5B45 / 5B46

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 5B45 and 5B46 are single-channel isolated frequency input

modules that produce a 0 to +5V output proportional to input

frequency. Model 5B45 accepts full-scale inputs ranging from

500 Hz to 20 kHz. Model 5B46 accepts full-scale inputs ranging

from 20 kHz to 275 kHz. Both models allow the user to set the

threshold to either 0 V (for zero crossing signals) or +1.4 V (for

positive level signals), and the hysteresis to either +25 mV or

+400 mV (all input types).

The 5B45 and 5B46 protect the computer side from field-side

over-voltage faults. All models withstand 240 V rms at their

input terminals without damage, thereby shielding computer-

side circuitry from field-side over-voltage conditions. In

addition, all 5B45 and 5B46 models are mix-and match and hot-

swappable, so can be inserted or removed from any socket in

the same backplane without disrupting system power.

Inside 5B45 & 5B46 Modules

– The 5B45/46 internal circuitry

frequency. The comparator output is then transmitted across a

proprietary transformer-coupled isolation barrier and

converted to a high-level analog signal. This signal is then

filtered by a multi-pole low pass Butterworth filter and buffered

to provide a low-noise, low-impedance output signal that is

accurately proportional to input frequency.

Simple Setup and Versatile Choices

– Setting the threshold

and hysteresis values is a simple matter of externally wiring to

the backplane screw terminals. The threshold for measuring a

zero-crossing voltage waveform (such as sine waves) is set to 0

volts by connecting the input signal across screw-terminals 4

and 3. The threshold for a positive level signal (such as a TTL or

pulse train waveform) is set at +1.4V by connecting the input

signal across terminals 3 and 2. Hysteresis for both input signal

types is set at +400 mV but can be changed to +25 mV by

adding a jumper between screw terminals 1 and 4. Response

time is a function of a modules rated input frequency range.

(See the 5B45 and 5B46 Model Table).

The input circuit is fully floating and isolated from the output

and power commons. In addition, the output section acts as a

third floating port towards eliminating possible problems from

ground loops and power supply noise. The output common

must be held within +3V of power common.

A series output switch eliminates the need for external

multiplexing in many applications. The switch is turned on by

an active-low enable input. If the switch is to be on at all times,

the enable-input should be grounded to power common as it is

on the 5B01 and 5B08 backplanes..

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Figure 2