Description And Specifications; Features And Applications - Emerson Rosemount Analytical HART 5081-A-HT Instruction Manual

MODEL 5081-A
• MEASURES dissolved oxygen (ppm and ppb level), free chlo-
rine, total chlorine, and ozone.
• SECOND INPUT FOR pH SENSOR ALLOWS AUTOMATIC pH
CORRECTION for free chlorine measurement. No expensive
reagents needed.
• AUTOMATIC BUFFER RECOGNITION for pH calibration.
• ROBUST TYPE 4X ENCLOSURE protects the transmitter from
hostile environments.
• COMPATIBLE WITH HART
(Asset Management Solutions).

1.1 FEATURES AND APPLICATIONS

The 5081-A Transmitter with the appropriate sensor
measures dissolved oxygen (ppm and ppb level), free
chlorine, total chlorine, and ozone in a variety of
process liquids and percent oxygen in gas. The trans-
mitter is compatible with Rosemount Analytical 499A
amperometric sensors for oxygen, chlorine, and
ozone; and with Hx438 and Gx448 steam-sterilizable
oxygen sensors.
For free chlorine measurements, both automatic and
manual pH correction are available. pH correction is
necessary because amperometric chlorine sensors
respond only to hypochlorous acid, not free chlorine,
which is the sum of hypochlorous acid and hypochlo-
rite ion. To measure free chlorine,most competing
instruments require an acidified sample. Acid lowers
the pH and converts hypochlorite ion to hypochlorous
acid. The Model 5081-A eliminates the need for
messy and expensive sample conditioning by using
the sample pH to correct the chlorine sensor signal. If
the pH is relatively constant, a fixed pH correction can
be used. If the pH is greater than 7.0 and fluctuates
more than about 0.2 units, continuous measurement
of pH and automatic pH correction is necessary.
Corrections are valid to pH 9.5.
The transmitter fully compensates oxygen, ozone, free
chlorine, and total chlorine readings for changes in
membrane permeability caused by temperature
changes.
For pH measurements — pH is available with free
chlorine only — the 5081-A features automatic buffer

DESCRIPTION AND SPECIFICATIONS

communication protocol and AMS
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SECTION 1.0
recognition and stabilization check. Buffer pH and
temperature data for commonly used buffers are
stored in the analyzer. Glass impedance diagnostics
warn the user of an aging or failed pH sensor.
The transmitter has a rugged, weatherproof, corro-
sion-resistant enclosure (TYPE 4X and IP65) of
epoxy-painted aluminum. The enclosure also meets
FM and CSA explosion-proof standards.
Circuits in the Model 5081-A transmitter are designed
and built to be intrinsically safe when used with the
appropriate safety barrier.
The 4 to 20 mA signal is fully scalable over the linear
range of the sensor. During hold and fault conditions,
the output can be programmed to remain at the last
value or go to any value between 3.80 and 22.00 mA.
Measurement results are displayed in 0.8 in. (20 mm)
high seven-segment numerals. Temperature and pH
(chlorine only) appear in 0.3 inch (7 mm) high digits.
Remote communications with the 5081-A is easy. The
hand-held, push button infrared remote controller works
from as far away as six feet. The 5081-A works with the
275, 375, or 475 HART hand-held communicator or
with any host that supports the HART protocol.
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HART is a registered trademark of the HART Communication Foundation.
SECTION 1.0
DESCRIPTION AND SPECIFICATIONS
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