bently nevada

[rogue]

I need to read about 75 points, time used by labview to do one loop (so one mesure) in my program is 250 ms (4Hz), I need to mesure 2000Hz frequencie vibration!!!! 

the max of my sensor frequency response   is 5500HZ

the max of my signal conditionig frequency response is 4000Hz

[unclebump]

75 data channels * 4000 samples/sec * XX (seconds of recording) = one heck of a lot of data. To measure a 2000HZ vibration you need to sample your data at least two times that fast and maybe even more than that. Even if the Bently device can store that much test data, Modbus really isn't meant to transfer that much info, it could be done but would take quite a bit of time.

[rogue]

What do you mean by time of recording? do you mean time to record the data in the registers in the rack???

[unclebump]

Are you recording 75 different channels of data?? The recording time is how long you want to monitor each signal.

[rogue]

hello unclebump

I use 6 sensor (velometer), so I obtain 6 signals , and I want to do an FFT for each signal, in a first time I want to record the signal during 10 or 20 second, it's enough for me,

so if my frequencie vibration is 2000Hz, the number of data is: 75 * 2*2000*10= 3.000.000 data

it's possible to buufer the data in the rack (in other way is there any buffer memory who can buffer this data and also I transfer this data in LabView??),

[rogue]

Help please!!!!

[preston_johnson]

I believe the modbus port in the Bently rack is designed for static data, ie transferring the 1x mag and phase measurements, speed, etc.  If you want to get the dynamic time series data into LabVIEW, you will need to digitize it by connecting the LabVIEW computer to the bufferred outputs with an a/d board .  You  might consider the compactDAQ with three (or six) of the 9205 I/O modules. 

http://www.ni.com/dataacquisition/compactdaq/

[rogue]

thank you Johnson for your reply

I have a question please?

what about the  4 to 20 mA recorder. can I use it to transfer my data to Labview? there is any chance that it's work?

[rogue]

can you explain why I might consider three (or six) of the 9205 I/O modules, the is 32 32 single-ended or 16 differential analog inputs in each module!!! 

[preston_johnson]

I am sorry, I had seen 75 channels somewhere in the thread.  You could use just one of the 9205, or two of the 9215 modules.