USB-6210 and Scaling for 12VDC

[dwe1945]

I've been using a USB-6210 device to monitor some optical readings on a medical device. These signals all have been the range of 0-5VDC. Now I have been asked to also monitor a 12VDC power supply associated with this circuit to see if power supply fluctuations might be the cause of some problems we are seeing.

I'm using LabWindows/CVI v9 and theDAQmx library functions. The USB-6210 has a maximum range of 10VDC I believe. What would be the best way to scale the 12VDC so that a USB-6210 can monitor it?

I thought of using a resistor voltage divider, but I wonder if that will give a precise enough scaling for us. I've thought of using an opAmp with a gain of 0.5 for scaling, however I am a software engineer and opAmps are somewhat of a mystery for me.

Maybe I need to upgrade from a USB-6210 with something that uses input conditioning modules?

Any thoughts appreciated, and Thanks.

D. Wendelboe

[dwe1945]

Hi,

I'd recommend using the USB-9162 device. It is only 4 channels, but maybe you can use both the USB-6210 for exitsing work, and tie the 12VDC into the USB-9162.

Cheer

[SnowMule]

Voltage divider will work fine.

[johnsold]

I agree with SnowMule. 

For monitoring a power supply a simple resistive voltage divider is all that is needed. The accuracy using an op amp would be exactly the same (or worse) than the simple divider because the op amp circuit uses a voltage divider to set the gain.

If accuracy is a concern, then run a calibration.  The resistors should be sufficiently stable that simply measuring the input and output voltages of the divider one time with a digital multimeter (while the divider is connected to the power supply and the USB-6210) will give you the scaling factor. Enter that into your program and everything should be fine.

Lynn