Intake Air Temperature

[Ord Millar]

I recently did a lot of worth with a temperature sensor in liquids - and a
sensor in flowing liquid has a time constant of 5 seconds or so (time to
reach 90% of the new value).  The TC for most sheathed  temperature sensors
in air is 30-90 seconds.  The problem is that dry air has low heat capacity
compared to solids or liquids, and gases are poor conductors of heat.

-----Original Message-----
From: C. Brooks <cbrooks1 at tqci.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Sunday, May 30, 1999 12:21 PM
Subject: Re: Intake Air Temperature


>Why don't you think faster response times are available?
>
>Charles Brooks
>
>-----Original Message-----
>From: Ord Millar <ord at aei.ca>
>To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
>Date: Sunday, May 30, 1999 1:14 AM
>Subject: Re: Intake Air Temperature
>
>
>>Depends on required accuracy... I like national LM34DZ - it outputs
>>10mV/degree F, doesn't require a fancy power supply, or any circuitry on
>the
>>output, and they're cheap.  They are good to around 1 celcius.
>>
>>Instantaneous is impossible, but with carefull design you should be able
to
>>get 15 second response from a semiconductor, RTD or TC in a fast flowing
>air
>>stream.  Be carefull with leads - this is one big source of error and
>delay.
>>Keep the wires a fine as possible so they don't conduct hear to or away
>from
>>the sensor.
>
>