PSN-L Email List Message

Subject: Re: capacitance to digital converter
From: "James Hannon" jmhannon@.........
Date: Wed, 31 Aug 105 08:31:17 CDT

I have been looking at these parts for a while and have some samples ordered. What I am planning to do is to interface the part to a DLP2232M The DLP2232M will talk I2C and plug into a USB port. There is software avaliable to interface with the I2C data but one would have to write an application to log the data. The DLP2232M is also a dual serial port to USB and other various serial and parallel interfaces.

Jim Hannon

---------- Original Message ----------------------------------
From: "Jack Ivey" 
Reply-To: psn-l@..............
Date:  Wed, 31 Aug 2005 09:09:57 -0400

>I just stumbled across something a few people might find interesting,
>it might also be relevant to the water seismo discussion.
>Analog Devices has a capacitance to digital converter. Basically, you
>hook up your capacitive (position) sensor to an excitation output pin
>and a sense input pin, and the chip puts out a 24-bit digital output.
>They're claiming
>from 16 to 21 useful bits at a 10+ Hz rate.  the '45, '46 are for
>floating sensors (single ended or differential) where you have 
>access to both sides of the capacitor, and the '47 is for a grounded
>differential sensor.
>Hooking it up isn't completely trivial, it requires 
>knowledge of microprocessor communications (I2C).  If it works
>out ok, the electronics for a non-feedback seismo might be reduced to
>this chip, an 8-pin microprocessor putting the data out on
>RS-232, and a few Rs and Cs.
>The part numbers are AD7745-AD7747. The AD7747 is not quite in 
>production yet).
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>See for more information.
Jim Hannon


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