RFI?

[securespark]

An alarm today was being triggered into a tamper fault by the operation of a fluorescent fitting.

An alarm guy I spoke to said it was a voltage being induced into the 0V tamper circuit and it was RFI.

That right?

Or is it more EMI?

 

[ColJack]

it depends..

what kind of fluorescent was it?
if it's a HF ballast then do they get into the radio frequencies?

 

[securespark]

It was switch start.

I appreciate HF can produce RFI, but that wouldn't induce a voltage in another cable, would it?

 

[ricicle]

Was it on start up ? Possibly suppression gear in starter not doing it's job.

 

[ColJack]

read your mains with a osciloscope and if you "zoom in" enough you'll see Radio 1's signal on the 50hz waveform... it's the strongest one out there so I was told..

so yes, if it's close and strong enough you can induce voltages on the other wires..

 

[securespark]

Guys - appreciate your help. I knew RFI could cause much interference, but never knew it could be strong enough to induce voltages elsewhere.

Thanks all.

 

[ColJack]

given that some older motors made the radios pop and crackle when they were used it's not really surprising..

it's probably a fluke that the circumstances are just right to induce a voltage that the alarm registers as tampering though..

 

[securespark]

Yeah, because the tamper circuit is a volt-free circuit, any voltage induced into it will be seen by the panel as a tamper and generate an alarm condition.