transistor equals temperature
transistor equals temperature
(OP)
Hello:
I am trying to get a general purpose transistor e.g. 2n4124,CA3046, or 2n2222, to yield 1 degree accuracy of the enviromental air temp. Using a delta Vbe, My Eq. is: T=(q(Vbe1-Vbe2))/(K(LN(Ic1/Ic2)). The circuit plus Eq. yields roughly 40 deg. at room temp 22 deg. Am I missing something that the highly predictable results of a transistor can give. Yes I know there are predeigned IC for this application; However, I would like to use a GP transistor.
thanks a bunch, too hot
I am trying to get a general purpose transistor e.g. 2n4124,CA3046, or 2n2222, to yield 1 degree accuracy of the enviromental air temp. Using a delta Vbe, My Eq. is: T=(q(Vbe1-Vbe2))/(K(LN(Ic1/Ic2)). The circuit plus Eq. yields roughly 40 deg. at room temp 22 deg. Am I missing something that the highly predictable results of a transistor can give. Yes I know there are predeigned IC for this application; However, I would like to use a GP transistor.
thanks a bunch, too hot





RE: transistor equals temperature
low enough current, so the series resistances don't cause significant error.
I don't understand the 40....22 ???
If you use conputer interface, the computer can take care of the calibration factors, too.
<nbucska@pcperipherals.com>
RE: transistor equals temperature
Cordially;
Xray
RE: transistor equals temperature
There are plug-in breadboards for PC with interface
Look up www.maxim-ic.com or linear, dallassemi etc
how they do it. and their AP notes.
<nbucska@pcperipherals.com>
RE: transistor equals temperature
Any help is appreciated.
RE: transistor equals temperature
<nbucska@pcperipherals.com>
RE: transistor equals temperature
RE: transistor equals temperature
S/H leakage, offset etc. error, non-linearity ?
<nbucska@pcperipherals.com>
RE: transistor equals temperature
A silcon junction as the base to emitter in a bipolar transistor is a good choice as a temperature sense element.
It has good liniarity from -55 to about +150C. With a current of about 1 mA, it changes about 2.2 mV per deg C, with the voltage drop decreasing as temperature increases. Calibrate with ice water for 0 deg C, and boiling water for 100 deg C (assuming you are close to sea level). This method of temperature measurement is commonly used in many systems because of its simple accurate and inexpensive approach.
Elecmec
RE: transistor equals temperature
John Markus, "Electronic Circuits Manual," McGraw-Hill Book Company, 1971
Substrate Temperature Control on page 833