Choosing the right USB DAQ device

[kat_l]

I'm a newbie to DIY labview (I've followed labscripts, etc but never started a solo project from scratch before). Can anyone provide some advice as to what equipment I'll need?

I want to take the output from 2 position sensitive detectors (1d linear photodiode arrays), perform a current-voltage/analogue-digital conversion, and record the value. Alongside this I'll need to control a stepper motor that will be rotating a light source ±60deg from the centre of each psd. And I need to be able to know which angle corresponds to which output from the psds. What equipment do I need? So far I've come up with the NI USB DAQ 6008. Would this be able to do what I've described above? I'm also a little unsure about the current-voltage conversion. Can the DAQ do this or will I need to use a cfb op amp before inputing the signal to the DAQ? 

Thanks! 🙂 

[Dominic.Walker]

Hey,

All our DAQ cards have ADC's inside them, so you wont need an op amp.  As for which specific one you'll need, it depends on the sample rate, accuracy, and resolution you require.  As for controlling the stepper motor, you will probably need a motor driver.  The 6008 can only put out 5V with 5mA current, which probably wont be anywhere near enough to drive your motor.  Most DAQ cards don't put out a large current so a driver will probably be needed.  

I suggest you ring your local Sales Representative, if you talk them through what you're planning to do, they can advise you on the best devices to buy. 

Kind regards,

[AnalogKid2DigitalMan]

The PSD's will still need a current to voltage converter (transimpedance amplifier). There are modules available off-the-shelf that are low noise, high gain, and high bandwith. The bandwith you need will depend on your application and also drive how fast your DAQ device will need to sample (sampling rate).

-AK2DM

[EdMotts]

Are you planning to provide a bias voltage to the PSD's?  The ones I have used required a reverse bias voltage of 5Vdc.

Ed