Maxim Integrated 6613_OMU_2+2S_URT_V100 - Manual (Page 6)

6613_OMU_2+2S_URT_V1_00 Firmware Description Document UG_6613_060
6 Rev. 1.1
2 Measurement Description
2.1 Basic Measurement Equations
The Teridian 78M6613 with firmware 6613_OMU_2+2S_URT_v100 provides the user with measurement
data referred to as “Wideband” (WB). Wideband measurements are generally of interest when measuring
non-sinusoidal current/voltage, a typical condition in switched mode power supplies or similar systems.
Table 1: Measurement Equations Definitions
Symbol Parameter Wideband Equation
V RMS Voltage V =
√∑ v
(t)
2
I RMS Current I =
√∑ i
(t)
2
P Active Power P =
∑ (i
(t) *
v
(t))
Q Reactive Power Q =
√(S 2
– P
2
)
S Apparent Power S = V * I
PF Power Factor P/S
PA Phase Angle ACOS (P/S)
The measurement outputs are continuously available to the user. To obtain measurement outputs, the
serial UART interface between the 78M6613 and the host processor must be set up and is described in
Section 3 .
2.2 Sample Rate and Accumulation Interval
This firmware utilizes an effective sampling rate of 3641 samples per second for each input.
The values described in section 2.1 are calculated over a period commonly referred as accumulation
interval. The registers containing the measurements are updated at the completion of every accumulation
time. The accumulation interval for this firmware is fixed at roughly 496 milliseconds.
3 Serial Communication
The serial communication with the 78M6613 takes place over a UART (RS232) interface. The default
settings for the UART of the 78M6613, as implemented in this firmware, are given below:
Baud Rate: 38400bps
Data Bits: 8
Parity: None
Stop Bits: 1
Flow Control: Xon/Xoff
The firmware allows communication through UART0 also known as CLI (Command Line Interface) mode.