AlienTek DM40C New Multimeter with some benefits [DM40A - DM40B - DM40C] - Page 1
Forum section: electronics / testgear

author: DaneLaw
author_rank: Frequent Contributor
timestamp: December 31, 2024, 12:07:31 pm
content: A new product from Punctual Atomic (AlienTek).DMM with scope & signal.Its a small unit at merely 140x83x25mm 260g with a 3.5" 480x320 IPS touchscreen but its quite feature-rich.Promo prices in China seem to be from around 60 to 120$ depending on the model-variant & the accessory kit, while a basic DM40C with MP01 test-leads is 107$(domestic Chinese sale prices not international prices)

author: tunk
author_rank: Super Contributor
timestamp: March 06, 2025, 04:08:59 pm
content: At aliexpress the prices start at around US$80.Compared to similar products this seems to be maybe $20-30 too much.Home page:https://en.alientek.com/Product_Details/59.htmlManual:https://en.alientek.com/download.html

author: Aldo22
author_rank: Super Contributor
timestamp: March 06, 2025, 04:24:30 pm
content: Quote from: tunk on March 06, 2025, 04:08:59 pmBut it seems to be quite nice as a DMM.The cheapest version has 39'999 counts and ±(0.03%+5d) DCV Accuracy. AC Response: 10KHz.

author: tunk
author_rank: Super Contributor
timestamp: March 06, 2025, 07:02:21 pm
content: A short intro, including a teardown. Looks like it uses a GD32F427.https://mysku-club.translate.goog/blog/discounts/102513.html?_x_tr_sl=ru&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=sc

author: BeBuLamar
author_rank: Super Contributor
timestamp: March 06, 2025, 08:00:29 pm
content: It's so cheap. The specs is about the same as top of the line Fluke handheld DMM.

author: S2084
author_rank: Regular Contributor
timestamp: March 09, 2025, 03:47:04 pm
content: I got mine a week ago. I made a video.https://youtu.be/TWQ6emMZALw

author: coromonadalix
author_rank: Super Contributor
timestamp: March 09, 2025, 03:54:06 pm
content: oh the fluke yellow color ?? guess fluke may chime in ? or block some imports ?

author: DaneLaw
author_rank: Frequent Contributor
timestamp: March 09, 2025, 09:07:59 pm
content: Quote from: coromonadalix on March 09, 2025, 03:54:06 pmMany DMMs carry that "Fluke" like color scheme, and even plastic molding that got that dense fluke-like feeling/appreance.Also from relative budget brands like "Victor / RuoShui" with older models like 70C.https://imgur.com/a/victor-70c-board-pictures-old-relaymeter-from-early-2010s-sub-40bucks-with-pc-conn-JwvLzlx

author: BeBuLamar
author_rank: Super Contributor
timestamp: March 10, 2025, 12:53:43 pm
content: I guess they are not sold in the USA because if they were the US custom will seize them like they did with Sparkfun DMM's.

author: S2084
author_rank: Regular Contributor
timestamp: March 13, 2025, 04:09:43 pm
content: I measured the temperature drift of this multimeter, with a temperature difference of almost 50°C0.1% resistor with unknown ppm/°C.... I tried to isolate it in a glass, but according to the thermohygrometer readings, the difference is still 0.4°C.... with unknown ppm, this can be significantAs a source of constant voltage I used a 1.5V AAA salt batteryAccording to this measurement, with a temperature delta of the multimeter itself of 46.8 °C, the temperature drift of the multimeter is:When measuring resistances in the range of 600 ohm8.55 ppm/°C, the error is +- 0.52%When measuring DC voltage in the range of 6.0000 V24.1 ppm/°C, the error is +- 0.51%I can't evaluate these results, because this is the first time in my life I've bothered with such crap😁. But as for me, with a temperature delta of almost 50°C, an error of 0.5% is, without exaggeration, an excellent result.

author: RAPo
author_rank: Super Contributor
timestamp: March 18, 2025, 01:39:04 pm
content: There is even a video stressing that the fluke colour is importantQuote from: coromonadalix on March 09, 2025, 03:54:06 pm

author: RAPo
author_rank: Super Contributor
timestamp: March 18, 2025, 01:41:00 pm
content: My A version arrived today, after some playing also ordered a C version

author: coromonadalix
author_rank: Super Contributor
timestamp: March 18, 2025, 02:33:59 pm
content: well the teardown shows an un-soldered touch screen connector mm is the fw contain touch functions ?? or not and this item exist under other names / brandand not sure if its the same hardware on all but software crippled or have different dmm chipsetand we saw an 10khz bandwidth ?? witch is very low ?we need teardowns, mostly under the shield plate lollthks

author: S2084
author_rank: Regular Contributor
timestamp: March 18, 2025, 02:58:33 pm
content: I measured the bandwidth, the results are shown in the graphs...

author: RAPo
author_rank: Super Contributor
timestamp: March 18, 2025, 03:56:37 pm
content: The scope is 10MHz bandwith (10 bit, time scale=100ns-50s.The Signal gen is 1-50kHz for sine,swatoothand triangle and 100kHz-100MHz for square wave.Quote from: coromonadalix on March 18, 2025, 02:33:59 pm

author: danno_cj
author_rank: Contributor
timestamp: March 20, 2025, 09:44:44 am
content: This meter was released three months ago totally broken. Had severe issues with measuring resistance in circuit reading wrong values, beeping on diode mode caused by minor vibration and was affected by switching power supply nearby. Firmware updates fixed the problems with beeping and resistance by adding online and offline. The first units came without shield on back case and now they have the shield glued. I don't know if cured entirely the interference or only improved by large degree.Under metallic shields on PCB:DMM side:hy3131 dmm chipTC1746B6 precision resistor network dividerMAX6190 AESA reference 5PPM (outside of shielded area)Osc side:HCF4051 8channel analog multiplexer/demultiplexer3PA1030 10 Bit 50MSPS ADCWhat is strange is the presence of BT hardware but without mentioned in specs. It could be added later as feature or maybe is related with calibration.

author: coromonadalix
author_rank: Super Contributor
timestamp: March 20, 2025, 09:54:25 am
content: could be for the bluetoothor this pup is sold under other names / clones with more features, and maybe finding some fw in the future could unlock more things ??

author: bobocher
author_rank: Newbie
timestamp: April 03, 2025, 10:38:17 am
content: There is an update adding Bluetooth support:QuoteThis update is currently available only through Chinese version of the alientek web site. The files are hosted on baidu.com and require a baidu account, which isn't easy to get. It would be great if someone having baidu account could reupload the files to more accessible hosting.https://pan.baidu.com/s/15ScThoPTyD-jJ3ulRLjHjAPassword to access this link: o59e

author: lycreturn
author_rank: Newbie
timestamp: April 06, 2025, 03:18:22 am
content: This is the DM40 V2.1 firmware and user manual

author: Taimer81
author_rank: Regular Contributor
timestamp: May 12, 2025, 11:24:07 am
content: Quote from: S2084 on March 13, 2025, 04:09:43 pmPlease tell me how the calibration is performed. Is it internal, and is it open to the user, or do you need external software, and it is not available for the user? Thank you.

author: S2084
author_rank: Regular Contributor
timestamp: June 15, 2025, 06:41:34 pm
content: New firmware version and android applicationhttps://t.me/S2084K/24367

author: Aldo22
author_rank: Super Contributor
timestamp: June 16, 2025, 02:40:47 pm
content: I would almost buy it, as I'm interested in the specs of the DMM.But I really don't need the 50MSa/s oscilloscope and the 50kHz signal generator.Does anyone know of a 40000 counts/ 0.03% DC accuracy or better DMM, for $60 or less? (No scope, no SG).

author: RAPo
author_rank: Super Contributor
timestamp: June 16, 2025, 05:36:54 pm
content: I had the same thoughts initially.But I bought the A version. After five minutes of play, the order for the C version was out.If you have the money, try it.Your question is a tough one. I don't have the answer.Quote from: Aldo22 on June 16, 2025, 02:40:47 pm

author: Aldo22
author_rank: Super Contributor
timestamp: June 16, 2025, 06:19:52 pm
content: Quote from: RAPo on June 16, 2025, 05:36:54 pmThanks!What exactly are the differences between the A and C version?I only see the DMM counts (40k vs 60k) and a few details. The accuracy is the same and so is the scope/SG.But the C model costs almost twice as much?Is there anything else?

author: Taimer81
author_rank: Regular Contributor
timestamp: June 16, 2025, 07:26:14 pm
content: You are really so poor, so there is a huge difference between $60 and $100 to you?This multimeter is really cheap for the price that it is being sold for.The actual cost of this multimeter equals the cost of its materials.I think the costs for its development and production are covered by government subsidies in China.This multimeter is accurate and stable.I own DMM7510 and Flukt289, as well as many other multimeters, and I find it to be very fast and precise.The price is clearly underestimated.

author: Aldo22
author_rank: Super Contributor
timestamp: June 17, 2025, 09:40:53 am
content: Quote from: Taimer81 on June 16, 2025, 07:26:14 pmI don't know what my question has to do with my financial situation. Apart from that, you definitely can't get the C version for $100 here.I would like to know from someone who owns both versions, if there are any other differences between version A and C apart from the 40k vs 60k counts and the AC+DC.Has anyone who owns both compared the measurement accuracy of the DMM?

author: RAPo
author_rank: Super Contributor
timestamp: June 17, 2025, 10:44:27 am
content: I have both- The reason I bought the C version is the display of AC/DC. Both have the same accuracy.

author: S2084
author_rank: Regular Contributor
timestamp: June 17, 2025, 11:40:30 am
content: According to unconfirmed information, alientek is planning to release a DMM without scope and AFG... Also, on the 20th of this month, sales of RLC tweezers LT1 should start, I will definitely buy the tweezers

author: Aldo22
author_rank: Super Contributor
timestamp: June 17, 2025, 02:35:23 pm
content: Quote from: S2084 on June 17, 2025, 11:40:30 amThank you, I'll wait and see.Something inside me is reluctant to pay for a scope and a signal generator that won't do me any good at all.

author: jebem
author_rank: Regular Contributor
timestamp: June 18, 2025, 06:28:26 pm
content: Quote from: Aldo22 on June 17, 2025, 09:40:53 amThat is a good question.Today I have ordered the C version from the official Alientek shop on AliExpress, as they are offering discount coupons for the summer sales, although only one equipment per customer benefits from this lower price.The advertised specs for the multimeter section are published in the official User Manual v1.5 page 2, included in the doc/software ZIF file available for download from AlienTek at:https://en.alientek.com/download.htmlIndeed, for the Multimeter section, they mention that:1. Maximum display range with 39999 counts for model A, 49999 for B, and 59999 for C2. AC+DC for models B and C.Usually, the higher the maximum counts, the better precision we may get as long as the offered accuracy is good.So it would make sense to go for the model C.They also mention additional differences that are related to the display range (1) and may require additional circuit/firmware tuning:3. Maximum Resistance of 40MR for model A, 50MR for B, and 60MR for C.4. Maximum Capacitance of 40mF for model A, 50mF for B, and 60mF for C.Additionally, a *mysterious* Multimeter parameter designated as "Frequency":5. Frequency of 10Hz ~40MHzfor model A, 10Hz ~50MHzfor B, and 10Hz ~60MHzfor C. Accuracy of +/- (0.01%+5d).This last Frequency parameter seems to be related to the multimeter display maximum range.There is a constant relationship of 1000 Hz/Count when dividing the Frequency value by the total counts per model.Is this a marketing "feature"? Does it have another technical meaning?I need to read and learn more about this DMM technology.Others may know the answer and they will share it here.Anyhow, if indeed Alientek is running some sections of the circuit (or some ICs) at a higher frequency, it may require more restrictive component selection, and that would also explain part of the extra asking price.Talking about hardware design choices, according tohttps://www.mydigit.cn/thread-486604-1-1.html, a DM40C Motherboard PCB with reference "DM40 V1.1" uses these main active components:IC HY3131 DMM Front-end measurement chipIC MAX6190 High-precision voltage reference chipIC GD32F427 ARM CPUIC W25Q128JV 128Mb memory and Bluetooth chipIC EL3H7 OptocouplerIC CA-IS3741HW By ChipAnalog, High-Speed Four-Channel Digital IsolatorsIC TP4056 Battery charging managementIC HC4051 Single-channel analog multiplexer/multiplexer,IC 3PA1030 By 3peak, 10-Bit, 50-MSPS, CMOS Analog-to-Digital ConverterIC TC1746B6 High-precision voltage divider resistor network divider - Mainly used for self-changing range digital multimeterIC RUH30J51M By Ruijun Semiconductor (Ruichips), dual-channel symmetrical N-channel MOSFET field effect tube, current 50A, withstand voltage 30VSome competing well known brands take the time to remove all the labels from the larger ICs.That is really annoying. What do they have to hide?But Alientek seems to be a different Chinese brand.Indeed all the components show the identification label. I like it a lot.Alientek is not afraid to show what are they offering and what were the design choices.And that was another reason why I chose it over the other apparently feature richer with hidden ICs well known brands at a lower price.Another major reason is the absolute higher precision offered by the DM40 models when compared to similar priced models.Other respected brands/models offering the same or higher precision will cost much more than this one.EDITED to correct the mistyped website link address.

author: Aldo22
author_rank: Super Contributor
timestamp: June 18, 2025, 07:34:03 pm
content: Quote from: jebem on June 18, 2025, 06:28:26 pmThe DC accuracy is ±(0.03%+5d) for all versions.The question is how much the jump from 39999 to 59999 counts is worth to you.I don't think it makes that much difference in practice.±5d also means that there is quite a lot of randomness in the last digit, right?

author: Taimer81
author_rank: Regular Contributor
timestamp: June 18, 2025, 07:56:14 pm
content: Quote from: Aldo22 on June 18, 2025, 07:34:03 pmYou're wrong. I think you understand this, but you are looking for support and trying to convince yourself. Why should you defend a clearly losing position?

author: jebem
author_rank: Regular Contributor
timestamp: June 19, 2025, 08:51:12 am
content: Quote from: RAPo on June 17, 2025, 10:44:27 amYes, the accuracy is specified to be the same for all 3 versions.So, what is the advantage of having 3 versions, each one with increasing maximumcounts(40000, 50000, 60000) ?I have asked this to Alientek and I am waiting for their answer.What I was expecting was a betterprecisionwhen the maximum counts increase, despite all 3 versions featuring the sameaccuracy.Otherwise I can't see the point of designing 3 distinct versions.The AC+DC reading is really useful and kind of unique at this price point. That was one of the reasons I have ordered my C version yesterday.This feature is available on version B and C, so it is not what makes the difference between these two versions.I would appreciate and thank you if you could to take a couple voltage readings on your A and C meters and let us know what you see in both displays. I would expect the C version to be more precise when compared to the A version.

author: Aldo22
author_rank: Super Contributor
timestamp: June 19, 2025, 09:08:19 am
content: Quote from: jebem on June 19, 2025, 08:51:12 amExactly!Quote from: jebem on June 19, 2025, 08:51:12 amThe Zoyi ZT-225 (approx. $35) also has the AC/DC display and AC+DC.

author: jebem
author_rank: Regular Contributor
timestamp: June 19, 2025, 11:27:09 am
content: Quote from: Aldo22 on June 19, 2025, 09:08:19 amZoyi is a popular brand, no doubt. Also the Aneng rebrand several Zoyi models.The Zoyi ZT-225 may be able to show AC+DC readings, but it will not show a oscillograph on the same display showing the voltage fluctuation along the time as the Alientek DM40 series doRecently I got a ANENG AN870 (same as Zotek ZT-219) for its low cost.It is one more cheap DMM to join the others. When in doubt, compare the measurements using more than just one meter.Coming back to the DM40, another interesting and technically advanced feature is the ability to take current measurements full range from a few uA to 10A, doing auto-switching and without the need to swap probes between 10A and mA connectors.Like any other equipment running management software/firmware, there will be bugs no matter what efforts the manufacturer do to fix them.If we are lucky, each released Firmware would fix some bugs and add new ones.If we are unlucky, ir will not fix the current bugs but will add new ones.Low end, low cost market brands like Zoyi, Aneng, Alientek and a few others will bother to release a few firmware updates.That is honorable imho.For each equipment, Alientek maintains a full ZIP package that includes software, all the firmware releases with history log, and documentation.This is a transparent policy by Alientek.Also they do not remove the IC's labels as Zoyi/Aneng are doing (among many other brands).I don't see this approach on Zoyi nor Aneng.These tend to maintain the latest firmware release and sometimes they fail to clearly specify what are they fixing.Alientek and its DM40 series are unique in so many aspects. You may regret to not have bought one yourself

author: Aldo22
author_rank: Super Contributor
timestamp: June 19, 2025, 11:44:07 am
content: @jebem: Of course, these are quite different DMMs.The Zoyi is more traditional with LCD display and 3AA batteries.Everything has advantages and disadvantages, I didn't want to compare them.I only mentioned the Zoyi because you said “The AC+DC reading is really useful andkind of unique at this price point.” and I can't let that stand.

author: jebem
author_rank: Regular Contributor
timestamp: June 19, 2025, 01:38:53 pm
content: Quote from: Aldo22 on June 19, 2025, 11:44:07 amRight, but the way the DM40 show the information is quite unique on this price range.The humble Zoyi shows the AC+DC values, but as I point out before, it will not complement with extra information available on the DM40.By the way, one video that I am seeing now, shows that this AC+DC feature covers both Voltage and Current on the DM40.Don't know what the Zoyi is doing.

author: David Hess
author_rank: Super Contributor
timestamp: June 19, 2025, 01:42:32 pm
content: I did not find any specifications for input resistance of the multimeter in the documentation.

author: MiroS
author_rank: Regular Contributor
timestamp: June 19, 2025, 02:26:46 pm
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: jebem
author_rank: Regular Contributor
timestamp: June 19, 2025, 05:33:29 pm
content: Quote from: David Hess on June 19, 2025, 01:42:32 pmFor what is worth, the author of this YT video atreplied in the comments section to the user @sugarcanchannel that the internal resistance in voltage mode was the common 10MR:剛剛特地測試過，電壓擋的輸入電阻是10MΩ

author: Taimer81
author_rank: Regular Contributor
timestamp: June 19, 2025, 08:05:03 pm
content: Quote from: David Hess on June 19, 2025, 01:42:32 pmDC - 11.1 MOmAC - 4.3 MOm

author: Aldo22
author_rank: Super Contributor
timestamp: June 20, 2025, 08:28:20 am
content: Quote from: jebem on June 19, 2025, 01:38:53 pmNo, the ZT-225 cannot do that. I have never heard of that.You would probably have to use a shunt resistor and measure AC+DC voltage.But I really don't want to compare the features of the ZT-225 with the DM40C. They are very different devices in a different price range. For one DM40B I get more than four ZT-225s. This is a pointless comparison.What you can compare are the accuracy specifications for voltage measurement.

author: jebem
author_rank: Regular Contributor
timestamp: June 20, 2025, 11:30:31 am
content: I keep learning about DM40 features that seems to be not advertised, but are indeed implemented after some of the firmware updates.Current Firmware version is V2.02.For instance, F/W V1.9 update log mentions that:"1. The multimeter resistance measurement adds an online measurement mode to effectively reduce the measurement error.".This reminds me of LCR meters, where we can usually select between two or more signal amplitude voltages on the test probes.This allows to take reasonably accurate measurements for in-circuit passive components when selecting a lower amplitude in order to avoid reaching the active components conducting threshold level.Usual signal levels are 0.6V, 0.3V, and 01V, although some LCR meters feature higher levels as well for a more accurate diode testing.I suppose the DM40 is doing two level signal amplitude voltage, selectable by user operation.One major feature addition released in F/W V2.01 is the BT connection to a dedicated Alientek app for Android.The documentation explains on how to enable and use it, although it seems to be absent in the specifications.The latest Alientek software/doc package includes this Android app as well.This was possible because the hardware design included a custom designed BP2A838-20A2 chip by JL (Zhuhai Jieli Technology Co., LTD), the associated 24.000MHz crystal oscillator, and PCB BT antenna.JL is famous for producing many BT/Media player chips that are customized to fulfill the customer needs. So, most of their chips identification are unknown on Google searches and datasheets are almost impossible to find.Among the bugs fixed by F/W, one is related to the DM40 excessive sensitivity to mechanical vibration, or just 10cm drops as demonstrated on some Chinese videos. This affects diode/continuity measurements.I suppose this is caused by the use of one mechanical relay (HFD4/3-LS DPDT) in the circuit.Either the relay vibration resistance is too weak, or else the relay coil steady voltage is being driven too low.Either way, I am curious on how a firmware update can fix this hardware issue. Unless the relay coil driver circuit is being controlled by a DAC line from the MCU which I find really unorthodox in circuit design to drive a relay.

author: jebem
author_rank: Regular Contributor
timestamp: June 21, 2025, 02:02:13 pm
content: Quote from: Aldo22 on June 20, 2025, 08:28:20 amYesterday I received my ANENG AN870 (same as Zotek ZT-219).Great multimeter at such low cost.And a pleasant surprise to be presented with stable readings to the last digit for most of the times, on steady DC supplies and on passivize components.Also accurate enough to agree with my other meters on resistance and voltage readings. I have no tools to find out how accurate they are.Zotek /Aneng are doing a great work, my respect to themI have ordered a small set of 0.1% tolerance resistors ranging from 10mR to 10MR to have a better reference than the common 1% ones that I have now. Using 1% resistors, all meters I have agree within the tolerance.

author: Aldo22
author_rank: Super Contributor
timestamp: June 21, 2025, 03:00:08 pm
content: Quote from: jebem on June 21, 2025, 02:02:13 pmI'm glad to hear that because I also think these devices measure very accurately for the price in low energy applications.I have both the AN870 and the ZT-225 and believe me, the ZT-225 is even better for not much more money.I don't just mean the obvious features, but it also measures more stable in certain lower ranges, especially AC mV.But I also like the rotary switch with more positions (less switching with the buttons), the LED for continuity and NCV, AC+DC, off positions at both ends of the rotary switch, the 3xAA batteries etc.Quote from: jebem on June 21, 2025, 02:02:13 pmCan you give a link to the product?For the middle ranges, I havethis(10R to 100k at 0.1% -> Attached photo)But to calibrate the LCR meter (it's on the way), I would need 0.01R, 0.1R and 10M.

author: jebem
author_rank: Regular Contributor
timestamp: June 24, 2025, 09:01:57 pm
content: Quote from: Aldo22 on June 21, 2025, 03:00:08 pmSorry, couldn't check here these days.I ordered from "IC Nobita Store" on AliExpress but they do not offer all the range in a single power dissipation package, so I had to order some values at higher power and the rest at 0.25W.Here for the lower range with higher power:https://pt.aliexpress.com/item/1005008113029467.html?spm=a2g0o.order_list.order_list_main.56.2cc5caa4ABDl7i&gatewayAdapt=glo2braand here for the higher range on 0.25W:https://pt.aliexpress.com/item/1005008077044186.html?spm=a2g0o.order_list.order_list_main.58.2cc5caa4ABDl7i&gatewayAdapt=glo2bra

author: jebem
author_rank: Regular Contributor
timestamp: June 25, 2025, 11:48:45 am
content: Just received my 0.1% resistors to have some low cost reference components to check the DM40C that is coming my way.Meanwhile checked them on my LCR meter.These resisters are sold as being non-inductive resistors and probably they are.

author: Aldo22
author_rank: Super Contributor
timestamp: June 25, 2025, 12:25:23 pm
content: Quote from: jebem on June 25, 2025, 11:48:45 amHi jebemHave you updated the ZT-DQ02 to 1.0.8? I got mine today.Can you tell me whether the measurement deviations were large after the update (say > 2%) and in which ranges?I'm ask myself whether I should update from 1.0.7 and whether I should buy these reference resistors at all.Won't a wire do for 0.01Ω?Sorry for off-topic. It would fit better here:https://www.eevblog.com/forum/testgear/new-lcr-meters-zoyi-zt-dq01-and-zoyi-zt-dq02-(march-2025)/msg5958053/#msg5958053

author: jebem
author_rank: Regular Contributor
timestamp: June 25, 2025, 03:10:06 pm
content: Quote from: Aldo22 on June 25, 2025, 12:25:23 pmHi Aldo,ok, I have replied on the other more appropriate thread.

author: jebem
author_rank: Regular Contributor
timestamp: June 26, 2025, 07:07:53 pm
content: Got my DM40C today. What a nice piece of equipment. Very good indeed.First impressions:1. Very good multimeter on resistance, current and voltage. The supplied test leads are excellent with just 0.05R total resistance, common probes will measure 0.1R.2. The capacitance meter is good but it's internal capacitance is around 32pF, with leads 65pF, so can't measure capacitance below 300pF accurately.3. The frequency meter on the DM40C is specified to be from10Hz to 60MHz. Furthermore, in the user manual ( page 8 ) they say that the signal amplitude should be within aminimum of 20Vrms and maximum of 250Vrms!!!So it only works under large signal amplitudes.I wonder what was their design choice here. It was much more useful if it could read low level signals, or at least in the common 1 to 3V region.I do not have access to my signal generator where I am, so used a small oscilloscope with signal generator that can only supply signals around 1Vrms.Under these conditions, and using sinusoidal waveform, the DM40C worked fine in the MHz region up to 4MHz where my poor signal generator dropped the signal below 1Vrms.4. The signal generator is ok to calibrate the oscilloscope probes.The sinusoidal and square waveforms are good up to the frequency limit but the triangular and sawtooth are deformed at the higher side of the frequency spectrum.Additionally, the signal generator stops working when selectin the DMM function, although it keeps working when selecting the Oscilloscope function.5. The 10MHz single channel oscilloscope is good. It acquires and trigger signals well above the specified bandwidth and handle low level signals well.It is a nice addition, despite the poor bandwidth and single channel.

author: Awp
author_rank: Newbie
timestamp: June 27, 2025, 07:09:19 am
content: As for the accuracy of this multimeter, it was tested in this review:https://s-audio.systems/blog/alientek-dm40c

author: Taimer81
author_rank: Regular Contributor
timestamp: June 27, 2025, 07:56:15 am
content: There are differences between the models.

author: Aldo22
author_rank: Super Contributor
timestamp: June 27, 2025, 09:09:26 am
content: Quote from: Awp on June 27, 2025, 07:09:19 amThat looks very good in part, but does it not show the μV digit?ZT-225 has three decimal places in the mV range.

author: danno_cj
author_rank: Contributor
timestamp: June 27, 2025, 09:11:36 am
content: TC1746B6 precision resistor network divider which has 0.1% precision and 10ppm thermal stability was change with regular resistors. DM40A would have a lower precision and bigger thermal drift compared with DM40C.ZT-225 has three decimal places in the mV range because has 25mV scale. The lowest voltage range for DM40C is 600 mV. In order to have microvolts resolution the DM40C should have 60mV range, which is missing.

author: Aldo22
author_rank: Super Contributor
timestamp: June 27, 2025, 10:56:17 am
content: Quote from: jebem on June 26, 2025, 07:07:53 pmHave you checked that?That can't be right.The manual says: “For frequency measurement, therecommendedinput signal amplitude iswithin20Vrms, with a limit of 250Vrms.”

author: jebem
author_rank: Regular Contributor
timestamp: June 27, 2025, 12:20:00 pm
content: I guess that something was lost in translation from Chinese to English.Taking the literal "recommended" expression, the signal source should be within the recommended 20Vrms to a maximum of 250Vrms.For me it is clear that the meter requires several Volts to be able to read frequencies from 10Hz to 60MHz.I wonder why... The simpler explanation is that the frequency bandwidth is narrower than 10Hz to 60MHz, therefore an higher signal amplitude is required to compensate for the attenuation on extremes.Anyhow, I tested successfully from a few kHz to 4 MHz with a basic 1Vrms signal generator.My guess is that these frequencies are well inside the frequency bandwidth of the DM40C and 1Vrms is sufficient to be registered succefully.Realistically, the practical application of such low sensitivity frequency meter is very small.Maybe one of our members have a proper signal generator able to supply above 1Vrms and check the sensitivity and frequency response of our DM40x meter?

author: Aldo22
author_rank: Super Contributor
timestamp: June 27, 2025, 12:43:08 pm
content: Quote from: jebem on June 27, 2025, 12:20:00 pmI also believe that this is a translation problem.I mean 20Vrms sine is almost 57Vpp.Normal signal generators can generate around 20Vpp. Less at higher frequencies.That just doesn't make sense.

author: jebem
author_rank: Regular Contributor
timestamp: June 27, 2025, 02:33:47 pm
content: Quote from: Aldo22 on June 27, 2025, 12:43:08 pmYap, 20Vrms is way to low sensitivity.The test I did prove that it can read up to 4MHz with just 1Vrms, the limit of my poor signal generator.A better DSO would be needed to find out what is the minimum trigger level along all the frequency band.I have been reading on AliExpress buyers comments.One in particular was unhappy with the DM40C because he was expecting to be able to read the 32.768kHz clock oscillator signal in his workplace and it failed to trigger the signal.As he said, while we can switch from DMM to Oscilloscope to take the clock reading, it is not as convenient as being able to take all readings in DMM mode.He also mentioned a Fluke they have at work that can read it without issues (this one remark goes against the Alientek Marketing team that tries to associate the DM40 to the Fluke top series).Despite this minor Frequency low sensitivity issue, I like the DM40C for what it does well.The last digit will take time to stabilize and may not fix the value, but I see this as normal on these low cost devices.Pictures taken using the included stock probes:1: Device information2: Reading mains AC interference from my body (240VAC @ 50Hz in my location)3. Probes loosely shorted, last digit slowly change between 0 and 14. Probes shorted with alligators5. Mains reading (240VAC nominal at 50Hz in my location)6. 0.01R 0.1% resistor, last digit slowly bounces between 1 and 27. 50MR 5% High Voltage resistor8. 1R 0.1% resistor9. 10MR 0.1% resistor10. 0.1R 0.1% resistor

author: jebem
author_rank: Regular Contributor
timestamp: June 27, 2025, 04:39:16 pm
content: Some random, non controlled, frequency tests.Pictures:01. 1.00 kHz sinus signal from the device at right, as seen by the DM40C DMM ACV scale02. Same signal as seen by the DM40C DMM Hz scale03. 1.00 MHz sinus signal from the device at right, as seen by the DM40C Oscilloscope (reading 1.52 Vrms)04. Same signal as seen by the DM40C DMM Hz scale05. 4.00 MHz sinus signal from the device at right, as seen by the DM40C Oscilloscope (reading 1.42 Vrms)06. Same signal as seen by the DM40C DMM Hz scale(The DM40C could not read above 4 MHz because the SG amplitude at 5 MHz and up is insufficient)07. 1 kHz sinus signal from the DM40C SG at left, seen on both oscilloscope devices (1.81 Vrms vs 1.74 Vrms)08. 50 kHz sinus signal from the DM40C SG at left, seen on both oscilloscope devices (1.66 Vrms vs 1.63 Vrms)

author: jebem
author_rank: Regular Contributor
timestamp: June 27, 2025, 05:01:01 pm
content: Some random testing on capacitance measurements.Pictures:C01. DM40C without test leads inserted: 32 pF stable reading after a few seconds. Will not give a lower reading.C02. With test leads inserted: 63 pF stable reading, as long as cables are not touched.C03. Reading a 221 (220 pF) capacitor: 284 pF - A very good reading if we subtract 63 pF parasitic from it to get 221 pF. Close to the ZT-DQ02 LCR is reading.(these are common non branded caps with no declared tolerance)C04. Reading a 470 uF electrolytic capacitor: 445.0 uF - A good reading, close to what a ZT-DQ02 LCR set to 0.6V / 100 Hz is reading.

author: jebem
author_rank: Regular Contributor
timestamp: June 29, 2025, 01:11:41 pm
content: For some strange reason, I thought that Alientek forgot to include a REL key.After all it was my fault. I totally forgot to properly read the damn manual.Concerning the low capacitance measurement, enabling the RLE feature (via touch screen soft key) will properly read my 10pF capacitors without issues.The only procedure to follow is to give a few seconds to let the DMM stabilize itself for each input condition.Pictures:RLE_disabled - Shows the parasitic capacitance seen by the DMM using the stock leads, plus a pair of alligators from another equipment.RLE_enabled - Enabling the Relative measurement will null the reading.RLE_10pF - The smallest cap (10pF) I have access at the moment, successfully registered.RLE_220pF - The 220pF is measured perfectly as well.Did I mention the almost luxurious box the DM40 came packaged in?Inside, a cut-out foam bed cradles the equipment.Although I would trade the box for a pouch to hold all the test leads and probes. Unfortunately the store did not offer that option.

author: jebem
author_rank: Regular Contributor
timestamp: July 01, 2025, 03:53:29 pm
content: I like to do some reverse engineering of my equipment internals. At least have a part listing with parts datasheets.After some Internet searching I have a partial hardware parts listing. Thanks for this forum, some Russian and Chinese sites for internal pictures and discussion.PARTS for DM40C versionMotherboard PCB reference: DM40 V1.1BATT LN425272 Battery LiPo 3.7V 2000mAh 7.4Wh with protection circuitIC HY3131 DMM front end, one High-precision 24-bit ADC, two high-speed 19-bit ADCs,XTAL 4.9152 MHz Crystal oscillator for HY3131IC MAX6190 High-precision voltage reference chip 5PPM/CUN metallic box Shielded case - Oscilloscope analog vertical amplifier??IC GD32F427VGT6 MCU 32-bit Cortex M4 core, 200 MHz, 1 MB ROM, 256 KB RAMXTAL 26.000 MHz Crystal oscillator for MCUIC W25Q128JV 128Mb memoryIC BP2A838-20A2 8-pin by JL (Zhuhai Jieli Technology Co., LTD), BT Bluetooth chipXTAL 24.000 MHz Crystal oscillator for BT ICIC EL3H7 OptocouplerIC EL3H7 OptocouplerIC CA-IS3741HW By ChipAnalog, High-Speed Four-Channel Digital IsolatorsIC LT61-117 6-pin VPS8505 transformerIC LT61-113 6-pin VPS8505 transformerIC VPS8504B Micropower Isolation Power SupplyIC VPS8504B Micropower Isolation Power SupplyIC TP4056 Battery charging managementIC HC4051 Single-channel analog multiplexer/multiplexer,IC 3PA1030 By 3peak, 10-Bit, 50-MSPS, CMOS Analog-to-Digital ConverterIC TC1746B6 High-precision voltage divider resistor network divider (DM40Adoes not use it - Just a few resistors in its place)IC RUH30J51M By Ruijun Semiconductor (Ruichips), dual-channel symmetrical N-channel MOSFET field effect tube, current 50A, withstand voltage 30VK HFD4/3-LS By Hongfa, Subminiature signal relay of 4th generation, DPDT, 100MHz contacts, 3V / 90R coilIC 174 F163H 4-pin smd (DM40A uses 174 F215H) - OptocouplerIC 174 F163H 4-pin smd (DM40A uses 174 F215H) - OptocouplerD's SD B0520LW Schottky Barrir Diode 20V 500mAConcerning the unidentified chips, I put a question on the another thread at:https://www.eevblog.com/forum/chat/what_s-this-please-(component-advice)/msg5964329/#msg5964329Hopefully someone will know what these chips are. datasheets would be nice too.EDIT: Many Thanks toGamalotmember who was able to identify the unknown components above.https://www.eevblog.com/forum/profile/?u=112468

author: jebem
author_rank: Regular Contributor
timestamp: July 04, 2025, 05:16:42 pm
content: Revisiting the less than optimal Frequency readings of the DM40C.I got a better low cost signal generator - the Juntek JDS-2900-60M, able to deliver a minimum of 5Vpp at 60MHz on sinusoidal waveform.I checked the output signal with a 120MHz oscilloscope, so even assuming an error of 10% of the oscilloscope readings, the signal generator sustains the claimed specificationsTook a few random tests on the DM40C.What I see is a severe decreasing in sensitivity with increasing frequency. So the bandwidth seems to be very poor.It requires a minimum of:->50 mVppto register low frequencies up to a few kilo-hundred Hertz;->1.7 Vppat 10MHz;->6 Vppat 20MHz;->More than 10 Vppat 30MHz and above. How much more I can't tell, as the SG is limited to 20Vpp up to 10MHz, 10Vpp between 10MHz and 30MHz, and 5Vpp above 30MHz.In the end I tend to believe that the Alientek statements found in the User Manual are actually credible to some extent.Pictures:1. 50mVpp at 60kHz - Ok2. 40mVpp at 60kHz - Fail3. 50mVpp at 10kHz - OK4. 1.7Vpp at 10MHz - OK5. 1.6Vpp at 10MHz - Fail6. 6Vpp at 20MHz - OK7. 5Vpp at 20MHz - Fail8. 10Vpp at 30MHz - Fail

author: Aldo22
author_rank: Super Contributor
timestamp: July 04, 2025, 08:46:48 pm
content: Quote from: jebem on July 04, 2025, 05:16:42 pmI think this is pretty normal for a frequency counter in a DMM.To be honest, at > 1kHz I use the oscilloscope anyway, so I'm generally not that interested in this feature.

author: jebem
author_rank: Regular Contributor
timestamp: July 05, 2025, 08:20:05 am
content: Quote from: Aldo22 on July 04, 2025, 08:46:48 pmAbsolutely, I didn't bought this one thinking it could be a useful frequency counter. A digital oscilloscope is good enough for most applications. For precise measurements I use my vintage professional Fluke 1920A.(I used these Flukes on my job as a RF telecom engineer back in the late 70's. I bought one of them at the time and later converted it from batteries to AC outlet only, by adding a power supply regulator to get rid of those pesky NiCd cells)

author: Aldo22
author_rank: Super Contributor
timestamp: July 05, 2025, 08:50:44 am
content: Quote from: jebem on July 05, 2025, 08:20:05 amA more interesting test would be to check if the AC accuracy is really ±(0.3%+15d) up to10kHz. According to the specifications it should be able to do that, afaics.That would be a small advantage over other inexpensive DMMs.

author: easa
author_rank: Newbie
timestamp: July 07, 2025, 12:07:04 pm
content: For some reason, no one noticed that such an advanced device does not show an incorrect connection of measuring probes in terminals. When trying to measure the voltage when the probes are in terminals for measuring the current.

author: S2084
author_rank: Regular Contributor
timestamp: July 15, 2025, 08:38:23 am
content: New firmware version and android applicationhttps://t.me/S2084K/15773/26022

author: BH3XON
author_rank: Contributor
timestamp: July 17, 2025, 08:11:29 am
content: I understand that the voltage divider resistors for A and B/C differ in both accuracy and package,so I’m considering getting the DM40B as the most cost-effective option.By the way, do you know if the DM40 can display both current and voltage at the same time?Something like the FLUKE 8808A, where you can press Shift + C/V to show both simultaneously.That would be really handy when testing power supply input and output, even if there’s some error introduced by wire losses.Quote from: Aldo22 on July 04, 2025, 08:46:48 pm

author: jebem
author_rank: Regular Contributor
timestamp: July 21, 2025, 03:39:41 pm
content: Quote from: easa on July 07, 2025, 12:07:04 pmAs far as I know, in this model there are no warnings of any form if the user makes such a mistake - I expect to see the built-in 10A ceramic fuse to blow off.But that is the normal way multimeters work, even top brands.Yes, some models will warn about mistakes, and just a very few will block you from making mistakes, the rest of it will allow you to go ahead and blow the current fuse as well.

author: jebem
author_rank: Regular Contributor
timestamp: July 21, 2025, 03:50:10 pm
content: Quote from: BH3XON on July 17, 2025, 08:11:29 amThat is not possible as far as I know.You select only one single option at a time from the offered six function buttons seen in the touch screen: V, A, R, C, D, Hz.Also, I wouldn't connect this DMM test leads to measure Voltage and Current at the same time. You either insert the red test lead into the panel V/R/C/D/Hz upper socket, or to the A/mA/uA lower socket.

author: BH3XON
author_rank: Contributor
timestamp: July 22, 2025, 12:55:54 am
content: Quote from: jebem on July 21, 2025, 03:50:10 pmIt would be great if it had that feature — even better if it could calculate and display power as well.The FLUKE 8808A can show both voltage and current simultaneously, and while there’s some inaccuracy due to voltage drop across the wires, it's still very convenient for quick, rough measurements.

author: VASILISK
author_rank: Newbie
timestamp: October 07, 2025, 10:50:48 am
content: I have made a new video you can watch it about the model c .✨Alientek DM40C 3 in1 Multimeter Oscilloscope & Signal Generator - full Review & Tear Down✨https://youtu.be/-CCQZ08o6qM?si=iZgEcIpw3J2QdWVF