KOEP Trancell VI DC Voltage Reference Standard - Page 1
Forum section: electronics / general

author: View[+]Finder
author_rank: Unknown
timestamp: August 14, 2021, 12:06:02 am
content: This is the sixth (I'm guessing) in the line of "Trancell" zener-based voltage standards. The only documentation I have found is for the model IV as made by Standard Reference Labs."Koep" refers to "Kenneth Koep  was born on October 9th, 1928 and began his career at Weston Instruments in Newark, New Jersey, USA, while he took night classes for bachelor's and master's degrees from the Newark College of Engineering. Later, he founded Standard Reference Labs and then Koep Precision Standards. Koep developed electronic calibration and measurement equipment, earning two patents. NASA used Mr. Koep's technology on early space shuttles. He was a senior member of the IEEE." (ETHW.org)One of these Model VI's showed up on my doorstep via eBay and is now showing off its PPM's on my test bench. The serial number is 351, so I'm seeking any schematics or "user experience" advice available.Unlike much old gear on eBay, this device worked as it should right out of the box (after the customary visual inspection for internal damage) and provides a "10VDC" reference. It is marked as to provide "10.1817 v" and the measured voltage is 10.18080VDC on a 6.5 digit meter. (+/- 1)

author: bob91343
author_rank: Super Contributor
timestamp: August 14, 2021, 03:48:19 am
content: 900 microvolts discrepancy? I would return it as defective. (J/K)

author: Vgkid
author_rank: Super Contributor
timestamp: August 14, 2021, 08:30:05 am
content: Ah, so you bought it. Definetly tear it down.

author: branadic
author_rank: Super Contributor
timestamp: August 14, 2021, 08:45:53 am
content: Interesting output voltage, by intention? Is this 1.018 V for comparison to Weston Cells amplified by a factor of ten or is it simply the zener voltage amplified by a factor of 1.4?-branadic-

author: tggzzz
author_rank: Super Contributor
timestamp: August 14, 2021, 01:35:16 pm
content: Pictures of my two Trancells:https://www.eevblog.com/forum/metrology/standard-reference-labs-trancells-any-information-available/msg1135761/#msg1135761one of which has 15µV popcorn noise.The better one's output is 9.999571V, i.e. 29ppm low. It has a trimpot on the back, but I'm definitely not going to touch that!Searching this forum for "Trancell" gives a few useful hits.

author: View[+]Finder
author_rank: Unknown
timestamp: August 14, 2021, 04:30:08 pm
content: Some photos of the Trancell VI.There are 11 colored wires out the back of the device: the black one is ground and the others are one-volt increments from 1 to 10 volts with the 10V being the front-side output voltage and the one-volt being 1.018069VDC (probably meant to be 1.01817VDC like a Weston cell as @Branadic surmised).The blue Vz post on the front panel is the zener voltage. My use of "panel" is mis-leading as the only panel on the box is the removable top; the case being from one piece of aluminum bent to shape and painted prior to installation of the electrical components. So a "tear-down" will have to wait until something needs fixing.From the Trancell IV documentation, it would appear that the two green trimmer pots are the 10V and 1V adjustments, but I'll do some testing before adjustment.

author: View[+]Finder
author_rank: Unknown
timestamp: August 16, 2021, 10:41:52 pm
content: Initial measurement of 10.1817VDC nominal from Trancell VIMeasurement by two Keithley meters factory calibrated within last 12 months. Power to DUT from 120VAC. Data collected sequentially from 05:45 to 18:47 PDT.There is an approximately 10 micro-volt difference between the meters 'zero' reading.

author: View[+]Finder
author_rank: Unknown
timestamp: August 18, 2021, 01:23:52 am
content: Data captured by HP3458a "Overnight" 20210816 (25C +/-1 ambient)Trancell power by LiPo battery (24.5-22.5 VDC range over measurement period)Six sets of 1000 observations approx. 10 seconds apart with ACAL DCV between each set.