At 09:37 PM 2/29/2004 -0600, you wrote:
>Hello,
>
>I am using an National LM60 temperature sensor that has Accuracy +/-=20
>3.0degC and Nonlinearity +/- 0.8degC in a project.  Am I correct in=20
>thinking that an accuracy error is an offset across the entire range,=20
>while nonlinearity varies across the scale, such that if the sensor was=20
>perfectly calibrated at one perfectly known temperature, the maximum error=
=20
>across the scale would be +/- 0.8degC?

NO. It says in the datasheet just what it means:

"Nonlinearity is defined as the deviation of the
output-voltage-versus-temperature curve from the best-fit straight line,
over the device=92s rated temperature range."

So, if you adjust it just do that the errors are equally distributed
all over the range from minimum to maximum, then the maximum distance
above and below a straight line should be +/-0.8=B0C.

Imagine the error was parabolic, for the sake of argument, and you
adjust the error at minimum to -0.8 degrees and the error at maximum
to be -0.8 degrees, then somewhere in the middle there would be an
error of +0.8 degrees.

Even double point calibration could leave errors of twice that if you
happen to calibrate it at points of maximum error (in the above example,
if you trimmed it in exactly at min and max, you'd be off by 1.6 degrees
at the middle. If you look at the typical error, it is actually more-or-less
parabolic (see graph 01268110 on page 4).

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the=
 reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body