Analog inputs
Analog inputs (AI) are for measuring analog values such as DC voltage, current and resistance. These values are produced by sensors which indicate multiple states such as thermometers, tensometers, distance meters, lux meters etc.
Analog inputs on Neuron and Axon
The functionality of AIs on Neuron and Axon is different on Group 1 and Group 2/3 and Neuron extensions.
On Group 1, the analog input is capable of:
- measuring 0-10V DC
- measuring 0-20mA DC
The Group 1 is also capable of measuring the resistance, but this is achievable with Analog output.
On Group 2 and 3 and the Neuron extensions, the analog input is capable of:
- measuring 0-10V DC
- measuring 0-2.5V DC with higher precision
- measuring of 0-20mA DC
- measuring of resistance 0-100kOhm via a 2-wire method
- measuring of resistance 0-2kOhm via a more precise 3-wire method
Changing between modes depends on the software you are using, please follow the relevant tutorial.
Analog inputs on Unipi 1.1
The Unipi 1.1 has two analog inputs and they are only capable of measuring voltage in a range of 0-10V DC.
Measuring resistance
To measure resistance from the Unipi 1.1's AI (ie. by using PT1000 thermal probes), it is necessary to add a resistor according to the following scheme.
R_sens = the sensor itself R_ref = the reference resistor
There is also a input resistor inside of the AI with the value:
R_ai = 12200ohm
For R_sens >= 200ohm, use R_ref = 1k. For R_sens < 200ohm, use R_ref = 10k
The value at the AI is calculated from the voltage you read from the AI (V_ai)
Vcc - V_ai R_ref * R_ai
R_sens = ------------ * --------------
V_ai R_ref + R_ai
The Vcc is the applied voltage (12V in the picture above).
