UNIT-T UT20B pocket multimeter teardown and review

[pablo]

Hello electronics lovers !!!!!

During the past months i saved some money to buy me a decent DMM. I wanted the best accuracy that almost $ 600 USD
could buy. My original idea was to get a Fluke, Tektronix or Agilent bottom of the range bench multimeter.
Those DMM really fulfill any of my requirements but they are pricey too. 
There was no way i could spend about $750 USD only in a bench DMM. So i decided to diversify my investment in some
other tools.

Finally i opted for a Fluke 287 I think that little baby will fit nicely in my arms...
I got my sister to buy it in the USA for me, because in this side of the border is almost $200 USD more, but she will come 2 or 3 months later....
damn... i hate to wait, and the worst part of it is that i sold my last crappy DMM so
i got no DMM meanwhile... i feel naked..

Well, i went to shop some tools and i found this little piece of crap.
Isn't lovely? It only costed about $5 USD. 

obviously i will use it only for pretty basic stuff.
So i took it apart  let's see what's inside.

Well, i'm not Mr. Dave Jones but i will do my best...

First off, there is only one screw to open the case, the test leads are directly soldered to the PCB which is thin (1mm thickness),
so this could be a cause of premature failure.

I noticed that there is some kind of residue in some solder joints (perhaps the hand soldered ones).
One of the SMT resistors, next to the fuse, seems to be soldered by hand. All of the other components
have no issues with the joints.  The board is pretty simple and almost has no components on it.
The majority are smt resistors.

The test leads seem decent (if we could say so..) considering the price.
The things i like are...
The price (only 5 bucks).
The size (it actually looks cute the bastard)
It does the job (pretty basic stuff, considering there are horses for courses)

The things i dont like are..
It has 1 megaohm input impedance.
No true RMS, data logging or graphing capabilities (just joking  )

The veredict.... thumbs sideways.
No thumbs up because it has very low accuracy and very low input impedance. I woundn't recommend this to a beginner
because nowadays you need more accuracy even if you are just starting with electronics.

No thumbs down because this kind of crap it's very useful in doing very simple things such as testing or checking for a presence
of voltage, current or resistance.

I've been working in the industry almost 10 years and many times i've found myself picking the DMM just to do something like that.

feel free to comment.

[pmrlondon]

Manual ranging, too - very unusual in a meter this size.

[stl]

I think for $5 is great, look at the shielding detail! I've seen a lot worst for more money (with a battery directly soldered to the cables)

[saturation]

Its certainly looks like $5 DMM.  But if it works why not?

I'd be curious about how it holds up to the temperatures in Mexico.  It gets wickedly hot late morning onwards, but the nights can be very pleasant.

Can you temperature test it to see what it does?  For an extreme test, just measure say anything on DC and AC that you know is relatively stable then put the DMM in your refrigerator for an hour.  Then remeasure, is there a difference?

[trueblue2k2]

You bet on the right stable, but picked the wrong horse.  I bought the UNI-T model UT10A as a pocket meter.  I  have owned this meter for a year and it is excellent in all respects with a great feature set.   
It can be had for as little as $13  at dealextreme  (search 51708)
- LCD 1.8" display
- Maximum reading 3999
- Measures Voltage, Resistance, Capacitance, Frequency, with Diode and Continuity tests
- Data Hold, Relative Mode, Full Icon Display, Duty Cycle, and Sleep Mode
- DC Voltage: 400mV/4V/40V/500V
- AC Voltage: 4V/40V/500V
- Input Impedance 10 megohms
- Resistance: 400 ohm/4k ohm/40k ohm/400k ohm/4M ohm/40M ohm
- Capacitance: 4nF/40nF/400nF/4uF/40uF/200uF
- Frequency: 10Hz~100kHz
- Battery (CR2032) life is excellent
- Meter automatically turns off if you don't use the switch or buttons for 10> minutes
- Re-activated by pressing any button or turning the rotary switch.
- When re-activated with SELECT button, Sleep Mode feature is disabled.
*Most pocket meters do not have amperage scales, but you can get around that with an external current shunt resistor allowing amperage measurement using the millivolts scale.