This conspicuously brandless device, of Chinese manufacture, is for sale through multiple listings on Amazon, with prices ranging from $10.66 up to $20.95. The one I bought cost $14.99 with free Prime shipping, and came from CyberTech with fulfillment by Amazon itself. Besides the actual instrument, the package included a padded blue nylon zipper pouch, a four page instruction booklet in passable English, and about 24″ of 1cm-wide sparkly reflective tape.
In recent years my prejudice against Chinese tools has been proven wrong over and over again, and the DT-2234C+ is no exception. Frankly, this is a fantastic little tool, at a fantastic price, that gets the job done without breaking the bank. Is it cheap? Sure it is, in both common senses of the word. But is it worth every penny of its rock-bottom price? Again: Yes. A couple times over.
To make a measurement, the tool requires a rotating surface with a reflective area that is smaller than its non-reflective area. The special sparkly-flake tape included is nice for this purpose, but it is not strictly necessary; I got equivalent readings using common aluminum foil tape and plain white grip tape. In many cases, in fact, the tape was not necessary at all. To measure the speed of a fan, for instance, it was sufficient to simply point the meter at the spinning blades, take a reading, and divide by the number of blades.
The DT-2234C+ has a 5-digit LCD display with 3/4″ tall letters, and a range of 1 – 99,999 RPM. To 1,000 RPM it has a resolution of 0.1 RPM, and above that of 1 RPM. It claims an accuracy of ±0.05%, or to within 50 RPM at its upper limit of 99,999, which I did not have any handy means of testing. The DT-2234C+ has a minimum sampling time of 0.8 seconds, which will be higher at very low speeds (i.e. below 60 RPM), and a useful maximum range of about two feet. It also includes a memory function button that cycles through minimum, maximum, and last available readings from the last sampling period. It measures about 5×3×1″ and, with a 9V battery installed, weighs just a bit under 6 oz.
My use, so far, has consisted mainly of comparing the real speeds of various nominally-equivalent case fans so I can swap out the underperforming coolers, and for this purpose the DT-2234C+ has proven completely satisfactory. Since I haven’t been able to test its accuracy, I still hesitate to recommend it for work that requires reliable absolute readings. But for this kind of relative comparison-based testing, this little unit is a value that’s hard to beat.