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From: Guenter Roeck <linux@roeck-us.net>
To: lm-sensors@vger.kernel.org
Subject: Re: [lm-sensors] [PATCH] hwmon: ntc: Improve precision of resistance calculation
Date: Wed, 03 Jun 2015 22:27:57 +0000	[thread overview]
Message-ID: <556F7F6D.8010407@roeck-us.net> (raw)
In-Reply-To: <1433270907-24933-1-git-send-email-chris.lesiak@licor.com>

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 <chris.lesiak@licor.com>

Applied to -next.

Thanks,
Guenter


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      parent reply	other threads:[~2015-06-03 22:27 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-02 18:48 [lm-sensors] [PATCH] hwmon: ntc: improve precision of resistance calculation Chris Lesiak
2015-06-02 20:19 ` Guenter Roeck
2015-06-02 20:57 ` [lm-sensors] [PATCH] hwmon: ntc: Improve " Chris Lesiak
2015-06-03 22:27 ` Guenter Roeck [this message]

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