NJTY T21D, Richmeters 113D

[sleemanj]

Quick open up of the NJTY T21D and comments.

Positive: Cheap ($15-20 USD Aliexpress) 6000 count TRMS hand-sized meter, sturdy construction with rubber boot.  3xAAA cell.  NCV, Capacitance, Temperature (usual K-Type banana probe included), frequency, magnet attachment, led light, APO, backlight.  No trouble lighting blue/white leds.  Seems fast in measurements.  Marked as Cat-II 600v (I rate this as a positive because it's at least "conservative")

Negative: minimum current range 60mA - there is no uA range.  Manual has many errors, it's been copy-paste-badly-edited from a 2000 count obviously.  Fuses are 5x20mm 250v (glass as supplied) but there is no warning on the current input jacks about that (there is a warning in the manual however not to use current ranges on more than 250v open-circuit voltage systems).  The battery compartment door has fuse ratings moulded into it, but they are wrong (again, from a 2000 count meter obviously).  The current shunt is a 0.005 Ohm surface mount resistor, for a 10A current input.  Input protection.... it has a tiny PTC.  Probes are... not great, even for a cheap meter, well, they're not hopeless, not like on one of those $5 meters, but they are not as good as the probes supplied with the PM8233E, or if memory serves even the RM102, they are rated 1000v and wire marked as such.

Sigh.  China.  Just a little more effort please. The general construction physical durability and features are great for the price range, but let down by details, needs a 600uA range (or at least 6mA), a proper current shunt capable of 10A continuous, a tiny bit more input protection, somebody to spend an hour correcting the manual, and change the silkscreen for the current ranges to "10A/250v" and "600mA/250v" respectively.


Larger/more photos at the Imgur gallery


Comparison with ADM02 (MS8233E and others)


About hand-sized


Magnet is removable, note that some sellers may not be sending with the magnet due to customs, this one got through with it still in place.



Bail is a resonable angle, but of course it's not a one-handed operation to change the dial while on the bail.


Rubber boot is easily removed and replaced


Tiny little PTC hanging off the board between the jacks, note the 0.005 Ohm "Shunt" and glass fuses.

[rsjsouza]

Sleemanj, I apologize for the necroposting but I just saw this thread. A few months ago I received a Richmeters RM113D and several of the less serious errors were fixed such as the PCB markings for fuses, the markings on the housing, several user's manual errors and the probes were quite standard - not bad, not great.

Of course the wimpy input protection is still a problem, the short backlight as well as the 250V glass fuses and the shared current input, but for US$13 landed I wouldn't really expect much more. It is a fast general purpose meter with rated 1kHz True RMS (I measured 3.3kHz at V level) and reasonably on point on measurements.

It also has good EMF detection. I like how the Chinese meters have that proeminent tip for this feature - The Keysight U1282A is shameful in this sense.

Oh well, it may also be due to my sense of crapiness being severely lowered by looking at too many dirt cheap meters (Surpeer AV4, etc.)

[AintBigAintClever]

I'll see your 1 year necropost and raise you 4.

If anyone's on the lookout for one, this meter is also badged as:-
Lomvum T18D
Mestek DM90A
Mufasha P21D
Proster PST237

I've got a Proster PST237 coming tomorrow for free courtesy of the Amazon Vine programme.

[rsjsouza]

Thanks for sharing these different OEMs. In my experience the original design is the Mestek DM90A.

I still have the Richmeters and it works quite well. It is my recommendation for this price range.