AC Line filtering

[kallileo]

I have installed a magnetostrictive level system on a tank in a farm and I have some problems.
Since the voltage on the farms isn't stable and bad filtered during the milking when all the motors are on I get errors on the controller of the sensor. Possible cause is that the power noise isn't dischared to the ground effectively.
I have been told that the solutiion is to use a active filtering device such as a an ONLINE type UPS. The problem is that the smaller I found is 750VA and I need no more than 30-40VA. The cost of the UPS is also very high.

Is there any other more cheap solution?

 

[VEBill]

"Possible cause is that the power noise isn't dischared to the ground effectively."

In general, that's not how noise and grounding works. Noise, like any other signal, travels around circuits in accordance with circuit theory. It doesn't necessarily want to be "discharged" to ground. (An exception is lightning that certainly does seek earth ground.)

"UPS. ...I need no more than 30-40VA. The cost of the UPS is also very high."

Is there a Costco or similar big box store near where you live? UPS sufficient to power a PC (serveral hundreds watts) are under $200.

A better long term solution (because UPS systems are, ironically, relatively unreliable) might be to fix the source of the problem. Perhaps the power company needs to provide a higher current service. Perhaps the wiring could be rearranged to avoid voltage drops.

 

[IRstuff]

Nonetheless, your controller and its sensors should be designed to handle, within their design specifications, a certain level of noise, which is presumably exceeded. Better shielding, grounding, and elimination of ground loops are the typical measures for reducing noise in the system. An obvious mitigation is to stagger the milking machines in time, if possible.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[hacksaw]

you might try clamp-on toroid ferrite filters, they'll cut the line noise

additionally most level transmitters also contain time delay filtering to eliminate splashing effects, if you are lucky, yours may be adjustable

 

[Comcokid]

Sounds like a AC voltage regulation issue at your farm. A UPS will keep your sensor system powered when all other power is lost - not exactly what I think you want to do. What you need is probably a 'power line conditioner' also sometimes called a 'ferro-electric transformer' or 'constant-voltage transformer'. A quick check shows that Sola makes a 60VA power line conditioner p/n 23-13-060-2 (available at Newark Electronics for $396). Not saying this is exactly what you need but just the first google hit I got. Probably could find something similar used on eBay.

 

[ScottyUK]

There's a good chance the first thing your level measurement system does is convert the AC line to an internal DC supply. Look at improving the regulation there rather than fighting the problem at line voltage. You may find that a wide-range power supply solves the problem, for example some switchers can handle anything from about 80V through to 250V in one continuous range. You may be able to provide battery backup to the DC bus if you have truly awful power problems and the input drops too low for a switcher to deal with.