TS-836A & D52-2048 Power meters are both Made in China products, both aiming home users, both close to 10$ mark.
TS-836A this is plug-in type.
D52-2048 this is for mounting over rail.
Both able for power factor measurement, and other electrical parameters. But here is the catch (trickery) = false advertising.
Only 1% of sellers they do mention that those meters they are exclusively for clean sine-wave and not for measurements of inverter output.
Non of them can measure True RMS and square-wave power.
Additionally both are tremendously slow, and this translates that they are usable for static loads ( heaters and incandescent light bulb or Air Cooling Fans). Especially for TS-836A the news here gets worst
in the regard of measuring consumption over time.
Due electronics limitations and slow sampling speed, recorded energy this is in huge error. What will never computed correctly this is energy consumed by
Computers power supply, mobile phone chargers, laptop chargers, inverter air conditioner, LED home lights, up to high speed power drills.
For me as professional electrician, both of them are toys, but there is a positive side in all this marketing scam.
Currently measurement of Power Factor this is not possible by a large number of handheld multimeter, power measurements these are somewhat work for dedicated equipment.
I did order one TS-836A for 11 Euro, but I did that by knowing all limitations, and because all that I care for this is VA , Watt, Power factor of static loads.
Speaking of measurements trust in static loads, I can accept 2% error, and therefore just for comparison purposes this TS-836A it does not considered as total waste of money.
True power meters they have sampling of 100ms and not of 500ms ( two times per second), as they have these cheap power meters.
100ms sampling translates to ten measurements in the unit of time ( 1 second), therefore any energy variations they are better recorded (more accurate measurement).
But because cheap ones are not able for True-RMS this translate to huge error despite sampling speed. http://en-us.fluke.com/training/training-library/measurements/electricity/what-is-true-rms.html
Speaking of pricing of true power meters (panel type) they hover at above 450 Euro mark, and them are far more reliable speaking of energy recording ability over time.