Keysight 34465A (6.5 digit) and 34470A (7.5 dight) share same hardware? - Page 1
Forum section: electronics / testgear

author: nightpanda
author_rank: Newbie
timestamp: December 16, 2015, 02:37:26 am
content: I was looking into the new Keysight DMM data sheet and found the specification of 34465A and 34470A are almost same.But 34465A (6.5 digit DMM) list price is 1395USD and 34470A (7.5 digit DMM) is 2890USD, which is a big difference.Take a look at the date sheet here:http://literature.cdn.keysight.com/litweb/pdf/5991-1983EN.pdf?id=2318052The measurement range, the accuracy, and speed, everything looks same to me. So why double the price?It seems like they are sharing the same hardware, only changes the firmware, which cut less digit from ADC, and make the resolution looks higher.Has anyone got a chance to teardown 34465A and 34470A and make a comparison?

author: Macbeth
author_rank: Super Contributor
timestamp: December 16, 2015, 02:45:14 am
content: Doesn't the 6.5 digit use an LM399 while the 7.5 is LTZ1000? ... and then with both those references you get into the territory of the volt-nuts with aging and temperature cycling, etc.

author: nightpanda
author_rank: Newbie
timestamp: December 16, 2015, 05:32:18 am
content: Well, thanks for all the information above, but I still have my doubt here.In the video, we can see there are 2 different main PCB board used for 344xx DMM. One is 34460-26501, which is for 34460A and 34461A (low end 6.5 digit DMM) and using LM399 as reference. And the other one is 34465-26501, which is for both 34465A (high end 6.5 digit DMM) and 34470A (7.5 digit DMM).34465A and 34470A share the same main PCB board and on this PCB board, Keysight removed LM399 and add a 8 pin connector. We know 34470A is using another small PCB board with LTZ1000 attach to this connector. But how about 34465A? Which is really bugging meAnother thinking is, in the data sheet, both 34460A and 34461A just have one temperature coefficient specification. While 34465A and 34470A have two temperature coefficient specification (with ACAL and without ACAL). I have no idea about this ACAL function (is it means the temperature stabilizer inside LTZ1000?) , but it makes them looks more similar to me.Any more information about what reference used by 34465A?

author: HighVoltage
author_rank: Super Contributor
timestamp: December 16, 2015, 11:52:51 am
content: The 34465A and the 34470A both use the same LTZ1000A referenceThe only difference is that the 34470A shows one more digit, based on Software.Otherwise they are identical Hardware, as far as I know.

author: commie
author_rank: Frequent Contributor
timestamp: December 16, 2015, 12:00:21 pm
content: Given the stark contrast in price differential between the 34461A and the 34470A, everything is saying get the 34465A. On the other hand check out the price of other branded 71/2 digit multimeters, then Keysights 34470A price doesn't look so bad.Cheers

author: deadlylover
author_rank: Frequent Contributor
timestamp: December 16, 2015, 12:03:46 pm
content: The 34465A still uses LM399, its spec clearly drifts way too much for a LTZ1000A, confirmed byteardown here by user radioFlash.

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 16, 2015, 01:25:01 pm
content: Hello,judging by the pictures from the different teardowns, both instruments share exactly the same motherboard, components and also firmware.The only difference is the voltage reference, i.e. an LTZ1000A for the 34470A, an LM399 for the 34465A.That is reflected in the specifications, they are exactly the same for all modes and ranges, only the DCVstabilitydiffers noteworthy, i.e. 8ppm/year instead of 20 ppm/year, due to the better reference in the 34470A.The displayed resolution is of course ten times higher for the 34470A (a bit less for some ranges), but over the bus, presumably both send about 8 digits.Also, they specify a slightly better linearity for the 34470A, which does not change the game, as it's not a factor of ten.Scott Stever, former designer of the 3458A and obviously PM also for the 34465A / 34470A (now retired) explained to me on phone, that they used better components for the 34470A, but I really doubt that, apart of the better reference.Maybe they measure the real INL of the individual A/D converters on the mainboard and chose the better ones for the 34470A instrument.In the end, the 7 1/2 digit resolution is just a flag in the firmware, like any other option like digitizing and memory size, and also coded into the serial number.I bet a dollar, that both instruments show exactly the same Allen distribution (short to mid-term stability figures), when measured with zero volt (TiNs DMM stability project) or when measuring the same stable 10V reference, always using the data over the bus.That would prove, that a 34465A is as stable and accurate as the 34470A, apart from the long term stability of course.Frank

author: 6thimage
author_rank: Regular Contributor
timestamp: December 16, 2015, 01:39:51 pm
content: As deadlylover said, the 34465A (with the 60 and 61A) use the LM399 where as the 34470A uses the LTZ1000A. If you look at the specifications this makes sense, as the 65A is closer to the 61A than the 70A.Quote from: nightpanda on December 16, 2015, 05:32:18 amThe ACAL function removes the vast majority of the temperature drift errors by measuring a very low tempco resistor in the multimeter (which is only present in the 65 and 70). The ACAL process takes around 10 to 15 seconds and can be performed as often as you like.Something that it worthwhile noticing with the specifications is that the 34465A is +/- 2 deg C, whereas the 34470A is +/- 5 deg C - which I am guessing is due to the different references (essentially, they are pulling as much as they can out of the LM399 in the 65).Something else that is easy to gloss over is that the ACAL needs to be run every 48 hours - footnote 1 on both the 65 and 70 specifications is:Quote from: Keysightwhich they should probably point out better.

author: nightpanda
author_rank: Newbie
timestamp: December 17, 2015, 03:43:49 am
content: Quote from: deadlylover on December 16, 2015, 12:03:46 pmthanks for sharing me this, seems this topic has been discussed before, I will look into it

author: nightpanda
author_rank: Newbie
timestamp: December 17, 2015, 04:45:01 am
content: Quote from: Dr. Frank on December 16, 2015, 01:25:01 pmHi Frank,Thanks for all the detail information. It's very helpful for me to understand the difference.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 17, 2015, 04:33:40 pm
content: Well, it seems I was wrong by expecting the 34465A also to have a LTZ1000A reference.Thanks Dr.Frank for explaining it in detail.May be it is time we put both of these great meters to a real comparison test.

author: plesa
author_rank: Frequent Contributor
timestamp: December 17, 2015, 06:28:11 pm
content: Quote from: Dr. Frank on December 16, 2015, 01:25:01 pmHi Frank,I made comparison between 34410A,34411A and L4411A as a prt of TiN DMM noise project and it seems that they select "better" 34410A boards to 34411A models, but I do not know where Agilent can use the boards which did not pass limits for L4411A, where is use different board compare to 34410A/34411A.Based on investigation 34411A can be downgraded to 34410A.https://www.eevblog.com/forum/testgear/possible-upgrade-agilent-34410a-to-34411a/Maybe someone with 34470A can try to sw downgrade to 34465A

author: HighVoltage
author_rank: Super Contributor
timestamp: December 17, 2015, 06:56:56 pm
content: Quote from: plesa on December 17, 2015, 06:28:11 pmMy 34470A still has full warranty.I doubt that anyone would try this during the warranty time period.What benefit would it serve? Just to see that the meter would show up as a 34465A?

author: plesa
author_rank: Frequent Contributor
timestamp: December 17, 2015, 07:03:47 pm
content: Quote from: HighVoltage on December 17, 2015, 06:56:56 pmIt is not so easy like I expected, firmware is shared, so it will needs further modification.