quote:

Originally posted by Gary Forsythe:
Help educate me! I have heard this argument before but have never actually tried it, therefore cannot establish an opinion. The question: taking two measurements simultaneously with the CSI box 2-channel capability.

When you must position 2 transducers, acquire data, remove the 2 transducers & reinstall them both on two different measurement locations, store the readings, etc., etc., etc., is it really that much faster than using a single transducer (fully understanding the benefits of 2 channel simultaneous data collection)?

I never really paid much attention to my college class dealing with time & motion study. Thought it was pretty boring. Probably why I earned a ‘D.’

Gary

2 channels will give you a phase relationship between 2 points whether they are 90 away on the same plane or one H one A. I have never heard of using 2 channels to collect 2 points simultaneously to speed up data collection. There are boxes that will utilize a triaxial transducer but they don't necessarily collect all 3 readings at once either.

Thanks Ron. Just like I suspected.

The advantage is time. It's certainly not twice as fast, but probably 1.5 times as fast.

It also let's me set things up so that I can do cross channel phase analysis in a few seconds.

It takes time to set it up properly and to think through the motions, but you really can save time doing this.

I have a 4 channel mux and could collect data with 4 channels, but it's hard enough to manage the cables with just 2-I can't imagine trying to handle 4.

And it does collect two reading simultaneously. There are very specific rules as to what it will collect simultaneously and what it will collect sequentially, but they are fairly easy to follow.

Also Ron is correct. It will give you phase and coherence of one accel relative to the other.

Sam is right. The DLI Hammerhead and the old 8603 collect 4 (3 for the 8603) channels simultaneously. For most DLI users, this means taking all three axes with a triaxial accelerometer in about the same time as a single measurement could otherwise be taken. Like so many things in this field, it's a matter of personal preference, but I find having 3 axes at each measurement point to be useful.

There is no reason (well, except perhaps DLI's expert system software) that 2, 3 or even 4 single axis accelerometers couldn't be monitored at the same time - great for phase but difficult to keep untangled.

Regarding the time savings possible, it really depends on the frequency ranges and resolution being used. A low frequency range can take a fair bit of time to acquire, so taking multiple channels at once really speeds things up. Higher frequency ranges, which can take only a few seconds/sample to acquire, won't be speeded up much.

Jon
Spintelligent Labs

Jon is right. You save seconds on high speed and minutes on low speed. I do lots of big slow gearboxes and at 5 or 10 rpm, the time adds up. Try doing readings on a Yankee Roll at 15 or 20 minutes per reading and see what you think.

The advantage of the 2 readings at once is you can grab your default route reading and then also a addtional peak vue configured reading at the same time. Thats how you save time. One transducer two different types of readings at the same time.

Gary,
You can do the 2-transducer thing if you want, but most people just use one. You can set your high-freq enveloping point to collect piggy-back with one of your regular data points. As far as my data collection time goes, I get all of my peakvue points for free.

David Eason

You can collect "normal" vibration data and Peakvu simultaneously with the 2130, I am not sure if that is possible with the 2120.
Commtest uses Demod instead of Peakvue. Demod works pretty much the same as Peakvue, accept I believe that Peakvue is supposed to be trendable, but Demod is not, at least I think that I remember that.
The Commtest Vb3000 has easy on board setups for Time Synchronous Averaging, Bump Test, Coast Down/Run Up, Cross Channel Phase, And Long Timewaveform. The Long Time Waveform is very handy because you can collect a waveform and asssign it to route data. The length of time that you can record is up to the 32 meg of memory that the VB3000 has. About the only thing that it is not capable of doing that the 2120 can do is Negative Linear Averaging.
As far as I can tell, there is very little if any difference in the speed of the VB3000 when compared to a 2120

Demodulation values, if measured with consistency, are trendable, contrary to anyone's marketing hype!

Thanks Duncan. I never understood why it would not be trendable.

Vibeguy2004,
Yes, you can collect simultaneous data with the 2120, but there are certain rules that apply to the 2120 that don't hinder the 2130. Even with the restrictions though, the 2120 works well for simultaneous collection.

David Eason

quote:

Negative Linear Averaging

I find that very useful on the 2120 for doing bump tests with a unit running, but that's about all I've ever used it for. What about the software? How does it compare to MasterTrend or RBMware? Unless I'm mistaken, the company that builds the Commtest unit builds a number of different analyzers that are sold under various names, so their specialty is 'boxes' that work with differnet software platforms. That would seem to be an advantage to me. I think Commtest would be on my short list of units to look at should I arrive at a point where I am ready to do something different. But I'd have to have one in my hands to try in the real world for a while before I'd commit to buying one, as I'm sure most of you would.

Believe nothing you hear, half that you see, but all that you do.

I am pretty sure that Commtest only makes the VB series analyzers. Maybe some online stuff too.
Having used both Mastertrend, RBMWare, and now Ascent, I find that the Ascent is much easier and I think a more user friendly true Windows based programs. Easy to build databases with copy and paste features and very easy to build and update alarms if you use them
I think that you can download a demonstration version of the software from their website. And Rusty, if I ever get back over to Arkansas maybe we could meet up and I could show you the analyzer.

Has anyone seen or used the Update International COIN system?

WOW! You guys are fantastic! You have gone above and beyond the call of duty as far as covering all bases in response to my inquiries. Now then, what are your plans as far as upgrading to the 2130 or getting away from CSI?

Nate, I would get the literature from CSI on the 2130 and see what it offers that your 2120 doesn't. Also, I'd find out what is missing from the 2130 that you like about the 2120 (something always seems to get 'dropped' on new-and-improved units).

If there is no compelling reason to upgrade to the 2130 now, then I'd wait awhile. Your 2120, in good condition, will always be worth more on the resale market than CSI will give you for a trade-in.

Any new-and-improved unit is going to have a few bugs and glitches and there are usually some component reliability issues the first year or so. And there will be incremental improvments in the firmware the first few years. I don't see any downside to waiting for the 2130 to mature into the solid unit that I'm sure it will become.

Commtest and CSI are both good instruments. Despite the minor "bells and whistles", both units will handle 99% of the work most vibe guys are doing.

As far as the other new instruments out there, I haven't really paid much attention ... my VB2000 is still running fine after almost 4 years in service.

Tech support from Commtest is still free (last I heard), however it is rarely needed. I only recall two support contacts in 4 years (both were my fault and quickly corrected within 24 hours).

I am sure the 2120 and 2130 users are proud of how much they paid. Add instrument costs and support contract fees together ... about twice the price of a Commtest system. With all due respect, my ROI was much easier to reach with Commtest. And I have yet to be called a "discount consultant" Rusty

If you are content with RBMware, then most likely you should stick with their line. However, the ease of use in setting up Ascent (Commtest's software), is simply sooooo easy that you would be amazed. I set up a new customer last week with 60 machines ... took me almost 5 minutes to build the whole database.

***Vendor warning***
Still not a vendor for Commtest, just a satisfied user.

Take Care,

Interesting thread.

I have been looking to move from CSI to another vendor for some time now. To be honest, Commtest is on my short short list. I like the box, software and service. Price is definitely right, too.

The one thing I'm hesitant on is the software. I am used to using Mastertrend or RBMware where you can tap the 'x' key to automatically highlight the harmonic families. Commtest does not have this feature, meaning I have to manually position my harmonic cursor over each peak to see where the harmonics are. This is a MAJOR analytical tool for me and I would be hamstrung without it. Hopefully they will add this in future revs as I've already made the suggestion.

I think more and more competion is going to be coming out, possibly outpricing CSI. The people have spoken and God knows they are tired of being held hostage by their test equipment vendor. Let the free market reign!!

Chris, I didn't mean to imply that someone who uses less expensive equipment is a "discount consultant".... if it works, it works... no matter what it cost. But in my opinion, most clients are not going to be impressed by how "little" a consultant pays for his equipment. Sure in the final analysis it's the value you add and the results you achieve that determine if you stick around. But first impressions do count, and in a political plant environment 'perception' is often as important as reality.

How does Commtest handle 'note codes' ? That's the biggie for me. Also, do they have anything equivalent to the SpeedVue laser sensor for determining true running speed, or will the box 'locate' the running speed in a spectrum as the CSI box does? I do a lot of variable speed equipment, and am seeing more machines converted to VFD's every day, so quickly finding the running speed is a big deal for me.