There is a wide variety of power monitoring equipment on the market. Much of this equipment was designed for the industrial market, and as such, typically has Modbus communication capability, but not necessarily SNMP capability. You can add SNMP capability to anything that has Modbus capability by using a Control Solutions Babel Buster gateway.

The Babel Buster BB3-6101-V3 is the ideal choice for SNMP access to Modbus devices using SNMP v1, v2c, or v3. The BB3-6101-V3 allows you to configure a set of registers local to the gateway, and then make these visible in the SNMP MIB. The type of register most commonly found in Modbus devices is a 16-bit integer. These will be converted to 32-bit integers in the SNMP MIB.

The registers are mapped into the MIB by simply listing the register numbers. The register numbers do not have to be sequential for sequential MIB OIDs.

The BB3-6101-V3 is then configured to read the remote Modbus device such as a backup generator, UPS, or other equipment. A map list is created that tells the gateway what registers to read from the remote equipment, and where to store the information locally. The following screen shot is an example of a read map list.

You have the ability to do some scaling or data conversion in the process of reading data from the remote device and storing it locally. You can also mask out individual bits that may be packed into a Modbus register. The expanded view of one of the read maps is illustrated below.

You can use SNMP GET to read the MIB in the BB3-6101-V3 (or GET-NEXT, WALK, etc). You also have the option of configuring traps to be sent to your SNMP Manager upon conditions that you specify. An example of a trap rule is illustrated below.

The most common application for SNMP monitoring involves equipment that already has some intelligence and a Modbus port. You can monitor simple switch contacts, voltage levels, and the like, by utilizing a ValuPoint Smart I/O device to convert the physical sensor levels into data readable via Modbus RTU.