The following details a photoelectric circuit. Q1 is light sensitive and while light hits its lens it will energize the relay and pull the contacts of the relay in. The contacts can be used to operate an alarm and also a latching circuit to keep the alarm activated until you reset it. What is it all for? Buy yourself an inexpensive compass and drill a small hole in the face under the widest part of the pointer for North. Mount the FET on the bottom of the compass face through the hole you drilled and a supply a light source on the top. Make the hole just big enough to allow just the right amount of light through to activate the relay. When you drill the hole, make it small at first, you can always make it bigger if you need to. Turn the compass so that the pointer blocks the hole and turns the relay off. Now you have an inexpensive ultra-sensitive magnetic detector that will monitor magnetic disturbances at great distances. Parts List: Transistor Q1 -- Siliconix P102 or equiv. Resistors (all 1/4 watt) R1 -- 10 Megohm R2 -- 150 ohm R3 -- 1050 ohm Relay -- Sigma 5F or equivalent (Many 12-15 vdc relays with 1000 ohms or less will do) 12 vdc 11ma supply (Either batteries or battery eliminator will do). The only problem I have come across is this approach is highly sensitive to the H.A.A.R.P. project in Alaska. H.A.A.R.P now publishes most of the high energy tests on their web site. You should consider using this circuit in the next project as well as an alarm for unusually high static levels. Use it in the same manner through the face of the meter dial.