Measuring Volts and Amps digitally

[The Master]

Hi, Is it possible to measure voltage (6-50V) and Amps (600mA-1A) and send the value to a PIC chip? Im more bothered about the Amps because i want to display how much current is being drawn from a transformer. I have a digital multimeter that does both so im sure there are components out there, i just dont know which ones.

[Acetronics2]

Hi,

I think you'd better browse Microchip AN's ... Energy meters described !

Alain

[The Master]

I assum AN means App Notes. I had a look on the microchip website and i found a document that describes how to measure watts. It seemed to be what i wanted because it measured amps and volts to get watts but it either wasnt clear enough or i just dont get it.

What i understand now is that i need a device to measure volts/amps. That device sends an analogue signal to the PIC through an ADC pin. I also read that 2 volts has to be added to the analogue signal and it needs amplifying so the PIC can read it more accurately.

First thing, did i understand it correctly? Second thing, what is the component used for measuring amps?

[skimask]

Measure volts? Easy enough with a voltage divider, Sounds like you already know that much.

Measuring amps? Low value series sense resistor (mainly DC), current transformer (mainly AC), hundred different ways to do it...
Check Wiki under 'current source', some halfway decent information there. Same thing for 'ammeter'.

[mikeh]

Look At Maxim
Try Max4372

[dhouston]

For current, see http://www.allegromicro.com/en/Produ...rentsensor.asp

[The Master]

dhouston, that looks like what i want except that they dont seem to measure below 5A. I do like the fact that they support both AC and DC though. I have 8 outputs that i want to monitor. The max output current ranges from 600mA to 1A and some are AC, some are DC. I want to measure how much current is actually being used even if its less than the output's max rating.

mikeh, ive had a look and it looks like that chip would simply replace a potential divider circuit.

skimask, i take it "voltage divider" is the same as a "potential divider". I remember learning about them in school but so far i dont think ive ever put one together. I think i can see how it would work though. It looks like it would simply lower the voltage to a level suitable for the ADC pin on the pic.

Ive read a wikipedia page about ammeters and it said that you put a resistor in series and measure the voltage accross that resistor and that will tell you how many amps are being drawn through it. This way sounds simple but you said its used *mainly* for DC. Does that mean i can use it on AC? Half of the outputs are AC. What resistor would i use? For the 50V 1A output i assume i need a 50W resistor with the smallest resistance i can find. Rapid sells an OR05 50W Aluminium clad power resistor. It seems a little big but i guess 1A at 50V is a lot for small components.