RE: [ts-7000] Measuring car voltages with a MAX197 [2 Attachments]

[Noel Diviney <>]

[Attachment(s) from Noel Diviney included below]

Hi Yan,

I had a similar need where I wanted to be able to measure a 24 volt battery. I level converted the voltage range 18 to 28 down to 0 to 5 volts for input to a PSoC using the attached circuit (See Screenshot011.png). I used Tina TI to model the circuit. You will have to adjust the resistor values to suit your particular requirements.

Tina TI is available freely from
http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html

Having installed Tina you can open the attached BattLevelXlator.TSC

Hope this helps,

Best regards,

Noel.

Noel Diviney Ayrenet Pty Ltd,1/5 Viewtech Place,Rowville, Vic. 3178, Australia Phone +61 3 9755 6466 email

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To:
From:
Date: Tue, 8 Jun 2010 15:29:28 +0000
Subject: [ts-7000] Measuring car voltages with a MAX197

 

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.

--Yan

--
If you have eight hours to chop down a tree
spend six sharpening your axe.
--Abraham Lincoln

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Attachment(s) from Noel Diviney

1 of 1 Photo(s)

ScreenShot011.png

1 of 1 File(s)

BattLevelXlator.TSC

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