Re: integrating true RMS wattmeter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Sparktron01@xxxxxxxxxxx 

Hi Dest

 -------------- Original message ----------------------
From: "Tesla list" <tesla@xxxxxxxxxx>
> Original poster: dest <dest@xxxxxxxxxxxxx>
>
> Hallo.
>
> this wattmeter has an awfully long display stabilization time - about 4
> sec! that`s real suxxx, so i just decreased C from 2.2uF to 0.47uF,
> and added first order low-pass filter to the oa output - just RC ckt.
> R=10KOhm, C=3.3uF, so now you can get very smooth readings 4 times
> faster with no impact on accuracy and at no cost : )
> p.s.
> you must use DVM with Rinput~10MOhm as display, if your DVM has
> Rinput~1MOhm, then better use R=1KOhm, C=33uF.
>
> -----
> I don't doubt that my logic is flawed, could somebody tell me where?
> 08-08-97 (c) Gary Lau
>
>

What op-amp are you using?  I also noted that improved accuracy could
be had by using a DVM, an analog meter is +/- 2% at best (and +/-5%
is more typical).

I found the original data set for this meter if anyone is interested, it is
in MS Excel format... (test performed in 1997)

Regards
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA. USA