External design of HOPI HP9800 & HP8713 this seems as very interesting, similarities with desktop power meters seems to be there
but they are not. 9800 portable power meter this is another nameless product with specifications that you can not trust.
By doing your own research you will discover that this product has limited bandwidth no more than 45~65Hz.
Most to all of such cheap meters they can measure efficiently only resistance loads,
switching power supply and LED lights these are excluded. They can get connected only to Mains voltage and not at AC invert-er output.
Some 9800 portable power meter they come with USB plug and also there is available windows XP compatible software (MICROSOFT .NET FRAMEWORK 4).
Software name this is:
HAND-HELD Power monitor analysis (software author unknown / last version 4/2017)
This software it does logging at PC screen but you can not save any recorded values for later review, neither this includes any harmonic content analysis.
In simple English this software it is just a toy.
Description of True RMS neither this can be verified.
This product comes branded as Antai , HOPI , Nicetu ST-9800, and even as totally unbranded.
Possibly ODM factory of it this is Lutron in Taiwan, I did spotted this information from some text over the PCB.
Beware of specific product pricing because similar gadgets they sold for no more than 10$ or Euro.
Regarding functionality beware of this Note: When the active and reactive power is displayed, the working time and power are displayed alternately every 5 seconds.
https://www.ittsb.eu/forum/index.php?topic=1236.0