Ralph, I don't think the magnet will matter as long as the accel is not physically moving when you take the data. As many of you know, most of my data is take "hand held" with a short stinger, and I seldom have ski slope problems with the 2130, unless the accel moves while I'm taking data (I usually have my hand, forearm, or elbow braced against something). I usually see some ski slope if the overall vibration is very low amplitude, say < 0.02 ips. I use analog integration and a low cutoff of 2-5 Hz for most route points. I will use 0 Hz cutoff and SST for slow speed stuff, but I always use a magnet for those readings. I use the DB-25 connector and try not to let the cable move, especially on low amplitude points.

I've not used the Turck connector for data because the one for my tach input doesn't seem very robust. Pretty sure it wouldn't hold up for me. But I have a cable, so I might try it sometime, just for comparison purposes.

magnet is 1 1/4" and similar magnetic pull as a standard transducer

No one mentions HP filter setting? Is the a default? I haven't use CSI for years!

Regards

W

Seems like most of the problems we encounter are with paper machines where some rolls are slow (60 rpm or less) and some are fast (300 and up). Some are high and require a long extension pole to reach. I agree that the movement of the cable sometimes will cause the problem. The long reach is where the magnet size is, to me, the crirical time. The smaller less strength ones will not hold when the reach is 10 to 15 feet away. Too weak to hold the transaducer and the added weight from the pole at that distance. Not all the problems are from the long reach, but most are. Some are caused from the curly coil cable being very flexiable and easily moved. I have recommended to my clients to use a regular non curlied coax cable, but sometimes old habits are hard to break.

In my old days when I was a full time datadog, I used a coax cable on a long extension pole, taped down about 4 feet from the transducer and just dragged it (the cable) on the floor. Sometimes the easiest and cleanest way (curly coil) to go is not always the best, IMO.

As far as using the analog mode for data collecting vs the digitial mode, I have not seen much if any difference in the data collected so I continue to use the digitial. But then again, that is just me and I might be a little different from everyone else.

I still like my reach pole because the accel is 'attached' to the pole (it won't fall where it's not supposed to), but the joint is flexible which isolates the pole movement somewhat.

I use a straight cable with my poles because it's much lighter as Ralph points out. And I use the strongest magnet I can find, which is the CTC 1.25" (I think).

CSI has always recommended analog integration because of the ski slope problem, going back to the original 2110.

Also cable noise will cause ski slope. The best way to test your cable is with the headphones if you have them. If you can hear noise when you move the cable, your meter can see it and there will be ski slope. My coiled meter cable has a BNC connection so that I can quickly attach various sensors. The little 'tabs' on the BNC will lay down after a while and not make good contact. I have to bend them back out a little which always works. So check all your connections as well.

The compressor that I am evaluating that has 25 g's at gearmesh frequency has produced a lot of ski slopes in the velocity spectrums - my thought may be similar to Michael S where this high frequency vibration / energy of significant value may be causing the magnet to wobble at a very low frequency and the instrument can not react to this information - I got up to 3 ips on some spectra. Go past the ski slope and the data seems plausible. I have moved my F Max to a higher frequency and see information that I did not believe was there. On certain equipment I have retaken data several times on the same point by reposition the magnet / holding the cable and still got the ski slope. Usually setting the F Min to 3 Hz or 180 CPM will cause the instrument to null the ski slope and calculate the overall to a true value for the spectral range one has set.
Any comments on some high frequency components being the factor causing magnet wobble?
William

Mec3, what analyzer do you use? Which cable?

Try analog intergration instead of digital on slow speed stuff.(<1 hz) Ski slope disappeared for me.

Kevin

Hi Ralph!

Has your 793L always given you problems--or just started w/the 2130?

I don't know if this relates to your problem or not, but I was getting concerned after 10+ years of heavy route use that my Wilcoxen 797 might let me down, so I purchased a new one for use w/my 2120, thinking I'd set the old one aside for a "spare."

After several routes with a whole lot of ski slopes, I went back to the old one w/no problems. Turned out the new one was made elsewhere/cheaper--and I wasn't the only one that complained. I understand that Wilcoxen has since pulled production of this line back to the USA.

For whatever it's worth...