bently nevada

[rogue]

hello

is somebody use labview to drive a rack 3500 from Bently Nevada?

[Bob_Y.]

I haven't done this, but maybe with some more information I could help you out.  What are you trying to do?  What are your questions?

If you are looking for a set of drivers, we don't have them, but perhaps you can ge them from Bently Nevada.

Hope that I can help,
Bob Young

[rogue]

hey Bob

first thank you for your reply

I want to do a rotating machinery diagnostic with the 3500 rack from Bently nevada, I try to make my own driver to collect informations from velometer and keyphasor.

My problem is that I did not succed to obtain the FFT (fast fourrir transform) from my signal, so I don't understand why it's not work...

I measure  a pompe vibrations wich frequencies vary from 50 to 2000HZ, but the 3500 rack use a Modbus protocol to communicate with my PC, my LabView Program use 250 ms (4Hz)  to do one measure, so is this the problem? the ModBus is so Slow???

[unclebump]

You will need somewhere to buffer the data. Modbus serial can't read that quickly. How many registers of data will you need to read?? How long are you recording the signal and at what sample rate?? There are lots of modbus vi's in the forums. You can only read 100 registers at a time with a read multiple holding registers modbus command.

[rogue]

You will need somewhere to buffer the data. Modbus serial can't read that quickly. How many registers of data will you need to read?? How long are you recording the signal and at what sample rate?? There are lots of modbus vi's in the forums. You can only read 100 registers at a time with a read multiple holding registers modbus comma

I m using a ''AIR '' Modbus Driver, I can't use a Labview Modbus library (because I use Labview 7.0 and when I convert 7.1 version of this library to 7.0 it doesn't work), I need to read  approximativly 70 registers, and my Baud rate is 9600.

what do you mean by ''to buffer the data''?

[rogue]

I m using a ''AIR '' Modbus Driver, 

I can't use a Labview Modbus library (because I use Labview 7.0 and when I convert 7.1 version of this library to 7.0 it doesn't work),

 I need to read  approximativly 70 registers,

and my Baud rate is 9600.

what do you mean by ''to buffer the data''?

did you know how to estimate serial transaction timing ? it's dipending on the number of registers?

[unclebump]

Here is a thread with the modbus library in 7.0 format and some example vi later in the thread.

http://forums.ni.com/ni/board/message?board.id=170&message.id=135288&requireLogin=False

I was expecting you to need to read several hundred registers to calculate an FFT. The amount of data transmitted will depend on how many registers you need to read and if they are in consecutive address ranges. If you need to do several read commands it will take longer. Modbus will work with higher baud rates than 9600. It also helps to use RTU mode (8 data bits) rather than ASCII mode (7 databits).

I had a similar application where I stored analog signals into consecutive registers for each plc scan. It was a string of over a thousand consecutive registers. I used this to make stripcharts in labview.

Message Edited by unclebump on 06-15-2006 07:14 AM

[preston_johnson]

It sounds like we are trying to get the dynamic data from the 3500 series rack into LabVIEW for signal processing.  Modbus is not designed for this.  The 3500 series uses Modbus to provide processed data - such as peak to peak vibration, speed, etc. 

The better bet is to use a daq board to acquire the data from the 3500 buffered outputs.  These are designed to support 0-scopes and other diagnostic instruments.  With a daq board and your computer, you can then leverage the signal processing of LabVIEW to create the FFTs, etc you need. 

If you want to create or use something more akin to the ADRE software, take a look at the NI order analysis toolset, or the Sound and Vibration Developer Suite bundle.  Also look at

www.vibdaq.com

These guys have a complete ADRE like package and provide a low cost USB DAQ device to go along with it.

[rogue]

thank you for your reply, but can you please explain  why LabView can't do a signal processing with Modbus???

[unclebump]

How many points of data do you need to use in you signal processing?? You can only read 100 points of data with a single modbus read. It will probably take about .25-.5 seconds for a single read.