multisim - Measure VCC current

[WardieB]

Can somebody tell me how to measure the current drawn by al  my digital IC, from the voltage source VCC.

I have tried analysis tools (without any training) and I am unable to get any sensible reading.

Ideally I would like to put a meter in the circuit and see the current changing as the output states of the components change.

regards

[JoshWY]

Hi there,

There are various ways in which you can measure current from the VCC. Of course we measure current in series/in line with the VCC itself. 

You can introduce a DMM in series with your VCC, this however will impact the current as it has its own electrical charateristics and properties.

However you can use a measurment probe to meaure current at a selected point. You can also use this point when carrying out analysis.

If you are stilling having issues it would be good to maybe see your circuit, so we can advise where best to place these components or probes.

Let me know how you get on.

Josh 

[aa232004]

hello everybody.

JoshNY is right.

if there are visible VCC pin - you could use or DMM or current probe - they are available in version 13 and 14 I believe.

but my question here is how to check current with hidden VCC pins?

thanks

Michael

[JoshWY]

So when VCC or GND pins are hidden, they are generally virtually conncetted to the global power and ground nets. The article below describes this rather well.

http://digital.ni.com/public.nsf/allkb/2E2C6574E8DC12F48625719D004D00E7?OpenDocument

That is why you may experience getting a get a dialog box when adding VCC to the schematic.

http://digital.ni.com/public.nsf/allkb/E7BE2A82B447A1F686257A80004E5B92?OpenDocument

Even thought they are hidden, it still requires us to have a VCC and GND somewhere on the schematic. The below article shows how you can introduce a bypass capacitor to a VCC source using an on page connector, the same method could be used to introduce a DMM or measurement probe.

http://digital.ni.com/public.nsf/allkb/BA0092DC8E51484486257B3B0053371F

In addition, when VCC is placed on the schematic it also enables an additional point that can be used for analysis, e.g ' I(VCC) '.

Have a go and see how you get on.

Thanks

Josh

[aa232004]

hello, thanks for response.

the original question was how to check current consumption of VCC.

I have checked these links - these is no answer for that question  it at all.

and as mush as I figured - the  last link gives  a wrong information  - they titled  the article 

- how to add bypass caps but explain how to connect caps in series with VCC and GRND nets which is very unusual way to supply power to ICs or I do not get it at all.

but back to original question - the last link gave me an idea - to do what they say in that article and to hook up ammeter  in parallel with these caps.

after caps charging process is over , the Ammeter 'll show the that IC's current consumption.

and might be even better way - to use high volume resistor instead of cap, or  to use just ammeter only .

with hope it helps

 
thanks

 
Michael