Good people, whilst carrying out a routine survey today on a coal stacker I was walking underneath the bottom of the machine and through my head set/listening device an AIRBORNE audible pulse was being picked up through my transducer. On inspection I was able to find the source and it was found to be the radio transmitter for the positioning of the stacker.

This got me thinking, if I can pick up this radio frequency from approx 2.5 meters away from the transmitter with a general purpose accelerometer through air would I be seeing this in my data on the pulley that is situated 3 meters away bolted to the same frame work as the transmitter?

I suppose I should take some data from the transmitter to find out what frequency it is transmitting and then look in my data off the pulley for that frequency.

So to my questions!

Do you have this same senario? Does wireless tranducers get interference with this type of thing? Would I expect to see a raised noise floor in the area of the transmission frequency?

Thanks in advance.

Hooch

Hooch,
What Make and Model analyzer are you using? It may be possible that the radio interference is only entering your amplifier and headphone circuit and not via the accelerometer. If that is the case, then the measured vibrations will be unaffected.

Walt

Walt is right. In all probability it could be a filling in a tooth -- nah! But as Walt suggest, it is real to your ear but probably doesn't affect the path from transducer to processing and storage.

Walt & Sam,
I placed the accelerometer on some steel work within 1 meter of the transmitter and you are 100% correct no transmission. I use a CSI 2130 with a CSI Headset(magnet mounted accelerometer). I have found once the accelerometer is grounded to the steel I can only just here the signal but there is nothing in the data(0-10k).
I'm still not to sure if the wireless accelerometers would be effected, as I have several points around this machine that we are contemplating using this technology. I guess so long as the radio frequency's are far enough apart on the frequency spectrum I shouldn't have a problem.
Would I be right in believing it would be similar to having a resonance if they were to close in frequencies?

Hooch

Normally the transducer transmission from a (wireless) transducer nowadays will be digital and there will be no interference part from the other transmitter being so strong and close so the signal is drowned. Olov

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

As Oli points out the signal is in code but walk out there with your blue tooth cell phone - can you communicate from your phone to your ear? I would be inclined to check a few things or get a sample with guarntee of communications before I buy.

Well, gentlemen, I experience similar behaviour on my surveys. We carry portable radio and I notice large ski slope on my spectrum while transmitting (speaking on the radio). I thought the cable actually acted as an antenna, inducing noise over my vibration signal. I wonder how the signal bandwidth from a radio influence the signal respond on the cable frequency wise? Maybe it depends on acquisition parameter and signal / noise ratio?
Best regard, Marcel

Marcel you make a good point for all those people out there carrying a two way etc. It can be hard enough to do the job let alone having interference. Something else to consider if you see the ski slope or bad data.

I got rid of my radio due to the fact I had alot of other things to carry whilst collecting data. I never noticed any interference from this but I would usually only use it to call the control room to get machines started etc. Most of the time I would not be taking data at this time.

Hooch

Thanks Walt, Sam, Oli and Marcel all good information. I'm sure this will not only help me but all the other vib guys out there.
Being able to bounce this type of thing off you people makes my day that bit easier.
Thanks again,

Hooch