3B45_15 Datasheet, PDF (2/8 Pages) Analog Devices – Isolated Frequency Input

GENERAL DESCRIPTION
The 3B45 and 3B46 are single-channel isolated frequency input
moduels which produce simultaneous precision voltage and
current outputs proportional to input frequency. Model 3B45
accepts full-scale inputs ranging from 25 Hz to 1100 Hz, while
Model 3B46 accepts full-scale input from 520 Hz to 25kHz.
Both models enable the user to set the threshold to either 0 V
(for zero crossing signals) or +1.6 V (for positive level signals),
and the hysteresis to either 0 or +4 V. Hysteresis can be set for
any value within this range using the supplied AC1310 ranging
card. The 3B45 and 3B46 shield their computer side outputs
from damage and loss of signal integrity from field-side over-
voltage faults, withstanding up to 220 V rms at their input
terminals. The current output withstands 130 V rms without
damage and interfaces user equipment through screw terminal
connections. In addition, all 3B45 and 3B46 models are plug-in,
mix-and-match and hot-swappable, so each can be inserted or
removed from any socket in the same backplane without
disrupting system power.
3B Series Custom-Ranging Program – Externally-
programmable Model 3B45-00 and 3B46-00 enable the user to
configure a special input range by using the supplied plug-on
AC1310 ranging card, which houses user-supplied resistors to
determine hysteresis, zero and span. To facilitate selecting
resistors, a Windows program, 3B-CUSTOM, calculates resistor
values based on the user-desired input/output ranges.
The 3B45 and 3B46 compare the input signal to the user-
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3B45 / 3B46
selected threshold (Vt) and hysteresis (Vh). Signals of virtually
any wave shape that exceed the combined threshold and
hysteresis levels (Vt + Vh) will trigger a comparator at a rate
determined by the input frequency. The comparator output is
then transmitted across a proprietary transformer-coupled
isolation barrier. A demodulator on the computer side of the
signal transformer recovers the original signal, which is then
filtered and buffered to provide a low-noise, low-impedance
output voltage; this output also drives a voltage-to-current (V/I)
converter to provide a simultaneous current output for
interfacing versatility.
Setting the threshold value is a simple matter of externally
wiring to the 3B Series backplane screw terminals. The
threshold for measuring a zero-crossing voltage waveform (such
as sine waves) can be set to 0 volts by connecting terminal 3 to
terminal 4. The threshold for a positive level signal (such as a
TTL or pulse train waveform) can be set at +1.6 V by
connecting terminals 1 and 2. Hysteresis for both input signal
types is set at 0 V, but can be changed to +4V by removing the
jumper that is installed on the AC1310 ranging card shipped
with each unit.
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Figure 2
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