(b) Equations

TM 55-4920-401-13&P tive out-of-range input signal causes an indicator’s display to flash on and off through the action of the blanking signal. (b) Equations. Dual-slope integration of a linear A/D) converter, like the % rpm converter, is defined by the following equation: V (amplified signal) x J signal counts = V (reference) x j reference counts. A linear A/D converter uses a constant reference voltage. A non-linear A/D converter, like the tem- perature converter, uses a stepped (shaped) refer- ence voltage. Nonlinear dual-slope integration is defined by the following equation: V (amplified signal) x j signal counts = V (refer- ence 1) x reference 1 counts + reference 2 counts +. . . . (c) Integrator. T h e V (reference 2) x j integrator (fig. 1-4) charges and discharges the integrating capacitor with current that is proportional to the integrator input voltage. Since the input voltage is applied to the inverting (-) input, the integrator charges the capacitor negatively when a positive voltage is ap- plied, and positively when a negative voltage is ap- plied. Figure 1-5 shows typical charge-discharge curves of a linear A/D converter and figure 1-6 il- lustrates curves of a nonlinear converter. Both fig- ures have two sets of curves representing positive readings R1 and R2. Note in figure 1-5 that the dis- charge rate of a linear A/D converter is a constant. Hence, a constant reference voltage is used by lin- ear A/D converters, such as the % rpm indicator, when standard day measurements are not being made. On the other hand, note in figure 1-6 that the discharge rate of a nonlinear A/D converter, such as the temperature indicator, varies in increments (S1, S 2 . . .) as the reference count increases. The discharge curve is an “amplified reflection” of the F i g u r e 1 - 4 . I n t e g r a t o r. 1-6