Date:         Thu, 7 May 2009 07:56:34 -0500
Reply-To:     Larry Alofs <lalofs@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Larry Alofs <lalofs@GMAIL.COM>
Subject:      Re: O2 sensor transition time
Comments: To: Scott Daniel - Turbovans <scottdaniel@turbovans.com>
In-Reply-To:  <048601c9cec1$311e2940$6401a8c0@PROSPERITY>
Content-Type: text/plain; charset=ISO-8859-1

I thought that David WAS the original poster.   :-)

My answer:
  The one I have watched recently took about 2 sec to go from low
voltage to high and vice-versa, at idle.  This may not be typical.  I
believe it is the original VW sensor in my '91 GL with about 160k
miles presently connected to a Subie EJ22.

Larry A.


On Wed, May 6, 2009 at 10:08 PM, Scott Daniel - Turbovans
<scottdaniel@turbovans.com> wrote:
> very good.
> what is your answer then, to the poster's question ?
>
>
> ----- Original Message -----
> From: "David Beierl" <dbeierl@attglobal.net>
> To: "Scott Daniel - Turbovans" <scottdaniel@turbovans.com>
> Cc: <vanagon@GERRY.VANAGON.COM>
> Sent: Wednesday, May 06, 2009 7:11 PM
> Subject: Re: O2 sensor transition time
>
>
>> At 09:39 PM 5/6/2009, Scott Daniel  - Turbovans wrote:
>>>
>>> a new Bosch, and using a digital volt meter......
>>> the voltage was going from about .2 to .8 volts very, very fast.
>>> Like several swings in voltage change  or range, per second.
>>> I had never bothered to check a new one much.....and boy, did this one
>>> change voltages fast.
>>
>> Hi Scott -- unfortunately, with a digital meter of the usual type it's
>> very tough to see what's really going on, only that something is.  This is
>> because most digital meters use a technique called "dual-slope
>> integration" to develop the reading.  They typically generate a new
>> reading about 2-3 times a second, and use a significant fraction of that
>> time to sample the input signal; so when the input is changing the results
>> appear somewhat random.  The ideal way to measure is with a scope, but an
>> LED bar-graph display driven by an LM3914 chip, like Ken's little gadget,
>> is a very good alternative for this particular signal.
>>
>> Cheers,
>>
>>
>>  --
>> David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
>> '89 Po' White Star "Scamp"
>