18 July 2009

3B46 Isolated Frequency Input Module

Interfaces, isolates, & filters frequency inputs.
The 3B45 accepts full-scale inputs from 25 to 1100 Hz
The 3B46 accepts full-scale inputs from 520 Hz to 25 kHz.
Modules provide simultaneous precision voltage and
current outputs.
Modules circuitry can withstand 130v rms at the input screwterminals.
All 3B45 & 3B46 series modules are mix-and-match and Hot

Industrial signal conditioning
Industrial signal isolation
Industrial signal filtering

The 3B Series of Signal Conditioning I/o Subsystems provide a
low-cost, versatile method of transferring analog transducer
signals to a data acquisition, monitoring or control system
without the inherent noise, non-linearity, drift and extraneous
voltages. The modules are designed to directly accept analog
signals from Thermocouples, RTD’s, AC and DC Strain Gages,
Torque Transducers, Frequency Transducers, LVDTs, millivolt
or process current signals. The modules amplify, isolate,
linearize and convert the transducer output signals to
standardized analog inputs for high-level analog I/O
subsystems. The 3B Series Subsystem consists of a 10” relay
rack with universal mounting backplane and a family of plug-in
(up to 16 per rack) input and output signal conditioning

Eight and four channel backplanes are also available. Each
backplane incorporates screw terminals for sensor inputs and
current outputs and a 26-pin connector for high-level singleended
voltage outputs to the user’s equipment.

The input modules feature complete signal conditioning
circuitry optimized for specific sensors or analog signals and
provide two simultaneous high-level analog outputs: 0 to +10V
(or +10V) and 4-20 mA (or 0-20 mA).

Output modules accept 0 to +10V (or +10V) single-ended
signals and provide an isolated 4-20 mA (or 0-20 mA) process
signal. All modules feature a universal pin-out and may be
readily hot-swapped under full power and interchanged without
disrupting field wiring.

The Analog Devices 3B Series Signal Conditioning Subsystem is
designed to easily handle signal conditioning problems in
measurement and control applications. Some typical uses are in
microcomputer-based data acquisition systems, programmable
controllers, analog recorders, dedicated control systems, and any
other applications where monitoring of temperature, pressure,
flow and analog signals are required. Since each input module
features two simultaneous outputs, the voltage output can be
used to provide an input to a microprocessor-based data
acquisition or control system while the current output can be
used for analog transmission, operator interface, or an analog
backup system.

Each input module is a single-channel signal conditioner which
plugs into a socket on the backplane and accepts its signal from
the input screw terminals. All input modules provide input
protection, amplification and filtering of the input signal,
accuracy of +0.1%, low drift of +1 uV/ oC (low-level input
modules), and feature two high-level analog outputs that are
compatible with most process instrumentation. The isolated
input modules also provide +1500 V peak isolation.

The choice of a specific 3B module depends upon the type of
input signal. Input modules are available to accept millivolt, volt,
process current, thermocouple, RTD, AC and DC strain gage,
frequency and LVDT inputs. The voltage output of each module
is available from the system I/O connector while the current
output is available on the output screw terminals.

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 overvoltage
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 – Externallyprogrammable
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 userselected
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.