# RMS to DC scheme

L

#### LemonPL

Jan 1, 1970
0
Hi!

I need scheme of RMS to DC converter.
What is important I cant use integrated circuits (except opamps)
in this approach.

LemonPL

J

#### John Larkin

Jan 1, 1970
0
Hi!

I need scheme of RMS to DC converter.
What is important I cant use integrated circuits (except opamps)
in this approach.

LemonPL

What other parts can you use?

John

E

#### ehsjr

Jan 1, 1970
0
LemonPL said:
Hi!

I need scheme of RMS to DC converter.
What is important I cant use integrated circuits (except opamps)
in this approach.

LemonPL

--->|---

K

Jan 1, 1970
0
C

#### Chris

Jan 1, 1970
0
LemonPL said:
Hi!

I need scheme of RMS to DC converter.
What is important I cant use integrated circuits (except opamps)
in this approach.

LemonPL

Hi, Lemon, or Lemone. You should have included your full name and the
technical college or university you're attending, as well as the class
and instructor. I'm sure your fellow students would be amused by your
s.e.b. post. Your professor also might be interested, although I doubt
he'd show his amusement in public.

You know, if you need a free clue (and oh yes, you do), it's sometimes
good to look through the existing literature rather than just re-invent
the wheel. The early manufacturers of op amps (Analog Devices,
Fairchild and National Semiconductor come to mind) published
application notes in the 1970s to help users of their newfangled
contraption, the IC op amp. A quick search of these sites using the
phrase "True rms detector" should give you some help.

But since it might actually involve work or thought to go to the
National Semiconductor website and type in the search term "true rms
detector", and actually scan a few of the links to see if they might
have what you want (Frith forbid, you might actually learn something
not connected directly with your homework assignment), retain the
purity of your beautiful mind by holding your mouse and sliding it
slowly until the pointer rests on the link below, to read National's
LB-25, "True rms Detector". It shows a true rms detector circuit that
uses five op amps, matched pair transistors, diodes and passive
components. Once the pointer is resting over this link, press the
mouse button.

http://www.national.com/an/LB/LB-25.pdf#page=1

then click the "Go" button to the right. If you need help with that,
please post again if you can, and it's not too much work.

Also, the link is in .pdf format. If you don't have the Adobe Acrobat
Reader or it's equivalent (and I would guess you don't), please go to

labelled "Get Adobe Reader" on the left of the page). If you have
trouble with this, you should contact somebody in the computer science
department. For 20 zloty, you can usually buy a clue -- they'll be
happy to give you a hand and set up your computer. Also, if you don't
understand the app note, please use another 20 zloty note to have one
of your classmates explain it to you. It's actually a pretty elegant
combination of an op amp precision rectifier, multiplier, and divider.

Daddy to ask for a big pile of 20 zloty notes. I'd guess you're going
to need them.

B

#### Bob Eldred

Jan 1, 1970
0
LemonPL said:
Hi!

I need scheme of RMS to DC converter.
What is important I can`t use integrated circuits (except opamps)
in this approach.

LemonPL

Many of the posters have assumed that you are doing a homework problem for
some class. But there are a number of questions that must be answered if you
frequency of operation. 3. What is the PAR, peak to average ratio expected.
4. What is the voltage expected? 5. What is the dynamic range expected? 6.
What are the waveshapes expected? 7. What precision is expected? 8. What
speed of response is expected? 9. What transient response is required?

The scheme picked depends on answers to these questions. For example, if you
know the waveform is ALWAYS a sine wave the problem is simple and is just a
calibration.

J

#### Jasen Betts

Jan 1, 1970
0

use a diode?
hmm, isn't their forwards voltage/current curve exponential?

Bye.
Jasen

Replies
2
Views
715
Replies
6
Views
699
Replies
6
Views
853
Replies
22
Views
3K
Replies
1
Views
775