Electromagnetic interference effects on low level instrumentation

[winfield]

Does any one know what possible effects EMI from high voltage power lines would have on industrial equipment such as a PLC, or DC devices such as strain gage/loadcell amplifiers. The ambient milli gauss from the power lines has been measured at approx. 47 mG, under the lines to about 10 mG @ 30 metres. Line frequency is 50 Hz.
If there are potential effects, how can we minimise them?

 

[nbucska]

1.) Shielding
2.) Reducing the loop areas. ( induced VTG is proportional with field strenght, frequency and loop area.)
3.) 50 Hx notch filter or a high pass filter
4.) arrange the orientation of the loops to minimize pick-up. <nbucska@pcperipherals.com>

 

[hacksaw]

Don't worry about it as long as you are using good industrial grounding / shielding techniques. Load cell manf. are very helpful, the PLC manf. have dealt with this issue for more than 30 years.

47 mG is pretty small. If it is a 238 KV line then the biggest problem is electrostatic...