From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Date: Wed, 03 Jun 2015 22:27:57 +0000 Subject: Re: [lm-sensors] [PATCH] hwmon: ntc: Improve precision of resistance calculation Message-Id: <556F7F6D.8010407@roeck-us.net> List-Id: References: <1433270907-24933-1-git-send-email-chris.lesiak@licor.com> In-Reply-To: <1433270907-24933-1-git-send-email-chris.lesiak@licor.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lm-sensors@vger.kernel.org On 06/02/2015 01:57 PM, Chris Lesiak wrote: > The function get_ohm_of_thermistor has both the measured voltage and the > pullup voltage available in microvolts. But it was promptly converting > both to millivolts before using them to calculate the thermistor > resistance. That conversion unnecessarily hurt the precision of the > calculation. > > For example, take the ncpXXwb473 connected to 5000 mV and pulled down > through a 47000 ohm resistor. At 25 C, the resistance of the thermistor > is 47000 ohms. The measured voltage will be 2500 mV. If we measure > instead 2501 mV, then the calculated resistance will be 46962 ohms -- > a difference of 38 ohms. So the precision of the resistance estimate > could be increased by 38X by doing the calculations in microvolts. > > Signed-off-by: Chris Lesiak Applied to -next. Thanks, Guenter _______________________________________________ lm-sensors mailing list lm-sensors@lm-sensors.org http://lists.lm-sensors.org/mailman/listinfo/lm-sensors