2002 Vs 3458a Vs 8588A? - Page 1
Forum section: electronics / general

author: toastedcrumpets
author_rank: Regular Contributor
timestamp: September 19, 2021, 07:42:21 am
content: I'm fortunate enough to be working in an engineering research group that is looking to buy a 8.5 digit meter. I was hoping I could ask for advice on what to buy. I'm sure I'd be happy with any of them, but want to be sure. I love the form factor of the 2002, hear the linearity of the 3458a is unmatched (plus it is "the one to have"), however I really appreciate the modern interface on my Keithley equipment and the 8588a is the only one that comes close.Now, about the use case:We have a range of devices (DMM/SMU) we use in physical measurement, including DMM7510, several DMM6500, 2450, 2461 etc. We build devices to measure things like thermal conductivity, so we measure transient pulses through platinum wires. I lead the group, but also have a side hobby in volt/time nuttery. I've repaired some old Fluke DCV/I calibrators, but also have a Datron 4708, fully optioned, waiting for repair.My plan was to get the 8.5 digit DMM annually calibrated, use it to verify the 4708 performance, then calibrate everything else as/when needed from there. I do not need professional certification of calibration for any legal/business reason, I just need to believe in my equipment for my research.What would you choose and why? Thanks in advance for your help.

author: TiN
author_rank: Super Contributor
timestamp: September 19, 2021, 08:05:43 am
content: Yet, you didn't list what requirements you have for DMM. And price budget as 8588 is double the price of 2002, while 3458 is halfway in middle. If you need speed and best DCV performance its the 3458. If compact size and scanner options its 2002. If need good resistance capability or high currents or just one of those folk who want latest and shiniest then its 8588.3458 also have advanced digitize capability, and 8588 has high speed digitizer. There is also crappier 8558 which is same price as 3458.

author: ScoobyDoo
author_rank: Regular Contributor
timestamp: September 19, 2021, 08:59:18 am
content: Hello toastedcrumpets - our club member e61_Phil also posted a way to add extra computational horsepower and USB/LAN to GPIB IF using one (or two)Rapsberry Pi 4 (RPI400) boards this is both useful for 3458A (and 2002/8558). It is rather low cost and works reliably.https://www.eevblog.com/forum/metrology/raspberry-pi-for-gpib-and-data-analysis-very-easy-and-fully-equipped/msg3631795/#msg3631795.As TIN explained both the 3458A and 8588A/8558A will shatter in performance in a certain domain - though the 2002 might have a lower accuracy on its 20V DCV range. First make up a list what's most important for you ...Best regardsScoobyDoo

author: toastedcrumpets
author_rank: Regular Contributor
timestamp: September 19, 2021, 10:59:29 am
content: Hi TiN,Apologies for not giving strict specifications but the truth is we don't need the 8.5 DMM for our immediate research. Typically it's cycles of feast and famine in research funding, right now it's good, so we want to buy capability while we can. The main capability we want is calibration/verification of our existing equipment. I didn't mention the 8558a as the 8588a is in budget, but it's an option.The DMM would sit and verify the performance of the repaired 4708. It will probably stay as part of the lab calibration setup, we'd probably offer it as a service to other labs in the university, most of who are happy with 5.5 digits of accuracy at DC.Our current research needs resistance accuracy, DCV accuracy around 10V, and digitisers, but we're happy with the ones in the DMM7510 and the dual digitisers in the 2461 for most purposes and would not need one in the DMM.Size isn't really that important, so I guess it's between 3458a and 85X8a.Thanks ScoobyDoo for the link, I spend a lot of time writing test automation so that's very interesting. I guess this means interface isn't massively important either, as we would script must stuff anyway for repeatability and long term measurements.So, in short, if you were setting up a DCV and resistance calibration lab, would you get a 8588a or a 3458a?

author: ScoobyDoo
author_rank: Regular Contributor
timestamp: September 19, 2021, 12:16:00 pm
content: Hello toastedcrumpets,Well it all depends upon available budget - for accurate DCV and resistive measurements you will also need a Metron/Wavetek/Fluke 7000 10V DCV source or Fluke 732C 10V DCV source and at least a 10kohm 4-wire Kaliber (F742-10k) to start your metrology Cal Lab.If such RaspberryPi 4 (RPI400) USB/LAN-to-GPIB bridge is acceptable than the lack of an USB/LAN IF on 3458A is no longer an issue - the RPI 4 will do all this work and computational MATH for you. Both Fluke and Keysight should be considered ... - maybe TCO is also important for your R&D rganisation.Best regardsScoobyDoo

author: toastedcrumpets
author_rank: Regular Contributor
timestamp: September 19, 2021, 01:27:12 pm
content: Thanks again for the input ScoobyDoo, I really appreciate being able to talk this over. Its a big purchase I want to get right, although I would probably be happy with either.Longer term I'd like to buy the DCV reference and a 4 wire resistor and build towards a full cal lab (we have some standards but they have not been verified for 30 years), but my naive idea was to send the 8.5 digit DMM for annual calibration for now to keep an eye on its drift and use it as our lab "standard". I planned to measure the 4708 calibrator against the meter and verify its DCV/Ohms etc, then use this to verify the other equipment in the lab. Am I wide open for some significant error without using a standard? I hoped the new DMM wouldn't drift much within a year compared to the precision of the daily driver DMMS we use. Noting that we primarily use 6.5 DMMs/SMUs and its them that need to be "accurate" in our work. We're also not selling calibration as a service, more just keeping an eye on our equipment and developing measurement capability. I am a bit worried about shipping of the DMM and power cycling of the DMM, I'd prefer to ship standards designed for this. I'll look up the costs on the standards and perhaps the savings from a 8588a to a 3458a can go in that direction.I've got costs for manufacture cals on the Fluke DMMs and this is something we can cover in our annual budget (I'm assuming the keysight is competitive/similar).Finally, I'm more than familiar with GPIB, SCPI, TSP, LXI and the rest, our lab runs on this, so the lack of USB/LAN on the 3458A really is not a problem. We already use jupyter and custom code to handle the math. The only downside of GPIB is its transfer speed, but this is not really an issue for cal work.

author: TiN
author_rank: Super Contributor
timestamp: September 19, 2021, 04:46:36 pm
content: New DMMs may drift quite a bit first few years. Also to have predictable (but additional) drift DMM would need to be on 24/7/365.732C is around 10k$, resistance 742A (one value) is around $3.8k. Fluke 7000 is not available new.3458A have benefit of ACAL (full self-calibration from 10V/10kOhm short of high frequency ACV) vs 8588A.

author: ScoobyDoo
author_rank: Regular Contributor
timestamp: September 19, 2021, 04:57:08 pm
content: Hello toastedcrumpets,some people in this forum will prefer the Fluke as it is populated with high end resistor networks and modern GUI - others will prefer the unrivalled linearity of the ADC from 3458A but the 3458A relies heavily on ACAL DCV. The 03458-66529 2ppm HFL A9 reference board is no longer available - so your best option is the model with 4ppm reference. HP (Keysight) designed the 3458A with low TCO in mind relying on ACAL DCV calibration with an external 10V DCV reference source - having access to such 10V DV source and 10kohm 4W resistor will offer you lowest TCO using the 3458A.The only thing you need to do is to submit the 10V DCV source and 10kohm 4-wire standard reference resistor for a yearly calibration session - which offers lowest TCO. These 10V DCV sources offer LTD < |+/-0.7ppm / YR|. Both instruments [3458A/85X8A] will give good customer satisfaction.Best regardsScoobyDoo

author: toastedcrumpets
author_rank: Regular Contributor
timestamp: September 19, 2021, 10:25:15 pm
content: Thanks guys, the TCO of the 3458a is very compelling and I didn't know this before for calibration. TiN, I found your discussion on the value of ACAL for tracking meter drift very compelling from the 85X8a release thread, especially as I have no real standards as of yet.Still not absolutely sure about what to get, the digitizer on the 85X8a is actually quite nice, so I'm just going to check its specifications a bit more carefully but I'm leaning towards a 3458a at this point.

author: martinr33
author_rank: Frequent Contributor
timestamp: September 20, 2021, 02:37:09 am
content: The 3458A autocal lets you use it over a wider temperature range than the Fluke units. So if your temperature is not well controlled, the 3458A can be better.The 10k/10V autocal is also pretty wonderful, although a full validation requires a lot more standards.The 3458A falls down on resistance, especially for the lower values. Everything is referenced off of one 40K standard.The 3458A has a LOT of compute resource, but you have to program it in BASIC or assembler. This approach makes up for the relatively slow IEEE488 bus. Seems that nobody uses it, although it would be helpful for fast digitizer readings.

author: toastedcrumpets
author_rank: Regular Contributor
timestamp: September 20, 2021, 11:05:27 am
content: I didn't know about the BASIC functionality, that's interesting, although typically I want all datapoints as we collect it all and process later.