What are the Key Differences between the NI 9233 and NI 9234?Hardware: CompactRIO>>Analog Input Modules>>NI 9233, CompactRIO>>Analog Input Modules>>NI 9237, CompactDAQ>>Analog Input Modules>>NI 9239
Problem: At a higher level, the specifications of the NI 9233 and NI 9234 seem to be quite similar. What are some of the key differences between both modules? Solution: The following points outline the main differences between the NI 9233 and NI 9234: The 9234 has better phase linearity than the 9233 The phase non-linearity of the 9233 means signal components at different frequencies will appear slightly out of phase (by as much as a couple of degrees) relative to each other. Although this is not significant for most machine monitoring applications, it might be a problem for testing professional audio equipment. IEPE and AC coupling are always enabled on the 9233, but the 9234 has them selectively enabled per channel Having IEPE always enabled means that the 9233 is meant for connecting to IEPE sensors. Although it will work with IEPE microphones, it may not be suitable for other microphones or for connection to non-IEPE amplifier outputs. In particular, any output it connects to must provide a DC bias voltage like IEPE devices provide. The NI 9233 and NI 9234 is that the 9233 only supports AC coupling, while the 9234 can be programmed to be either AC or DC coupled. If you are planning to do DC measurements, use the NI 9234. The 9233 has a high-pass cutoff frequency (-3dB) of .5 Hz, so any low-frequency signals in your signal will be attenuated and any DC shift in your AC signals will also be removed. See the attached Developer Zone document below for more information on AC and DC coupling. The phase delay is different between the 9233 and 9234 In order to synchronize a 9233 and 9237, the customer needs to compensate acquired data by referencing the phase delay specs. 9233 ..................... 12.8 ÷ fs (for <= 25 kS/sec) 9233 ..................... 9.8 ÷ fs (for >25 kS/sec) 9237 ......................(38.4 ÷ fs) + 4.8 μs 9229 ......................(38.4 ÷ fs) + 2.6 μs 9239 ......................(38.4 ÷ fs) + 3 μs 9234 ......................Similar to the 9237 and 9239 for easy synchronization with these modules The 9234 has a native sampling rate of 51.2 kS/s, instead of the 50 kS/s of the 9237 and 9233 Valid Sampling Rate = (Master Timebase) / (256*n), where n is an integer from 1 to 31 The NI 9233 has a 12.8 MHz Timebase, giving a maximum sampling frequency (n = 1) of 50.0 kS/s. The NI 9234 has a 13.1072 MHz Timebase, giving a maximum sampling frequency ( n = 1) of 51.2 kS/s. The 51.2 kS/s of the 9234 may make it more desirable for some audio applications. The 9234 can either use its native sampling rates or it can synchronize to one of the other modules. So if you synchronize a 9237 and a 9234 together, you can either set the 9234 as the master and get 51.2 kS/s for both modules (or 25.6 kS/s or other divisors), OR you can set the 9237 as the master and get 50.0 kS/s for both modules (or 25 kS/s, etc.). Noise attenuation Finally, the 9234 has slightly better noise attenuation, especially with crosstalk between paired channels (1 and 2, 3 and 4). Related Links: KnowledgeBase 42NC6EZN: How Can I Trigger a NI 9233 or 9234? NI Developer Zone: AC and DC Coupling Product Manuals: NI 9233 Operating Instructions and Specifications (September 2008) Product Manuals: NI 9234 Operating Instructions and Specifications (August 2008) Product Manuals: NI 9237 Operating Instructions and Specifications (August 2008) Product Manuals: NI 9229/9239 Operating Instructions and Specifications (July 2008) Attachments:
Report Date: 05/13/2008 Last Updated: 06/07/2009 Document ID: 4LCMH307 |
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