Can anyone give me some guidance on how to set up my analyser to do a waterfall plot? is cascade another name for the same thing? I have a CSi 2120 and access to a 2130 as well. I'm planning on getting some data on a variable speed pump from startup through to maximum speed of 5500rpm. speed variation is through a fluid coupling. Do I use a photo tach? Never done one before so no suggestions will be considered too basic.

Thanks

The terms are one in the same. Your interest are of frequency as one parameter and sequence is another (what spacing do you want or one display spectra and delta f to the next). So if you're doing a coast-down and start at 1X ---- 3600 RPM; where do you want the next 3500, 3400 etc.

Typically I use a RTA where you can store the signal in real-time and perform test from different perspectives but still speed is a major consideration so you won't miss a resonant frequency or. This basically is why I also use a peak-hold and trace the frequency. Generally I use the minimum windows that will still give info of interest. Too many window slow the operation. My suggestion is never use more than you need. If 400 lines are adequate, then 1600 doesn't make it better.

Phase is not required. You can use phase or you can use a photo-tach or clock as a trigger although not necessary but check your particular instruments manual as this may not apply to all analyzers. All do not require an event trigger. You may also want to pretrigger by -128 or -64 lines.

Another technique I use is to set the analyzer to auto-capture. This way you just start the analyzer and it starts auto-storing the spectra in memory until all the blocks are full. So some machine knowledge specific to your machine of interest is necessary - how long does it take to go the full speed range, etc. If you can control the speed of the machine, then you probably can setup the test to suit your instrument preferences.

This message has been edited. Last edited by: Sam Rme1,

Thanks for the reply Sam, Just indulge me for a moment while i explain what I want to do.
Its a boiler feed pump and Id like start collecting data at about 2400 rpm and get additional spectrums at 100 rpm increments through to the maximum 5500rpm. Machine already has a 4-20ma sensor mounted at pump D.end horz that gives the control room an overall mm/sec figure, The pump is going into alarm at approx 7.3mm/sec. at ?? rpm, (The pumps own tacho is out of action.)
Can I manually take the data at each rpm increment and have it presnted back to me in a cascade/waterfall style plot after all the spectrums are collected?
I'm trying to establish what is causing the pump to go into alarm and at what speed.

This message has been edited. Last edited by: Jonesy,

I'm sorry I can't help with the 2120 as I have only used it for a PdM route data collector. I've used a wide array (another term for cascade) of analyzers but probably like Ono Sokki best. 1 RPM may be a bit much though. 100 RPM increments or close may be acheivable.

But start by doing the math on how much resolution you must have as the minimum. Next, what't your highest frequency of interest; if you can go to the lowest you'll have the highest resolution but less speed and the greatast separation between spectra. So planning is important and paramount unless you have an instrument tape recorder. With the tape recorder you can play it as much as you like. I'm prone to assume you will have only one-shot to collect your data; so, the planning is very important or you'll have egg on your face.

There are a several ways to accomplish what you would like to do, here are a couple
1) In route mode, under general setup, it asks if you want to overwrite data or store all data, select store all data. You will need only one point from a machine, let's say motor horizontal.Start the machine up,get to desired speed and collect your first reading, change speed 100 rpm, staying on the same point you just collected, and collect data in this fashion. In your plot data area select multiple spectra and you will see a "waterfall" of all your points with a maximum of 18 spectra viewable at one time.
2)Make a machine with points that are named for each rpm you will collect. Use the same AP set for each point. In plot data use multiple point spectra and select each rpm, max of 18, and you will also get a "waterfall" of collected data
Hope this helps
Dave
402-660-1522

Doesn't the 2120 have a "Run up-Coast down" function?

D

Hi Jonesy,
In preparation I would spend a half a day practicing on a big pedestal grinder that takes a long time to coast down. (and has nice resonance) The help button on 2120 is very, very good and that will let you explore all the settings in the cascade program. Just highlight the setting and press help. I agree with Sam, use only the resolution you need since the number of blocks the meter can keep in memory is inversely proportional to resolution. i.e the higher res, the fewer spectra. You need to practice with it. If you feel like getting in touch drop me an email, I am in Melbourne, your timezone. rgds

This message has been edited. Last edited by: Vibe-Rater,

Gents -

One point of clarification. Waterfall and Csacade are not the same plot.

I am not sure if you meant the were the same in CSI terms, but in general they are not the same plot.

A cascade requires speed on the Z-axis while waterfall does not.

If I remeber correctly there was a good discussion on this a few months back on this site.....

Here is the link to the discussion I mentioned in my previous reply: Cascade VS Waterfall

Hi to everybody,

In my opinion If you make a waterfall is because you want to see the machine behaviour during its "normal" work, if there are any change due to any changes in the process, so in that case the set up of your spectrum involve the same set up when you monitoring this machine, but If you want to make a cascade is beacause you want to analyze the machine behaviour during the startup or shutdown, maybe find critical speeds, etc..so in that case I attach a pdf where I explain how to set up this kind of spectrum.

Best Regards,

Raul G.

Set_up_Spectrum.pdf (114 KB, 42 downloads)

Mostly cascades, arrays or waterfall plots are used during start-up or coast down.

The terms are all the same as they denote the type of display. They type of data may vary with the interest of the user. One can trigger internally or externally via key phasor or clock per event of interest or _____. No vendor can dictate how all are to use or define data as it may vary from instrument OEM to vendor to country. It would be nice to create an icon and then claim the nomenclature the only to be correct and set yourself up as the authority. I don't think that dog will hunt. Even though it has a number of times in our industry. Change the language.

Some instruments will allow peak-hold and extract from frequencies of interest. Some allow real-time zooming.