From: John Larkin
Subject: Re: Quickie Thermal Probe
Date: Thu, 12 Dec 2002 16:47:09 -0800
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On Thu, 12 Dec 2002 17:46:24 -0800, Mike Monett wrote:
>I can see it now - one to drive, one to hold it out the window, and one
>to record the speedo and meter readings. And onlookers shaking their
>heads in amazement!
>Your approach sounds good, and probably worked very well. I'm thinking of
>a much smaller temperature rise in the sense transistor - perhaps several
>degrees above ambient. Hopefully this will allow it to sense small
>changes in temperature as well as air currents.
>I'm not actually trying to measure wind velocity. The problem is mold
>spores coming up from the basement. I have carefully sealed all the floor
>trim and other cracks in the appartment, shut off the heating system and
>sealed the vents, sealed the entry holes for the pipes in the kitchen and
>bathroom, and sealed the light fixtures and wall switches. So there's no
>great rush of air, just a constant seepage. This allows spores to enter
>the appartment that make me very ill.
>I felt some suspected areas with my finger but could not feel anything.
>There are other places too difficult to reach, which is why I'm looking
>for a sensitive probe. A diffamp looks promising, and from your
>description the SOT-23 seems a bit better than a TO-92.
Heck, when we want a qualitative indication of air flow, we just go
around the corner to the Chinese gift shop and buy some incense
sticks. They're great for tracking air flow in fan-cooled widgets and
It's interesting that one usually can't predict the direction of air
flow within a box, much less the velocity.