Hi there, this is
Part 3: the PCBof the Extech MN16 Teardown.
Pic 24: Detail Input section seen from bottomPic 25: Detail Input section seen from topPic 26: Detail Input section seen from side.The input section shows no magic (Pictures 24 to 26). It seems to be well constructed and laid out. The large cutouts for the jacks fit into extruded plastic tubes in the top of the case wich for sure will suppress any arching. The high current paths are very large and also there is additional solder on them. This seems to be able to handle any high currents one wants to pass through this small meter. The fuses on the other hand are only the small ones but seem to be HRC-Types (That was the word, right?).
There are some Movs and most devices are larger SMD types that seem to be able to handle some power.
What I clearly dislike is the construction of the jacks themselves: There is only one post going to the PCB and in the back half of the case is no support underneath the jacks. This means every time one puts the connectors in or takes them out, the single solderjoint is stressed. Bad, bad...
Also, the very large soldered areas do not all look well. As if the termal mass of the area was too high to get a proper soldering.
Also, can anyone tell me, what the large blobb of solder on the shunt is good for (Picture 26)?
Pic 27: Detail main IC seen from bottomPic 28: Detail main IC seen from aboveThe main chip cannot be identified, sorry folks (Pictures 27 & 28). But one can clearly see which screws have to be taken out to rip out the PCB. Also one can see lots of trimpots. I wonder if this meter can be calibrated to do better than the poor ratings stated in the manual.
Pic 29: Detail of operational amplifier section from topPic 30: Detail of operational amplifier ICPic 31: Overview of operational amplifier section from the other sideThere is one TI chip that I suspected to be an ADC (pictures 29 to 31), but in fact it seems to be an operational amplifier. I did not dive into this section any deeper, go figure it out yourself if this is of interest.
Pic 32: Detail battery wiresPicture 31 shows also the connection of the battery: The wiring goes through the PCB to be soldered on the top then. Maybe to take some stress out of the connection, or maybe they decided it would be more easy or cheaper to solder it on that side. Who knows. But then take a look at picture 32... just one more addition to the cheapish look and feel.
So for a conclusion... I don't really know.
This meter gives lots of functions that may be nice to have in many situations. But the accuracy is too bad to make it a good solution for any special task. I feel this is a good allrounder to have on your bench but no specialist by any means. For example, if there is a load of capacitors to be sorted the capacity funktion will serve you well, but if you need to know what capacity one capacitor really has you better look out for a more accurate device.
The 10A range is a plain joke: "
For 30 sec. MAX every 15 min.". Well, large fuses are expensive... What the hell am I supposed to measure with such a device?!
I cannot get rid of this "that's just a toy" feeling. I have not worked with it yet, therefore I cannot say how it does in the daily routine.
I would clearly not recommend this meter to anyone who wants to have a robust meter for everyday use. There are better cheap ones out there for this requirement. In this case I would suggest a very basic but robust meter with only the most basic functions, if it has to be very cheap.
On the other hand this was one of the cheapest devices I could get with autoranging, which was important to me, and the option to take a standard thermocouple. Also I had no devices that gave all those bonus-functions: I had no possibilities to check capacities, frequencies (ok, my scope, but that is overkill most of the times), temperature and I wanted a relative-function as well. Since I have a basic robust meter, I only needed a cheap addition that also gives some more bonuses along the way. And this is the only situation in which I would recommend the Extech MN16: As addition to an existing meter and only if you can get it very cheap and only occasionally need those bonus functions (and have no other device that has them).