The OMB-DBK5 current-output card provides OMB-DAQBOARD-2000 Series data acquisition systems with the ability to control four isolated 4 to 20 mA current loops. The OMB-DBK5 acts as a current loop transmitter by modulating current from an external source. The OMB-DBK5 can be programmed with a static value whenever the data acquisition system is not transferring A/D data. As many as sixty-four OMB-DBK5’s can be used in one system, to obtain up to 256 outputs.

Architecture
Each of the OMB-DBK5’s channels contains a 12-bit D/A converter to set the loop current. All channels are optically isolated from the data acquisition system and from one another by 500 V.

Current Loop
The OMB-DBK5 is compatible with regulated or unregulated loop supplies of 12 to 45 Vdc. It also provides compliance with loop resistances of up to 1950 ohms, depending on the source magnitude.

Current Loop-Powered Outputs
Since the isolated outputs of the OMB-DBK5 are loop powered, the card maintains control of the loop current even when the data acquisition system is powered down. When loop power is first applied, the OMB-DBK5’s outputs assume their 4 mA default state. If at any time the data acquisition system’s power is lost or communication with the data acquisition system fails, the OMB-DBK5’s outputs retain their last set values.

Specifications
Connectors:
DB37 male, mates with P1 pinout on OMB-DAQBOARD-2000 Series; screw terminals for signal outputs
Accuracy/Linearity: 0.1% full scale
Resolution: 4 µA/LSB, monotonic
Isolation: 500 V
Voltage Range:V loop = 12 to 45 V
Compliance: R loop = (V loop - 6) / 0.020
Example Voltage
@ Vexc = 35 V; MDR* = 1450 Ohms
@ Vexc = 15 V; MDR* = 450 Ohms
* MDR (maximum drive resistance)
Cables: Use OMB-CA-37-x with OMB-DAQBOARD-2000 Series

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Related Links

4-Channel Current Output Card for OMB-DAQBOARD-2000 Series