simple sampling algo question

Hello Ron,

>>
>>But for this stuff you don't need an analog input.
> 
> That may be true.  But the last few laptop PC's I looked at
> in the store didn't have any simple digital inputs (other than
> the keyboard keys).  They did have audio inputs though.
> Wonder how common that situation is getting to be...
> 
> Don't know if the OP stated whether the capacitive humidity
> sensor in question has analog or digital outputs, and at
> what levels.
> 

Well, he was saying that he uses a uC. Those have a dozen port pins or 
more and usually a comparator as well.

On a PC you are right, I'd probably do that job via the sound card. It's 
almost free since most PCs come with these standard.

Regards, Joerg

http://www.analogconsultants.com

Ron N. wrote:
> Joerg wrote:
> 
>>>>I'm still confused. If you want to count zero crossings with a computer,
>>>>how does an ADC help?
>>>
>>>It's the only analog input on many computer systems, other than
>>>those involving complex protocols such as USB, Firewire, ethernet,
>>>etc.   e.g. The microphone jack.
>>>
>>
>>But for this stuff you don't need an analog input.
> 
> 
> That may be true.  But the last few laptop PC's I looked at
> in the store didn't have any simple digital inputs (other than
> the keyboard keys).  They did have audio inputs though.
> Wonder how common that situation is getting to be...
> 
> Don't know if the OP stated whether the capacitive humidity
> sensor in question has analog or digital outputs, and at
> what levels.

The sensor controls the frequency of an oscillator, a good strong 
oscillator probably putting out a 3-volt square wave at low impedance. 
V-to-F converters are an alternative to 3-20 ma current loops. They are 
intended for industrial environments and don't need coddling.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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