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Don Kelly
Guest
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"Phil Allison" <philallison@tpg.com.au> wrote in message
news:69s5rvF349nrpU1@mid.individual.net...
The data sheet that you reference tells how the device is made- with two
black boxes-the squarer/divider and the current mirror. It does not explain
what each of these components actually do.
So -no new information. As I said, the pdf reference at Analog devices
doesn't come through completely- just a few lines on a few pages -enough to
hint and tantalise but not enough to be of use.
It's not for lack of trying for information.
What I wanted to know was what was in these boxes in broad terms of their
terms of their operation as there are several ways to get a true rms
measurement (assuming component frequencies outside the meter's bandwidth
can be ignored).
If you don't know, say so.
Don Kelly dhky@shawcross.ca
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"Phil Allison" <philallison@tpg.com.au> wrote in message
news:69s5rvF349nrpU1@mid.individual.net...
"Don Kelly"
The " true rms" function on a DMM is *not* obtained by sampling. It
is
normally obtained by the use of a " true rms to DC" converter IC -
generally one made by Analog Devices like the AD736.
-----------
If it is not sampling- then what is it? Thermal? There is a little black
box in the device which is just that- a little black box.
I presently have problems getting the applicable pdf from the Analog
device site.
** Analog Devices have been supplying " true rms to DC converter " ICs for
about 30 years.
The data sheet for the AD636 will give you some idea how it computes the
DC value of an AC input.
http://www.farnell.com/datasheets/57885.pdf
Use Google for more info.
Don't be so damn lazy.
..... Phil
----
The data sheet that you reference tells how the device is made- with two
black boxes-the squarer/divider and the current mirror. It does not explain
what each of these components actually do.
So -no new information. As I said, the pdf reference at Analog devices
doesn't come through completely- just a few lines on a few pages -enough to
hint and tantalise but not enough to be of use.
It's not for lack of trying for information.
What I wanted to know was what was in these boxes in broad terms of their
terms of their operation as there are several ways to get a true rms
measurement (assuming component frequencies outside the meter's bandwidth
can be ignored).
If you don't know, say so.
Don Kelly dhky@shawcross.ca
remove the X to answer