Re: [volt-nuts] Fluke 750a batteries.............
Four Tadiran 5955 2/3 AA lithiums have worked fine for me. They come with leads that I just soldered onto the battery holder terminals. Hello All, I posted this over at the HP yahoo group as well, so pardon the redundancy if you belong to both or more. My new to me Fluke 750a reference divider arrived last evening and I have been having one heck of a time finding info on replacement battery options others have used on their 750a's. Fluke spec'd (2) 6.7v mercury cell batteries for the overload protection circuit and these are clearly no longer available. What is everyone using for power? I am hoping to not use a separate DC supply for this app. The only manual I can find is here: http://bama.edebris.com/manuals/fluke/750a/ < http://bama.edebris.com/manuals/fluke/750a/> I have been able to find Wein batteries that are 1.35v zinc/air and I could stack and shrink wrap 5 of those in series to arrive at 6.75 very stable volts, but they are a minimum of $4.50 each cell. I was hoping to find a more affordable / elegant solution. Will the circuit handle (2) 3.6v Li-Ion in series instead? Any thoughts? Cheers, David ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fluke 720a self calibration repair
David: Run the numbers. Assuming that the 5K-20 turn pot R1005 is set in the middle of it's travel (2.5K), that all of the other resistors, in series and parallel ( R1006,R1007,R1008 and R302), that make up one step of the "A" decade have a "0" TC, only R1005 has a maximum of +/- 100 ppm per degree C, then the maximum change on the total resistance between step 0.9 and 1.0 of the "A" decade would only be 0.00410 % change over the entire +/- TC of R1005. That is 0.00410 ppm. The "Absolute Linearity" of the "A" decade is specified at 0.1 ppm at +/- 1 degree C, without a temp correction chart. Of course all of the other resistors mentioned have a TC also, which could be + or - to the total nominal of 10,000. Therefore, unless I am mistaken, the less expensive +/- 100ppm pots would work just fine and you could not observe or measure the changes. This is also why I didn't worry about my "trimming" R1008, the "factory selected" resistor, slightly to get the 20 turn pots to adjust to the middle of their ranges, when necessary. IMHO Bill - Original Message - From: "David Garrido" To: Sent: Saturday, September 26, 2015 5:05 AM Subject: Re: [volt-nuts] Fluke 720a self calibration repair > Thank you for all of the input on this folks. > > Does anyone have a copy of the datasheet for the original Ramo-Eltra P/N 3800P-502? > > The reason I ask is that the price of these parts is driven in part by the tempco and I found info that indicated 20ppm/C on one website, but that was not a DS, just a listing of the info. If they can be 50ppm/C or even 100ppm/C, then the price drops exponentially. > > I will do whatever is necessary to maintain or (LOL) improve the 720’s legendary performance. > > Cheers, > > David > ___ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fluke 720a self calibration repair
I noticed that some of the vendors listed overall end-end tcr and at least one that listed the wiper tcr too. Hopefully you can get the datasheets with both. Todd On Saturday, September 26, 2015, David Garrido wrote: > Thank you for all of the input on this folks. > > Does anyone have a copy of the datasheet for the original Ramo-Eltra P/N > 3800P-502? > > The reason I ask is that the price of these parts is driven in part by the > tempco and I found info that indicated 20ppm/C on one website, but that was > not a DS, just a listing of the info. If they can be 50ppm/C or even > 100ppm/C, then the price drops exponentially. > > I will do whatever is necessary to maintain or (LOL) improve the 720’s > legendary performance. > > Cheers, > > David > ___ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Fluke 720a self calibration repair
Thank you for all of the input on this folks. Does anyone have a copy of the datasheet for the original Ramo-Eltra P/N 3800P-502? The reason I ask is that the price of these parts is driven in part by the tempco and I found info that indicated 20ppm/C on one website, but that was not a DS, just a listing of the info. If they can be 50ppm/C or even 100ppm/C, then the price drops exponentially. I will do whatever is necessary to maintain or (LOL) improve the 720’s legendary performance. Cheers, David ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
