What is impedance?
As you probably know if you’ve been shopping for cables, coax for most video applications is “75 ohm” coax–but what the heck does that mean, anyway? This article is a short, non-technical explanation of impedance, and its significance in video and other circuitry, for those who have always scratched their heads at this one. Every signal input, and every output, has an impedance–this “impedance” represents the relationship between voltage and current which a device is capable of accepting or delivering. But it’s hard to talk about electrons flying around in wire, and volts and amps, without making the whole subject seem abstract and obscure. Let’s think about another situation with which we’re all familiar: an automobile and its transmission. An automobile engine can put out a certain amount of power–horsepower, we call it. But the engine, itself, isn’t the only thing in the drive train. Between the engine and the road lies the transmission, and a transmission controls the relationsh
The impedance of a battery is a measure of how easily it can be discharged. The lower the impedance the easier it is to discharge the battery. The impedance of the ODYSSEY battery is considerably less than that of a conventional SLI battery, so its high rate discharge capability is significantly higher than that of a conventional SLI battery.
Now here comes one of the most confusing aspects of electronics – which I will de-mystify by taking an extremely casual approach, so what’s new!. I have known electronic enthusiasts who still couldn’t even mentally visualise the concept even after 25 years. I’ll keep it dead simple, very inelegant but dead simple and give all the purists heart palpitations. I bet you walk away with a better understanding though. If you need to know the technical answer for impedance and you should, then consult one of the must read texts I have suggested elsewhere. Assume you have available these 4 items on your bench: (a) A series of eight fresh AA type 1.5 volt cells to create a total of 12 volts supply. (b) A 12 volt heavy duty automotive battery – fully charged. (c) a small 12v bulb (globe) of very, very low wattage. and; (d) a very high wattage automotive high-beam headlight. Now if we connect the extremely low wattage bulb to the series string of AA cells we would expect all to work well. Similar
Impedance measures how easily a circuit conducts current when a voltage runs through it. Measured in ohms, impedance is a way of telling you how much of the voltage introduced at one end will really make it to the other end. Impedance depends on other qualities of electricity, such as resistance, reactance, inductance, and capacitance. Most injectors fall into two categories: High or Low Impedance High Impedance. These have a typical coil resistance of 12 – 16 ohms and are the most commonly used. Drive circuitry for this type of injector is simple and sometimes referred to as a saturated driver circuit. Low Impedance. Low Impedance Injectors has normally a coil resistance of 4 ohms or less and is typically found in larger sized or high performance injectors. Driver circuitry for these types is called a Peak – Hold type and is more complex and costs more than the saturated type. In a Peak – Hold system, the driver circuit allows a high current for a short time to help turn the injector
