3458A Datasheet, PDF (9/27 Pages) Keysight Technologies – Shattering performance barriers of speed and accuracy

3458A Technical Specifications
Section 1:
Section 2:
Section 3:
Section 4:
Section 5:
Section 6:
DC Voltage 10
Resistance 11
DC Current 13
AC Voltage 14
AC Current 19
Frequency/Period 20
Section 7: Digitizing 21
Section 8: System Specifications 23
Section 9: Ratio 24
Section 10: Math Functions 24
Section 11: General Specifications 25
Section 12: Ordering Information 26
Introduction
The Keysight 3458A accuracy is specified as a part
per million (ppm) of the reading plus a ppm of range
for DCV, Ohms, and DCl. In ACV and ACl, the speci-
fication is percent of reading plus percent of range.
Range means the name of the scale, e.g. 1 V, 10 V,
etc.; range does not mean the full scale reading,
e.g. 1.2 V, 12 V, etc. These accuracies are valid for a
specific time from the last calibration.
Absolute versus Relative Accuracy
AII 3458A accuracy specifications are relative to
the calibration standards. Absolute accuracy of
the 3458A is determined by adding these relative
accuracies to the traceability of your calibration
standard. For DCV, 2 ppm is the traceability error
from the factory. That means that the absolute error
relative to the U.S. National Institute of Standards
and Technology (NIST) is 2 ppm in addition to the
DCV accuracy specifications. When you recalibrate
the 3458A, your actual traceability error will depend
upon the errors from your calibration standards.
These errors will likely be different from the error of
2 ppm.
EXAMPLE 1:
Relative Accuracy; 24 hour operating
temperature is Tcal ±1 °C
Assume that the ambient temperature for the
measurement is within ± 1 °C of the temperature of
calibration (Tcal). The 24 hour accuracy specification
for a 10 V DC measurement on the 10 V range is
0.5 ppm + 0.05 ppm. That accuracy specification
means:
The following examples illustrate the error correc-
tion of auto-calibration by computing the relative
measurement error of the 3458A for various
temperature conditions. Constant conditions for
each example are:
10 V DC input
10 V DC range
Tcal = 23 °C
90 day accuracy specifications
EXAMPLE 2:
Operating temperature is 28 °C; with ACAL
This example shows basic accuracy of the 3458A
using auto-calibration with an operating tempera-
ture of 28 °C. Results are rounded to 2 digits.
(4.1 ppm x 10 V) + (0.05 ppm x 10 V) = 42 µV
Total relative error = 42 µV
EXAMPLE 3:
Operating temperature is 38 °C; without ACAL
The operating temperature of the 3458A is 38 °C,
14 °C beyond the range of Tcal ±1 °C. Additional
measurement errors result because of the added
temperature coefficient without using ACAL.
(4.1 ppm x 10 V) + (0.05 ppm x 10 V) = 42 µV
Temperature Coefficient (specification is per °C):
(0.5 ppm x 10 V + 0.01 ppm x 10 V) x 14 °C = 71 µV
Total error = 113 µV
EXAMPLE 5:
Absolute Accuracy; 90 Day
Assuming the same conditions as Example 4, but
now add the traceability error to establish absolute
accuracy.
(4.1 ppm x 10 V) + (0.05 ppm x 10 V) = 42 µV
Temperature Coefficient (specification is per °C):
(0.15 ppm x 10 V + 0.01 ppm x 10 V) x 10 °C = 16 µV
factory traceability error of 2 ppm:
(2 ppm x 10 V) = 20 µV
Total absolute error = 78 µV
Additional errors
When the 3458A is operated at power line cycles
below 100, additional errors due to noise and gain
become significant. Example 6 illustrates the error
correction at 0.1 PLC.
EXAMPLE 6:
Operating temperature is 28°C; 0.1 PLC
Assuming the same conditions as Example 2, but
now add additional error.
(4.1 ppm x 10 V) + (0.05 ppm x 10 V) = 42 µV
Referring to the Additional Errors chart and RMS
Noise Multiplier table, additional error at 0.1 PLC is:
(2 ppm x 10 V) + (0.4 ppm x 1 x 3 x 10 V) = 32 µV
Total relative error = 74 µV
0.5 ppm of Reading + 0.05 ppm of Range
For relative accuracy, the error associated with the
measurement is:
(0.5/1,000,000 x 10 V) + (0.05/1,000,000 x 10 V) =
± 5.5 µV or 0.55 ppm of 10 V
Errors from temperature changes
The optimum technical specifications of the 3458A
are based on auto-calibration (ACAL) of the instru-
ment within the previous 24 hours and following
ambient temperature changes of less than ±1 °C.
The 3458A’s ACAL capability corrects for measure-
ment errors resulting from the drift of critical
components from time and temperature.
EXAMPLE 4:
Operating temperature is 38°C; with ACAL
Assuming the same conditions as Example 3, but
using ACAL significantly reduces the error due to
temperature difference from calibration tempera-
ture. Operating temperature is 10 °C beyond the
standard range of Tcal ±5 °C.
(4.1 ppm x 10 V) + (0.05 ppm x 10 V) = 42 µV
Temperature Coefficient (specification is per °C):
(0.15 ppm x 10 V + 0.01 ppm x 10 V) x 10 °C = 16 µV
Total error = 58 µV
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