78M6610+LMU Data Sheet
Voltage Channel Measurements
Instantaneous and quadrature voltage measurements are updated every sample while RMS Voltage and
Peak Voltage are updated every accumulation interval (n samples). An AC voltage frequency
measurement is also updated every low-rate interval.
Register
Description
Time Scale
VA
VB
VC
Instantaneous Voltage @ time t
1 sample
VQA
VQB
Quadrature Voltage @ time t - 90°
AC Voltage Frequency
FREQ
VA_PEAK
VB_PEAK
Peak Voltage in last interval
1 interval
VA_RMS
VB_RMS
VC_RMS
RMS Voltage of last interval
Quadrature Voltage
The quadrature voltage is instantaneous voltage that is phase shifted (delayed) 90° from the respective
input voltage.
Voltage Frequency
This output is a measurement of the fundamental frequency of the referenced AC voltage source with a
range from 0Hz to 128Hz - LSB. This is a single reading per device.
Peak Voltage
This output is a capture of the largest magnitude instantaneous voltage source sample during the
previous accumulation interval.
Instantaneous
Voltage (Vx)
ABS
MAX
maximum
Vx_PEAK
Figure 17. Peak Voltage Computation
RMS Voltage
The 78M6610+LMU reports true RMS measurements for each input. An RMS value is obtained by
performing the sum of the squares of instantaneous values over a time interval (accumulation interval)
and then performing a square root of the result after dividing by the number of samples in the interval.
Instantaneous
Voltage (Vx)
N-1
Vx2_SUM
Vx2
X
∑
N
Vx_RMS
n=0
Figure 18. RMS Voltage Computation
28
Rev 0
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
