3B39 Isolated Process Current Output


Model 3B39The 3B39 is a single-channel signal conditioning current output module that interfaces, isolates and filters a 0 to +10 V or +10 V to +10 V input signal and provides an isolated process current output across loads of 0 to 850 Ω. 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 ±1500 V 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.

Inside the 3B39 Series Module

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 220 V 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, a common requirement in microcomputer-based control systems.

Input and Output Ranges

3B39 Functional Block Diagram
Figure 1. 3B39 Functional Block Diagram

3B39 Input Field Connections
Figure 2. 3B39 Input Field Connections

Input Type
Dual Outputs
0 to +10 V
4 mA to 20 mA
-10 V to +10 V
0 to 20 mA

3B39 Models Available

Model  Input Range Output 
Order Now 3B39
0 V to +10 V or -10 V to +10 V
0 mA to 20 mA or 4 mA to 20 mA

1 Output current range may be user programmed to 4 mA to 20 mA using jumper supplied.

3B39 Specifications

(typical @ +25°C and ±15 V dc, and +24 V dc Power)

Description  Model 3B37
Input Range
Input Voltage Standard Ranges1 0 V to +10 V or -10 V to +10 V
Input, Without Damage -20 V to +20 V, maximum
Input Resistance 10 kΩ
Output Range
Standard Ranges (RL = 0 to 850Ω)
4 mA to 20 mA or 0 mA to 20 mA
Custom Ranges
Not Available
Initial @ +25°C
±0.1% Span + CJC Sensor Error
±0.01% Span
Stability vs. Temperature
Current Output
   Zero ±25 ppm of Span/°C
   Span ±25 ppm of Reading/°C
Zero and Span Adjustment Range
±5% of Span
Input, 0.1 Hz to 10 Hz Bandwidth
0.2 µV rms
Output, 100 kHz Bandwidth
50 µV rms
Bandwidth, -3 dB
3 Hz
Output Rise Time, 10% to 90% Span 2 ms
Common Mode Voltage (CMV)
Input-to-Output, Continuous
±1500 V peak, maximum
ANSI/IEEE C37.90.1-1989
 Common Mode Rejection (CMR)
1 kΩ Source Imbalance, 50/60 Hz 90 dB
Output Protection
Continuous, Normal Mode
220 V rms, maximum
 Transient ANSI/IEEE C37.90.1-1989
Power Supply Voltages3
±15 V dc Supplies
   Rated Operation ±(11.5 V dc to 16.5 V dc)
   Current ±10 mA
   Sensitivity ±0.01% span/V
+24 V dc Loop Supply
   Rated Operation +12 V dc to +30 V dc
   Current +27 mA @ lout = 20 mA
   Sensitivity ±0.0002% span/V
Mechanical Dimensions
3.15" x 3.395" x 0.775"
(80.0 mm x 86.2 mm x 19.7 mm)
Temperature Range
   Rated Performance -25°C to +85°C
   Storage -55°C to +85°C
Relative Humidity, 24 hours
0 to 95% @ +60°C noncondensing
RFI Susceptibility
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

1 Input and Output Range may be selected using jumpers supplied.
2 Includes the combined effects of repeatability, hysteresis, and nonlinearity.
3 +24 V dc loop power is required for driving the current output at loads up to 850Ω. If a current output load of 400Ω or less is applied, +15 V dc is sufficient for loop power. If only voltage output is used, loop power is not required.

Specifications subject to change without notice.