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mv to 5vdc isolation circuit?

B

Brad Woods

Jan 1, 1970
0
I'm trying to set up a data aquisition system and am looking for a circuit
that will let me convert a 50mv DC signal from a current shunt to a 5v dc
signal that can be input to a PLC. the measurement is on the high side of
ground so it will need to provide isolation also. I've extensively searched
but could not find good info on the net could anybody point me in the right
direction .
Thanks
 
J

John Popelish

Jan 1, 1970
0
Brad said:
I'm trying to set up a data aquisition system and am looking for a circuit
that will let me convert a 50mv DC signal from a current shunt to a 5v dc
signal that can be input to a PLC. the measurement is on the high side of
ground so it will need to provide isolation also. I've extensively searched
but could not find good info on the net could anybody point me in the right
direction .
Thanks

Why build what is available as an industrially hardened product?
e.g.
http://www.actionio.com/
 
L

legg

Jan 1, 1970
0
I'm trying to set up a data aquisition system and am looking for a circuit
that will let me convert a 50mv DC signal from a current shunt to a 5v dc
signal that can be input to a PLC. the measurement is on the high side of
ground so it will need to provide isolation also. I've extensively searched
but could not find good info on the net could anybody point me in the right
direction .

Is the input to the PLC required to be ~linearly scaled or do you
simply require a specific preset level indicator, with a tolerance?

Wouldn't simple level translation suffice for either a linear or
switched signal? Isolation could be an added complication, requiring
interface power on the 50mV side.

RL
 
T

Tom Seim

Jan 1, 1970
0
Brad Woods said:
I'm trying to set up a data aquisition system and am looking for a circuit
that will let me convert a 50mv DC signal from a current shunt to a 5v dc
signal that can be input to a PLC. the measurement is on the high side of
ground so it will need to provide isolation also. I've extensively searched
but could not find good info on the net could anybody point me in the right
direction .
Thanks

Burr-Brown (TI) has self-contained isolation amps.
 
T

Tom Seim

Jan 1, 1970
0
Fred Bloggs said:
NO!!!!? REALLY?!

Yes, REALLY!! You ought to check them out, fredrook. Maybe you don't
know who Burr-Brown is?
 
F

Fred Bloggs

Jan 1, 1970
0
Tom said:
Yes, REALLY!! You ought to check them out, fredrook. Maybe you don't
know who Burr-Brown is?

Nope- never heard of them. Is that some kind of clothing store chain?
And why would they sell iso-amps?
 
P

Product developer

Jan 1, 1970
0
Yes, REALLY!! You ought to check them out, fredrook. Maybe you don't
know who Burr-Brown is?

I have used a few of those. I used the ISO107 in a PCI card-based
Brainwave Analyzer back in 1988. I had to provide Ul544 patient
isolation to the instrument card. Unfortunately it wasn't very
reliable over time. It was a great part while it lasted but its life
span was only a few years.

This device was a PC version of the brainwave analyzer that was
invented by Dr. John Ertl, A PhD who pioneered the correlation between
brainwave activity (Average processing speed) and intelligence. After
a government study of 8,000 students, both black and white and was
able to demonstrate his theory and create a substantial data base of
EEG samples that were used in conjunction with thousands of other
samples to provide a look up table by age and brain maturation. The
EEG sample was processed using an algorithm created by Ertl. It was
touted as the world's first electronic IQ test and it is in use still
today in clinics around the world primarily for the detection of
learning disorders in school aged children. Since the good doctor has
passed away I have been tempted to resurrect my design and
commercialize it. I can think of a few posters in here that I would
love to take samples on!
 
R

R Adsett

Jan 1, 1970
0
Is the input to the PLC required to be ~linearly scaled or do you
simply require a specific preset level indicator, with a tolerance?

Wouldn't simple level translation suffice for either a linear or
switched signal? Isolation could be an added complication, requiring
interface power on the 50mV side.

RL
Standard Industrial module from DataForth or Analog Devices
http://www.dataforth.com/catalog/doc_generator.asp?doc_id=266

Robert
 
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