7B39

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 7B39 is a single-channel signal conditioning current output

module that interfaces, isolates and filters a 0 V to +10 V or +1

V to +5 V input signal and provides an isolated process current

output of 0 mA to 20 mA or 4 mA to 20 mA across loads of 0 Ω

to 850 Ω . The output current appears at the 7B Series backplane

screw terminal block. Model 7B39 features a nonlinearity of

+0.02% maximum and an accuracy of +0.1% maximum

(+0.01% typical). Providing 1500 V rms of galvanic transformer

based isolation, output-to-input and power, the 7B39 offers a

common mode rejection (CMR) of 110 dB @ 50/60 Hz to

preserve the integrity of low level signals in noisy environments.

The 7B39 is mix-and-match and hot-swappable with other 7B

Series modules, so it can be inserted or removed from any

socket in the same backplane without disturbing system power.

Model 7B39 is rated to operate with a nominal +24 VDC supply.

The input signal from the user’s system is buffered and then

used to modulate the amplitude of a square wave carrier. The

modulated signal is transmitted across the signal transformer

and demodulated to retrieve the original input voltage signal.

This voltage is then filtered by a two-pole low pass 100 Hz filter,

buffered and converted to a current output signal. The nominal

+24 VDC module supply voltage powers the input side of the

7B39. The oscillator on the input side provides the square wave

carrier signal used by the modulator and also drives the power

transformer. The signal at the secondary of the transformer is

used in the demodulator and is also converted to a DC voltage

that powers the circuit on the module’s output. The floating

isolated current output of Model 7B39 is fully protected to 120

V rms line voltage.

Figure 2