The Sentry is a single zone corrosion monitor.  

LED’s provide indication of the vessel or structure's level of cathodic protection.  For example, you may wish to monitor the hull of a marine vessel. Install the Sentry and a reference electrode. Press the test button and the LED's will light. A green indication shows the vessel is correctly protected, a red indication warns of corrosion susceptibility.

Other zones may include the insides of sea chests, ballast tanks, water jet tunnels etc. The Sentry provides a convenient way of monitoring the cathodic protection of a structure without having to inspect the sacrificial anodes.

The Sentry kit comprises a Sentry monitor, mounting screws, 3 AA batteries, and an earth lead. 

sentrykit.jpg (43105 bytes)
Click picture for larger image
Sentry kit

Note: A reference electrode has to be ordered separately. 

Refer to: Reference electrode installation and Order information


  1. The Sentry can be bulkhead mounted in any convenient location such as in the engine room or in the vessel’s bridge/pilot house.  The box dimensions are 115 mm x 65 mm x 40 mm deep.
  2. Drill two 3.8mm diameter holes at 83.5 mm by 52.5 mm centers on the hull bulkhead or other suitable mounting location. See the schematic drawing of the Sentry below.
    Sentry_template.gif (14054 bytes)
    Click picture for larger image
    Schematic of Sentry with wiring and installation details
  3. Remove the Sentry lid taking care to keep it supported. Mount the Sentry box using the two 8g x 12 mm self tapping screws provided. 
  4. Insert the 3 AA batteries supplied. Refasten the Sentry lid.
  5. Connect terminal E to the hull with the earth lead provided.
  6. Connect terminal 1 to the reference electrode.

Monitor operation

Press the test button. The LEDs will light.  To conserve battery life the Sentry operates normally in ‘power down’ mode. The Sentry will auto power down after one minute.  

The reference electrode must be connected to the corresponding terminal on the Sentry and it must be in contact with sea water. Only then will the Sentry indicate the cathodic protection level correctly.    


  Home   What's New   Sentry   SentryLog   Multizone   Electrodes   Corrosion Basics    Downloads   Order Info   Contact us/links