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In the DC mode, a zero-to-5-volts DC level is produced at G1 and G2 on the front panel. The polarity of the level is controlled by the positive and negative buttons. By pressing the positive button, you enable a positive DC output and disable the negative button. By pressing the negative button, you enable a negative DC voltage only if the positive button is in the off position. The WIDTH control knob has no effect in the DC mode of operation. CRT Display The CRT deflection drivers boost the low-level outputs from the signal section to the higher voltage levels needed by the deflection plates in the CRT. The HORIZ (horizontal) and VERT (vertical) controls on the front panel adjust the position of the CRT trace. The TRACE ROTATE control on the front panel is used to adjust the short circuit vertical trace to be parallel with the vertical axis on the CRT graticule. Three other controls (INTENSITY, FOCUS, and astigmatism) are used to adjust the proper brightness and clarity of the trace. The front-panel INTENSITY control is the primary way to adjust the visual quality of the trace. FOCUS is located on the back panel and is used as your trimming adjustment. Astigmatism is an internal adjustment and is set at the factory. Power Supply The power supply is an ac-line-operated power supply that is turned on and off by the POWER/INTENSITY knob located on the front panel. Once power is turned on, the power supply provides 12 V dc (nominal) and 5 V dc (regulated) for normal circuit operational use in the oscillator, pulse generator, signal, and control logic sections of the Tracker 2000. The other outputs from the power supply are provided to the CRT display section. The CRT is provided with a filament voltage of 6.3 V rms, +180 V dc for the deflection driver circuits, and a regulated -1320 V dc for the CRT acceleration voltage. Now that you have a basic understanding of how the Tracker 2000 works, we will show you a few examples of different components with values and their associated displays. Because of the large number of different values that can be given to any component, this section will present only a few. Testing Resistors A resistance across the test probes will cause the trace of the Tracker 2000 to rotate in a counterclockwise direction around its center axis from an open circuit position. The degree of rotation is directly related to the resistance value. The higher the value, the less rotation will be observed. LOW RANGE. - The low range is designed to test for resistance values between 1W and 1K. Figure 5-30 shows the effect of resistance on the angle of rotation in low range. A 1 W resistor causes almost 90 of rotation, and a 50W resistor produces a 45 rotation. A 400W resistor causes a very small rotation angle. Resistors lower than 1W will appear as a short circuit (vertical trace), and resistance values above 400W will look like an open circuit (horizontal trace).
Figure 5-30. - Effects of resistance on the rotation angle in low range.
MEDIUM 1 RANGE. - The medium 1 range is designed to test for resistance values between 50W and 10KW. Figure 5-31 shows the signatures for a 50W resistor, a 1KW resistor, and a 10KW resistor using the medium 1 range. Resistors that are smaller than 50W display a signature that is almost a vertical line. A 1KW resistor causes a change in the angle of rotation of 45, whereas the display of a 10KW resistor shows only a slight rotation. Resistance values under test higher than 10KW produce a signature with such a small rotation angle that it almost appears to be a horizontal line. Figure 5-31. - Effects of resistance on the rotation angle in medium 1 range.
Q.11 Medium 1 range is designed to check what resistance values? MEDIUM 2 RANGE. - The medium 2 range is designed to test for resistance values between 1KW and 200KW Figure 5-32 shows the signatures for a 1KW resistor, a 15KW resistor, and a 200KW resistor in the medium 2 range. Resistance values that are smaller than 1KW will appear to be almost a vertical line. A 15KW resistor causes a change in the angle of rotation of 45, whereas the display for a 200KW resistor shows only a slight rotation. When resistance values being tested are higher than 200KW, the displayed signature that they produce will have such a small rotation that it appears to be almost a horizontal line. Figure 5-32. - Effects of resistance on the rotation angle in medium 2 range.
HIGH RANGE. - The high range is designed to test resistance values between 3KW and 1MW. Figure 5-33 shows the signatures that would be displayed for a 3KW resistor, a 50KW resistor, and a 1MW resistor using the high range. Resistors that are smaller than 3KW will appear to be almost a vertical line. A 50KW resistor will cause a change in the angle of rotation of 45, whereas the display for a 1MW resistor shows only a slight rotation that is very close to a horizontal line. Resistance values higher than 1MW will produce such a small rotation that it appears to be a horizontal line. Figure 5-33. - Effects of resistance on the rotation angle in high range.
Testing Capacitors When you test capacitors, the signature will be displayed as an ellipse. The size and shape of the ellipse depend on the capacitor value, test signal frequency, and the selected impedance range. Figure 5-34 shows the signature of a 0.22mF capacitor in each of the 12 combinations of range and frequency. As you review this figure, you will notice that the signature appears to be an open circuit in the low range at 60 Hz; while in the high range at 2000 Hz, the signature appears to be a short. Between these, the signatures displayed are a variety of ellipsoids, which demonstrates that certain range and frequency combinations are better than others for examining a capacitor. Figure 5-34. - Signature of a 0.22mF capacitor.
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