Chapter 21 Electrical Test and Measurement Equipment 413 Cursors ΔV Δt Voltage measurement Time measurement Cursors Goodheart-Willcox Publisher Figure 21-23. Oscilloscope cursors serve as reference points for measuring voltage and time. often used with a 10:1 probe, resulting in circuit loading of 10 MΩ. Some oscilloscopes may also select an imped- ance of 50 Ω to match equipment with a coaxial cable output. With a direct coax cable connection between the scope and the equipment being measured, the imped- ance is matched and the scope should read accurately. Figure 21-25 shows the input channel connections and the scope calibrator connection of a digital oscilloscope. Often, oscilloscope probes have a switch labeled X1/ X10 on the probe body. X1 is considered direct, and in this position the probe impedance is the same as the input impedance of the scope. In order not to load a high impedance circuit under test, switch the probe to the X10 position. Th is position allows the probe to present a high impedance and not Goodheart-Willcox Publisher Figure 21-24. A portable oscilloscope. Notice that this oscilloscope does not have any knobs. Instead, settings are accessed through the use of on-screen menus and navigation buttons. This portable oscilloscope also makes automatic measurements and functions as a multimeter. Goodheart-Willcox Publisher Figure 21-25. Oscilloscope inputs and calibrator output. load the circuit under test. When in the X10 position, multiply the reading on the oscilloscope screen by ten to obtain the actual voltage measured. Some oscilloscopes have a menu option that allows you to specify which probe is connected, such as X1, X10, X100, or X1000. Copyright Goodheart-Willcox Co., Inc.