XT2640 Operating Manual
13 July 2016
Page 168 of 187
28.2.2.1
PRIMARY
VOLTAGE
MEASUREMENT
ACCURACY
TABLE
Add relevant errors from the table below for the maximum error in primary voltage measurements (e.g. DC, AC, AC+DC, Rectified,
Peak, Valley, Peak‐Valley).
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
S
Channel
Type
A
Channel
Type
L
Channel
Type
W
Channel
Type
Base
Scaling
Error
Apply to all results
0.1%
0.03%
0.1%
(0.2% if 2ms LF/PERIOD)
Frequency
Dependent
Scaling
Error
Apply to all results other than DC or
MAINS
AVIONICS
None
0.005%
None
LF or VLF
0.01%
0.05%
<10kHz
F*0.005%
F*0.002%
10k‐40kHz
0.05%+(F‐10)*0.012%
40k‐100kHz
0.41%+(F‐40)*0.025%
0.08%+(F‐40)*0.004%
100k‐1MHz
Typically (F/1000)
2
*100%
0.32%+(F‐100)*0.013%
>1MHz
Not specified
Typically (F/3500)
2
*100%
Self
‐
Heating
Scaling
Error
Apply to all results (only significant at higher voltages)
1 minute nominal time constant
0.05%*(V
AC+DC
/1000)
2
0.5%*(V
AC+DC
/1000)
2
0.15%*(V
AC+DC
/1000)
2
Temperature
Scaling
Error
Apply to all results if outside of ±5C from calibration
temperature
0.005% per C outside of ±5C from calibration temperature
Bandwidth
Limit
Scaling
Error
Apply if using USER bandwidth setting
10%*(F/F
BW
)
2
, unspecified for F > 0.3*F
BW
MAXIMUM
FLOOR
ERRORS
Apply to all results as shown below in Volts (generally only significant at low input levels)
Specification
S
Channel
Type
A
Channel
Type
L
Channel
Type
W
Channel
Type
Base
Floor
Error
Apply to all results
1.8mV
450µV
45µV
1.8mV
DC
Floor
Error
Apply to DC and RECTIFIED results
Apply to AC+DC results after multiplying by V
DC
/V
AC+DC
3mV
1mV
100µV
5mV
AC
Floor
Error
Apply to AC, AC+DC, and
RECTIFIED results
MAINS, LF, VLF & F
BW
≤10kHz
100µV/V
RDG
100µV/V
RDG
4µV/V
RDG
200µV/V
RDG
AVIONICS & F
BW
≤50kHz
300µV/V
RDG
300µV/V
RDG
8µV/V
RDG
650µV/V
RDG
Otherwise
1.1mV/V
RDG
1.1mV/V
RDG
11µV/V
RDG
1.5mV/V
RDG
Peak
Floor
Error
Apply to PK, VLY and PK‐
VLY results
MAINS, LF, VLF & F
BW
≤10kHz
40mV
40mV
8mV
60mV
AVIONICS & F
BW
≤50kHz
75mV
75mV
11mV
125mV
Otherwise
125mV
125mV
17mV
175mV
Common
Mode
Error
Apply to AC, AC+DC, and RECTIFIED results
Apply using voltage on V LO terminal relative to chassis
ground. Error has 90° phase shift to common‐mode
voltage
1µV per V.Hz
(11.5mV@230V/50Hz)
100nV per V.Hz
(1.15mV@230V/50Hz)
700nV per V.Hz
(8.05mV@230V/50Hz)
Adjacent
Channel
Error
Apply to AC, AC+DC, and RECTIFIED results
Apply using adjacent channel A LO or V LO terminal
voltage relative to chassis ground. Error has 90° phase
shift to adjacent channel voltage
300nV per V.Hz
(3.45mV@230V/50Hz)
30nV per V.Hz
(345µV@230V/50Hz)
210nV per V.Hz
(2.415mV@230V/50Hz)
28.2.2.2
SECONDARY
VOLTAGE
MEASUREMENT
ACCURACY
TABLE
Specification
S
Channel
Type
A
Channel
Type
L
Channel
Type
W
Channel
Type
Crest
Factor
Error
(Total Floor Error from preceding table for PK results) / V
AC
Form
Factor
Error
(Total Floor Error from preceding table for AC+DC results) / V
RECTIFIED
Inter
‐
Channel
Error
For 120° between equal amplitudes
(Relevant Voltage Errors from preceding table at the inter‐channel voltage) + 0.0015%*F
Harmonic
or
Spectrum
Error
AC Voltage Errors from preceding table at V and F of the harmonic or spectrum point
+ (H/N)
2
*0.3% of reading
+ (if not fundamental) from below using the frequency of the harmonic or spectrum point
<10kHz
0.01% of V
AC+DC
0.006% of V
AC+DC
0.015% of V
AC+DC
10k‐115kHz
0.05% of V
AC+DC
0.03% of V
AC+DC
115k‐435kHz
Not Available
0.08% of V
AC+DC
Inter
‐
Channel
Fundamental
Phase
Error
0.02°+0.15°*F
0.01°+0.07°*F
Harmonic
‐
Fundamental
Phase
Error
(typical,
BANDWIDTH
configured
as
UNFILTERED)
0.02°+0.1°*F+0.001°*H
0.02°+0.03°*F+0.001°*H
%THD
Error
Errors shown are all expressed in
%THD units
(0.005+0.000025*N)*%THD+0.00005*N*√N
+ from below using the frequency of highest included harmonic
<10kHz
0.025+1.25/V
AC
0.015+1/V
AC
0.015+0.2/V
AC
0.03+1.5/V
AC
10k‐115kHz
0.15+3.5/V
AC
0.15+0.35/V
AC
0.06+4/V
AC
115k‐435kHz
Not Available
0.15+4/V
AC
28.2.2.3
EXAMPLES
Example
1
For an A type channel the maximum error of a measurement of the AC+DC voltage of a 230Vrms signal at 50Hz is a worst case of
±0.034% of reading as calculated by:
Scaling Errors:
Base Scaling = ±0.03%
Frequency Dependent Scaling = None at MAINS
Self‐heating Scaling = ±0.05%*(230V/1000)
2
= ±0.002645%
Temperature Scaling = none within 5C of the calibration temperature
Bandwidth Limit Scaling = none when using AUTO‐TRACK