7B22

Rev. 0 | Page 2 of 8

GENERAL DESCRIPTION

The 7B22 is a unity gain single-channel signal conditioning

output module that interfaces and filters a +10 V input signal

and provides an isolated precision output of +10 V. The output

voltage appears at the 7B Series backplane screw terminal block.

Model 7B22 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 7B22 offers a common mode rejection (CMR) of

100 dB @ 50/60 Hz to preserve the integrity of low level signals

in noisy environments. The 7B22 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 7B22 is rated to operate with a

nominal +24 VDC supply.

The input and floating isolated voltage output of Model 7B22

are protected up to +35 VDC. 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 400 Hz filter. The nominal +24 VDC module supply

voltage powers the input side of the 7B22. 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 two-pole output filter and subsequent

buffer ensures that a low noise, low impedance (<1Ω) signal is

available at the isolated output to drive loads down to 5 kΩ.

Figure 2