02-11-2021 02:55 AM
Hello
We are looking to purchase an ADC for voltage flicker noise measurement with the following specifications:
1) 24-bit resolution
2) Low intrinsic noise
3) AC input coupling
4) Sampling rate>50k S/s
5) Dynamic input
The PXIe-4464 unit sounds perfect for our purpose. But due to budgetary constraints(PXI units require a chassis and a controller), we will prefer if a more affordable option exists(which can be mounted directly inside a desktop's PCI slot).
The user manual of PXIe-4464 and PCI-4462 have almost similar specs, in particular, both of them have the same intrinsic input noise, sampling rate, resolution and 6 gain input.
I have two concerns regarding picking PCI-4462 :
1. Can it be bought as a standalone unit, or does it require any external controller or chassis?
2. The -3dB cutoff frequency for PXIe-4464 is 0.72 Hz, which is an order of magnitude smaller than it is for PCI-4462(3.4 Hz). Since we are primarily interested in low-frequency signals, I understand that it will affect the signal flatness on low-frequency end. Moreover, this link states that "Using AC coupling results in a drop in the low-frequency response of the AI circuitry. The AC coupling circuitry is usually characterized by a 3 dB cut-off frequency. However, the roll-off from the high-pass filter can have a measurable effect even at frequencies several times greater than the 3 dB point."
Keeping these two things in mind, which ADC would be more suitable? Please recommend an alternative unit if available.
Thanks
Solved! Go to Solution.
02-11-2021 12:13 PM
For #1, since it is a PCI card, you can just buy the card and plug into PC's PCI slot and no additional hardware would be required (external cables as needed).
For #2, since you're looking to measure low frequencies the PXI 4464 seems to be a better option (with the caveat of PXI Chassis investment).
Alternatively, you could also look into C Series Sound and Vibration modules along with a USB cDAQ
https://www.ni.com/en-us/shop/hardware/products/c-series-sound-and-vibration-input-module.html
cDAQ-9171 is a low-cost single-slot USB chassis for cDAQ
Other chassis options https://www.ni.com/en-us/shop/hardware/products/compactdaq-chassis.html