[time-nuts] Some pics of the Datron 491x DC reference cell
I've uploaded some photos of the Datron 10 volt cell and reference board, as requested by a few members. I've kept them full-resolution so you can see fine detail. But, that means they are about 3 mb each. The schematics for the cell board I previously posted are also still on the FTP site. DatronCell.jpg is an image of the entire cell board. The reference board is piggybacked on it. Note the thermal shield around the LTZ1000, and the completely shielded sections on the board. Those contain the digital circuitry. The cell board itself goes into a shielded enclosure along with the other three cells and the output buffer amp. DatronLTZCloseup.jpg is exactly that, a closeup of the LTZ with thermal shield removed. The interesting detail here is the mounting. Note the cutouts on the board to provide thermal isolation. This board is also very thin; I didn't measure it, but it's on the order of 0.5 - 1 mm thick. DatronRefCloseup.jpg is a closeup image of the rest of the reference board. The ref board is permanently soldered in place on the cell board, so I can't show the back of it. The ftp login is: ftp ftp.quackers.net login: f...@quackers.net password: (none required) Or, directly from a browser. I know this works for Firefox, I haven't tried it with anything else: ftp://f...@quackers.net:f...@ftp.quackers.net/ Some of you are also waiting for the schematic for the LTZ board itself; I'm recreating it now (since I lost it) and will post when ready. -- Bill Ezell -- They said 'Windows or better' so I used Linux. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Some pics of the Datron 491x DC reference cell
I tried to access the photos... got to an empty pub directory... Cutouts in a circuit board around a reference chip are usually more to relieve mechanical stress from the chip package caused by the PC board expanding/contracting/warping. This stress can affect the refereence voltage more than you might expect. Malone does this on his little Xicor X6008C voltage reference boards. (BTW that chip has been discontinued). That is why I prefer his boards over the other one that is available on Ebay that does not cut out around the ref chip. If you can live with that, you can get a packaged 5V / 0.01% reference for $14.50 shipped... see Ebay item 250366551770... the guy that builds them is closing them out... and he ships worldwide. _ Windows Live™ Hotmail®…more than just e-mail. http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t2_hm_justgotbetter_howitworks_012009 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Some pics of the Datron 491x DC reference cell
Mark Sims wrote: I tried to access the photos... got to an empty pub directory... Cutouts in a circuit board around a reference chip are usually more to relieve mechanical stress from the chip package caused by the PC board expanding/contracting/warping. This stress can affect the refereence voltage more than you might expect. Malone does this on his little Xicor X6008C voltage reference boards. (BTW that chip has been discontinued). That is why I prefer his boards over the other one that is available on Ebay that does not cut out around the ref chip. If you can live with that, you can get a packaged 5V / 0.01% reference for $14.50 shipped... see Ebay item 250366551770... the guy that builds them is closing them out... and he ships worldwide. _ Windows Live™ Hotmail®…more than just e-mail. http://windowslive.com/howitworks?ocid=TXT_TAGLM_WL_t2_hm_justgotbetter_howitworks_012009 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. Second method works fine (Linux machine) with Opera, Firefox, Epithany, Seamonkey however only Epithany and Opera save the jpeg files correctly. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Some pics of the Datron 491x DC reference cell
Bill, thank you very much for the schematics and the photographs! Using XP / firefox, I was able to retrieve the files with the given special link, and also very easily with the FileZilla Client. The most interesting part, i.e. the precision resistor circuitry, obviously resides on the bottom side of the ref board. Would be great to get a photo also from that side, as Datron made some efforts to get rid of strain and heat conduction effects. Best regards - Frank Stellmach ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Some pics of the Datron 491x DC reference cell
Dr. Frank Stellmach wrote: Bill, thank you very much for the schematics and the photographs! Using XP / firefox, I was able to retrieve the files with the given special link, and also very easily with the FileZilla Client. The most interesting part, i.e. the precision resistor circuitry, obviously resides on the bottom side of the ref board. Would be great to get a photo also from that side, as Datron made some efforts to get rid of strain and heat conduction effects. Best regards - Frank Stellmach Frank The precision resistors are more likely to be inside the metal can labeled vishay. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Some pics of the Datron 491x DC reference cell
Bruce, good hint, I think you are right.. Then it's a custom specific R array, metal foil technolgy (S105 or similar) from Vishay, perhaps oil filled. Makes it very difficult to read the circuitry and design a replacement with discrete resistors. Frank ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Some pics of the Datron 491x DC reference cell
Dr. Frank Stellmach wrote: Bruce, good hint, I think you are right.. Then it's a custom specific R array, metal foil technolgy (S105 or similar) from Vishay, perhaps oil filled. Makes it very difficult to read the circuitry and design a replacement with discrete resistors. Frank Frank The core circuit probably doesn't differ too much from the positive reference circuit shown on the LTZ1000 datasheet. It certainly wont be identical to the negative reference shown on that datasheet which has the heater pins reversed (as shown it will cause a large current to flow in the parasitic shunt diode connected across the heater resistor). NB use the latest datasheet which has a corrected schematic showing the location and polarity of the parasitic diodes. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Some pics of the Datron 491x DC reference cell
NB use the latest datasheet which has a corrected schematic showing the location and polarity of the parasitic diodes. Bruce Thank you, I already got that... When I used the first datasheet, I reversed the heater as there was no hint, just to discover those hidden parasitic diodes. I obviously did not damage the device (hope so), but sent that info to LT, and then they did the correction. Frank ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Some pics of the Datron 491x DC reference cell
Dr. Frank Stellmach wrote: NB use the latest datasheet which has a corrected schematic showing the location and polarity of the parasitic diodes. Bruce Thank you, I already got that... When I used the first datasheet, I reversed the heater as there was no hint, just to discover those hidden parasitic diodes. I obviously did not damage the device (hope so), but sent that info to LT, and then they did the correction. Frank Frank Yes but they didn't correct the negative reference circuit. I notified them about that - maybe that will be corrected in the next revision. I've located my Vishay brochure on resistor networks from the 70's. The TO-5 can resistor networks used 50 mil x 50 mil (50mW) and or 150 mil x 50 mil (100mW) resistor chips wire bonded to the header pins. Either 8 pin(2 different pin circle diameter options) or 10 pin variants were available. Other than the resistor chip specifications (TCR, pwer dissipation, etc) there's not much else. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
