11. The nominal level and the reference voltage against which it is expressed depend on the line level being used. 12. During the run-down phase, the switch selects the reference voltage as the input to the integrator. 13. The inputs are an unknown voltage and a reference voltage , usually referred to as v u and v r. 14. All scope probes contain some facility for grounding ( earthing ) the probe to the circuit's reference voltage . 15. In the case of the basic design, the output of the converter is in terms of the reference voltage . 16. Each single comparator detects the common input voltage against one of two reference voltages , normally upper and lower limits. 17. This particular circuit uses an LM431 adjustable divider of R 1 and R 2 provide the reference voltage for the LM431. 18. A front end processor provides a reference voltage , measures the output of the network, and calculates the dew point. 19. The output of the comparator is used by the converter's controller to decide which reference voltage should be applied. 20. While the nominal levels themselves vary, only two reference voltages are common : for consumer applications, and for professional applications.
