Siemens MD-BMS - Selecting a Scalar

Prepping for Installation
Meter Setup
32
Building Technologies 125-202
06/06/2017
CT Style Part Number CT Rated
Amps
CT Phase Shift
Value
Recommended Data/Digital Scalar for
3-Phase Loads
Nominal CT
Accuracy
230V 460V
SCT-RGT12-0050-U 50 Scalar 1 Scalar 2
SCT-RGT12-0100-U 100 Scalar 2
Revenue Grade Split
Core
SCT-SRS-005-U 5 359.90° Scalar 1 Scalar 2 0.2%
SCT-SRS-050-U 50 359.77° Scalar 1 Scalar 2
SCT-SRL-100-U 100 0.06° Scalar 2
SCT-SRL-200-U 200 0.06° Scalar 2
SCT-SRL-400-U 400 359.94° Scalar 2
1. Select a Digital Output from the drop-down list, if being used.
2. Select a Data/Digital Scalar from the drop-down list.
Selecting a Scalar
The use of Modbus protocols limits the data registers to a maximum of two bytes (16
bits) or a maximum decimal value of 65535. Modbus requires that the data be
unsigned (positive) integer values. To overcome these limitations, some measured
(and stored) values must be scaled to fit into the Modbus registers. The raw value read
from the Modbus registers is multiplied by a scalar to convert the raw data. The
following table lists the data scalars and the respective values for the MD-BMS or MD-
BMED Power Meters:
Table 7: Data Scalars and Values for Registers 44001 through 44061.
Scalar Value
Data Scalar kW/kWh
Demand
kVAR/ kVARh kVA/kVAh Power Factor Amps Volts
0 .00001 .00001 .00001 .01 .01 .1
1 .001 .001 .001 .01 .1 .1
2 .01 .01 .01 .01 .1 .1
3 .1 .1 .1 .01 .1 .1
4 1 1 1 .01 1 1
5 10 10 10 .01 1 1
≥6 100 100 100 .01 1 1
The data scalar is stored in register 44602.
When selecting a data scalar, consider the following guidelines:
● If the data scalar selected is too low, an incorrect data result is returned from the
register.