Re: circuit too temperature sensitive

"John Popelish" <jpopelish@xxxxxxxx> wrote in message
news:DP2dnbJ4LtV0bnLbnZ2dnUVZ_sOrnZ2d@xxxxxxxxxxxxxx
Thomas wrote:
Experimenting with an proximity sensor based on the ST TDE0160. It is
showing a huge temperature dependancy, if ambient temperature changes
more than a little then the "range adjustment" is lost. Adjusting Rh
brings it back in tune... can I just put a PTC thermistor in series with
Rh? or what?

I assume this is the device in question:
http://www.tranzistoare.ro/datasheets/185/325768_DS.pdf

Page 4 shows the temperature sensitivity of the oscillator negative
resistance but it isn't extremely large (maybe 9% over more than 160
degrees C range).

The operation is also affected by the temperature sensitivity of the
resonator coil resistance, the resonator capacitance and losses and
probably most important, the core permeability and losses.

What kind of capacitor are you using in the resonator?

What kind of core material are you shaping the coil field with?

Yes, that's the part. newer spec ***:
http://www.st.com/stonline/products/literature/ds/1513/tde0160.pdf

The resonator cap is a .001uf multilayer ceramic, currently only an X7R.
The core is "P" ferrite, 2500 permeability:
http://www.mag-inc.com/pdf/2006_Ferrite_Catalog/2006_Materials.pdf.
The "sensitivity" pot is 50K, TCR=150ppm/C


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