Fluke Hart Scientific 1575 Super-Thermometer, Руководство пользователя

Страница: 15 / 156

2 Introduction
2.1 General Description
The 1575 “Super-Thermometer” and 1590 “Super-Thermometer II” are two of
the most accurate resistance and temperature readout instruments available. The
1575 can deliver resistance measurements with up to 4 ppm accuracy while the
1590 can achieve 1 ppm accuracy. In terms of temperature, 1 ppm is equivalent
to 0.00025°C with an SPRT at 0°C. When using the 1590 with a stan-
dards-quality thermistor it’s possible to achieve measurements as accurate as
0.000125°C.
In addition to accuracy, the 1575 or 1590 has a variety of features and functions
that make it an indispensable tool in a precision temperature calibration labora-
tory. With a wide input range of 0 to 500k
Ω
it can be used with just about any
type of resistance sensor including RTDs, PRTs, SPRTs, HTPRTs, and thermis-
tors. The driving current is programmable to best suit the sensor. Resistance to
temperature calculations are performed automatically using any of a variety of
algorithms including the International Temperature Scale of 1990 (ITS-90),
IPTS-68, Callendar-Van Dusen, Steinhart-Hart and polynomial equations. The
1575/1590 can even calculate ITS-90 coefficients and generate a report based
on resistance and temperature measurements.
The 1575/1590 features an LCD graphics display that shows in a clear and
easy-to-read manner a variety of information such as present and past measure-
ments, statistical results, and instrument settings. Measurements can be viewed
in numeric and graphic plot form. The display is easily configured by the user
for various applications. Contrast, brightness, and colors (1590 only) can be ad-
justed. Even the tilt of the display on the 1590 can be set as desired. Operation
of the 1575/1590 is made simple and convenient with the use of soft-keys.
These are buttons having associated labels on the display. The functions of the
soft-keys can change between various contexts.
The 1575/1590 features exclusive gold-plated patented DWF connectors (U.S.
Patent No. 5,965,625) that are specially designed for this product. Operated
with a quick, easy push, the patented DWF connector accepts bare wires, spade
terminals, and banana plugs.
The 1575/1590 is able to communicate with computer systems through a vari-
ety of interfaces. RS-232, IEEE-488, and parallel printer interfaces are all built
in. The convenient 31/2" disk drive allows temporary or permanent storage of
measurement data, probe coefficients, and instrument settings.
2.2 Theory of Operation
The 1575 “Super-Thermometer” and 1590 “Super-Thermometer II” require a
unique electronic design to achieve the necessary accuracy while meeting size,
weight, cost, and speed constraints. This section explains the measurement
5
2 Introduction
General Description