1840-05-A3 - 

The Bourns® 1840 Series Signal and Dataline Protectors are designed to protect sensitive electronic circuits and components from damaging surge voltages and currents. Their extremely fast response and low clamping voltages make them particularly suitable for the protection of sensitive signal and datalines associated with computer, data communication, instrumentation, broadcasting and industrial controls. They may be used directly with EIA standard interfaces RS-232, RS-422, RS-423, RS-485 and with 4-20 mA and 50 mA instrumentation loops. The Model 1840 Series Signal and Dataline Protectors are fast, rugged and capable of protecting against fast rising voltage transients as well as the severe current surges associated with lightning discharges, in each case up to rated limits.
Method of Operation:
The Bourns® 1840 Series are heavy-duty, multi-staged protectors. A solid-state 3rd stage protection component intercepts the leading edge of the surge within sub-nanosecond response time. Within microseconds, a primary stage 3-electrode common chambered heavy-duty gas discharge tube capable of handling 20,000 ampere lightning currents operates and crowbars the majority of the surge energy to ground. The Model 1840 also utilizes Bourns’ TBU® High-Speed Protector (HSP) technology as a key 2nd stage. Any current through the protector exceeding 300 mA will cause the TBU® HSP to quickly transition into a high impedance state, thus isolating any harmful voltage and/or current from damaging the protected equipment. The gas discharge tube protector remains in the crowbar state until the surge has passed and line voltages return to safe levels. The TBU® HSP then automatically restores the line to normal operation by resetting to a low impedance state. There is no need for resetting a breaker or replacing a fuse to address a transient surge event.
Applications:
Protectors are generally placed at each end of a signal, dataline or current loop. In the case of daisy-chain configurations (such as RS-485), protectors are placed at each node.
Related Bourns® Protectors:
For outdoor applications with 1⁄2 inch NPT ports (such as field-mounted 4-20 mA transmitters), please refer to the Bourns® Model 1669 Series Protector. In this application, the mixed use of a Model 1840 Series Protector at the controller and a Model 1669 Series Protector at the field is recommended.