# How many bits would an ADC require to measure...

1. May 9, 2015

### lcr2139

1. The problem statement, all variables and given/known data
How many bits would an ADC require to measure the output of the preamp?
What minimum frequency would the ADC need to sample at to measure the 4KHz signal accurately?
What would the data rate from the ADC need to be at the minimum sample rate?
Given a hydrophone with the following characteristics:
Sensitivity -186dB re 1V/uPa
Capacitance 12 nF
Dissipation factor (AKA Tan Delta, Loss Angle) 0.015

2. Relevant equations
I am not very familiar with ADC's, numbers of bits, sample rates and data rates. Could someone put me in the right direction by teaching me a little about digital circuits, ADC's, sample and data rates, and bits?

3. The attempt at a solution

2. May 9, 2015

### Svein

This is a bit like asking "How high is up?". As many bits as you want!
As per Nyquist theorem: 8k samples/s.
Again: Whatever you want. You cannot get more than 8000 samples/s, but it is up to you how often you read the ADC.

Check out http://www.ti.com/product/ads1291. You can choose between a 16 and a 24 bit ADC - which means a resolution of 15.2ppm or 0.06ppm (parts per million). Consider yourself lucky if your analog part has a precision of 1%.

3. May 11, 2015

### CWatters

You can buy 16 or 24bit USB ADC intended for capturing music. Sample rates 44kHz -96kHz. Companies like Behringer or Focusrite perhaps. Beware some very cheap ADC may say they are 24 but won't really be 24 bit quality.

4. May 11, 2015

### Svein

As I said - the analog part probably won't be better than 1% - which is the equivalent of 7 bits.