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
