Line Conditioners for Home Theaters
I keep showing my age here but back in the day, the old fashion television was rather immune to minor fluctuations in the power source. There was a nice range in voltage that was acceptable to the performance of your trusty old TV set, record player and radio. Now, microchips and computers seem to run everything. Even refrigerators have CPUs now. Networks have moved out of the financial word and into our homes. The difference between your computer and home theater grows smaller each day. Because of this most of us now have to consider the technical specifications of our power source. Plugging your equipment directly into those holes in the wall is becoming an increasingly bad idea.
There is a very wide range of devices whose purpose is to moderate and correct variations in your power source. They range from the simple surge protector up to full blown Uninterrupted Power Supplies or UPS. These devices are now so popular that you can get a fairly decent surge protector at the local super market. Basically the reason behind the need for these devices is the very small currents required to run a microchip. With the old vacuum tune a sudden drop or increase in voltage would take time for the filaments of the tube to respond. Typically the event would be over before the tube even knew the power changed. When the world switched to the microchip the response time became so small that the human mind can not really appreciate the time span of milliseconds and nanoseconds. Microcircuits and other computer components expect a nice, steady flow of electricity.
The most common type of surge protector is technically called the MOV protector. Donít you just love all the initial we have to know now? MOV stands for Metal Oxide Varistor. A piece of metal oxide is placed between the hot wire (the one with the current) and the ground wire. The ground wire is the little round prong on the electrical plugs that too many people cut off or get one of those little grey plastic three prong to two prong adaptors that few actually install correctly. The metal oxide is connected to these two wires by little semiconductors. The semiconductors have a variable resistance which is dependant on the actual voltage. Normally the resistance is very high so the electricity doesnít flow through the metal oxide strips from the hot to the ground. If the voltage suddenly increases, a power spike, the resistance decreases and the excess voltage is shunted away from the hot wire harmlessly into the ground. So, when the voltage is correct the MOV does nothing. If there is a spike it acts like a pressure relief valve to draw off the harmful, excess current. Just in case the increase in the power or the draw of the equipment is too large or too prolonged there is usually a fuse connected that will blow out, sacrificing itself to save your equipment. How noble of it.
At this point lets clarify a couple of terms we have been using; a spike is defined as an increase in power that lasts for only one or two nanoseconds (billionths of a second). If the event lasts longer than three nanoseconds it is referred to as a surge. See what I mean about extremely short time periods? The old TV show Mister Wizard once showed how damaging an increase in voltage could be by hooking up a light bulb to a variable power source. When the current was increased too high the bulb blew out. The same can happen to your equipment. Even if it doesnít out right harm your equipment it will put more strain on your system.
More up-scale protectors may use ionized gas instead of a metal oxide strip to divert the extra current away from your equipment. These are called the gas discharge arrestor. Here an inert gas is used in a very similar fashion to a florescent light. At low current levels the gas is a very poor conductor. When the voltage increases the properties of the gas are such that its ability to conduct electricity improves and draws the extra current away. In both types of protectors the shunt is wired into the circuit in parallel to the main circuit. That means an alternate path is provided for the current. In some protectors a series circuit is used where the protection is in the same path that goes to the equipment. Here, the extra current is not moved away but delayed, being gradually released later. The though behind this is the response time is faster.
Many surge protectors now offer methods to clean the current. This is called line conditioning and it basically filters most line noise (fluctuations the current). The way this is done is pretty easy. A coli of magnetic material called a toroidal choke coil is wrapped around the wire with the current. This sets up a simple electromagnet that creates a magnetic field that acts to smooth out minor ups and downs in the current.
What causes these surges? Actually its your other appliances. Air conditions, refrigerators and other common household necessities are constantly turning on and off changing the demands on your household current. Lightening is also another good source of current disruption. Even if your home is not hit the lightening does ground out somewhere there considering the amount of wires under the streets, the strike is going to be near the power source for your home. Problems with the electric companyís transformers, power lines and generators also contribute to an unsteady power source.
The outlets on the protector are usually divided into two types, switched and unswitched. The switched outlets let you turn single outlets or groups of outlets on and off from the protector. This is handy when you want to turn on groups of equipment like computer, monitor and printer or TV, receiver and decoder. The unswitched outlets are always on. Use these for things like TiVo and your VCR since you will want to record while the rest of the equipment is off.
For those that are worried about even the slightest disruption in power that might ruin that computer download or getting your favorite program on TiVo there is the UPS. The uninterrupted power supply is a large battery that is constantly hooked up to a trickle charger. This runs low amounts of power into the battery at all times making sure it is at peak charge. If the current is interrupted a small circuit changes the power source from the line to the battery. Usually a power inverter is used to transform the DC battery current into usable AC current. The time you can stay on these batteries is very limited ranging from a few minutes to about an hour for large, business UPC units.
Now letís look at which level of protection is best for you. Remember, you donít need a protector on everything. A light bulb for example couldnít care less about minor power spikes and the worse thing that could happen is a large spike would cause it to blow out.
Now, you should be better informed to understand why we canít just get extension cords and shove everything directly in the wall outlets. You paid a lot for your computer and home theater. Consider a top notch surge protector as insurance that will protect your investment. You have thousands invested, add another hundred to the budget to make sure you have years of enjoyment.