XT2640 Operating Manual
13 July 2016
Page 178 of 187
28.5
POWER
FACTOR
MEASUREMENT
SPECIFICATIONS
28.5.1
PF
MEASUREMENT
ACCURACY
TABLE
Add relevant errors from the table below for the maximum error in PF measurements. For PF
FUND
apply only the Base Floor and
Phase Errors.
Note:
DC PF is 1.0 by definition and has no error; the table below applies to AC, AC+DC and FUND PF results.
Specification
Channel
Type
Option
H
Option
D
HI
Range
Option
D
LO
Range
Option
X
HI
Range
Option
X
LO
Range
Base
Floor
Error
Apply to all PF results
L
(56µA/A
AC+DC
) +
(45µV/V
AC+DC
)
(38µA/A
AC+DC
) +
(45µV/V
AC+DC
)
(250nA/A
AC+DC
) +
(45µV/V
AC+DC
)
(6µA/A
AC+DC
) +
(45µV/V
AC+DC
)
(0.15µA/A
AC+DC
) +
(45µV/V
AC+DC
)
A
(56µA/A
AC+DC
) +
(450µV/V
AC+DC
)
(38µA/A
AC+DC
) +
(450µV/V
AC+DC
)
(250nA/A
AC+DC
) +
(450µV/V
AC+DC
)
(6µA/A
AC+DC
) +
(450µV/V
AC+DC
)
(0.15µA/A
AC+DC
) +
(450µV/V
AC+DC
)
S or W
(225µA/A
AC+DC
) +
(1.8mV/V
AC+DC
)
(150µA/A
AC+DC
) +
(1.8mV/V
AC+DC
)
(1µA/A
AC+DC
) +
(1.8mV/V
AC+DC
)
(23µA/A
AC+DC
) +
(1.8mV/V
AC+DC
)
(0.6µA/A
AC+DC
) +
(1.8mV/V
AC+DC
)
AC
Floor
Error
Apply to all PF results using voltage and
current AC Floor Error from previous
tables, this error always causes a
reduced PF reading
All
‐PF
RDG
*((Current AC Floor Error/A
RDG
) + (Voltage AC Floor Error/V
RDG
))
DC
Floor
Error
Apply to AC+DC PF result after
multiplying by (1‐PF)
L
(0.23mA/A
AC+DC
) +
(0.1mV/V
AC+DC
)
(0.15mA/A
AC+DC
) +
(0.1mV/V
AC+DC
)
(1µA/A
AC+DC
) +
(0.1mV/V
AC+DC
)
(40µA/A
AC+DC
) +
(0.1mV/V
AC+DC
)
(5µA/A
AC+DC
) +
(0.1mV/V
AC+DC
)
A
(0.23mA/A
AC+DC
) +
(1mV/V
AC+DC
)
(0.15mA/A
AC+DC
) +
(1mV/V
AC+DC
)
(1µA/A
AC+DC
) +
(1mV/V
AC+DC
)
(40µA/A
AC+DC
) +
(1mV/V
AC+DC
)
(5µA/A
AC+DC
) +
(1mV/V
AC+DC
)
S
(0.45mA/A
AC+DC
) +
(3mV/V
AC+DC
)
(0.3mA/A
AC+DC
) +
(3mV/V
AC+DC
)
(2µA/A
AC+DC
) +
(3mV/V
AC+DC
)
(80µA/A
AC+DC
) +
(3mV/V
AC+DC
)
(6µA/A
AC+DC
) +
(3mV/V
AC+DC
)
W
(0.68mA/A
AC+DC
) +
(5mV/V
AC+DC
)
(0.45mA/A
AC+DC
) +
(5mV/V
AC+DC
)
(3µA/A
AC+DC
) +
(5mV/V
AC+DC
)
(120µA/A
AC+DC
) +
(5mV/V
AC+DC
)
(8µA/A
AC+DC
) +
(5mV/V
AC+DC
)
Phase
Error
Apply to all PF results
S, A or L
(PF
FUND
‐ cos(cos
‐1
(PF
FUND
) ± 0.015°*F))
Alternately, as a worst case (at PF=0) this can expressed as F*0.00028
W
(PF
FUND
‐ cos(cos
‐1
(PF
FUND
) ± 0.007°*F))
Alternately, as a worst case (at PF=0) this can expressed as F*0.00013
28.5.1.1
EXAMPLES
Example
1
For an AD channel (HI range) the maximum error of a measurement of the AC+DC PF of a 240V, 5Arms, PF=0.5 (caused by phase
shift) signal at 50Hz is a worst case of ±0.000029 as calculated by:
Floor Errors:
Base Floor = (38µA/5A) + (450µV/240V) = ±0.000009475
AC Floor = ‐0.5*(((1.5µA/5A)/5A) + ((100µV/240V)/240V)) = ‐0.5*(0.00.0000000017) = ‐0.00000003
DC Floor = (1‐0.5)*((0.15mA/5A) + (1mV/240V)) = ±0.00001708
Total Floor Errors = ±0.000018
Phase Errors:
(0.5 ‐ cos(cos
‐1
(0.5) + 0.015°*0.05)) = (0.5 ‐ cos(60° + 0.015°*0.05)) = ±0.000011
Total Phase Errors = ±0.000011
Example
2
As Example 1 but where the PF=0.5 is caused by load distortion instead of phase shift, the maximum error of the measurement of the
AC+DC PF is a worst case of ±0.000018 as calculated by:
Floor Errors:
Base Floor = (38µA/5A) + (450µV/240V) = ±0.000009475
AC Floor = ‐0.5*(((1.5µA/5A)/5A) + ((100µV/240V)/240V)) = ‐0.5*(0.00.0000000017) = ‐0.00000003
DC Floor = (1‐0.5)*((0.15mA/5A) + (1mV/240V)) = ±0.00001708
Total Floor Errors = ±0.000018
Phase Errors:
PF
FUND
= 1.0 since load has no phase shift only distortion.
(1 ‐ cos(cos
‐1
(1) + 0.015°*0.05)) = (1 ‐ cos(0° + 0.015°*0.05)) = 0
Total Phase Errors = 0
Example
3
For a WD channel (HI range) the maximum error of a measurement of the AC PF of a 100V, 5Arms, PF=0.01 (caused by phase shift)
signal at 50kHz is a worst case of ±0.0062 as calculated by:
Floor Errors:
Base Floor = (150µA/5A) + (1.8mV/100V) = ±0.000048
AC Floor = ‐0.01*(((250µA/5A)/5A) + ((1.1mV/100V)/100V)) = ‐0.01*(0.00001+0.0000011) = ‐0.0000001
Total Floor Errors = ±0.0000481
Phase Errors:
(0.01 ‐ cos(cos
‐1
(0.01) + 0.007°*50)) = (0.01 ‐ cos(89.427° + 0.007°*50)) = 0.006152
