[time-nuts] Frequency referenced temperature regulator

[Bob Camp]

Hi

If you run through the major distributors, there are a wide variety of parts available. You either dig in on thermistors or on RTD's. The RTD is more linear and normally made from platinum. The thermistor is a better choice for a single point controller. Both are available in glass packages for sub $5 prices. Traditionally the glass parts have been the most stable. 

You can go off to people like Hart and get stainless steel sheathed versions of either one that are certified to be quite accurate over a very wide range. You will pay a bit more for the high accuracy stuff (like kilo bucks). 

Bob


On Nov 11, 2010, at 12:02 AM, Perry Sandeen wrote:

> List,
> 
> Looking for a stable temperature sensor I first went to YSI.  They have sold their sensor products to.  Measurement Specialties, Inc.
> 
> Perusing their site I came upon a Ni1000 SOT temperature sensor.  It is a nickel based unit that has a basic resistance of 1K ohms at 20 degrees C and rising to 1482 ohms at 80 degrees C. .  It has close to a 6 ohm change per degree.  I tried to find one of their distributors without success.
> 
> Entering the part number in Google, I found it is also made by ZETEX.  ZETEX calls it an  IC TEMP SENSOR NI1000 SOT23-3.  The Digi-Key catalog as part number is ZNI1000CT ND.  They are $2.77 each.  
> 
> The ZETEX data sheet has a nice circuit for a digital thermometer.  
> 
> Perhaps a LM 331 precision voltage-to-frequency IC or using a change in a bridge circuit to a varactor on a VCXO might provide the lack of aging problems that exist with a thermistor when precisely trying to obtain a temperature-to-frequency conversion.
> 
> From another site:  DIGI-KEY   Did you know that you can get FREE shipping on your order? Yes, that's correct -- no minimum order fee and no shipping charges.  The "secret" is that you must send them a check or money order by mail. Time-wise, it will add a couple days to get your parts over ordering them via internet or phone -- the time it takes your letter to get to Minnesota.  (See their "terms and conditions" on their website -- they cover themselves for very heavy cheap items.)
> 
> Regards,
> 
> Perrier
> 
> 
> 
> 
> 
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