Teardown of an HT118A Multimeter

[@KerryWongBlog]

Please turn off "Stable Volume" in the video playback setting (the first menu item after clicking the gear icon) as for some reason, this new KZbin playback feature made the video much noisier than usual.

[@Bob-y4x1t]

Thanks! Had the ball bearings and springs pop out of mine! Couldn't find where they went until I watched your video

[@vitajazz]

My other multimeters are over 20 years old (Fluke and B&K) and what strikes me is just how damned sophisticated this meter is, having the complexity allowed by huge production runs under various names.

[@J0cK3rFr3aK]

You said the smoothing capacitor is a cost measurement. Can you recommend a capacitor which I could solder on it? It should be a cheap and easy upgrade, right? Edit: great video, thanks for the disassembly!

[@KerryWongBlog]

You could solder in a cap around 100uF (exact value doesn't matter much) to reduce the ripple as the battery internal resistance increases (as being discharged).

[@deepbloo580]

@@KerryWongBlog I have a 100uF 25v electrolytic cap. Would that work. Is their a specific dimension?

[@KerryWongBlog]

@@deepbloo580 as long as it fits and the polarity is correct.

[@freddiesoft]

Mine gone innacurate only en VCA, it measures aproximatly 86% less voltage in any range, but in VCC and Resistance is working fine. Any idea where to look or what could happended?

[@ashchbkv6965]

6:04 Do you think it's a good idea to replace the resistor with a thick copper wire and solder it into the two holes there?

[@nick1f]

It would be a bad idea in my opinion. You need to use a metallic alloy that has a zero thermal coefficient - if the shunt gets warm, the current indication should not drift. Copper is not such a material. Besides, you will need to adjust the length of the conductor (resistor) to match exactly the original resistor, otherwise the indication may be off.

[@JuanJose-tn8yd]

10:00 Seems that chip controls the leds in the sockets and probably the backlight, maybe an I/O expansor ?

[@kcuhc84]

I own a couple of these with the Habotest name. These are very good value. The "CAT 4" designation is extremely optimistic. I can just imagine someone climbing up a ladder to a distribution transformer with one of these and everyone else running for cover! :) A very good review though.

[@stephendeepu]

I have a HTC DM 98 mutimeter, when I connect to AC supply and check the voltage. It shows as OL, not showing the value. I use another meter tot check the voltage its shows 220 V. Any ide what would be the issue with DM 98 multimeter.

[@chesterbuck1841]

my meter lasted about a tear then when i measured the voltage on a computer the display went out, the meter seems to work but no display... not sure if these are a good value or not. fuses are ok.

[@houvt230]

Thanks for posting, very interesting teardown. I just bought an AstroAI that has a near-identical PCB and ran across this. I’m assuming that IC with the markings sanded off is a small MCU that controls additional functions such as NCV, socket lighting and flashlight that are not handled by the main DMM IC. Of course we can’t see any markings on the DMM IC, but it wouldn’t seem to make sense to use a version with an LCD driver while using a separate IC for that function. I can’t read the Chinese datasheet on the LCD driver, but I can see SDA and SCL terminals, which seem to imply an I2C interface, likely shared by both the DMM IC and the additional MCU. I would be interested if you know of any DMM ICs that have an I2C interface and no onboard LCD.

[@AndrewR2130]

the eprom does have i2c interface i havent tried anything

[@DanzZerous]

Rel Δ option?

[@glenng.8254]

I just had to service the rotary contacts on mine. I found the calibration menu by pressing the function+light buttons, THEN power on which brings to CAL menu. Next, if you want to turn off the timer, hit function+max/min at power on. It actually does quite a lot, but the rotary contacts are less than desirable. They do wear out over time and need to be either replaced or cleaned.

[@jreumay]

Are there any real cat III meters at this price point?

[@ahmedalazazi2895]

Great video Can you please help me to solve the following problem I have the same multimeter I can’t see any thing on the screen Batteries and fuses are okay I heard only sounds during continuity tests One strange thing that when I test the LED while it is on the board When the board is out side the case the LED glows during testing But when the board is inside the case it doesn’t glow Many thanks to you in advance

[@Shil6480]

Sir tell me ptc value in kilo ohm

[@thietbigiaoducdiy846]

my HT118A wrong value voltage, resitor, can you fix it? thanks

[@lolvivo8783]

You dared to open the other side! Nice review

[@asepsaepudin2082]

My multimeter, in temperature measurement mode, the temperature displayed on the screen is not correct. how to calibrate it? my multimeter is Kaiwets HT118A

[@KIAMokhtari]

I have a device similar to this device, but the device beeps completely. I checked all the parts of the circuit and they were healthy. Can you guide me how to fix it?

[@abdelhamidkhattab3325]

this is a great device when comes to consider value for money and it have many good features I needed and with a very good accuracy. But I have done a big mistake with it when tring measure Over voltage value than rated and it is gone , some feature still working like amp and ohm measurement an buzzer but not any thing else. considering you have disassymplyed it colud it be a problem in the processor or in the eprom of it and any sugestion to fix it

[@josegabrielandrade4927]

Cuáles son los mods??

[@DerekWoolverton]

Another good design pattern I saw on the board, double resistors in series coming off the voltage input. This way if one resistor shorts out, you still don't have a total short.

[@Shil6480]

Sir my meter show in wrong value Ac/dc voltage, resistance sir What fault

[@diycreativeaustralia6071]

Hey bro? Can you read value resistor r1 r2 r3 r4 r5 r6 in ht118a? Thank. Because i don't know read resistor.

[@JL-bo4bh]

Very good review. I bought a Kmoon HT118A with V1.5 board 4 months ago. Used it for 2 weeks and put it aside. I recently picked it up but found something wrong. When the dial is set at the 5 light blue colored gears(for alternating signals), ALL lights(top green, entire screen, 4 insert jacks) are blinking and sound beeping at 1Hz. Everything is normal when the dial is at orange gears and NCV/Live. Changed batteries but no help. Do you have any idea what might go wrong? The chip failed to initialize in alternating signal mode? Thank you.

[@KerryWongBlog]

Does the other ranges give correct reading (e.g. Ohm range)? Also, when you are in the V measurement range, does the "Func" button allow you to change from DC to AC measurement?

[@JL-bo4bh]

@@KerryWongBlog Yes, I was able to test resistors, caps, temp and NCV. The "func" button does not do anything when the dial is at light blue gears(V, mV, uA, mA, A) and all lights are blinking with beeping sound. I cleaned the dial contacts with alcohol but no help. I'm thinking the Kaiweet V1.8B board might have fixed a few bugs. Mine is V1.5 board. Thanks.

[@radius.indrawan]

great video, Kerry. have you played with the EEPROM in this meter? i did some with my Richmeter 114A (twins of HT118A), and i think that the chip is indeed a DTM0660L, but with a twist. i'm able to change default to DC first in V-mV-uA-mA-A measurement, but i can't change the backlight on timer. have you find a way to do that? 🙂

[@E-GaN2]

Where can I get the EEPROM file?

[@bumohamedubualooy7111]

could you please do a video regarding the circuitry of wavetek 142 function generator, to be specific the hysterysis switch (ca3049)

[@KerryWongBlog]

Well, I don't own a Wavetek 142 unfortunately.

[@asifshaikh-lx5lq]

I am using same multimeter that buzzer sound is very low please help how to increase buzzer sound

[@avgear2694]

when I turn it on it shows the AC display, can the display display be DC without pressing the Func button?

[@KerryWongBlog]

Looks like you have a different firmware as mine works the opposite as yours (it goes to DC range first and you have to press the Func button to switch to AC)

[@avgear2694]

@@KerryWongBlog Can this firmware be changed?

[@KerryWongBlog]

@@avgear2694 From my previous experience, configuration values for all DreamTech DMM chips are stored in external EEPROM, so in theory you can change it if you know which location corresponds to what.

[@varadrajanmudliyar7258]

Hi Kerry What a comprehensive technical review , its very helpful for many electronics professionals. I am from India and want to buy a basic entry level multimer for smd components testing as well as ac/dc , diode , capacitor testing. I have no great knowledge of electronics but still I am looking for following parameters - 1) Very good accuracy for smaller voltages ( I am checking mostly hard disk pcb's and SSD's) 2) Sturdy reliable Auto / manual both functions. 3)Though I am atrracted to fancy color display I think they are of no practical use and consume large battery power so I will be happy with backlight colour display 4) price upto $ 50 5) Good fuse protection in case of accidental wrong connection 6) Multicomp , astroai , kaiweets all seems too be from someone OEM type which model you suggest Pls. help. Thank you Keep it up. My Best Wishes.

[@Asyss_Complex]

Looks a lot like my multimeter, but in mine the port connectors don't light up.

[@AlexAlex-em6ct]

is it good for 30$? This or MASTECH MS8268? Thank you!

[@KerryWongBlog]

In the $30 range, there's quite a bit of competition. I haven't encountered any major issues so far so it's pretty good for a 6000 meter. I don't own a MS8268, so I can't quite comment. MASTECH is a more established brand for sure.

[@andreaburrini8522]

I bought a kmoon branded ht118a, but mistakenly measuring the ac voltage on a board with the multimeter set to dc it burned out

[@KerryWongBlog]

Really?! Did you recall which DC range it was in (mV or V)? And what was the voltage being measured? I am surprised to hear that as the input section to AC and DC voltage measurements are identical and even the cheapest meters should handle this with no problems. (BTW, I just tried on mine, no issues)

[@lucbeauvais1847]

Thanks for the video. I own this meter and I love it. I am wondering if there is any pots inside to do calibration procedures? I didn't see any and you didn't mention them. I wonder if there is none because it's an auto ranging meter??? If Anyone could clarify this, that would be awesome. Thanks

[@KerryWongBlog]

There's no pots. Calibration correction data is stored in the EEPROMs.

[@lucbeauvais1847]

@@KerryWongBlog thanks very much for the reply

[@samygold100]

How is so far? Still working good?

[@lucbeauvais1847]

@@samygold100 haven't used it much since I have 5 meters. Yes still works

[@AndrewR2130]

on my meter that top right chip is marked dt1501b-1

[@KerryWongBlog]

I couldn't find any information about it. But it looks like a Dream Tech DMM chip.

[@AndrewR2130]

@@KerryWongBlog the epromm has an i2c interface their is also an Arduino library for it to pull data off it

[@mahdavimail]

Thanks for the videos

[@florinarnautu8393]

Hello, I opened up mine after it started to show only a fraction of the measured voltage , nothing seems wrong , the last good measurement was on an output pin of an ESP 32 when it measured corectly 3.27V , after this : ( measured voltage with aproximation - shown voltage) 12V -1.836V 6V-0.913V 5V-0.721V 10V-1.506V Basically it shows a 6.6 times lower value than real.

[@MrJinXiao]

wow! still definitely the same oem as my multimeter, but /way/ more price optimized. The got rid of most of the input section

[@nejoh713]

The shunt resistor too small. Just 3 second for 5 amp, resistor will burn out.

[@pulesjet]

Cheap is CHEAP. Not for CAT III chit but not going to burn or fry you.

[@johnsmith-tr3dh]

Its a POS full of "Chineseium", got it . Excellent video BTW .

[@mrdouble]

I don't know, I think I'd kinda like the flashlight feature

[@KerryWongBlog]

It's just a white LED, not that bright.

[@SeanBZA]

@@KerryWongBlog If you are working in a vehicle that light will be enough to see the connector you are probing deep in the underside of the dashboard, and as it is a part of the meter you do not need an extra thing or hand as well. Useful, but not going to be a see in the woods item.

[@felixcat4346]

Pretty obvious video. Nothing much to see here.