[sdiy] Temperature Compensated Exponential ConverterUsingSSM2164

[Ian Fritz]

At 10:02 AM 9/1/2009, Ingo Debus wrote:

>Am 01.09.2009 um 14:58 schrieb cheater cheater:
>
>>>I think we need to have some heater/tempsensor hooked to it only
>>>for the
>>>purpose of trimming.
>>
>>How will you know your temp sensor isn't lying?
>
>How precise do we need it to be? Maxim, for instance, makes some nice
>digital temperature sensors with up to +/- 0.5 °C precision. I think
>the bigger problem is to keep the sensor and the device under test at
>the same temperature.

Yeah, I just used the old National whatever deg Kelvin sensor.  Being off 
by a couple of degrees doesn't much matter, especially since you only use 
the *change* in temperature.

I mount the board in an Al box, which spreads the heat out quite 
evenly.  As an extra, I surround the board with crumpled-up newspaper to 
eliminate drafts.  Oh, and I mounted the T sensor close to or incontact 
with the expo pair. Even if the sensor isn't well coupled it doesn't matter 
much, again because we are interested in temperature *differences*.

We do not need super precise or accurate results here.  But I agree that 
previous experience in doing this kind of work does help.


Ian