TEARDOWN - RuoShui 86E - 22000 count DMM - 50 EUR - Page 1
Forum section: electronics / testgear

author: hve
author_rank: Regular Contributor
timestamp: March 16, 2021, 01:09:04 pm
content: ES51932_log.zip(1.6 kB - downloaded 73 times.)ES51932_log.zipJust decided to replace my 40 year old expensive non-auto ranging DMM with 2000 counts for an inexpensive 22000 count meter:https://www.aliexpress.com/item/4000178957414.htmlSo in conclusion:- 22000 counts- Nice big screen- Rugged pretty sturdy case- Temperature, in device and with external thermocouple (included in package).- Manual HOLD- Chipset documentation online- Trimmers on the mainboard, so you might be able to calibrate the device yourself.(please share if you know how TODO this)- Cheap-ass fuses as Dave would say and minimal clearances so keep well below the suggested maximum voltages.- Only low voltage stuff with RS232 connected. Even though it seems optically isolated.- DMM Chip-set: ES51932- UART: CP2102- Serial Communication protocol: 19200 baud, 7 data-bits, 1 stop-bit, odd parityData packet out: 14 Bytes = [ range, digit[4,3,2,1,0], function, status, option[1,2,3,4], CR , LF ]In the attachment is a little Perl serial decoder script as a proof of concept, it expects device at /dev/ttyUSB0 but you can easily change that.Example session:Code:./ES51932_log.pl...00060e-4 V DC auto-22112e-5 V DCOL V DCOL Ω auto00061e-12 F auto00000e-2 Hz auto00207e-1 °C00000e-8 A DC autoAll in all not a bad investment for 50 euro.

author: LeonR
author_rank: Regular Contributor
timestamp: March 16, 2021, 03:40:14 pm
content: Is the PCB discolouration around RT1 just flux residue or is it a heating issue?

author: coromonadalix
author_rank: Super Contributor
timestamp: March 16, 2021, 05:18:16 pm
content: i would say flux residue

author: DaneLaw
author_rank: Frequent Contributor
timestamp: March 16, 2021, 07:25:46 pm
content: IN lack of software included , it looks like RuoShui is an official name of Victor and highlighted on their site-banner alongside Victor & Yitensen so same-same Victor86E and likely identical software.http://www.china-victor.com/index.php?m=content&c=index&a=show&catid=42&id=31Got the 70C myself.https://imgur.com/a/JwvLzlx//http://www.china-victor.com/index.php?m=content&c=index&a=show&catid=42&id=18

author: Pinpi
author_rank: Newbie
timestamp: March 16, 2021, 07:30:03 pm
content: What would you say is a good thing for novice people to pay attention to as a red flag when tearing down things and observing the board?

author: Algoma
author_rank: Frequent Contributor
timestamp: March 16, 2021, 09:00:42 pm
content: That USB port doesn't appear to have any real isolation at all. Avoid testing anything remotely high voltage with that USB connected.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 16, 2021, 09:12:49 pm
content: With mechanical trim pots this looks like a really old design. The main chip seem to have a 2014 date-code. One other code looks like 2018 - which is odd for a meter usually made in at least some quantety.The solder quality (or lack there of) is not that great - the flux residue with white discolurations may be future corrosion problem.Safety wise there is not much to expect from 600 V CAT rating with 250 V fuses (kind of Chinese standard). Besides the fuses the optocoupler for the PC interface is also a bit odd: they take the effort of the cut out under the OK, but the LCD interface is closer, with no cut.The 2 metal encases blocks look odd - are these relays ?

author: DaneLaw
author_rank: Frequent Contributor
timestamp: March 17, 2021, 03:04:32 am
content: On the older model 70C from Victor / RuoShui that is like a 35Euro meter, though numerous years back (2012 dated)..They do seem to use an optical chain before the USB Mini socket..IMO not a bad relae-meter and the used feels plastichousing feels way more sturdy than I usually remember seeing in multimeters in this price bracket, and comes with with a PC interface and software incl from scratch..(haven't tested the PC SW., so not sure how useable it is)- as long you have the price in mind, it's a decent meter, so far been a pleasant companion for the last 6 years in my case, and after pod-adj., quite accurate.https://imgur.com/a/JwvLzlx

author: hve
author_rank: Regular Contributor
timestamp: March 17, 2021, 12:19:20 pm
content: Totally agree with Algoma & KleinsteinI would say definitely a red flag that the serial interface seams not optically isolated,Might be interesting to hook up a scope to see the impact on noise levels, might do that later on.Do not recommend doing any serious high voltage stuff keep, it well below the advertised 1000 DC and 750 AC.I would probably not harm to probe the 240V AC mains voltages and the 400V DC, with serial disconnected!But further than that I would not go...

author: hve
author_rank: Regular Contributor
timestamp: March 17, 2021, 12:22:18 pm
content: Quote from: Kleinstein on March 16, 2021, 09:12:49 pmI have wondered about that, no markings in the cans. Only thing I can think of, since there are two, is some sort of precision resistor / resistor array..Bottom of PCB:

author: hve
author_rank: Regular Contributor
timestamp: March 17, 2021, 12:39:26 pm
content: Quote from: DaneLaw on March 17, 2021, 03:04:32 amLooking at the weird diode configuration now I would assume the serial interface is optically isolated. The USB2serial chip is powered from the host and then the data is transmitted over the (foto)diode....Revisiting the 86e:This is indeed an optocoupler, so same arrangement as in the 70C...Did you have any luck in decoding the serial output?

author: Kleinstein
author_rank: Super Contributor
timestamp: March 17, 2021, 12:53:28 pm
content: There is optical isolation, but the creep distance on the baord does not look great.The old VC70 design looks even worse in some aspect. Powering a USB-UART bridge chip via USB and than have an optical isolated UART is kind of the logical way, but there is no clear separation visible between the chip and rest of the circuit.With just RS232 one can kind of hack togeter a direct optical link with no extra power. It would not fully meet the RS232 levels, but most of the old style serial mice were working with similar levels (e.g. usually no negative voltage).

author: Algoma
author_rank: Frequent Contributor
timestamp: March 17, 2021, 01:00:09 pm
content: The Opto-Isolation is between U1 and U4 .. its U4's (Serial-USB interface) Isolation that is in most question. and doesn't benefit at all from the cut below the opto-Isolation.

author: hve
author_rank: Regular Contributor
timestamp: March 17, 2021, 01:13:55 pm
content: Have found a datasheet on the 70C chiphttps://datasheetspdf.com/datasheet/FS9922-DMM4.htmlOn page 30 there is a complete info on the serial protocol, might be a good start for the 86ECode:...RS232 transmission format is 14 byte. Its transmission rate is 2400 bps. The format is as follow14 byte output code location:a) Sing byte 1: 0f0H； h) SB1 byte: 0f7H；b) Data byte 2: 0f1H； i) SB2 byte: 0f8H；c) Data byte 3: 0f2H； j) SB3 byte: 0f9H；d) Data byte 4: 0f3H； k) SB4 byte: 0faH；e) Data byte 5: 0f4H； l) BAR byte: 0fbH；f) Space byte: 0f5H； m) EOF byte: 0fcH；g) Point byte: 0f6H； n) ENTER byte: 0fdH....

author: Kleinstein
author_rank: Super Contributor
timestamp: March 17, 2021, 01:19:29 pm
content: U4 is a standard USB to UART bridge chip (CP2102) the pins may only look odd as not connected pins may not show up. So the isolation distance is even worse than I originally thought. There is only margunal spacing from U4 to the rest of the circuit. The UART signal than goes via the opto-coupler near the USB connector to U1. It looks like only 1 way data from the DMM to the ouside.

author: hve
author_rank: Regular Contributor
timestamp: March 17, 2021, 02:50:19 pm
content: Yep now it makes sense: 19200 baud, 7 data-bits, 1 stop-bit, odd parity

author: Pinpi
author_rank: Newbie
timestamp: March 17, 2021, 05:45:26 pm
content: How can you tell if it has optical isolation?

author: Kleinstein
author_rank: Super Contributor
timestamp: March 17, 2021, 06:04:09 pm
content: The 4 pin part DB1 is an optocoupler - at least it very much looks like one and it in the right spot.

author: DaneLaw
author_rank: Frequent Contributor
timestamp: March 17, 2021, 09:50:24 pm
content: Yep..(Opto) NEC25012501 Pin-outProduct code: 07042020TBrand: OtherPhoto (opto) NEC2501 PS2501 2501 SOP-4.https://linhkienst.com/products/photo-quang-dan-opto-nec2501-ps2501-2501-sop-4-moi-chinh-hang-100

author: hve
author_rank: Regular Contributor
timestamp: March 18, 2021, 10:21:28 pm
content: I think in theory this multimeter might be supported by sigrok:https://sigrok.org/wiki/UNI-T_UT61EUnfortunately I could not get it to work, despite using the latest git version:Code:/usr/local/bin/sigrok-cli --driver=uni-t-ut61e-ser:conn=/dev/ttyUSB0 -O analog --samples 5No devices found.So i wrote a little Perl serial decoder as a proof of concept:Code:./ES51932_log.pl...00060e-4 V DC auto-22112e-5 V DCOL V DCOL Ω auto00061e-12 F auto00000e-2 Hz auto00207e-1 °C00000e-8 A DC autoFeel free to experiment if you like, I have attached the script to the first post in this topic.

author: Trader
author_rank: Frequent Contributor
timestamp: March 19, 2021, 04:46:00 pm
content: RuoShui 86E # AC Frequency Response (Bandwidth) (40~400Hz)UNI-T UT161E is up 20kHz AC

author: jebem
author_rank: Regular Contributor
timestamp: July 22, 2025, 02:55:40 pm
content: There is a new version of this VICTOR/RuoShui 86E DMM.The new version shares the same color scheme with the old one, but a few differences are visually detected when comparing the OP pictures above against the ones posted by "onlyevo" on 2024-june-12 at the Chinese MyDigit forum, here:https://www.mydigit.cn/thread-457678-1-1.htmlSome of the obvious differences:- Mainboard:Old version is 86E 2018-01-18 V0.9;New version is 2024.03.09 F052C2024 V1.2.While both versions share the same essential components, the motherboards have many differences in the layout.- Power Supply:Old version on 9V;New version on 4 x 1.5V "AAA".- Test leads sockets:Old version uses four directly soldered posts;New version uses four terminals fixed with screws.- Fuses:Old version uses two fuses in a tight space and not accessible from the exterior;New version uses two identical fuses but externally accesible. Additionally there are PCB place holders for bigger/safer fuses by installing proper fuse supports.- Input protection:Old version uses 3 x PTC;New version uses 3 x PTC and what it seems to be 2 x MOV (marked RV1 (bigger) and RV3 (smaller) in the PCB silkscreen).- Computer interface:Old version uses one internal 2501 5KV optocoupler with a USB socket on the top;New version uses one internal IR LED and a removable IR to USB adapter inserted at the rear.- Cabinet:The form factor is a bit different, the new version seems closer to what UNI-T is doing;Old version has a USB socket at the top and a 9V battery compartment/cover at the bottom;New version has a optical interface at the rear and a 4x1.5V AAA battery compartment/cover that gives access to the fuses as well.- Front panel:The two versions are nearly identical;New version uses a larger display, orange/grey rotary knob color, CAT IV 600V and CAT III 1000V, secondary REL function on the Hz/DUTY key, and the RS232/BL key of the old version is now the USB/BL key.Please see the new version pictures below, taken from the MyDigit forum referred above.Note: The last picture is from the older version taken in 2021.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 22, 2025, 03:42:16 pm
content: too lazy to put the "big" fuses

author: jebem
author_rank: Regular Contributor
timestamp: July 26, 2025, 06:06:39 am
content: It is interesting that they included this option in the design.I think they use the smaller fuses for the Chinese domestic market despite selling it to world wide via web shops, but for specific Western markets they install the bigger fuses.I think Uni-T has the same offer on some models.Anyway, I have ordered one of these new models, and some 10x38mm bigger fuses with terminals.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 26, 2025, 02:33:57 pm
content: With the larger spacing at least the 6 x 38 mm fuses could fit. It could still be a good compromise between costs and rating.

author: jebem
author_rank: Regular Contributor
timestamp: August 12, 2025, 09:09:26 pm
content: Quote from: Kleinstein on July 26, 2025, 02:33:57 pmGot my Victor 86E version 2024; this is the new version using 4x1.5V AAA batteries and removable IR Interface adapter.It is using the sameF052C2024 V1.2 2024.03.09hardware version as posted above for the new 2024 version where the pictures were taken from MyDigit Chinese forum.The component list is similar (but not identical) to the older version. Among several other components, it uses:- a 385B12/TO-92 LM385B-1.2 voltage reference;- a Cyrustek ES51932F 22000 DMM with a 4.000MHz XTAL;- a 27L2C/TS27L2C 8-pin Precision dual opamp;- two shielded precision resistors dividers;- a P6KE11CA TVS DIODE BIDIRECTIONAL 11V 5W 600W/100A peak pulse;- two MOVs and three PTCs;- a few trimmers caps/pots;- Also an Erased marking, 14-pin SMD IC, where pin-6 is connected to the RS232 button, and power pins matches a TL084 quad opamp.The bi-directional removable IR USB interface uses a CP2102 USB to UART Bridge by SiLabs, two transistors and two IR LEDs.However, the DMM can not receive commands as it uses only a single LED to transmit data.Concerning the fuse replacement, now I realize that this DMM have spare pads to install one 10x38mm (10A) and one 6x30mm (200mA) fuse supports to replace the stock 5x20mm fuse supports.I already have the 10x38mm fuse supports, and have now ordered the 6x30mm ones.