SHT20 vs SHT10, or SCD30 sensor recommendation?

Hello,

Edit: Does this belong more in the coding forum?

I'm currently working with this SHT20 I2C temperature and humidity sensor: https://www.dfrobot.com/wiki/index.php/SHT20_I2C_Temperature_%26_Humidity_Sensor_(Waterproof_Probe)_SKU:_SEN0227

In their documentation it places the SCL and SDA specific pins above the AREF pin.

However in the sample code provided using their supplied library SDA is commented to be A4 and SCL as A5.

I've tested the sample code with the sensor connected to both configurations and it works fine.

My first question is, can I have two SHT20's connected to both my SDA/SCL specific pins and the A4/A5 configuration? Or does the I2C interface prevent this?

My reason for asking this is because I would like to have multiple tmp/hum sensors working from my uno. A similar sensor, the SHT10 (a little less accurate) has the pins defined as any set of 2 pwm DIG pins. Would the SH10 be a better use case for me because of the multiple desired sensors?

Follow up question, could an UNO + Ethernet Shield support 3 SHT10's? Shield taking pins 4,10,11,12, & 13, leaving pwm pins 3,5,6, & 9, I guess the limit is two in this case.

For an uno paired with an ethernet shield is there a better tmp/hum sensor that would only use analogue pins?

Lastly, what's the communities thoughts on this one: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/0_Datasheets/CO2/Sensirion_CO2_Sensors_SCD30_Datasheet.pdf

Could I run three of those on an UNO + ethShield? one set to modbus and the TX/RX interface, and the other 2 set to 12C where one is connected to my SCL/SDA specific pins and the other to A4/A5?

I'm starting to get the feeling that it might be a better idea to upgrade to the mega at this point.

Thanks for any help!

In their documentation it places the SCL and SDA specific pins above the AREF pin.

However in the sample code provided using their supplied library SDA is commented to be A4 and SCL as A5.

On the UNO these pins are internally connected. On other boards you should use the pins labeled SCL/SDA and not A4/A5!

My first question is, can I have two SHT20's connected to both my SDA/SCL specific pins and the A4/A5 configuration?

No.

You could use multiple SHT20 on the same Arduino buy connecting them through a PCA9548 bus multiplexer. The chip has eight buses, each one can be selected separately. You could connect up to 8 of these chips so you get a maximum of 64 SHT20 theoretically. The problem you might get: each I2C bus has a maximum length of about 50cm. If you get above that limit the transmission gets unreliable.