3B39

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 3B39 is a single-channel signal conditioning current output

module that interfaces, isolates and filters a 0 to +10V or -10V

to +10V input signal and provides an isolated process current

output across loads of 0 to 850Ω. The output current appears at

the 3B Series backplane current output screw terminal block. It

is intended for high-accuracy process control and monitoring

applications requiring complete galvanic isolation and

protection against damage from transients and faults between

systems or separated system elements. Either of the two input

voltage ranges can be converted to either of the two output

current ranges via programming jumpers provided on the

bottom of the module. Model 3B39 features a nonlinearity of

+0.01% and an accuracy of +0.1%. Providing +1500V peak of

galvanic transformer based isolation output-to-input and power,

the 3B39 offers a common mode rejection (CMR) of 90 dB @

50/60 Hz to preserve the integrity of low level signals in noisy

environments. The 3B39 is mix-and-match and hot-swappable

with other 3B Series modules, so it can be inserted or removed

from any socket in the same backplane without disturbing

system power.

Signal isolation by transformer coupling uses a proprietary

modulation technique for linear, stable and reliable

performance. A demodulator on the output side of the signal

transformer recovers the original signal, which is then filtered

and converted to an accurate current output by a current (V-to-

I) converter output stage. Output protection enables the 3B39 to

withstand accidental connection to 220V rms power lines

without damage, isolating computer-side circuitry. The 3B39

provides total ground isolation and transient protection when

interfacing DACs to standard 4-20 mA current loops, common

requirement in microcomputer based control system.

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Figure 2