dr.diesel
author_rank: Super Contributor
timestamp: December 06, 2016, 05:44:59 pm
content: I'm still digesting all the linked info and have been lurking around on the 38hot forum!Considering my ultimate goal is a 3458A, I think I'm set on either finding a used Data Proof/Prema/etc or DIYing something.Fairly smick latching relays are available (from the linked info)- Omron G5AK-237P (discontinued, but perhaps surplus)- Omron G6AK-234P -- Axicom V23079B1201B301 at <10uV- Panasonic TQ2/TN2I will order some of the above and test.Also, designing something with the relay contacts etched on the PCB surface with some mechanical actuation is within my fab capabilities.

author: macboy
author_rank: Super Contributor
timestamp: December 06, 2016, 05:53:06 pm
content: Quote from: Echo88 on December 06, 2016, 04:43:59 pmThe 7011-S uses relays. Contrary to my previous post, they are not latching relays. Instead, the card uses a dynamically adjusted power rail for the relays which drops the coil voltage lower than nominal (but still higher than the hold-on voltage) to reduce coil dissipation. When the relay configuration is about to change, the rail is boosted from 3.5 V to 5.7 V for 100 ms, the relays are switched, then it drops again.The 7168 card uses matched pairs of FETs in some kind of thermally-stabilized unit per pair The Keithley part number is "617-600" and it is a "Transistor, Selected". The part is also used in the 617 and 6512 electrometers, but their manuals give up no additional information either. The only way to know is to physically look at one of those instruments, and even then the part number on the FETs may be the Keithley number rather than the OEM one.

author: branadic
author_rank: Super Contributor
timestamp: December 06, 2016, 06:15:38 pm
content: <50nV/°C in the Prema MUX 2010 sounds really great:http://www.prema.com/index.php/de/service/messgeraetewartung/item/download/116_124e71e4309f5edffbaa2bfc370ef7b5