I have different wattmeters and different smart plugs with wattmeter function.
I m so confused lately because all of them shows different values
This is the one which i hae been using for 5 years. It work well.
https://www.banggood.com/Bakeey-16A-Plug-in-Digital-Wattmeter-LCD-Display-Power-Meter-Electricity-Usage-Socket-Adapter-Electric-Consumption-Monitor-EU-Plug-p-1643668.html?rmmds=myorder&cur_warehouse=CN&ID=530036
This is the new one i have bought latelt. And this is the startf of the problem. It shows +150W than the first one around 1600W/hour.
https://www.banggood.com/EU-Plug-Intelligent-AC-Power-Meter-Wattmeter-Socket-Billing-Socket-Power-Monitor-p-1815410.html?cur_warehouse=CN&rmmds=search
For example:
First one shows 1650W, second one shows 1800W
This is the best smart plug i have used. It shows +20W than the first one. But the warranty is so bad. I have no warranty for my country.
https://www.banggood.com/Broadlink-Wifi-Smart-Plug-SP3S-Power-Meter-Monitor-16A-Timer-Socket-Outlet-Remote-Wireless-Control-p-1249628.html?cur_warehouse=CN&ID=43101&rmmds=search
This is the worse smart plug i have used. It shows +75W than the first one. It sometimes can be out of order after electrcity is gone and come back. But the warranty is perfect, they send the new one.
https://www.swapp.com.tr/tr/urun/s-link-swapp-sl-01-16-amper-akilli-priz-wifi-tuya-destekli
I have also several smart plugs which all of them shows different values. I have no any idea which one shows correct values.
There is no any difference if i use lower than 700W, all wattmeters shows the real usage.
Help me to choose a perfect wattmeter.
Well you can just make a current probe and measure the current on one of your wires from the wall and just multiple by voltage and you will get the correct wattage reading and just throw away the meter which is giving you the incorrect reading.
Most likely the issue is the meter isn't accurate at wattages that high, if you pull less power, say 700 Watts and measure with both, then I think they would get the identical reading. However if its too high of a load, it might get incorrect reading.
Same reason how the KillAWatt can't measure the wattage properly of a microwave. Just shows crazy values.
I have power supplies with a built-in wattmeter, but this application does not work in Hive OS.
You can use Wi-Fi sockets with a built-in wattmeter, but this is expensive, although very convenient.
I use a budget wattmeter for $ 12, and check its data with the data from the power supply wattmeter. A reading difference of 2-5% does not lead to a serious error