Emerson ROC827 instruction manual Multi-Variable Sensor MVS Interface Modules, MVS Termination

ROC827 Instruction Manual

5.10 Multi-Variable Sensor (MVS) Interface Modules

The Multi-Variable Sensor (MVS) provides differential pressure, static pressure, and temperature inputs to the ROC827 unit for orifice flow calculation.

The MVS module consists of interface electronics that provide the communications link between the ROC827 and the MVS. The interface electronics controls communications with the sensor module, provides scaling of process variables, aids calibration, stores operating parameters, performs protocol conversion, and responds to requests from the ROC827.

The ROC827 handles up to two MVS interface modules. Each MVS module provides the communications interface and the isolated, short- circuit current-limited power required to connect up to six MVS sensors.

The MVS modules create six points automatically for each of the six possible MVS channels. The points include 1 through 6 and if you have a second MVS module installed, points 7 through 12 are available. Points are assigned based on which module is in the first slot. For example, if an MVS module is in slot three, it automatically assigns the points 1 through

6.If you then install an MVS module into slot one, the points are re- assigned so that slot one holds points 1 through 6 and slot three holds points 7 through 12.

The ROC827 allows six MVS devices to be connected on its communications bus in a multi-drop connection scheme. You must set the address of each MVS prior to final wiring of multiple MVS devices. For proper operation of multiple MVS devices, each MVS device must have a unique address. None of the addresses can be 240. For details on MVS configuration, refer to the ROCLINK 800 Configuration Software User Manual (Form A6121).

Once you set a unique address for each MVS, connect the MVS units in a multi-drop arrangement. The only requirement for wiring multi-drop devices is that all like terminals be tied together. This means all the “A” terminals on the devices are electrically connected to the ROC827’s “A” terminal and so on. To do this, daisy-chain wire each remote MVS.

Terminations are required on the two MVS modules located at the extremities of the circuit. That is to say, the two outside modules require terminations in order to complete the communications circuit. The MVS termination jumper is located at J4 on the module. Refer to Table 5-15 and Figure 5-6.

Table 5-15. MVS Termination

Terminated Not Terminated

Jumper

	TER	OUT	TER	OUT
J4	x			x

Issued Mar-06 Communications 5-14