Help understanding this sample schematic for an electrochemical cell sensor

[chogi]

Im trying to understand this sample schematic for a type of sensor i need to incorporate for a project. I understand the active low pass filter but not the ref for virtual earth or v set supply. Are these just voltage dividers between 5V rail and ground to achieve the desired voltages? I looked a bit online and on this forum and found nothing.

Also im brand new to pcb design. Am i going to need an additional power plane layer for this 2.5V virtual ground? Can i split the power plane into 0 and 2.5 V sections if i use the back of the pcb as a power plane? anything else to look out for when designing a schematic like this/ with this kind of sensor? Thanks in advance.

[inse]

Are you willing to share the datasheet (or link) so everyone will be able to get an understanding of what kind of sensor this is?
Or do you prefer a load of guesswork?

[chogi]

Data sheet
https://www.sgxsensortech.com/uploads/f_notes/PS1_PS4-Oxygen%20SGX%20Sensortech%20Circuit.pdf

Sample schematics
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.sgxsensortech.com%2Fcontent%2Fuploads%2F2014%2F08%2FA1A-EC_SENSORS_AN2-Design-of-Electronics-for-EC-Sensors-V4.pdf&psig=AOvVaw0YtcxnywPsIj6W6EQXU4Lg&ust=1736100604731000&source=images&cd=vfe&opi=89978449&ved=0CBcQjhxqFwoTCOj7jfDU3IoDFQAAAAAdAAAAABAE

[chogi]

I didn't think this was necessary as the question is about the meaning of the schematic on the left not the sensor itself

[Analog Kid]

It would help to know exactly what kind of opamp IC1 and IC2 are.
My guess™ is that they're using a split-supply opamp as a single-supply device, hence the "virtual ground" (splitting the supply in half).

[TimFox]

Note that IC2 is an inverting amplifier.  When operating from a single supply (+5V here), an intermediate voltage (+2.5V here) for “virtual ground” is mandatory, since as its input goes positive the output goes negative (and vice versa).  In the old days, split supplies were used with “real ground” so that the output could go positive or negative.
Any op amp will work with a single supply:  the question is what range of common-mode input voltage is tolerable and what range of output voltage can happen.  Older op amps intended for split supplies often require input voltage (common mode) substantially positive with respect to the negative power terminal.  Newer units designed for single supply operation can have input voltage somewhat negative wrt the negative supply, but the output is always positive wrt that terminal (grounded for single supply operation).
To forestall quibbling, there are very few op amps with an actual ground terminal (e.g., uA702) and some special ones have internal charge pumps to enable the output to go a bit negative of the power supply.

[inse]

Everything is pretty much explained in the datasheet from the second link.
As you see in the first schematic, the virtual ground is only a voltage divider.
For sure you will not need a ground plane for that as it is only a virtual ground without loading and in principle only attached to a single component.

[chogi]

I did some reasearch and found some op amps that can operate "rail to rail" I think this solves the issue as I dont think the sensing electrode will output a negative voltage (will it?). i'm just confused on the left side of the circuit how to construct each of the virtual ground and v ref voltage circuits. Also the bias listed for the specific sensor im using is listed as -300 mV. Is that the same as listed here with different notation? im not sure how bias voltage is defined here.

What would i need to change to accomplish a bias voltage of -300mV instead of 300mV if needed? would that change anything with the IC2 op amo?

[inse]

Why not take the MCP6032 as proposed in the first link?