I believe there would be zero problems with the signal passing through the 115 volt connection. The safety agencies only care about 50 volt stuff or higher. It sounds like this would be in an industrial environment so UL508 would apply. If it is a consumer item then I believe it is UL247? that would apply. I do know that OSHA and UL collaborate on standards and ultimately OSHA has a lot of say in what is considered safe. So following the UL standards will definately keep you out of trouble. These standards mostly address spacing (traces), failure analysis, and enclosure testing (open or closed device). All are worried about safety (fire and shock). The FCC will address the EMI and EMC issues. If your selling to Europe, then CE marking a product should encompass safety,EMC, and EMI. In your case, likely the machinary directive will be used, amongst others. Where will your device be used?

ccaserta
The problem is that you should always isolate hazardous live voltages from signal voltages. If you can show/prove you meet reinforced insulation between hazardous live and signal voltages your all set. It dosen't matter if it's UL, CSA or a European standard. they all require you meet the right creepage and clearance specifications for primary and secondary circuits. The second issue is  you take a big chance in messing up your signal information because of EMI and RFI issues (RF stuff). Keep in mind if you ship to Europe you have to show in your Technical file you passed the EMC testing. It's also true of the US, you have to meet FCC requiremnts. All electrical comoponents must meet FCC regulations, it's just that it's not enforced like it is in Europe.

Christopher Caserta
President & Sr. Regulatory Engineer
European Compliance & Certifications, Inc.
P.O. Box 15193
Fernandina Beach, FL 32035
ccaserta@enorthhampton.com
Ph:904-225-0360
Fax:904-225-0340

FCC part 15 only applies to devices with a frequency of 8KHz or higher(or maybe this is radiated emissions testing-I think this 8KHz applies to FCC and radiated testing).

FCC requirements are for both Conducted and Radiated Emissions, The actual end frequencies will vary depending on the type of product being tested. It does tend to overlap the European specs which are pretty exact for conducted emissions 150 KHz to 30 MHz and for Radiated emissions 30 MHz to 1 GHz. Please keep in mind these are the radiated specs not the power input frequency or the clocks of the product.

Christopher Caserta
Sr. Regulatory Engineer
ccaserta@enorthhampton.com
Ph:904-225-0360
Fax:904-225-0340

I do remember in reading through the 1000 series standards (IEC 61000) they made a reference to radiated emission testing is not required for devices with switching frequencies below 8kHz. This number was for internal electronics and made no reference to radiated frequencies in this regard (when not to test). Sorry I can't reference a particular standard. It may have been a EN standard for auxillary motor control circuits and overload relays (IEC947) that I read that in too.

I'll have to look at that, as a rule of thumb I have always followed, if it's electrical or has electronics it falls under the 89/336/EEC. I agree if the product is not an active component there is no point in the test. I will do some research to see if I can find the clause your talking about in EN 55011 or one of the other emission standards.

Christopher Caserta
Sr. Regulatory Engineer
ccaserta@enorthhampton.com
Ph:904-225-0360
Fax:904-225-0340