Fluke 5790A, Руководство оператора

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Introduction and Specifications
Introduction
1
1-3
1-1. Introduction
The 5790A AC Measurement Standard is a systems instrument that measures ac voltage
with the uncertainty of a thermal transfer standard. You control the 5790A's operation
from the front panel or remotely over the serial or IEEE-488 interface.
You can operate the 5790A in measurement mode or transfer mode. In measurement
mode, the 5790A operates as a digital ac voltmeter with up to 8 digits of resolution.
Measurement mode uses an internal dc reference. In transfer mode, you apply an external
dc or ac reference source. The 5790A automatically performs switching and calculations,
and displays the resulting ac-dc or ac-ac difference on the vacuum fluorescent Control
Display.
The 5790A covers a voltage range of 700
μ V to 1000 V (70 mV minimum in transfer
mode), and a frequency range of 10 Hz to 1 MHz. A wideband voltage option extends
frequency range to 30 MHz. The 5790A is also compatible with Fluke A40 current
shunts, which permit you to make ac-dc or ac-ac current transfer measurements up to
20 A. Refer to the Specifications for details.
A variety of input connections allows you to use the one that best suits your application.
There are four sets of input terminals on the 5790A, two 50
Ω
Type "N" connectors and
two sets of five-way binding posts. One 50
Ω
Type "N" and one set of binding posts is
dedicated to the ac measurement and transfer modes. AC or DC voltages can be applied
to either input connection, allowing you to perform automated ac-dc transfer
measurements. The second Type "N" input connection supports the optional wideband
mode, and the SHUNT binding posts are for Fluke A40 Series current shunts.
1-2. Inside the 5790A
Two patented internal standards contribute the most to the 5790A's ability to measure rms
ac voltage with such low uncertainty. These two standards are a stable and precisely
variable dc source similar to the one in the Fluke 5700A Calibrator and a high-
performance thermal rms sensor similar to the one in the Fluke 792A AC/DC Transfer
Standard.
Reference amplifiers establish the accuracy and stability of the internal dc source. A
patented 26-bit digital-to-analog converter (dac) provides the 5790A with the ability to
precisely vary its internal dc source. This is a pulse-width modulated dac with linearity
typically better than 0.2 ppm of full scale.
On the ac side, the Fluke rms sensor is similar in principle to a thermal voltage converter
(thermocouple), but has faster settling time, low dc reversal error, higher signal-to-noise
ratio, and excellent frequency performance.
1-3. Measurement and Transfer Modes
With the 5790A you can measure an ac or dc voltage just as you would with a voltmeter
(measurement mode), or you can connect an external dc standard for comparison to an
applied ac voltage as you would do with an ac-dc transfer standard (transfer mode).
When in measurement mode, among many other things the 5790A automatically does the
following:
1.
Compares the heating effect of the incoming signal to that of the 5790A internal dc
source, through the Fluke rms sensor. This results in direct detection of true rms
value.
2. Adjusts its internal dc source for a null at the output of the rms sensor, in the process
eliminating many sources of error.