A data acquisition system (DAQ) is the interface between your sensors and your analysis software. For acoustic and vibration measurement, the DAQ must capture signals accurately across the full measurement frequency range, supply IEPE current to microphone preamplifiers and accelerometers, provide sufficient dynamic range to capture both quiet and loud signals in the same recording, and do all of this simultaneously across all channels to preserve phase relationships.
Determine the minimum number of simultaneous input channels your application requires. Sound power measurement to ISO 3744 with a 10-point hemisphere array needs at least 10 channels. Intensity measurement needs 2 channels per probe. A single sound level measurement at one position needs 1 channel. Buy enough channels for your current application plus reasonable growth, but note that 8- and 16-channel systems cost more and are larger than 4-channel systems — do not buy 16 channels if you only ever need 4.
24-bit ADC resolution is the current standard for acoustic measurement DAQ. It provides approximately 144 dB theoretical dynamic range, though practical dynamic range is typically 110 to 120 dB due to noise from the input stage and reference voltage circuit. For acoustic measurement, 110 dB dynamic range is sufficient for most applications. Verify the specified dynamic range is measured at the sample rate you will use — dynamic range degrades at higher sample rates in sigma-delta ADC designs.
PLACID measurement microphone preamplifiers and most professional accelerometers use IEPE (ICP) signal conditioning that requires a constant current supply of 2 to 20 mA at 18 to 30 V compliance voltage from the DAQ input. Verify that the DAQ provides IEPE current supply on all channels you intend to use, and that the current and compliance voltage match your sensor's requirements. 4 mA at 24 V is standard for most PLACID preamplifiers.