Are these GRAY resistor standards any good?   - Page 1
Forum section: electronics / general

author: kawal
author_rank: Frequent Contributor
timestamp: April 15, 2020, 01:22:25 am
content: Got a few resistor standards to complement my self built resistor box.Can't find any info on these Gray company resistors. Are these accurate and do they need to be calibrated ?How should I take care for them ? Need special cleaning ?Thanks in advance.

author: TiN
author_rank: Super Contributor
timestamp: April 15, 2020, 02:18:25 am
content: Any resistor need to be calibrated and characterized, before it can be used for precision measurements. These usually designed to be used in stable temperature oil bath, so tempco measurement would be important to do and factor in.

author: TimFox
author_rank: Super Contributor
timestamp: April 15, 2020, 01:39:45 pm
content: Is the Gray company related to Leeds and Northrup, another Philadelphia manufacturer of metrology equipment? A short Wikipedia article says they existed until 1952.

author: LaserEng
author_rank: Regular Contributor
timestamp: April 15, 2020, 03:05:27 pm
content: I suspect either badge engineering or sharing parts suppliers between L&N and Gray as those resistors are definitely have the same construction as the L&N ones. I suspect L&N were the OEM of the resistors. Perhaps. Mr Pettis, our resident resistor guru knows.From a 1993 bookThe Gray company prospered during the war, and then slumped. By 1951 it was reduced to a skeletal staff, and recorded sales of only $50,000. During the 50's the company expanded once again. In 1963 it was bought out by the James G Biddle Company, became the Biddle-Gray Corporation, and continued to manufacture the Gray line of precision electrical testing equipment. The Biddle-ray name was dropped in 1967, but the Gray line of instruments has continued in production to the present day.There is definitely some tie up between the two companies as later on in the same book it saysAnother former Queen (Gray Instruments company name before changing to Gray) employee Morris Evans Leeds of Queens Electrical Department, established Morris E. Leeds and Co. in 1899, and bought out the electrical instrument workshop founded by his former co-worker, Elmer G. Willyoung. In 1903 Leeds joined forces with another friend from Queen, Edwin Fitch Northrup to form Leeds and Northrup.

author: kawal
author_rank: Frequent Contributor
timestamp: April 15, 2020, 06:39:34 pm
content: Thanks guys for the history. That is the reason i cant find any info on these as they where made when manuals where on paper. I will see what I can find on Northrup resistors.

author: Bill158
author_rank: Regular Contributor
timestamp: April 15, 2020, 08:53:27 pm
content: attached is the only information I ever found on the small diameter resistors.I am sure that L&N made the Grey units. L&N would never allow Grey to do such a identical copy without permission.Bill

author: kawal
author_rank: Frequent Contributor
timestamp: April 17, 2020, 04:36:11 am
content: BillVery interesting about the Mercury used to improve contact. Did not know that about these resistors. Thanks for posting.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: April 17, 2020, 03:06:23 pm
content: The round ones sure look like L&N to me. Remember if they were made before the resistance correction of 1948, expect them to be 495 ppm off, as are some of my old L&N resistors.https://www.nist.gov/system/files/documents/calibrations/87mscohm.pdf

author: kawal
author_rank: Frequent Contributor
timestamp: April 21, 2020, 04:31:03 pm
content: Mr HoffmanWow that is a lot of information. 495ppm is quite a bitI measured the GRAY 10K at 18C and using 4 wire on HP 3457AI get 9.9996357 kOhm on a HP 3457A averaged over 100 samples that seems like 36ppm versus modern -ish meter.So the Grays must have been made after 1948 ?I think these where made to be used in oil bath at 25C ?

author: Grandchuck
author_rank: Super Contributor
timestamp: April 21, 2020, 04:55:36 pm
content: 495 ppm does sound like a lot but it is correct:"The unit of resistance, the ohm, is intended to be the closest practical approximation to the International System (SI)unit of resistance. A more complete discussion of SI units may be found in ANSI/IEEE Std 268-1976, Standard MetricPractice. The value of the unit of resistance was adopted in 1948 by international agreement and has been maintainedsince then with negligible fluctuation by a group of standard resistors. This unit is usually designated as the legal ohm, theabsolute ohm, or simply the ohm. Before 1948, the unit was designated as the international ohm and was 495 partsper million larger than the present unit."

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: April 21, 2020, 05:19:04 pm
content: BTW, that hole in the middle is for a thermometer.