7B39 Isolated, Process Current Output


7b39-01The 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 V DC supply.

Inside the 7B39 Series Module

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 V DC 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.

Input and Output Ranges

Figure 1. 7B39 Functional Block Diagram

Figure 2. 7B39 Input Field Connections

Input Types Output Options
0 V to +10 V
+1 V to + 5 V
0 mA to 20 mA
4 mA to 20 mA

View and Order Models

Input Range  Output Range 
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7B39-01 +1 V to +5 V
+4 mA to +20 mA
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0 V to +10 V
0 mA to +20 mA


7B39 Specifications
(typical @ +23°C ±5°C and Vs = +24 V dc)

Model 7B39 
Output Range (RL = 0 Ω to 850 Ω)
Standard Range
0 mA to 20 mA or 4 mA to 20 mA
(30 mA, maximum)
Custom Ranges
Not Available*
Input Range
0 V to +10 V or +1 V to +5 V
Initial @ +25°C
±0.01% Span (±0.1% Span, maximum)
±0.02% Span, maximum
Span vs. Temperature
±25 ppm/°C
Output Offset vs. Temperature
±0.0035% Span/°C
Input Resistance 
Power ON
  Model 7B39-01 2 MΩ
  Model 7B39-02 40 kΩ
Power OFF
30 kΩ, minimum
 Output Noise
5 MHz Bandwidth
160 µA peak
10 Hz to 100 kHz Bandwidth
4 µA peak
10 Hz to 100 kHz Bandwidth
25 nA peak
Bandwidth, -3 dB
100 Hz
Output Rise Time, 10% to 90% Span
3 ms
Common Mode Voltage (CMV)
Output-to-Input and Power
1500 V rms continuous
Common Mode Rejection (CMR)
Output-to-Input and Power @ 50/60 Hz
110 dB
Input Protection
±35 V dc, continuous
120 V rms, continuous
Ouput Transient Protection
ANSI/IEEE C376.90.1-1989
IEC 255-4, Class II
 Power Supply
Voltage Range, Operating
+14 V dc to +35 V dc
+60 mA, maximum
±0.0001%/% of Vs
Mechanical Dimensions
1.663" x 2.11" x 0.563"
(42.24 mm x 53.6 mm x 14.3 mm)
60 grams
Temperature Range
  Operating -40°C to +85°C
  Storage -40°C to +85°C
Relative Humidity, 24 hours
0 to 90% @ +60°C noncondensing
ESD Sensitivity
IEC 801-2, Level 2
RFI Susceptibility
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

Warm-up time required to meet specifications is approximately 10 minutes.
* Contact factory for OEM requirements.
1 Includes the combined effects of repeatability, hysteresis, and nonlinearity.
2 Nonlinearity is calculated using best-fit straight line method.
Specifications subject to change without notice.