Hioki 3237  5.5 digits meter teardown - Page 1
Forum section: electronics / testgear

author: coromonadalix
author_rank: Super Contributor
timestamp: October 29, 2023, 01:58:03 am
content: Just grabbed this on Fleabay, i was curious of its internals199999 count Bench DMMDac : Burr Brown ADS1250U 20 bit ??Next to it IC22 : An OPA2277 10µV, 0.1µV/˚C, High-Precision, Low-Power Operational AmplifierReference : An LT1027 thks @AVGResponding Very Low Drift: 2ppm/°C Max TC Precision reference with extra-low driftFor sure not the LM199 399 or even an LTZ1000 lollMain Cpu : Renesas H8S/2134F Web says : Microcontroller for Office Equipment ApplicationsEeprom i think : 8 pins Soic 3771 if someone find a datasheeti could try to read it ?0026343ADC clock : An EXO 3 clock module 18.432 Mhz ??Precision Resistor : Caddock 1776-C4Display Drivers : 2x TD62083F 8CH DARLINGTON SINK DRIVERThe front panel plastic is very thin / brittle, i dont think it would survive some impact, sure its now yellowishUnder the pcb i only see some transistors, no other ic's, i dont want to dismantle more than thisFor sure they have put the cpu far away from the front panel ??

author: coromonadalix
author_rank: Super Contributor
timestamp: October 29, 2023, 01:59:51 am
content: ReservedSeems more an ADC on steroids than a real meter ??They exist as 3237, 3238, 3239 way overpriced for what they are ...I did start a thread about Hioki calibrations ... but never got any responsesNo schematicsJust some user manual and code snipets : Labview C# C++ Mathlab Python VBA

author: dobsonr741
author_rank: Frequent Contributor
timestamp: October 29, 2023, 03:00:38 am
content: The Manual - no schematics however.

author: Martin72
author_rank: Super Contributor
timestamp: October 29, 2023, 10:32:29 am
content: QuoteHioki also consistently does not give out anything, and if the devices have not been manufactured for ages...

author: coromonadalix
author_rank: Super Contributor
timestamp: October 29, 2023, 11:43:44 am
content: some of theses 3237 goes down to 2001

author: AVGresponding
author_rank: Super Contributor
timestamp: October 29, 2023, 12:38:57 pm
content: Quote from: coromonadalix on October 29, 2023, 01:58:03 amThe reference is the LT1027. Bit of a strange/old fashioned choice, but then that's Hioki...https://www.analog.com/media/en/technical-documentation/data-sheets/1027fcs.pdf

author: coromonadalix
author_rank: Super Contributor
timestamp: October 29, 2023, 01:04:52 pm
content: Maybe they tried the best bang for the buck in thoses daysHaven't found a thing for the 8pins soic ic, i do think it's an eeprom for the cal constants or more ??OK Works so far with Termite, null modem cableAs per manual*IDN?HIOKI,3237,0,V1.10So far, nothing is shown on the rs232 port when the meter boot's up

author: coromonadalix
author_rank: Super Contributor
timestamp: November 30, 2023, 11:03:45 pm
content: you have +8v and -8v symetrical supply (ic71 and ic72) and +5vdc (ic74) coming from the xformer secondaries / blue wiresaround 7vdc for the 2 small xformer wires who goes on a rectifier bridge, and regulated (ic75) at 5vdc for the cpu sectionblue wire pin 1 and 2 = 4.8 ohmsblue wires pin 3 4 5 = 3-5 = 14 ohms, 3-4 or 4-5 = 7 ohmstwo small yellow "ish" wire = 0.9 ohmssome front pcb section ground is not common with othe meter ground sections, that's normal, you have to know where your probing is grounded

author: AVGresponding
author_rank: Super Contributor
timestamp: December 01, 2023, 04:36:05 pm
content: I thought RS232 needed +/-15V or so?I bet even with the somewhat odd choice of reference, it has pretty good performance.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 01, 2023, 04:43:35 pm
content: RS232 could be just OK with +-8 V, especially modern parts usually already accept +-5 V. The old PCs used +-12 V. New designs often use max232 or similar charge pumps to run of 5 V and create a voltage a bit under +-10 V.

author: fzabkar
author_rank: Super Contributor
timestamp: December 07, 2023, 07:27:37 pm
content: Quote from: coromonadalix on October 29, 2023, 01:58:03 amMB3771 power supply monitor:https://www.mouser.com/datasheet/2/100/002-08511_MB3771_Power_Supply_Monitor-931495.pdf

author: coromonadalix
author_rank: Super Contributor
timestamp: December 07, 2023, 10:01:37 pm
content: could be that one THKSif it is, i dont see on the pcb where the calibrations would be stored, unless it's directly in the mcu?

author: fzabkar
author_rank: Super Contributor
timestamp: December 07, 2023, 10:15:15 pm
content: H8S/2138 Group, H8S/2134 Group,H8S/2138F-ZTAT™, H8S/2134F-ZTAT™,H8S/2132F-ZTAT™Hardware ManualRenesas 16-Bit Single-Chip MicrocomputerH8S Family/H8S/2100 Serieshttps://www.renesas.com/document/man/h8s2138-group-h8s2134-group-h8s2138f-ztat-h8s2134f-ztat-h8s2132f-ztat-hardware-manualI think I can see a NiCad (?) battery on the PCB. Maybe the settings are stored in RAM???

author: coromonadalix
author_rank: Super Contributor
timestamp: December 08, 2023, 01:27:47 am
content: no sorry loll the green one is a capacitor ... or a mov due to its thickness, but an input part you see a line of resistors / voltage dividerand the black round thing 5A1 marking is the buzzer, had to put a tape on it, very loud loll