Subelement F: Installation, Maintenance & Repair— Topic 45: Equipment Faults-2
Question 8-45F4
Element 8 (RADAR)In the circuit contained in Fig. 8F12, there are 5 volts present at points B and C, and there are zero volts present at points A and D. What is the voltage at point E?
Explanation
In the circuit (Fig. 8F12), points A and D are at 0 volts (ground), and points B and C are at +5 volts. In a simple resistive network powered only by positive voltage and ground, all intermediate nodal voltages must fall between 0V and +5V.
For "the voltage at point E" to be -1.5 Volts, E must represent a *differential voltage* across two points within the circuit, typical of a Wheatstone bridge configuration. If E represents the voltage difference between two nodes, say Vp1 and Vp2, such that E = Vp1 - Vp2, then a negative value is possible if Vp2 is greater than Vp1. For example, if Vp1 = +2.0V and Vp2 = +3.5V, then E = 2.0V - 3.5V = -1.5V. This indicates an unbalanced bridge where one potential is lower than the other.
Options B, C, and D are incorrect because they represent positive voltages, which would be expected for a single node's potential referenced to ground in a simple voltage divider, but not for the specific condition that yields a negative result from a differential measurement.
Related Questions
8-45F2 A defective crystal in the AFC section will cause:8-45F3 The RADAR display has sectors of solid video (spoking). What would be the first thing to check?8-45F5 If the TR tube malfunctions:8-45F6 The indicated distance from your own vessel to a lighthouse is found to be in error. What circuit would you suspect?8-46F1 Silicon crystals are used in RADAR mixer and detector stages. Using an ohmmeter, how might a crystal be checked to determine if it is functional?