I'm getting four more digital thermostats from Mcmaster Carr. Its a
Johnson controls A419 unit. This makes eight units on my place. I want
to get spare sensors and I'm thinking this must just be a
thermistor??? I see it can be ordered from the maufacturer, but I know
it will be a rip off price. Ideas for Digikey, etc.?

A419 thermostat:
http://www.prothermostats.com/produc...a7K godW3Jdaw
manual
http://cgproducts.johnsoncontrols.co...PDF/125188.PDF
sensor
http://cgproducts.johnsoncontrols.co...ID=A99BB-200C#

manual
http://cgproducts.johnsoncontrols.co...PDF/125188.PDF

P.S. page 10 shows resistance vs. temp of sensor

On 03/26/2011 05:02 AM, Karl Townsend wrote:
manual
http://cgproducts.johnsoncontrols.co...PDF/125188.PDF

P.S. page 10 shows resistance vs. temp of sensor

"PTC" generally means thermistor. Different thermistor materials have
slightly different curves, and of course moving the curve up and down is
just a matter of changing the thermistor area.

For the little ones that I've used there is no standard. There may be
an industrial standard for things like this, though.

This pretty much leaves you with having to shop around, and seeing if
you can find a sensor that looks like it has the same curve.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On 3/26/2011 7:22 AM, Karl Townsend wrote:
I'm getting four more digital thermostats from Mcmaster Carr. Its a
Johnson controls A419 unit. This makes eight units on my place. I want
to get spare sensors and I'm thinking this must just be a
thermistor??? I see it can be ordered from the maufacturer, but I know
it will be a rip off price. Ideas for Digikey, etc.?

Many years ago, I got good service from RCD.

http://www.rcd-comp.com/rcd/rcdpdf/ATB-ATS-PTB.pdf


Kevin Gallimore