I followed the Arduino Code | Adafruit 4-Channel ADC Breakouts | Adafruit Learning System single ended conversation code using an ADS1115 to begin trying to convert a signal from a signal generator outputting 100 KHz and -5 dBm of power. I put the signal in A0 and get results of
AIN0: 24
AIN1: -672
AIN2: -622
AIN3: -668
Are these normal results? They hover around these values. I can provide pictures if necessary. Im also very new to everything circuits.
Read the spec sheet. The maximum sample rate is less then 1KHz. Trying to sample a 100KHz signal is not going to work!
As stated by @oldcurmudgeon 100k is way too fast. Next is, what is -5dBm? dBm is measured in milliwatts so we would need to know into what impedance is your signal going to?
the results are pretty much what you would expect. If there is no connection to an adc port what should the reading be? (THINK - the answer is NOT zero)
So if the maximum sample rate is 1KHz then you will have to put your signal generator down to about 50Hz to see anything resembling the shape of your signal. The highest you can detect information about a wave's frequency is 500Hz, but then you will only have two samples per cycle so it won't look like a waveform.
As to what happens when you leave an input unconnected with no signals on the other pins you get this:-
However, if the other pins have a signal on them, then the unconnected pin will tend to follow this signal, like this:-
This is due to there being only one analogue input on an Arduino with the 6 so called inputs you have being switched internally. The sample and hold capacitor on the A/D input carries some of the charge from the last measurement.
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