ADI ADMX3652 - 6½ Digit, ±20 V DVM - Page 1
Forum section: electronics / general

author: Jendas
author_rank: Newbie
timestamp: October 15, 2023, 09:10:10 pm
content: Hi All,some new ADC module or rather DVM withrange ±20 V, 6½ digit resolutionand UART interface withSCPIsupport from ADI. Maybe for some voltnuts hereMore specs on ADI page:https://www.analog.com/en/products/admx3652.html#product-overviewand ADI wiki:https://wiki.analog.com/resources/eval/user-guides/admx3/admx3652and is available on Farnell too, for 660 USD:https://www.newark.com/analog-devices/eval-admx3652z/evaluation-board-digital-voltmeter/dp/72AK1816?st=admx3652Jendas

author: dobsonr741
author_rank: Frequent Contributor
timestamp: October 15, 2023, 11:18:09 pm
content: Wow. Could not wait to see a teardown. Or a guessing game what ADI parts are making it up.The specs only suggests and did not state the two input channels are galvanically isolated, only hints with the 70V max rating. Does anyone know?

author: jbb
author_rank: Super Contributor
timestamp: October 16, 2023, 02:08:18 am
content: I think this will make test engineers somewhere happy; might be able to solve a problem without forking out for a whole new 6 1/2 digit DMM. Especially if there are multiple testers.I wonder how the go/no-go decision was made. It’s not exactly an evaluation board… but I guess Analog does make some modules / mini bench gear.

author: coromonadalix
author_rank: Super Contributor
timestamp: October 16, 2023, 02:22:44 am
content: what a joke at this pricebut i must admit, they permit you to CAL the unit directly if you have a reference source ....very high baud rates speeda few goodies, but hard to justify this pricing for methey should be honest from the start they use FTDI drivers it seems, instead of a no name driver package loll have to read their spec sheetsand i would have made some provision say, 2x external relays controls pins, say to provide 200v and 1kv input, just add precision dividers and tvs / gaz tube discharge etc ...

author: jbb
author_rank: Super Contributor
timestamp: October 16, 2023, 05:33:30 am
content: Quote from: coromonadalix on October 16, 2023, 02:22:44 amYeah, it's pretty expensive. Still cheaper than a comparable multimeter though (assuming 2V and 20V ranges will be sufficient)!Quote from: coromonadalix on October 16, 2023, 02:22:44 amThat sounds suspiciously like a multimeter to me...I expect that by the time someone designs a multimeter-like front end for this sort of module it probably makes sense to go all-in and deploy a reference and ADC yourself.

author: Andreas
author_rank: Super Contributor
timestamp: October 16, 2023, 06:58:54 am
content: Hello,for a multimeter I would at least expect a INL specification.And the 70V Maximum rating between analog input and digital GND is also too low for a serious DMM.My best guess for the parts used:Some microcontroller with integrated sigma delta converter like ADUCM36xA ADR1399 voltage reference divided by factor 3.With best regardsAndreas

author: guenthert
author_rank: Frequent Contributor
timestamp: October 16, 2023, 07:23:39 am
content: Quote from: jbb on October 16, 2023, 02:08:18 amBut it's not a DMM. It's a multi-range DC ADC + voltage reference only. Building a DMM with commonly available features using that will double the prize I'd think.I rather expect to find it to be part of very specialized (and very expensive) gear.I couldn't find it stated, but I miss galvanic separation between input and digital output and power supply.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 16, 2023, 07:43:34 am
content: The infos on the module are a bit sparse and in part contradictory (different accuracy specs in the datasheet, Wiki page and product page).A point that is not clear is if the inputs and the power are isolated from each other.The noise and claimed accuracy look good, but the input bias (1 nA) and input resistance are not that good. It may not be possible to just add an input divider divider.Lower input resistance for the 200 mV range is odd. Noise for the high PLCs looks no longer that good - maybe some 1/f noise from a non AZ input amplifier.Given the noise specs, especially for low PLC this suggests a relatively good SD ADC with some +-2.5 V FS range. It may well be separate µC and ADC chips.There also seems to be a 2.5 V internal "supply" that seems to be critical to have an error message for it.The protection specs also don't look that good - external connections may want added buffers and protection. To me this does not look like a very practical product.

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: October 16, 2023, 08:33:32 am
content: Hi all,for 6.5 digits resolution 200 seconds are needed (datasheet),limited to 2000m altitude (nothing for a mountain-man),no isolation (at that price!) and limited range.For someone who can affort it the small form-factor is nice,else get a used HPAK/Fluke-DMM.Best regards

author: iMo
author_rank: Super Contributor
timestamp: October 16, 2023, 08:35:28 am
content: Quote from: dobsonr741 on October 15, 2023, 11:18:09 pmYep, at least we'll get how to design the AFE, finally..QuoteWith the ADUCM360 and such a trimmed AFE it is easily achievable, indeed..The INL of the ADUCM360 itself is +/-10 - 20ppm of the FS based on the DS.The 310mA power consumption indicates the module has got a part of the ADC ovenized, imho.PS:For example:ADUCM360+others around 10mA@5V .... 10mA@5VVref 30mA@15V .... 100mA@5V (switcher)AFE 15mA@+/-25V .... 200mA@5V (switcher)Total ~310mA@5V..

author: coromonadalix
author_rank: Super Contributor
timestamp: October 16, 2023, 01:02:53 pm
content: i can understand this design or applicationsbut as other(s) wrote, specs are somewhat incompleteand yes we should see that module as an advanced ADC .... not a dmm loll i thought so, my badYou can get very good adc in the 12-14-16 bit ranges and more, some can go at 125Mbs of sampling too or way higher ...As a DMMYou have many pci pci-e pxi pxie card / devices who can be bought cheaper in some models, sure the form factor is not helpful .... and some rare usb dmm's from keysight or NIThere is some ideas or project here about an 6.5 digit front end ... even the lm399 zenner or the famous ltz1000 pricing has gone bonkersI can't go over this Analog pricing ....

author: miro123
author_rank: Frequent Contributor
timestamp: October 17, 2023, 08:42:27 am
content: I've looked at proveded documentation.My conclusion - It is definitly not substitute of DMM even if you need limited DC range.Spec is marketing pumped. No exception here any semiconductor manufacture do it. Mixing typical with most likely and average parameters.e.g. ADMX3652 vs HP 34465a DMM6500- AD - 90 days accuracy: <17 ppm of reading range at 2 V range- HP34465a - 90 days 10V native range - 0.0020% + 0.0004% - Tacal = +-2C- DMM6500 - 90 days 10V native range - 0.0020% + 0.0005% - Tacal = +-5CGiving the noise parameters where all integrated SD ADC excels and not giving INL is another example of marketing trick.Application that require decent DC accuracy and small size is the niche of this product.

author: Jendas
author_rank: Newbie
timestamp: February 03, 2025, 11:14:54 am
content: Hi,Just out of curiosity, I found a photo of the PCB on this website:https://www.armbbs.cn/forum.php?mod=viewthread&tid=127097Best regards,Jendas

author: MadTux
author_rank: Frequent Contributor
timestamp: February 04, 2025, 01:42:52 pm
content: Likely for similar applications, where those ready to use DC/DC converter modules are used, high end servers, FPGA boards, scopes....Lazy engineer and like xray machine or electron microscope and you want accurate beam voltage/current but are too lazy to implement you own ADC+reference+input circuitry, just drop a few of those, especially if the price doesn't matter.....