Re: METRA Standard VS Honeywell Rubicon , Leeds&Northrup  standards  - Page 1
Forum section: electronics / general

author: eevblogfan
author_rank: Frequent Contributor
timestamp: September 18, 2013, 11:07:27 am
content: HeyI just saw METRA 100 Ohm standard resistor , are they any good ?I didn't found any result in here ' so I thought to askthank you

author: Hydrawerk
author_rank: Super Contributor
timestamp: September 18, 2013, 03:35:45 pm
content: Metra is a brand from Czech Republic or former Czechoslovakia. It should be decent. The company still exists.http://www.metra.cz

author: eevblogfan
author_rank: Frequent Contributor
timestamp: September 18, 2013, 05:01:04 pm
content: HeyThank youThough ,I wonder what decent means ...I Got one Otto wolff 1 OHM 0.01% Afaik ... but he perform within 20ppm ....I don't really mind absolute accuracy stuff ... the stability over time is the crucial factor .and without calibration data ... that can't be achieved ,Although . If I am going to ask opinion about fluke meter ... I think some are going to tell me that as lng as it wasn't abused tough , it is going to perform within 1 year speck at least ...But hand held measuring equipment is no way near the ppm level .. ( the Gossen is exceptional XD )Hence I asked if the name sounds familiar , any how , I am basically may be able to measure it with HP3458A . so is that resistor adjustable ? ( Kinda assurance for the money)after the adjustment , 2 years of settling ? or few weeks at high load ? ( Burn -in ) - if so ... for 100Ohm presumably 1 or 3 W ... what is the power I shall keep it at ?thank you in advance

author: Hydrawerk
author_rank: Super Contributor
timestamp: September 18, 2013, 05:11:49 pm
content: Sorry, but I am not familiar with Metra standard resistors. But they are used at FEEC in Brno.http://www.feec.vutbr.cz/fakulta/home.php.cz

author: eevblogfan
author_rank: Frequent Contributor
timestamp: September 18, 2013, 05:17:10 pm
content: Thank youI am not sure if it is right to ask it here .... I got another offer , 2 resistors , one is Honeywell rubicon , and the other is Leeds&Northrup , the honey is 100Ohm and the leeds is 1000 Ohm , both shipped for 105$ , while the Metra is ~129$ shipped ...Now as far as I know . the power rating might be different ? ... the metra may be 3W while they are 1W ?(O.T:) I wonder how do you get those links and from where did you knew the Feec are using Metra's standards ?

author: Vgkid
author_rank: Super Contributor
timestamp: September 19, 2013, 03:00:29 am
content: That is a very good deal if you can get those 2 standard resistors for that price

author: mzzj
author_rank: Super Contributor
timestamp: September 19, 2013, 08:12:17 am
content: Quote from: eevblogfan on September 18, 2013, 05:01:04 pmStandard resistors are not adjustable.Usually you don't need exactly 100,0000 ohm standard resistors. For example You can use 99.3141516982 ohm resistor usually just as fine, as long as you know the resistance value and the standard is stable with time.Another thing to consider is the resistor temperature coefficient, some are better and some worse depending on model and make.

author: eevblogfan
author_rank: Frequent Contributor
timestamp: September 19, 2013, 09:38:09 am
content: Heythank youI think it was in here , I saw one opened Leeds&Northrup and showed series 2 Ohms or so resistor who's there for adjusting the resistor ,I used fluke 742A's , I know they arent 1.000000 , hence the calibration data . on the papers you see 1,000.01822 Ohm or so .. then you enter the data you the meter you are calibrating (or) adjusting .what I meant with adjusting is in case the actual value is 70~90ppm under or above , that is above the usual 20ppm I use to see on good ones ,before adjusting suck A device , it is way better to send it to proper NIST certified lab and see the actual value they measured , plus uncertainty in order to see if it was mistake of measuring the resistor or simply drift of both the standard I've used in order to determine the actual value of unknown value standard ( let's say I pass 1mA or so . via good CC source or say fluke 5XXX calibrator , through fluke 742A(1K) and say old Leeds&Northrup one , I then connect each one to ratio capable meter ( is HP34401A good enough ? Keithley 2700 ? ) and perhaps average the result and I am going to get something near the value , right ?Anyhow , thank you for the confidant of buying those resistorsP,s: Does anyone know the max power *That will not * harm the Leeds&Northrup ? and the Honeywell Rubicon ?