The DST1000 targets the market for inexpensive digital thermostats, the most popular being the STC1000. The novel features to the DST1000 is that it uses a DS1820B digital temperature sensor (well probably a Chinese clone).
The problem with thermistor based thermostats is that they commonly have significant error, and although most firmware allows the user to enter a calibration adjustment, it is a fix at one temperature and does not solve the problem that the thermistor equation implemented in the firmware does not match the behavior of the thermistor. In my experience, calibrating at 20° might result in an error as much as 5° at 80°, unacceptable for lots of wide ranging applications.
It is sold with brief and inadequate / incorrect user instructions. Two were purchased to give a good chance one would work, and you guessed it, only one worked. The lower display segment of the first digit did not work on the fautly one, and the seller thought that was not a problem. The seller frustrated attempts to obtain a refund for the faulty unit.
Above, the seller’s pic of the DST1000.
Above, the topside of the main PCB of the DST1020. Note the relays.
The keen observer will note it uses a switched mode power supply (bottom left), implied by the voltage rating.
I could not find a good English language datasheet on the JQC3FF relays. The label on the relays claims 10A AC current rating, it is almost certainly for resistive loads, and motor loads might be more like 4A. The relays are physically small compared to those in many of this sized thermostat.
The DUT was powered and the temperature calibration checked at 20° and 80°, and it was within 1° of correct, quite good for most purposes and far better than NTCs tend to be.
Having powered it radiated RF interference was evaluated. It is rotten with RFI, much like the STC1000 (which was banned from sale by the regulator in NZ due to RF emissions). The device takes a few seconds from power on before the display lights up.
The 12-72VDC version probably has a switched mode power supply, and might have similar RF noise associated with such.
For my purposes, I usually use Inexpensive Chinese thermostat – MH1230A. It does not use a switched mode power supply, it does not make substantial RF interference, it has a large relay, they have proven reliable but accuracy of the NTC characteristic curve is wanting.
In summary, the DST1000 is
- without clear instructions;
- more accurate than similar NTC based thermostats;
- rotten with RFI;
- no mention of the controls you may need if controlling a compressor.