valutazioni - 2, GPA: 4.5
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Static electricity can build up on your body and can easily damage sensitive internal circuit elements when discharged. Static discharges too small to be felt can cause permanent damage. Devices such as calibration components and devices under test (DUTs), can also carry an electrostatic charge. To prevent damage to the test set, components, and devices: • always wear a grounded wrist strap having a 1 MW resistor in series with it when handling components and devices or when making connections to the test set. • always use a grounded, conductive table mat while making connections. • always wear a heel strap when working in an area with a conductive floor. If you are uncertain about the conductivity of your floor, wear a heel strap. • always ground yourself before you clean, inspect, or make a connection to a static-sensitive device or test port. You can, for example, grasp the grounded outer shell of the test port or cable connector briefly. • always ground the center conductor of a test cable before making a connection to the analyzer test port or other static-sensitive device. This can be done as follows: 1. Connect a short (from your calibration kit) to one end of the cable to short the center conductor to the outer conductor. 2. While wearing a grounded wrist strap, grasp the outer shell of the cable connector. 3. Connect the other end of the cable to the test port. 4. Remove the short from the cable. Refer to Chapter 6 , “Replaceable Parts,” for part numbers and instructions for ordering ESD protection devices. Figure 3-1 ESD Protection Setup 3-2 85032B/E Use, Maintenance, and Care of the Devices Visual Inspection Visual Inspection Visual inspection and, if necessary, cleaning should be done every time a connection is made. Metal particles from the connector threads may fall into the connector when it is disconnected. One connection made with a dirty or damaged connector can damage both connectors beyond repair. In some cases, magnification is necessary to see damage on a connector; a magnifying device with a magnification of .10. is recommended. However, not all defects that are visible only under magnification will affect the electrical performance of the connector. Use the following guidelines when evaluating the integrity of a connector. Look for Obvious Defects and Damage First Examine the connectors first for obvious defects and damage: badly worn plating on the connector interface, deformed threads, or bent, broken, or misaligned center conductors. Connector nuts should move smoothly and be free of burrs, loose metal particles, and rough spots. What Causes Connector Wear? Connector wear is caused by connecting and disconnecting the devices. The more use a connector gets, the faster it wears and degrades. The wear is greatly accelerated when connectors are not kept clean, or are connected incorrectly. Connector wear eventually degrades performance of the device. Calibration devices should have a long life if their use is on the order of a few times per week. Replace devices with worn connectors. The test port connectors on the network analyzer test set may have many connections each day, and are therefore more subject to wear. It is recommended that an adapter be used as a test port saver to minimize the wear on the test set’s test port connectors. Inspect the Mating Plane Surfaces Flat contact between the connectors at all points on their mating plane surfaces is required for a good connection. See Figure 2-1 on page 2-3. Look especially for deep scratches or dents, and for dirt and metal particles on the connector mating plane surfaces. Also look for signs of damage due to excessive or uneven wear or misalignment. Light burnishing of the mating plane surfaces is normal, and is evident as light scratches or shallow circular marks distributed more or less uniformly over the mating plane surface. Other small defects and cosmetic imperfections are also normal. None of these affect electrical or mechanical performance. If a connector shows deep scratches or dents, particles clinging to the mating plane surfaces, or uneven wear, clean and inspect it again. Devices with damaged connectors should be discarded. Determine the cause of damage before connecting a new, undamaged connector in the same configuration. 85032B/E 3-3 Use, Maintenance, and Care of the Devices Cleaning Connectors Inspect Female Connectors Pay special attention to the contact fingers in the female center conductor. These can be bent or broken, and damage to them is not always easy to see. A connector with damaged contact fingers will negatively affect electrical performance and must be replaced. NOTE Inspection is particularly important when mating nonprecision to precision devices. Cleaning Connectors Clean connectors are essential for ensuring the integrity of RF and microwave coaxial connections. 1. Use Compressed Air or Nitrogen WARNING Always use protective eyewear when using compressed air or nitrogen. Use compressed air (or n...