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Company Background and Products
Clarke-Hess Communications Research Corp., founded in 1969 by Dr. Kenneth K. Clarke and
Dr. Donald T. Hess, is an electronics test and measurement company specializing in dc/low
frequency applications. The company's customers include the worlds national standards
laboratories, military agencies and commercial and industrial firms. Dedicated to
precision instrumentation, Clarke-Hess has earned a reputation for quality, service and
outstanding performance.
VOLT-AMPERE-WATTMETERS
The family of Volt-Ampere-Wattmeters covers the frequency range from dc to over 1000kHz.
These instruments have wide voltage and current ranges and are able to make precise
measurements under difficult signal conditions. Typically, most wattmeters (sometimes
called "power analyzers") have very poor performance at high frequencies and /or
low power factors. The family of Clarke-Hess wattmeters overcomes these problems.
Customers of the Clarke-Hess Wattmeters include NIST, I.B.M., General Electric,
Philips, Underwriter's Laboratories, the Canadian Standards Association, Branson
Ultrasonics and General Motors as well as most of the computer, aircraft, telephone, power
supply, electric locomotive, transformer, ferrite, fluorescent lamp and lamp ballast,
ultrasonics, and motor control companies throughout the world. They include any company
that needs to measure the loss in iron core or ferrite components, the loss in electronic
lamp ballasts, the loss in capacitors, or the power in any sort of distorted, low power
factor, or broadband wave-shape. They are also used in modern university teaching
laboratories.
PHASE STANDARDS AND CALIBRATORS
The Model 5500-2 Digital Phase Angle Standard is now generally
accepted as the world standard for phase generation. The instrument offers two digitally
controllable sine waves with a relative phase adjustable in 0.001 degree steps over
+/-999.999 degrees. The frequency range covered is from 1Hz to 200kHz with each channel
having an adjustable amplitude from 50mV to 120.0V. Typical distortion is below -84dB over
much of the range from 1Hz up to at least 10kHz. An optically isolated IEEE-488.2
interface is included as an integral part of each Phase Standard.
The phase accuracy of the Phase Standards is traceable not only to intrinsic standards
but also to NIST in Washington and to NPL in England. In addition to these two
laboratories, Clarke-Hess Phase Standards are in use by most of the national laboratories
throughout the world.
In the U.S., other agency and commercial users of Clarke-Hess Phase Standards include
T.V.A., N.A.S.A., Boeing, Northrop-Grumman, Rockwell, Honeywell, Dranetz/BMI, Fluke,
Krohn-Hite, Litton, TRW, LTV, Plessy, Philips, GTE Duke Power, Southern California Edison,
Consolidated Edison, GEC/Marconi, Scientific Atlanta, Delta Airlines, General Electric and
many other companies and testing laboratories.
PHASE METERS, PHASE ANGLE VOLTMETER (PAV) AND GAIN/PHASE ANALYZER
Since one of the uses of Phase Standards is to check Phase Meters and PAV’s, a
natural outgrowth of the production of the Phase Standard was the introduction of the Model 6000 Phase Meter and Model
2500 Gain/Phase Angle Voltmeter (GPAV). The Model 6000 measures the phase
difference between two input signals from 5 Hz to 500 kHz with a resolution of
0.01degrees. The Model 2500, in addition to measuring phase, also measures the in-phase,
quadrature, fundamental and total components of an input signal. The unit also can provide
"Bode" plots, measure AC ratios, impedance and power.
In head-to-head comparisons, the Model 6000 and Model 2500 have always proven to be far
superior to the "similar" units manufactured by the competitors of Clarke-Hess
This instrument has many users including G.E.C., Fluke, Northrop, Rockwell, Honeywell,
Hughes Aircraft, Nippon Electric, many electric utilities, NIST and NPL.
The Model 2505 Gain Phase Analyzer
is particularly suited to situations where signals are not referenced to ground or are
buried in noise and distortion, like the characterization of closed loop feedback systems
in power supplies or plotting filter responses. Often doing the job of several
instruments, the Model 2505 offers a wide range of measurements associated with frequency
response/transfer function analysis and wideband power measurements.
Typical users of the Model 2505 include power supply, filter and magnetic component
manufacturers.
VOLTAGE AND CURRENT SOURCES AND/OR CALIBRATORS
The Model 828 Voltage and Current Calibrator provides
voltages from 1mV to 1100V and currents from 1A to 5.00A at dc and at frequencies of 50Hz,
60Hz, and 400Hz.
Accuracy in the 0.1% to 0.2% range makes the Model 828 suitable as a portable source
for checking the calibration of analog meters as well as a source for calibrating 3 1/2
digit digital meters and as a general purpose voltage and current source. As such, it
fills a niche between the more sophisticated, and much more expensive, calibrators
produced by companies such as Hewlett-Packard, Fluke, and Wavetek and the low level
calibrators produced by several other companies.
The Model 828 is used by electric utilities, calibration laboratories, relay
manufacturers, military services, service organizations, and all sorts of industrial users
throughout the world.
The new Model 8080 Multifunction
Calibrator is an ideal and easy to use instrument featuring a variety of calibration
capabilities. The instrument functions as a Voltage, Current, Power, Resistance,
Capacitance and Thermocouple Calibrator. Having very low uncertainties, it is ideal
as a standard of these electric quantities in calibration laboratories. It also has the
feature of supplying several different waveshapes in additional to the traditional
sinusoidal output. This feature makes it ideal for testing meters which are true
rms reading or crest factor sensitive. These signals are also suitable for the basic
calibration of oscilloscopes. The calibrator has the capability of measuring temperature
with TC and RTD temperature sensors. A built-in multimeter can be used independently or in
simultaneous operation with the calibrator output.
TRANSCONDUCTANCE AMPLIFIER
The most recent product developed by Clarke-Hess is the precision, 100Ampere, 100kHz
Transconductance Amplifier, Model 8100. This unit is closely based
on the NIST design.
The Model 8100 generates output currents which are directly proportional to its input
voltage over the frequency range from dc to 100kHz. The Model 8100 is highly stable for
inductive as well as capacitive loads. The units accuracy, uncertainty and quick
warm up exceed, by a wide margin, any other commercially available transconductance
amplifier.
The high output compliance voltage of 7V rms for all ranges allows the series
connection of devices, for comparison purposes, even with 100A at 100kHz. The Model
8100 is protected by both over-current and over-compliance circuits as well as by thermal
cut-outs in the high current power supplies.
Typical customers include the U.S Air Force the NIST, the National Laboratory of
Australia, Taiwan Power, Sandia National Labs, LCIE (French national lab) Boeing and PTB
(the National Laboratory of Germany).
Clarke-Hess exhibits its products at the Measurement Science Conference (MSC), the
National Conference of Standards Laboratories (NCSL), and the Conference of Precision
Electromagnetic Measurements (CPEM). It presents technical papers at national,
international, and specialized conferences and publishes technical papers in the leading
technical journals. These papers are generally considered to be excellent application
notes for our instruments. A list of these publications may be obtained by sending us an
e-mail requesting them.
In early 1999, Kenneth K. Clarke officially retired. His role as President and
Marketing Manager was filled by Kenneth Salz, who was previously the President of North
Atlantic Instruments. Donald T. Hess is still working actively as Vice President and Chief
Design Engineer. |
