collecting watt meter information from 20 sources

Hello all
I would like to get input from members about a new project .
Its getting current information using 20 ferrite toroid from 20 safety switch ,getting a count higher or lower depends on the current and getting a bcd or digital readout with leds .
one simple bcd to 7 seg can be used with plug to get a reading at any time or once a month.
the idea is to be able to find out how much electricity used on each of the 20 sources at a fix known 230vac its doesn't have be be accurate.
Please if possible no micro processor (maybe a pic ) or software
thanks in advance
dselec

The toroid will provide a tiny AC signal at the leads. This can be amplified and fed to a voltage-to-frequency converter. The pulses are counted. The count goes to the readout.

Any additional circuitry besides the toroid will need to be powered. Will you use battery power, or draw from a source in the compartment?

You mention a plug. Will you plug in a readout device that you carry with you as you make rounds?

The two wires to the toroid must have a solid connection to the amplifier. Anything that reduces current flow will throw off the reading.

It seems to be a question how much equipment you'll install each location.

Perhaps the happy medium is to install 20 circuit boards. Each circuit board contains an op amp soldered to the toroid leads.

You carry the readout device. A plug comes from it carrying 3 lines. Two are supply leads and one is output from the op amp.

This setup will only give you a moment-to-moment amp reading.

Or are you aiming to find out the sum total for a month? This will require 20 circuit boards, each having the V-to-F converter, and a counter IC (a 4060 or 4020).

The specification snippets don't fit well together yet, I think.
- "watt meter" refers to real power measurement or what? A range and resolution specification seems necessary, however.
- "collecting from 20 sources" means one device with 20 channels or 20 devices?
- "get a reading at any time or once a month" means to read instantaneous power, averaged power or accumulated energy?
- if any averaging or energy summing feature is intended, how about volatile/nonvolatile data storage?

The wattmeter is an instrument for measuring the electric power (or the supply rate of electrical energy) in watts of any given circuit.

An instrument which measures electrical energy in watt hours (electricity meter or energy analyser) is essentially a wattmeter which accumulates or averages readings; many such instruments measure and can display many parameters and can be used where a wattmeter is needed: volts, current,in amperes, apparent instantaneous power, actual power, power factor, energy in [k]Wh over a period of time, and cost of electricity consumed.

Thanks all
Ok brad good point we will get analog value for current , so now can we do it cheap with 555 or with and simple op mulch-vibrator that will change freq with dc-level change ?
Next the counter is great for getting read digital with lcd i dont mind doing the math myself or calculator .
all the rest is not important supply and other stuff .
first ill use ltspice to work your way and see what i get .

fvm you too are right getting a wide freq range for 0.1-10 amp will need a range so ill have to do some kind or auto range saying multiply reasult by 10 or hundred... good will ltspice that too .

power.. u are right too meeening how much electricity did i use ?
watts for second is quite close to real life ... meaning if i use 1 w for 1 sec it will count 1 and if the next second suddently ill use 2000w it should count 2000 in one second ... ltspice get ready for this too

in general ill read digital output from 20 cd4060 one by one with 20 position selector switch.
all i need is to get a general idea of whats happening in my system over at the end of each month
Thanks all keep the ideas going maybe 1 day well have a cheep 10 $ gadget that every house hold can just plug in any place they need ....