On Tue, 8 Jun 2010, Yan Seiner wrote:
> I'm going to be using the TS7200 with the on-board MAX197 to measure car
> battery voltages. Load dumping is not an issue - the batteries I am using
> aren't connected to the alternator.
>
> The chip has a 0-10 VDC range and I need to measure voltages from about 8
> to 16 VDC. I had thought of using a simple resistor divider but now I'm
> not so sure. The voltage I'm measuring is pretty steady, so speed of
> measurement is not an issue; I will be recording once per minute.
>
> The MAX197 http://datasheets.maxim-ic.com/en/ds/MAX197.pdf claims a "input
> dynamic resistance" of 21kohms.
>
> Does anyone know what that means? Can I just add 21Kohms in series and
> drop the voltage in half? Should I use a 10.5K + 21K divider, and count
> on the resistance of the MAX197 to cut that in half?
>
> I don't need absolute accuracy; I can calibrate the resulting readings to
> a known-good voltmeter. I do need accuracy over the range I'm expecting.
I've always added an opamp to buffer, and put my resistor divider networks
in front of the high impedance opamp input.
cheers
Jim
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