Applications

 4 to 20 mA sensors and controllers

 Industrial process control

 HART Street light controllers

 Toll booths, drawbridges, railroad crossing gates & signals

 Pulse input circuits

Features

 Protection for up to three pairs of lines plus

provisions for shielded cables

 Three-Stage protection

 Weatherproof ABS enclosure

 Removable screw terminal blocks

 Available in 12V, 15V and 24V models

Description

The AL-CL3W-xx series are high performance 3-stage weatherproof protectors that provide superior protection of

differential or common mode lines from transients and surges. These units will protect up to three 4-20 mA

circuits. Provisions for use with shielded cable are provided.

The first stage is comprised of a differential gas discharge tube. Stage two is a pair of current limiting series

resistors and the final stage is a low capacitance diode array. The use of three terminal differential gas discharge

tubes provides superior common and differential mode protection against conducted transients versus the use of

lower cost two terminal tubes. The second stage series resistance limits the power dissipation of the fast diode

clamp array in the third stage. This allows time for the slower but higher power gas tubes to flash over. The diode

array clamps the leading edge of fast transients to safe levels until the high power gas tubes turn on. This

eliminates the damaging leading edge spike that single stage gas tube

protectors let leak through. The diode array’s low capacitance assures that the

suppressor will not degrade the high-speed signals. The 3-stage design can

handle higher-level transients than a protector that uses only diodes.

Failsafe Feature

The AL-CL3W series is designed to convert into a failsafe mode in the rare case

of a catastrophic surge or lightning event. For this mode, the resistors in the

second stage will fuse and portions of the diode array will short. This

effectively disconnects the line from sensitive equipment thus limiting damage.

The units are factory repairable.