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Agilent E1538A Enhanced Frequency/Totalize/PWM SCP 9
Input and Output Characteristics
This section describes the E1538’s channel input and output electrical
characteristics. Refer to Figure 6 for the following discussions.
Input Characteristics When configured for input, E1538 channels provide digital input through the
threshold comparator. The digital input threshold level is programmable with
a SCPI command from -48 to +47.625 VDC in .375V steps (relative to the
Lnn terminal). The threshold amplifier also provides typically 0.5 volts of
hysteresis regardless of the threshold level setting. The input impedance in
this configuration is greater than 100KΩ (as long as the 10KΩ pull-up resistor
is OFF).
Channels 0 and 1 also provide the capability (when the VRS switch is ON)
to read the output of variable reluctance sensors. Because the output of a VRS
varies in relation to the velocity of the toothed wheel it is reading, the E1538A
provides adaptive amplifiers for these channels. The function of the amplifier
Figure 5. Recommended Connections and Voltage Limits