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Edge
Tech
Model 2000 Series DewPrime
Dew Point Hygrometers
Introduction
1.1 GENERAL
he
EdgeTech
Model 2000 Series
DewPrime
Dew Point Hygrometer (Figure 1-1) is a
micro-
processor based, programmable dew point
instrument
with many built-in features. It has a
measurement range
of -50
to+100°C.
Two sensor types are available for
a
depression of either 45 or
60°C.
The DewPrime Series is presented in two major
con-
figurations.
The
first
,
the Model
2001,
is a dew
point
only measurement instrument. The second, the
Model
2002, is a dew point, relative humidity, and
ambient
temperature measurement
instrument.
This instrument has been designed to include the
most
desirable
I/0
options in the standard
configuration
.
By
"
buildin
g
in" these options, the cost is reduced
signifi-
cantly when compared to "added in"
options.
Using a primary measurement technique,
including
provisions for self-checking and automatic
balancing
,
the Model 2000 Series verifies its own performance on
a
timed sequential basis, and is ideally suited for
process
control and
continuous unattended
operation.
Devel·
oped primarily for industrial process use, the
Model
2000 Series is also useful for
laboratory,
scientific,
and
research
applications,
and can be equipped with a
mirror
microscope when used as a
calibration standar
d
.
It
is
designed to meet reliability
requirements
of
high
temperature, high dew point process drying and
curing,
and the Model 2000 Series is finding broad
applications
in areas where energy
conservation
is a major
consider-
ation.
1.2
DESCRIPTION
The Model 2000 Series consists of a Control Unit
and
either a single or dual stage dew point Sensor and
a
built-in cooling jacket (S2 Sensor only). The
Model
2000 Series is equipped with a timed,
electronic,
automatic
selfs·tandardization
circuit
;
a Track or
Hold
output
;
mode indicators; and an Alarm
Set.A platinum
resistance
thermometer
(PRT)
continuously measures
the mirror
temperature,
directly
displayed
in °C or °F
on
the front of the 4-digit Digital Panel Meter, with a
resolution of 0.1°C. Standard outputs of 0 to 5 VDC
and
4·20 ma are available directly on the rear panel
connec-
tor (Figure
1-2).
The Model 2000·S2 is also equipped with
(I)
a
mirror
overtemperature protection circuit, which shuts down
the
thermoelectric cooler at a mirror temperature
over
100°C; and (2) an additional
overtemperature circuit,
which also shuts down the cooler if base
temperatures
exceed
100°C.
The Sensor
incorporates
an inert Rhodium
(nickel
electroplate-based
surface) mirror that has a hard, bright
surface to provide superior abrasion
resistance
,
and
an
inherent
antiwetting
characteristic
to enhance dew
and
frost formation. The Rhodium mirror was developed as
a
result of on-going material evaluation studies
coupled
with applied research in the physics of dew and
frost
formation on a mirrored
surface.
Extensive field tests
in
harsh industrial applications show that the
Rhodium
mirror provides significant advantages over
conventional
mirrors, especially gold-surfaced
mirrors.
The S2 Sensor has a depression capability of
60°C
(108°F) at an ambient temperature of 25°C and the
S
1
Sensor has a
depression
of 45°C
(81
°F)
.
Depression
decreases approximately 1o for every 3° drop in
ambient
temperature and increases approximately 1° for every
3
°
rise in ambient temperature from 25°C.
Depression
capability is sufficient at any temperature to permit
dew
point
measurement corresponding
to less than 1%
RH.
The S2 Sensor
has
a built-in cooling jacket that
should
be used when the dew point to be measured exceeds
the
cooling depression of the Sensor
itself.When
the
jacket
is used, Sensor cooling is based on the temperature
of
the coolant, which can be water, ethylene glycol,
etc.
Response is 1.7°C
(3°F)/second
at dew points above 0°C
(32°F).Below
0°C, less water is available for
condensa-
tion, and the response is governed by both the frost
point
and the sample flow
rate
.
The Sensor is usually mounted on the
instrument's rear
panel; however, it can be mounted remotely up to
75
meters (250 feet) from the instrument by using
the
optional Remote
Mounting
Cable
Kit.
The Model 2000 Series is equipped with
convenience
features such as: (1) a Sensor spin-off cover that
permits
1-1
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