Also, there are quite a few LT431 options. Could you point me to one that I can use from Digikey? --> https://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&KeyWords=TL431
Any thing that is in stock. I would use one in a TO92 package.
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Also, there are quite a few LT431 options. Could you point me to one that I can use from Digikey? --> https://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&KeyWords=TL431
Yes, 5V will work.
I am not familiar with Arduino-Uno. Most uPs I have worked with can optionally make the internal reference available on one of the pins of the microcontroller. If so, we could use that voltage as a reference source instead of having a secondary reference. Advantage of that is since the ADC inside the Atmega is ratiometric with respect to the internal reference, then there will be no relativer drift between the external and internal reference...
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Finally, I will look into seeing if the controller has an internal reference available. If so, where will this internal reference line be connected to in the schematic?
Also, will the ground of this circuit be connected to the ground of the sensor as well?...
Okay. Does this mean that I can have V1 as 5V?
I'm not sure what you meant by a reference into the controller, but I think this will answer your question: https://arduino.cc/en/Reference/AnalogReference
The controller is an Arduino-Uno.
Hi Mike, thanks alot so far for your help. I had another question. What is the V1 for? why do we need it and where will I get that power from?...
Attached is a single supply circuit with offset. The voltage reference can be a TL431 or op amp. All op amps will need to be single supply type if you only have a positive supply.
Question: How is the sensor generating negative output voltage if it's powered only by a positive supply?
View attachment 70341
Stileto, I reread the entire thread and I think I finally understand what you want. What caused the confusion is your use of the word "map". It has a meaning which does not apply to what you want...
You need a preamplifier (opamp) with two adjustable pots, one labeled GAIN and the other labeled OFFSET. The Gain pot needs to adjust the gain of the opamp stage from a minimum of about 0.3 to a max of about 3. The Offset pot should add or subtract an offset to the output of the opamp from ~-1V toss +3V. This will let you adjust things so that you can fill the ADC's 0V to 5V dynamic range with your sensor signal.
Furthermore, the input impedance of the preamp stage should be high enough so as not to load the sensor, which apparently has a high output impedance.
The problem will be that you will have to make several iterative adjustments while monitoring the ADC input signal with an oscilloscope to make sure that the ADC signal is centered at 2.5V, and its peak-to-peak amplitude doesn't go below 0V, or above +5V.
.... What do you mean I will have to make adjustments while monitoring the adc input signal? ...
You will have to look at the signal with a scope to determine if it clips at 0V or +5V.
Let me ask another question. Do you really care about the steady-state output of the sensor (DC level), or do you just care that when the sensor has a time-varying (AC) output that it be centered on 2.5V, and that the peak-to-peak amplitude is adjusted to swing from 0V to 5V?
That could be done by using a DC blocking capacitor, and only a single adjustable gain stage.
U1 is a rail-to-rail 5V OpAmp. X1 is a 100K pot. Sensor output can be anywhere from 1Vpp to 15Vpp. Output is always referenced to 2.5V.
...Also can you explain what is going on in each segment or part of the circuit as it takes in the sensor's signal?