ADCMT 7480T 8.5 digit multimeter - Page 1
Forum section: electronics / general

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:13:17 am
content: Thought everyone might enjoy some details and pictures of the the ADCMT 7480T 8.5 digit multimeter.ADCMT separated from Advantest in 2003.The 7480T was made by ADCMT for Advantest, they don't sell it and I've been told to contact Advantest for information. I have not received any reply from Advantest. There are no public docs on the meter, I have only found details on its little brother the 7470 7.5 digit version.The details I do know:LTZ1000CH ref - 13K/1K temp set point.9K ohm hermetic AE branded resistor ref.Artifact calibration - 9-11 VDC/9-11Kohms.DCV and 2/4 wire ohms support. 1000 VDC/10 meg ohm top ranges.Has internal calibration which is recommended to be used every degree C/ 24 hours. A full DCV/resistance internal cal takes 4.5 minutes.When the meter boots it says 6581T on the display, it also reports 6581T via GPIB. USB is disabled.Fan airflow only runs over the power supply/digital section.Front/rear jacks selected electronically(rather useful).No idea when it was calibrated but it arrived reading within 1 PPM of the last cal value of my 732A - hard to complain about that.

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:15:23 am
content: pics:

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:16:50 am
content: pics

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:17:51 am
content: pics

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:19:13 am
content: pics

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:20:25 am
content: pics

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:22:06 am
content: pics

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:23:35 am
content: pics

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:24:53 am
content: pics

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 05:26:43 am
content: picsAnd docs - I had google translate the 7470(not the 7480) manual which is 98% the same in term of the menus and such. I can find no actual 7480 documents.

author: Vgkid
author_rank: Super Contributor
timestamp: January 04, 2018, 05:44:34 am
content: Thanks for all of those pics , the board in img 2426 with the transistor array in interesting.

author: Pipelie
author_rank: Regular Contributor
timestamp: January 04, 2018, 06:07:21 am
content: Thanks for all of those pics.I saw a ADCMT 7408T a yeas ago on 38Hot , here it is:http://bbs.38hot.net/thread-193743-1-1.htmlThe seller asking 2.88W RMB for this unit, last time I checked it still there. I have a change to have a look what's inside recently, it appears to be a Simplified version of 6581?

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 06:10:26 am
content: Quote from: Pipelie on January 04, 2018, 06:07:21 amI believe an updated version of the 6581 is exactly what it is. I have a feeling Advantest has a need for it, possibly for internal testing etc and commissioned ADCMT to make it for them.It would be really nice to find published specs for the unit.

author: zhtoor
author_rank: Frequent Contributor
timestamp: January 04, 2018, 06:58:09 am
content: LTZ1000CH rebranded PHILIPSanybody know of such an arrangement?-zia

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 07:00:21 am
content: Quote from: zhtoor on January 04, 2018, 06:58:09 amUmm, try again. The ref was made in the Philippines.

author: Pipelie
author_rank: Regular Contributor
timestamp: January 04, 2018, 07:01:09 am
content: Quote from: TheSteve on January 04, 2018, 06:10:26 amSPEC in the manual you uploaded, check page 80. hmm, that's the manual of 7470http://www.adcmt.com/techinfo/product/catalog_ducument/pdf/catalog_Gene_7470.pdf

author: 3roomlab
author_rank: Frequent Contributor
timestamp: January 04, 2018, 07:02:44 am
content: hmmm the manual only states accuracy spec to 7.5 digits. did i miss anything? or it wasnt intended for 8.5D operation? (i assume 8.5D in GPIB?)and running my eyes over the R7/R4 in pic 2442, is that really a precision 120 ohm in SMD format?

author: zhtoor
author_rank: Frequent Contributor
timestamp: January 04, 2018, 07:05:35 am
content: Quote from: TheSteve on January 04, 2018, 07:00:21 ammy bad!!!

author: TheSteve
author_rank: Unknown
timestamp: January 04, 2018, 07:15:56 am
content: Quote from: 3roomlab on January 04, 2018, 07:02:44 amThose are the specs for the 7470, not the 7480. The 7470 is limited to 7.5 digits, the 7840 allows 8.5 digits.That is a 120 ohm SMT resistor, right above the super tiny 13k/1k divider resistor.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: January 04, 2018, 07:48:08 am
content: Thanks for all of those pics!Only one question: what is a lower limit of the integration time in this meter (how fast is it)?

author: Andreas
author_rank: Super Contributor
timestamp: January 04, 2018, 06:29:08 pm
content: Hello,interesting.Are the blue resistors FLCY from Alpha Electronics?With best regardsAndreas

author: branadic
author_rank: Super Contributor
timestamp: January 04, 2018, 06:48:19 pm
content: QuoteThey are networks with 2 resistors, so maybe SLD series? You can see the designations "7K34 XF 10K0", "17K0 XF 19K0" and "..K0 XF 17K0". The last one is not fully visible on none of the pictures.I also wonder what this magic board with SOT23-3 ic is for.-branadic-

author: Mickle T.
author_rank: Frequent Contributor
timestamp: January 04, 2018, 06:48:46 pm
content: Its SLD and SS resistor networks from Alpha Electronics.I think "..K0 XF 17K0" - is a 10k-17k.

author: Andreas
author_rank: Super Contributor
timestamp: January 04, 2018, 07:36:42 pm
content: Quote from: branadic on January 04, 2018, 06:48:19 pmPerhaps a multiplexer built with discrete FETs?with best regardsAndreas

author: branadic
author_rank: Super Contributor
timestamp: January 04, 2018, 08:13:19 pm
content: QuoteOkay... you seem to have a schematic of this section, can you link it here?-branadic-

author: TheSteve
author_rank: Unknown
timestamp: January 05, 2018, 07:26:26 pm
content: Quote from: branadic on January 04, 2018, 06:48:19 pmI assume it is the multislope converter.

author: TiN
author_rank: Super Contributor
timestamp: January 05, 2018, 07:49:09 pm
content: Similar to Keithey 2001/2002 ADC, that module with epoxied discrete SOT23's JFETs likely to be part of ADC charge switches. Epoxy and separate substrate to help with isothermal construction and stable leakage conditions. You can also sorta guess presence of 0402 or 0603 SMD resistors in between the active parts, perhaps setting ratio currents for multislope ramp operation. Resistors near the module look like normal 5% 0603's, so those likely just digital control lines pullups/series.

author: TheSteve
author_rank: Unknown
timestamp: January 05, 2018, 08:36:35 pm
content: A better closeup of it.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 05, 2018, 09:04:15 pm
content: I don't think the extra substrate is for the ADC - my guess is more like the main multiplexer. The part on the right of the ref. board looks more like the input stages. Just on top of the od board there seem to be 4 LM399 - like used to control a bunch of JFETs. This would be too slow if used for switching the ADC.The ADC is more like on the other side of the reference board. There are silk screen prints with slope an integ and comp.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: January 05, 2018, 09:16:34 pm
content: This is a 12:1 (or so) guarded input multiplexer.ADC is here:

author: TheSteve
author_rank: Unknown
timestamp: January 06, 2018, 05:13:05 am
content: Quote from: Mickle T. on January 04, 2018, 07:48:08 amFastest is 1 millisecond, slowest is 100 NPLC.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: January 08, 2018, 07:36:56 am
content: Quote from: TheSteve on January 06, 2018, 05:13:05 amThank you.As far as I can see, 7480T Input amplifier and ADC are simpler than 6581(D,T) due to lack of high speed modes. 6581 have a second, wideband Inp. Amp. channel, second pair on Cint/Caz capacitors with selector, HS x1 mode of the slope amplifier e.t.c. Both 6581 and 7840T have a lack of input precharge compensation, have the same ADC and potentially the same INL and TC problems. 7480T don't have a DCI measurement mode, all of the DCI shunts are used as artifacts only for Ohms calibration.

author: martinr33
author_rank: Frequent Contributor
timestamp: January 10, 2018, 05:44:29 am
content: Advantest units have always had funky resistor arrays. Here's one from an old 6.5 digit unit.It is in the reference amplifier section.

author: zhtoor
author_rank: Frequent Contributor
timestamp: January 10, 2018, 03:23:23 pm
content: Quote from: martinr33 on January 10, 2018, 05:44:29 amwhat are those coiled copper (?) wires, temperature compensators?regards.

author: HalFET
author_rank: Frequent Contributor
timestamp: January 10, 2018, 07:15:30 pm
content: Quote from: martinr33 on January 10, 2018, 05:44:29 amTrue, but their RF gear its build quality is pretty ludicrous. I have really old units from them that internally look as if they were designed yesterday with modern CAD software.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: January 11, 2018, 11:15:30 am
content: Quote from: zhtoor on January 10, 2018, 03:23:23 pmMy guess, and it is only a guess, is that it is to mechanically divert stress from expansion or contraction of the leads. So distantly a type of temperature comp. Zlymex worked out a system to provide temperature compensation to wire wound resisters which utilized trim resisters and short sections of copper wire for final trim. You will have to search his posts to find it. I think if they wanted to do that type of T.C. they would have included those trim components on the hybrid itself and trim it while it is still separate from the main board for ease of manufacture.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: January 24, 2018, 06:53:34 pm
content: Good news: 7480T hybrid MUX is pin-to-pin compatible with the R6581 oneBad news: it does not have one FET switch