Since there's little information to find about this instrument on the web and I recently acquired one as part of a "package", I decided to follow Dave's prime directive to take it apart instead of turning it on
The PCB is labeled DT-989 so it obviously is a CEM as reported before. Yet, since I wasn't expecting anything stellar, I was quite surprised by the amount of detail put into the instrument. The fuses are proper HRC SIBA ones, there are isolation slots in several places in the PCB and as it seems, the manufacturer went through some effort to put several varistors and PTCs in the frontend (not visible directly in the photos, they are located on the other side and somewhat visible through the isolation slots). The main components are the HYCONTECH HY3131 front end together with a ISL21107CFZ12 reference (not too shabby, rated 5PPM/°C -- should do the job for a 50k count instrument). I'm really amazed the manufacturer decided to use a "proper" Caddock divider network! The controller is a Texas TIVA C Series TM4C123GH6PZ low power ARM Cortex M processor, accompanied by a soldered-on bluetooth module for connectivity.
The instrument comes with a recent (signed two months ago) test report by a PekTech Technician that appears to be authentic. Anyway, finally I had to turn it on... A cross-check with my Rigol DM3068 shows the measurements to match up to a maximum difference of two or three least significant digits (of the 3440 that is
). The measurement update rate of the instrument is pretty fast at round about five readings per second in the voltage/current/resistance ranges. Auto-ranging could be a tad faster, especially in capacitance mode it's quite slow. Yet, measurements appear to be spot-on compared to my AT826 LCR meter. Continuity is a little bit awkward: Usually, it's reasonably fast (latched) but sometimes there seems to be a noticable delay, especially if there are several consecutive shorts of the probes. It appears that the display update interferes with the evaluation of the input signal. Maybe a firmware update (if there will be made one available at all) could solve this.
The logging and graphing function is quite nice and works well and is easy to access. As yet, I didn't test the connectivity. As a bonus, a USB/Bluetooth dongle was included in the package in order to be able to establish a connection to a computer that isn't equipped with an internal BT device. The menu structure could be a little more elaborate, designations of the menus are sometimes misleading. One thing that is quitre annoying is that the cancel/close key always leaves the menu completely and reverts back to measuring mode instead of stepping back one menu level. This makes changing several menu items quite a hassle. The main selector switch is very "snappy" and requires quite some torque to turn. I would have wished it was a little bit bigger in diameter. Yet, as it is, it's virtually impossible to place it between the detents unintentionally. It definitely feels solid.
"Outing" myself as a color TFT afficionado, I've got to say the display is really nice. Even though the resolution is only 320x240, due to its compact size, it looks always crisp and detailed. Especially the modes with several values to be displayed (actual reading plus min/max/average for example) are very comfortably legible compared to a seven-segment arrangement. There are three fonts to choose from which can be considered more or less a "gimmick".
I like the small form factor of the instrument and the thick "rubberization" of the casing. It appears very sturdy, yet the areas that are not rubber-coated appear a little "cheap". The enclosure of the instrument is not sealed so it's not recommendable to use the instrument in moist environments. If I would trust the CAT ratings printed on the instrument is another question, sure it appears to be better designed and built than the "usual suspects" but it's still some way apart from a recent Fluke or most other "A-brand" meters. I won't hesitate to use it on household electrical installations though -- and that's the worst thing it will see energy-wise in my hands anyway -- mostly it will be used for electronics stuff, so I guess I'll be fine with it. Altogether, so far I'ld say the instrument is worth what I've paid for it
.
I hope this short report may be useful to others to make a decision if they consider to buy this meter.
Cheers,
Thomas
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