You should know about a couple of notable specifications for oscilloscopes. One of the most important specs is bandwidth. Bandwidth is the highest frequency signal that you can reliably test with your oscilloscope, measured in megahertz (MHz). PC-based scope probes tend to have the lowest bandwidth, usually about 5-10 MHz. This bandwidth works just fine for many tasks, including working with hobby circuits and even servicing VCRs and audio equipment. The average bandwidth of a low-cost bench scope falls in the 20-35 MHz range. This range does the job for all but the most demanding applications. Specialized troubleshooting and repair, such as work on computers and ultrahigh- frequency radio gear, may require bandwidths exceeding 100 MHz. But remember that the price of an oscilloscope goes up considerably as the bandwidth gets higher. 

Another important specification is resolution. The resolution of the scope has to do with its accuracy. The X (horizontal) axis on an oscilloscope displays time, and the Y (vertical) axis displays voltage. The horizontal amplifier indicates the X-axis resolution. Most scopes generally have a resolution of 0.5 microseconds (millionths of a second) or faster. You can adjust the sweep time so that you can test signal events that occur over a longer time period, usually as long as a half a second to a second. Note that the screen can display signal events faster than 0.5 microseconds, but such a small signal may appear as a fleeting glitch or voltage spike. The sensitivity of an oscilloscope indicates the Y-axis voltage per division. The low-voltage sensitivity of most average-priced scopes is about 5 mV (millivolts, or thousandths of a volt) to 5 volts. You turn a dial to set the sensitivity that you want. 

When you set the dial to 5 mV, each mark on the face of the scope tube represents a difference of 5 mV. Voltage levels lower than 5 mV may appear, but you can’t accurately measure them. Most scopes show very low voltage levels (microvolt range) as a slight ripple.