B
Electronic Calibration of the 3458A (Product Note 3458A-3)
120
Keysight 3458A Calibration Manual
and offset correction for each function and range.
These correction constants were then stored in
non-volatile memory and used to correct the
errors of the internal circuitry. Calibration was
improved because covers were removed during
calibration and the multimeter's internal circuits
required no adjustable components.
The 3458A goes beyond these techniques by
conveniently correcting errors due to time or
environmental variations. Adjustments primarily
consist of offset and gain constants, although all
other errors are considered. A patent pending
technique prevents the loss of calibration
constants in non- volatile memory.
The analog-to-digital converter's linearity and
transfer accuracy are fundamentally important to
the calibration technique used in the 3458A
multimeter. The linearity of the analog-to-digital
converter gives the instrument the ability to
measure the ratio of two DC voltages at state-of-
the-art accuracies. In other words, this converter
maintains its accuracy over the entire
measurement range, without any internal
adjustments. The speed of the analog-to-digital
converter allows an internal DC to AC transfer of
accuracy, again state-of-the-art.
The analog-to-digital converter achieves this
performance using a patented technique known
as “multislope integration.” This technique uses
charge balancing, where the charge from the
input signal is canceled by charge injected from
reference signals. Multi-slope integration also
allows the integration aperture to be changed so
that measurement resolution can be traded for
measurement speed.
Measurements using a Josephson junction
standard confirm linearity of the
analog-to-digital converter design. These
measurements reveal integral linearity below 0.1
parts per million and differential linearity of 0.02
parts per million. This performance, incidentally,
is comparable to a Kelvin-Varley divider.
The only errors not removed in the 3458A
multimeter calibration are drifts of the internal
voltage reference and the internal resistance
standard. The internal reference voltage has an
average drift during its first 90 days of less than 2
parts per million. As shown in Figure 1, the three
sigma points are less than 4 parts per million. For
DC volt transfer measurements, the 3458A
multimeter's short-term stability is within 0.1
parts per million of reading.
The internal reference resistor has a specified
drift of 5 parts per million per year and a
temperature coefficient of 1 part per million per
Celsius degree.
Auto-calibration adjusts for time and
temperature drifts in the rest of the circuitry,
relative to these internal references.
Figure 1.
This plot shows stability with time of the reference voltage
standard used in the 3458A multimeter.
Содержание 3458A
Страница 1: ...Keysight 3458A Multimeter Calibration Manual ...
Страница 10: ...10 Keysight 3458A Calibration Manual THIS PAGE HAS BEEN INTENTIONALLY LEFT BLANK ...
Страница 14: ...14 Keysight 3458A Calibration Manual THIS PAGE HAS BEEN INTENTIONALLY LEFT BLANK ...
Страница 16: ...16 Keysight 3458A Calibration Manual THIS PAGE HAS BEEN INTENTIONALLY LEFT BLANK ...
Страница 18: ...18 Keysight 3458A Calibration Manual THIS PAGE HAS BEEN INTENTIONALLY LEFT BLANK ...
Страница 39: ...Adjustment Procedures 3 Keysight 3458A Calibration Manual 39 Figure 3 1 4 terminal short ...
Страница 52: ...3 Adjustment Procedures 52 Keysight 3458A Calibration Manual THIS PAGE HAS BEEN INTENTIONALLY LEFT BLANK ...
Страница 59: ...Performance Verification Tests 4 Keysight 3458A Calibration Manual 59 Figure 4 1 General test procedure ...
Страница 109: ...Command Summary 5 Keysight 3458A Calibration Manual 109 Related commands ACAL CAL SECURE ...
Страница 116: ...A Specifications 116 Keysight 3458A Calibration Manual THIS PAGE HAS BEEN INTENTIONALLY LEFT BLANK ...