The Shop > Electronics & IC Programing

True RMS wattmeter = buy or make suggestions

(1/4) > >>

picclock:
I need one !!. Am considering a design I found in Elektor 1983 May

Any better ideas appreciated.

Best Regards

picclock

philf:
How accurate does the meter need to be and does it need to be true RMS?

I have a plug-in meter which reads W, KWh, A etc. Mine has similar functions to:

http://www.ebay.co.uk/itm/Plug-in-Power-Consumption-Meter-Energy-Electricity-Usage-Watt-Calculator-Monitor-/162113034987?_trksid=p2141725.m3641.l6368

I don't know how accurate they are but it gives some idea of power consumption. On mine you can input the cost per KWh and it works out how much you're spending.

Phil.

awemawson:
"Hot Wire ammeters" were the old school method of getting true rms values and they cover a wide frequency spectrum.

picclock:
@ awemason
For Ammeters only thats true. I once used a wattmeter which summed two moving coil movement to produce results. However, in todays world the current is often taken in short pulses, and at differing points on the voltage waveform, so calculating the average power use is tricky, requiring fast calculation of the power value and averaging over the whole cycle.

The Elektor meter (May 1983) used a 4 quadrant multiplier to allow for power being taken and returned to the source and averaged it using an LM13600/ 13700 chip with some buffers and stuff.

In truth measuring power accurately these days is tricky  :smart:, hence my post. I have looked for true RMS meters but they seem very rare, and although I am reluctant to make a pcb and assemble it, it appears I may have no alternative, unless someone at madmodder comes up with a better solution  :thumbup:.

Best Regards

picclock
 

PK:
If we rephrase the question: "Need electronic device, should I buy one or build one" then the answer these days is nearly always "Just buy it"

There are some exotic bits of kit that are worth building. But not many.
Of course, if you just want to make one, then fine. But it almost always costs a fair bit more to get a similar result.

PK

Navigation

[0] Message Index

[#] Next page