A string monitors system is the advanced version of AJB. AJB with string monitor unit is called SMB (string monitoring box). A string monitor system has the main objective to monitor the individual string current & common bus voltage on real time basis. It also has the temperature measurement facility for the keeping a check on the temperature inside the box. The string current, voltage & temperature are measured & communicated through a RS-485/Zigbee over Modbus protocol. It should be compatible with SCADA system. It helps in easy detection & identification of fault in any string. After getting the location of the fault through a computer we can rectify the same easily.

There are two types of string monitoring systems.

1. Shunt based
2. Hall effect type

The main components of SMBs are

1. Enclosure
2. PV fuses
3. Surge Protection Device
4. DC Disconnector/Isolator:
5. Cable Glands/Connectors
6. Monitoring card