Analog Current Meter with LCD display

[Dino1400]

I have analog circuit that generate several type of waveforms (sine, tri, and sqrt) of frequencies from 10Hz to 1KHz trying to display the current and the frequency both on a LCD or through usb port in a PC.

any selections

 

[wp100]

Hi,

There are lots of free frequency counter diy projects on the web using various micros, typically pics or ardunio etc.

Your problem will be conditioning the sine and tri waves to be read easily by a micro and as for the current ?

 

[KlausST]

Hi,


it sounds easy, but there are so much details to take care of.

Waveforms:
Is there DC offset in those waveforms?
If yes, should the current reading include the DC or not?

If the waveforms are clean (low noise) then a zero cross comparator (take care of DC?) can generate a square wave to measure (fundamental) frequency of your signal.
Either you wait a defined time (eg. 1s) and count pulses to get frequency,
or you measure the time between two rising edges and calculate frequency by f = 1/t (maybe some filtering is necessary)

Measuring current is the complicated one ... at least if you want a "defined" current reading.
Definitions are: peak, peak-to-peak, RMS, average, (all with or without taking care of DC)
* peak is problematic with unsymmetrical signals like rectified sine.
* peak-to-peak is only a good information if you additionally know the waveform
* RMS is good if you want to know how much power it produces
* average is problematic for symmetrical signals. (The average value of a sine is zero).
* what is your input current range?
* What resolution do you need, what accuracy do you expect?

Measuring interval:
* the most difficult is if you need high speed real time information
* for a display you maybe need 3 results per second
* for USB and some diagrams you maybe need more than ten (hundred?) results per second.

What hardware do you use?
* what microcontroller?
* what analog circuitry? Amplifiers, filters, RMS-to-DC converters....
* what ADC with resolution and sampling frequency?

Klaus

 

[D.A.(Tony)Stewart]

Many solutions may be explored here https://www.google.ca/search?q=ardu...a=X&ei=w3g9VPCBE4icygTS-IDoCg&ved=0CAgQ_AUoAQ