Author Topic: KKmoon KKM828: opinions?  (Read 4168 times)

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Offline DiTBhoTopic starter

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KKmoon KKM828: opinions?
« on: April 14, 2021, 04:38:39 pm »
The KKmoon KKM828 is a 2Mhz "visual" multimeter. I am tempted to buy one just to have something cheap on hands to check if the code of my MPUs are starting to move, plus a couple of measures about the batteries.


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Offline ledtester

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Re: KKmoon KKM828: opinions?
« Reply #1 on: April 14, 2021, 05:13:28 pm »
Be careful of the "2MHz" specification... it's listed as 2 mega samples per second but the bandwidth is stated here as 1 MHz:

https://www.aliexpress.com/item/4001249211470.html

but I doubt the bandwidth is even that -- it's probably more like 200 KHz.

If you just want to see if your digital I/O lines are twitching you can build a logic probe, e.g.:

https://learn.adafruit.com/some-digital-tools/logic-probe
 

Offline ledtester

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Re: KKmoon KKM828: opinions?
« Reply #2 on: April 14, 2021, 05:18:39 pm »
The KKMoon unit looks the same as the one reviewed here:

 
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Offline DiTBhoTopic starter

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Re: KKmoon KKM828: opinions?
« Reply #3 on: April 14, 2021, 06:14:00 pm »
If you just want to see if your digital I/O lines are twitching you can build a logic probe, e.g.:

I need to measure the duty cycle of I couple of PWM operating at 100Khz, some voltages here and there, if possible I would like to avoid to carry on a multimeter only for this, and I have a couple of low DAC units operating at 200Hz.

That's what I need for my simple tasks in automotive.

Umm, a colleague has just told me about her latest purchase: it's a funny DSO-shell that is found with three band-labels on Amazon
  • Kuman
  • Arceli
  • Kmoon (it looks "kkmon" but with only one "k"?!?)

Who is the original company who designed it? Who knows ... anyway, according to what she told me, she  bought Arceli which looks quite a nice little bugger and its analog bandwidth looks to be down just 1 dB @ 5 MHz.

It's declared 20 Msps sample at 5 MHz, she said the the sine wave still looked like a sine wave at 5Mhz, so probably the actual bandwidth is something close to 5Mhz. She concluded the phone telling her new little toy is still much better than anything in its price range.

It's a very low cost DSO-shall powered by a little litium batter, it's not a combined DMM + DSO, and it looks very nice. I am tempted to buy one. It's priced between 50 and 65 Euro on Amazon.

Mumble ... ;D
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Offline tunk

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Offline DiTBhoTopic starter

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Re: KKmoon KKM828: opinions?
« Reply #5 on: April 14, 2021, 09:34:05 pm »
I think they're made by Fnirsi: http://www.fnirsi.cn/

wow, it looks this. Unbelievable!!! Three companies cloning the same product  :o :o :o
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Offline gby

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Re: KKmoon KKM828: Mini Review
« Reply #6 on: June 12, 2022, 04:05:43 pm »
More out of curiosity than anything else I grabbed one of these KKM828 graphical meters. 

I have found this exact same device branded 4 different ways:
   KK Moon     KKM828
   BangGood   MT8208
   Unbranded  ET828
   Liumy         LM2020
The price is all over the place.  If you shop you should be able to get one in the US for $50 to $60 delivered.

For comparison, from the same designers/factory there is
   MT8206 20 KHz BW, 200 ksample/sec
          240x160 monochrom LCD
          2000 count not TRMS, no Temp DMM
          See HKJ's review at https://lygte-info.dk/review/DMMMustool%20MT8206%20UK.html
   MT8208 1 MHz BW, 2.5 Msample/sec
          320x240 color display
          4000 count not TRMS, no Temp DMM
   MDS8207 40 MHz BW, 200 Msample/sec
          240x160 Monochrome LCD
          6000 count TRMS with Temp DMM
          See HKJ's reveiw at https://lygte-info.dk/review/DMMMustool%20MDS8207%20UK.html

There are many hand held "real" oscilloscopes in the $100 and up category that would put the KKM828 to shame for oscilloscope functionality.  Most importantly, any "real" oscilloscope should have at least two channels to be able to do debugging with.  Any single channel scope will be inherently a limited use case item.  Looking at any signal with a meter's unshielded leads compared to an oscilloscope probe is asking for trouble above 10 MHz and maybe even between 1 and 10 MHz.

What really impressed me about the 8208:
   - The oscilloscope function is actually reasonable.  Yes limited but for what it is reasonable.
   - The oscilloscope function works for the current measurement mode!!
The higher BW 8207 has a dedicated input terminal for the oscilloscope function and presumably only works for voltage mode.  "Real" hand held oscilloscopes also would only measure voltage.

In conclusion, I was less impressed with the DMM part than I expected and more impressed by the scope part than expected.  As an additional tool I think this "graphical meter" can justify itself via quick portability to check for existence of signals or for signal tracing.  As a starter oscilloscope or "real" oscilloscope replacement it would be a poor choice.

Pros:
   Oscilloscope function works on the current ranges!!!  30 mA/div is very clean/noise free.
   Pretty good color display (twice resolution of other ones)
   Controls are reasonable
   Trigger works surprisingly well

Cons:
   Fairly poor battery life for a hand held DMM...probably 65 Hour
   Not TRMS
   I couldn't figure out how to make scope ac coupling.  Always dc coupled
   mA current range is only 250 kHz BW while voltage is over 750 kHz
   10A current range is probably lower BW also but didn't readily have 1+ ampere test signal handy
   Fastest sweep is only 2.5 uSec/div. Quoted 1 MHz BW implies 0.35 uSec step rise time
   
Quirks:
   Must enter scope from V/I ac and not dc.
      - Scope is dc coupled even started from ac mode
   If you enter from V/I dc step response is way under calibrated....unusably so
   You can enter oscilloscope mode from mV range for 30 mv/div.  But, step response is waaaay under calibrated.
      - There is no mV ac mode to start in.  Only dc.
   F4 held at turn on can turn beeps off...but setting is not remembered
   To measure higher capacitances must switch leads to two middle meter terminals

FYI:
   Works fairly well with 3 rechargeable NiMH batteries.  Fresh battery shows half full symbol.

IMHO:
   For this category best would be use meter leads and have 5-10 MHz BW, 25 Msample/sec
       - Higher BW makes no sense with meter leads.
       - Leave higher BW applications to "real" 2 or more channel scopes with scope probes.
   Like the 8208 also work with current mode.
      - clamp meter would be awesome...but perhaps struggle with screen size
   At least twice battery life
   ac/dc coupling switchable
   
 
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Offline janoc

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Re: KKmoon KKM828: opinions?
« Reply #7 on: June 12, 2022, 07:16:33 pm »
I think they're made by Fnirsi: http://www.fnirsi.cn/

wow, it looks this. Unbelievable!!! Three companies cloning the same product  :o :o :o

More like rebadging and selling under their own brand. Completely common.

And I wouldn't touch FNIRSI anything with a bargepole. Complete waste of money.
 

Offline janoc

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Re: KKmoon KKM828: opinions?
« Reply #8 on: June 12, 2022, 07:22:04 pm »
If you just want to see if your digital I/O lines are twitching you can build a logic probe, e.g.:

https://learn.adafruit.com/some-digital-tools/logic-probe

Well, specifically that one is pretty useless because there is nothing there to extend the duration of short pulses so that one can actually see them.

The probes of old had a monostable flip-flop for that. Another option that I have found and built some 30+ years ago used a binary counter with 4 LEDs for this (probably a 7493 TTL chip). If you saw the counter state change, it told you not only that a pulse (e.g. a memory access strobe) has arrived but also how many of them. That was useful to debug e.g. switch bounces or my Didaktik M hacks (Slovak ZX Spectrum clone).  Oscilloscope was an unaffordable luxury for me back then.
« Last Edit: June 12, 2022, 07:26:18 pm by janoc »
 


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