I'm just beginning on the universe of Arduino, so I would like to make some questions about the connection between 3 types of sensors and Arduino:
PT100: I just read about the connection on many topics, but I would like to know if it's possible, instead of adding an amplifier (like MAX31865), add an analog-digital converter with 24 bits (like CJMCU-1232) and send a digital signal directly to Arduino?
Inclinometer: range of measure between -1 and 1 degree, with a millimetric precision, the output is between 4 and 20 mA.
LVDT: another sensor, with properties of measuring displacements between 0 to 50 mm, the output is -2.5 to 2.5v.
Could I do the same scheme of PT100 with the ADC converter to the Inclinometer and the LVDT to send the digital signal directly to Arduino?
Another question is: how to choose the correct resistence R1.
Thank you in advance
No you can't do any of those things !
A Pt100 sensor is used with a specific current in conjunction with amplifier , output change per deg of temperature is very small.
You can't send a negative voltage to your A-D or Arduino.
You need to google these sensors and how they work and how to use them .
Yes, the output is very small, and because of that, I'm suggesting to use an annalog-digital converter with 24 bits. Let's do a numeric example with PT-100:
Let's suppose I need to measure a range of 100 degrees with a precision of 2 digits, using a resistance of 3.3k on R1 and V1 = 5v:
Resistance at 0 °C = 100 Ω; voltage range on Vout = 147,06 mV
Resistance at 100 °C = 138.5 Ω; voltage range on Vout = 201,40 mV
Calculating the voltage range on Vout = (201,40 - 147,06) = 54,33 mV; precision of 2 digits: 0.01°C = 0,005433 mV, this is the minimum resolution I will need.
Now, using a ADC with 24 bits on 5v, resolution = 5/2^24 = 0,00029 mV
In this example, I will have more resolution than I need, and this is great. There is any problem to read a sensor with this mode?