If you are taking a measurement and are unsure of the actual voltage, start at the highest scale and work your way down. Using the 200 V or 1000 V scale works, but the readings at 5 V and 12 V are so small in proportion to the maximum that accuracy is low. Making these measurements on the 200 mV or 2 V scale could “peg the meter” and possibly damage it because the voltage would be much higher than expected. Because computers use both +5 V and +12 V for various operations, you should use the 20 V maximum scale for making your measurements. DC voltage, for example, usually can be read in several scales, to a maximum of 200 millivolts (mV), 2 V, 20 V, 200 V, and 1000 V. Usually, each system-unit measurement setting has several ranges of operation. Figure 20.6 shows a typical DMM being used to test the +12 V circuit on an ATX motherboard. Depending on the meter’s setting, the probes measure electrical resistance, direct-current (DC) voltage, or alternating-current (AC) voltage. The test leads make the connections so that you can take readings. The DMM has a pair of wires called test leads or probes. The meter can be an analog device (using an actual meter) or a digital-readout device. You take these measurements by using a handheld digital multimeter (DMM). Some troubleshooting procedures require that you measure voltage and resistance. Note: Serial, parallel, and USB loopback plugs and testing software are available from PassMark Software, and Ethernet loopback connectors are available from Smartronix. However, these are active bus-powered devices that require compatible drivers and software from the plug manufacturer. : Problems During POST, Running Software, And Adapter Cards.: Troubleshooting: Replacing Parts And The Bootstrap Approach.: Passive Preventive Maintenance Procedures Continued.: Passive Preventive Maintenance Procedures.: System Disassembly And Cleaning Procedures.: Test Equipment: Logic Probes, Outlet Testers, And Memory Module Testers.: Test Equipment: Electrical, Loopback Connectors, And Meters. : Windows 7/Vista And Windows 8 Startup.: DOS And Windows 9x/Me Boot Processes And Windows 2000/XP Startup.: The Hardware Boot Process: Operating System Independent.: Commercial Diagnostics Software And Free/User Supported Diagnostics.: Peripheral And Operating System Diagnostics.: BIOS POST Beep Codes, Checkpoint Codes, And Onscreen Messages.: PC Diagnostics, Testing, And Maintenance.Test Equipment: Electrical, Loopback Connectors, And Meters
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |