Just a quickie, about an upgrade I made yesterday. Well, it was not an upgrade like we do all the time, it was an upgrade involving some screwdrivers and some hotline maintenance. And by hot I mean 250V AC live wire, not the kind of hot you might enjoy. :)
I measure the power consumption of the servers at multiple places using metered PDUs and node-red, but I also have some offline power meters. I bought some cheap power meters from eBay years ago, they measure the voltage and the current. Well those are really what I needed, those were just what I had at hand.
Now I replaced the meters by a similarly cheap eBay meters that actually measure power consumption. I need to know how much I will have to pay at the end of the year for powering my servers, not measuring the wash machine, the water heater, the fridge and so on and so forth. The three boxes on the photos are holding the three phase, I replaced the meters one by one, so I did not even had to power down my server farm. All the servers have at least two power supplies, all of them are getting two different phases, so it is all redundant.
The new meters measure the voltage, the current, the time, the cos φ, the cosine of the angle between the voltage and the current. Well this last one is for the big boys who already finished high school and learned the delicate details of the alternating current, but if it is unknown for you don't be intimidated, it is suffice to say this is something worth measuring. Out of these the meters calculate and display the running sum for the energy consumption in kWh. There is a little push button to switch the display between the Watts and kilowatt-hours. Long press resets... great.
Now I am ready to do some experiments, to extrapolate how much money I actually spend... but wait, how accurate is this thing? And why is my cos φ so low when the load is low?