Brymen BM155 clamp multimeter

This unit have a nice and rare capability of measuring electrical power. The body is very light and thin apart from large clamp. The slide function selector is inconvenient to use compared to rotary selectors known from other meters. It is hard to find a proper position without going too far. The voltage and ohm accuracy is perfect with a good agreement to others own meters. The current readings depends on the wire alignment inside the clamp but are fairly accurate. I've tested the power measuring capability with small loads up to 2 kW. It seems, that probes order is very important for measuring small loads. If the COM probe is connected to neutral and plus probe to live, the power offset with empty clamp is about -2 W, which is acceptable. After reversing the probes i.e. connecting com probe to live, the power offset jumps to about -21 W. It is not a big problem if measuring single phase system, but can be annoying while measuring unbalanced power is 3-phase power system with Aron method as shown on page 10 of manual. Then both probes have to be connected to live terminals, which introduces large negative power offset. Another misleading function is VAR power measurement. It is stated in manual, that this function measures reactive power usually denoted by Q1 symbol. This is not true for general case. It seems, that the VAR value displayed by a meter is a nonactive power denoted by N. That is quite a difference. In most countries only P1 (active power) and Q1 (reactive power) are measured and counted by main energy meters installed by power companies. N (nonactive power) is usually higher than Q1 (reactive power) due to current harmonics. Let's give an example. In a hair dryer with 1 kW of maximum power on the first power level the heating element is connected to mains through a diode. That reduces mean power by a half to 500 W. The BM155 meter measures correct active power 500 W. The VAR power displayed by the meter is about 220 VAR, which is nonsense. There is no capacitance or inductance inside the hair drier. No reactive power is counted by power company. So the VAR value displayed by the meter is misleading and cannot be used for selecting reactive power compensation components.