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Topic: Creating ones' own analog multiplexer (Read 819 times) previous topic - next topic

oric_dan


EDIT - Just realised, this may belong in the multiplexing forum...


This is "definitely" an electronics problem. And as everyone else says, there's not enough info given to even guess at what to do with this. I hope you're not trying to run 1-Amp through an analog multiplexer channel.

jtw11


I hope you're not trying to run 1-Amp through an analog multiplexer channel.


Nope - fear not.

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so 5v peak to peak and only a few mA are the requirements.


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It is only an issue if there is sufficient current flowing to drop a voltage across it that could interfere with your measurements.
The Bosch sensors use a precision laser trimmed resistor that account for manufacturing variations in each sensor - adding an ohm or so to this resistor would throw the sensor way out of cal.

The monitoring cell in a wideband sensor is maintained at 450mV by the pump cell, so adding an ohm or so there would offset the result into the controller - this however would be a known, and I could account for this in software. Unfortunately that's not the case with the calibration resistor.


tmd3


The monitoring cell in a wideband sensor is maintained at 450mV by the pump cell, so adding an ohm or so there would offset the result into the controller - this however would be a known, and I could account for this in software. Unfortunately that's not the case with the calibration resistor.
Rethink this.  Adding an ohm or so in series with the analog input, impedance of around 100 megaohms, won't make much difference.

If you expect to connect your analog mux some way other than in series with an analog input, I'd like to know what you're planning.

Grumpy_Mike

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adding an ohm or so to this resistor would throw the sensor way out of cal.

I too think this is wrong.

DVDdoug

Even mechanical relays have a fraction of an ohm resistance.    Connnectors too...   I assume you'll need to add a pair of additional connectors in-line...

If you are measuring voltage, a small series resistance should't be an issue.  If you are measuring resistance (or current) you may need to add a buffer circuit of some kind before the multiplexer.   If that's not practical, the whole concept may not be practical. :(

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