DrDAQ Resolution

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luckyjimmy
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DrDAQ Resolution

Post by luckyjimmy » Wed Jul 31, 2013 7:01 pm

I've been asked to write an application for the Raspberry Pi that uses the DrDAQ data logger to record a low level voltage (100 - 200mA at most). I've written the application but found there are only three data points at a peak in the signal. Is it possible to reduce the voltage range using the SDK, from the default DrDAQ setting of +10 to -10V, increasing the resolution?

I'm using the scope input set, as mentioned, at +10 to -10V. With an ADC of 8bits, this is a resolution of approximately 78mV (unless I've got my sums wrong).

If there is a way to switch ranges to say +2.5 to -2.5V using the SDK, that would give me a resolution to about 20mV. I would have about ten data points per peak if this was possible.

Thanks in advance for any help given.

Martyn
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Re: DrDAQ Resolution

Post by Martyn » Thu Aug 01, 2013 8:59 am

Take a look at the UsbDrDaqGetScalings and UsbDrDaqSetScalings commands. They are +-1.25V, +/-2.5V, +/-5V, +/-10V for the scope channel.
Martyn
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luckyjimmy
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Joined: Wed Jul 31, 2013 6:32 pm

Re: DrDAQ Resolution

Post by luckyjimmy » Thu Aug 01, 2013 2:47 pm

Thanks for the information Martyn, I did not appreciate what these functions did (I just had a vague idea that they were for external sensors).

Anyway, after altering the signal source slightly to try and improve its sensitivity, I changed to the +-1.25V range using the functions you suggested. The system is now being tested as we speak...many thanks, JHC.

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