Optocouple analog input
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Posts: 46,084
Hello Group:
Does any one know how can I built a optocouple analog
input?, this input has a range of 0 to 10 V dc.
I appreciate any help.
Thanks.
=====
Alberto Zamora Estrada.
Phone: (506) 220-6736.
Cell: (506) 374-3846.
Fax: (506) 220-8684
Investigaci
Does any one know how can I built a optocouple analog
input?, this input has a range of 0 to 10 V dc.
I appreciate any help.
Thanks.
=====
Alberto Zamora Estrada.
Phone: (506) 220-6736.
Cell: (506) 374-3846.
Fax: (506) 220-8684
Investigaci
Comments
ACJacques
Alberto Zamora wrote:
>
> Hello Group:
>
> Does any one know how can I built a optocouple analog
> input?, this input has a range of 0 to 10 V dc.
>
> I appreciate any help.
>
> Thanks.
>
> =====
> Alberto Zamora Estrada.
> Phone: (506) 220-6736.
> Cell: (506) 374-3846.
> Fax: (506) 220-8684
> Investigaci
differential because this card will operate in a plant
where there are a lot of problems with grounds, the
signal may vary between 0 and 1 mA, the MUX 8 to 1 and
the Analog to digital converter is done.
Thanks.
--- "A.C.Jacques" <acjacques@i...>
escribi
Most optically isolated INPUT systems use a pair of analog FET
opto-isolators. This requires a separate power supply for the front end
circuitry (usually floating battery pack). A few companies have developed
these kind of systems with 12 bit converters for use as headstages in
neurobiological research.
It might be easier to power a serial converter, send it's output to the
stamp through a more conventional 6N series opto-isolator.
Remember, all fully differential measurements are made with three wires!
Mike
At 12:12 PM 6/21/2001 -0500, you wrote:
>I'm doing a 8 analog input card, this input has to be
>differential because this card will operate in a plant
>where there are a lot of problems with grounds, the
>signal may vary between 0 and 1 mA, the MUX 8 to 1 and
>the Analog to digital converter is done.
>
>Thanks.
>
>
>
>--- "A.C.Jacques" <acjacques@i...>
>escribi
are a led that draws 10 ~ 30 mA. Probably you will need a
buffer/amplifier before to enter the signal in the opto.
Take a look in optoisolators page at the digikey.com
ACJacques
Alberto Zamora wrote:
>
> I'm doing a 8 analog input card, this input has to be
> differential because this card will operate in a plant
> where there are a lot of problems with grounds, the
> signal may vary between 0 and 1 mA, the MUX 8 to 1 and
> the Analog to digital converter is done.
>
> Thanks.
>
>
> --- "A.C.Jacques" <acjacques@i...>
> escribi
>input?, this input has a range of 0 to 10 V dc.
Agilent makes something for you...
DESCRIPTION
The HCNR200 high-linearity analog optocoupler consists of a high-performance
AlGaAs LED that illuminates two closely matched photodiodes. The input
photodiode can be used to monitor, and therefore stabilize, the light
output of the
LED. As a result, the nonlinearity and drift characteristics of the LED can be
virtually eliminated. The output photodiode produces a photocurrent that is
linearly related to the light output of the LED. The close matching of the
photodiode and advanced design of the package ensure the high linearity and
stable gain characteristics of the optocoupler.
Infineon's IL300 is similar. <www.infineon.com>
Also look here: http://www.ssousa.com/products/slc800.htm
Mike Hardwick, for Decade Engineering -- <http://www.decadenet.com>
Manufacturer of the famous BOB-II Serial Video Text Display Module!
there to build very good isolators. I built a couple with one ISO122P
isolator chip, two DCP010515DP isolated power supply chips and eight
small tantalum capacitors each. Very simple.
--- In basicstamps@y..., Alberto Zamora <azestrada@y...> wrote:
> Hello Group:
>
> Does any one know how can I built a optocouple analog
> input?, this input has a range of 0 to 10 V dc.
>
> I appreciate any help.
>
> Thanks.
>
>
> =====
> Alberto Zamora Estrada.
> Phone: (506) 220-6736.
> Cell: (506) 374-3846.
> Fax: (506) 220-8684
> Investigaci
clip.....
> Remember, all fully differential measurements are made with three
wires!
> Mike
Can you elaborate?
Aaron
Sure. On a truly fully differential voltage measurement, you are measuring
the difference in voltage potentials between to points relative to a
reference. If you simply use two wires, all bias currents flowing through
one input MUST return through the other. The ideal difference amplifier
used to make this measurement has high (ideally infinite) input impedance.
Therefore, the input characteristics (mostly input bias currents) will
cause an error in the measurement.
One solution, if high input impedance isn't a requirement, is to return
these currents through resistors to signal ground at each input. Again, a
mismatch in these resistors will give a I*R voltage error with the input
bias currents.
Usually, this doesn't present a problem in a low resolution (12 bits or
less) application where you are trying to just eliminate common mode noise.
This is just one of many reasons for using a fully differential
measurement. Even on low impedance measurements like thermocouple
amplifiers and bridge amplifier applications, a balanced current return is
provided to inputs.
Analog Devices and Burr Brown (TI ????) have good discussions of this on
their sites. http://www.burrbrown.com/applications/ and
http://www.analogdevices.com/industry/amplifiers_linear/inAmps.html
Hope that helps.
Mike
At 07:43 PM 6/21/2001 -0400, you wrote:
>On Thu, 21 Jun 2001 10:40:19 -0700 Mike Walsh <walsh@c...> writes:
>
>clip.....
> > Remember, all fully differential measurements are made with three
>wires!
> > Mike
>
>Can you elaborate?
>Aaron
>
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_________________________________
Mike Walsh
walsh@i...