Question about average circuit

[hiwar]

site:www.edaboard.com ad736

I'm designing a circuit to average a pulse signal, which frequency is from 120 to 600Hz and amplitude is variable. How can I get the exact average value of the amplitude in 100ms?
Thanks.

 

[IanP]

I don't think there is a simple solution to this issue.
You will need true RMS to DC converter similar to the LH0091 from National Semiconductors ( https://web.mit.edu/6.301/www/LH0091.pdf ) AD736 from Analog devices, or LTC1967/8 from Linear Technology ( https://www.linear.com/pc/viewCategory.do?navId=H0,C1,C1154,C1086 ) ..
Regards,
IanP

 

[Humungus]

Rectify the signal using a precision rectifier and pass it through a LP filter. The time constant of the filter gives you the averaging time. Make simulations in Matlab and compare it to the what you obtain from the circuit simulator.

The result is not the "exact" average but very close to it.

Another solution is to sample the signal, pass it through and A/D and then make the average inside a microcontroller. If exact averaging is needed, maybe this is the only response. Any other?