help on select M-series DAQ card

[Xiuping]

I have a resistive type sensing element in response to impact (special potentiometer). I want to first test its dynamic property (how sensitive to pipe flow) and then design a simple circuit to trigger a transistor output with pre-determined impact threadhold.

I will need a DAQ card to log data for a voltage between the potentiometer, as well as my transistor output. I estimated a 250KS/s, and 16-bit (even 12) input is good, and no specific requirement for AO/DO.

I prefer using a laptop for data analysis. My questions:

1. Is a USB type DAQ proper for this application? If not, I will go back to a PCI.

2. If USB is selectable, I am struggling with Bus-powered (USB-621x) and non bus-powered (like USB-622x); and isolated and non-isolated. Note that none of external powered DAQ has isolated function.  As among my preference: USB-6221, USB-6215, or USB-6211, which is more suitable for my data acquisition?  

Thank all.

Sue

[nayer]

Hello Sue,

From your post, USB DAQ is perfect for you application. All the USB-621x cards have agrregate rate is 250KS/s hence if you use two AI channels the effetcive rate is half i.e. 152KS/s. Hence the best bet for you is USB-622x card. Also the external power USB DAQ have more stable communication and no connection failure when using with laptop; as USB port on laptop is generally low powered. Hence, I would go with USB-622x series. better than that would be USB-625x also. keep us posted if you have more question.

Thanks

NI-khil

[Xiuping · Accepted solution]

Super! This morning I have decided to place the order with USB-6221 and I am very happy you assured me. Thank you, Khil.

I acctually overlooked the term "single channel and aggregate" of 621x. I did doubt the rate of bus powered devices before but did not found where was wrong. I also found out that 6221 provides both sinking and sourcing DI that I will be using both types. Now I am comfortable with the 200 more bucks on the external powered one.

Sue 

[nayer]

Hello Sue,

Just FYI USB-622xand USB-625x both still have aggregrate sampling rate, but they are faster than 621x.

Thanks

NI-khil

[zhm0204]

Hi NI-khil,

Do you have a USB card as USB 6221 but have a 24bit AI resolution and work with a external sampling clock.

Or a USB 4431 but can work with a external sampling clock.

Best Regards. Have a nice day.

Zhang