XT2640 Operating Manual
13 July 2016
Page 176 of 187
28.4.1
WATTS,
VAR
AND
VA
MEASUREMENT
SPECIFICATIONS
28.4.1.1
PRIMARY
WATTS,
VAR
AND
VA
MEASUREMENT
ACCURACY
TABLE
Add relevant errors from the table below for the maximum error in all Watts, VA and VAR measurements except harmonic Watts.
Note that by definition DC Watts and DC VA are identical, and DC VAR is zero.
MAXIMUM
SCALING
ERRORS
Apply to all results as shown below as a percentage of the reading
If signal contains significant levels at multiple frequencies, apply to each level & frequency
Specification
Channel
Type
Option
H
Option
D
HI
Range
Option
D
LO
Range
Option
X
HI
Range
Option
X
LO
Range
Base
Scaling
Error
Apply to all results
A or L
0.045%
S or W
0.15% (0.3% if 2ms LF/PERIOD)
Frequency
Dependent
Scaling
Error
Apply to AC component of
all results other than DC or
MAINS
LF or VLF
S, A or L
0.01%
W
0.05%
AVIONICS
A or L
0.005%
S or W
None
<10kHz
S, A or L
F*0.006%
W
F*0.0025%
10k‐40kHz
S, A or L
0.06%+(F‐10)*0.014%
W
F*0.0025%
40k‐100kHz
S, A or L
0.48%+(F‐40)*0.032%
W
0.1%+(F‐40)*0.005%
0.1%+(F‐40)*0.0055%
100k‐1MHz
S, A or L
Typically (F/1100)
2
*150%
W
0.4%+(F‐100)*0.018%
0.43%+(F‐100)*0.02%
>1MHz
W
Typically (F/5000)
2
*150%
Typically (F/3000)
2
*150%
Self
‐
Heating
Scaling
Error
Apply as % of Power reading to all
results using voltage and current Self‐
Heating Errors from previous tables
All
Add Voltage and Current Self‐Heating Errors
Temperature
Scaling
Error
Apply to all results if outside of ±5C from
calibration temperature
All
0.005% per C outside of ±5C from calibration temperature
Bandwidth
Limit
Scaling
Error
Apply to AC component of all results if
using USER bandwidth setting
All
20%*(F/F
BW
)
2
, unspecified above 0.3*F
BW
MAXIMUM
FLOOR
ERRORS
Apply to all results as shown below in Watts, VA or VAR as applicable (generally only significant at low input levels)
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 results
L
(V
AC+DC
*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)
A
(V
AC+DC
*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)
S or W
(V
AC+DC
*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)
DC
Floor
Error
Apply to DC and AC+DC results using the
Voltage and Current DC Floor Errors
from previous tables
All
(V
DC
*Current DC Floor Error) + (A
DC
*Voltage DC Floor Error) + (Current DC Floor Error*Voltage DC Floor Error)
AC
Floor
Error
(VA
and
VAR
only)
Apply to AC and AC+DC VA & VAR results
using voltage and current AC Floor
Errors from previous tables
All
(V
AC
*Current AC Floor Error) + (A
AC
*Voltage AC Floor Error)
Common
Mode
Error
(VA
and
VAR
only)
Apply to AC component of VA and VAR
results using the Voltage and Current
Common Mode Errors from previous
tables.
All
(V
AC
*Current Common Mode Error) + (A
AC
*Voltage Common Mode Error)
Common
Mode
Error
(Watts
only)
Apply to AC component of Watts results
using the Voltage Common Mode Error
from previous table
All
(A
AC
*Voltage Common Mode Error)
Adjacent
Channel
Error
Apply to AC component of all results
using the Voltage and Current Adjacent
Channel Errors from previous tables
All
(V
AC
*Current Adjacent Channel Error) + (A
AC
*Voltage Adjacent Channel Error)
Phase
Floor
Error
(Watts
only)
Apply to AC and AC+DC Watts results
S, A or L
VA
FUND
*(PF
FUND
‐ cos(cos
‐1
(PF
FUND
) + 0.015°*F))
Alternately, as a worst case (at PF=0) this can expressed as F*0.028% of VA
W
VA
FUND
*(PF
FUND
‐ cos(cos
‐1
(PF
FUND
) + 0.007°*F))
Alternately, as a worst case (at PF=0) this can expressed as F*0.013% of VA
Phase
Floor
Error
(VAR
only)
Apply to all VAR results
S, A or L
VA
FUND
*(1 ‐ PF
FUND
‐ cos(cos
‐1
(1‐PF
FUND
) + 0.015°*F))
Alternately, as a worst case (at PF=1) this can expressed as F*0.028% of VA
W
VA
FUND
*(1 ‐ PF
FUND
‐ cos(cos
‐1
(1‐PF
FUND
) + 0.007°*F))
Alternately, as a worst case (at PF=1) this can expressed as F*0.013% of VA