YOKOGAWA EXA DO402G, Руководство пользователя

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<1. Introduction and General Description>
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IM 12J05D02-01E
1.3 General information
Flexibility, reliability and low maintenance are among the benefits provided by the EXA DO402G
dissolved oxygen analyzer. Designed to meet the exacting requirements of measuring dissolved
oxygen in the modern industrial environment, it contains many features to ensure the best
precision whatever the application.
This 4-wire converter is housed in a robust IP65 field mountable case. Two mA outputs, four
relays, digital communication and a clear LCD make the DO402G a truly comprehensive
package.
The DO402G features PI control on both the auxiliary mA output and the pulse proportional relay
outputs, thus avoiding the need for a separate controller.
The famous EXA sensor diagnostics are now expanded with a logbook facility in combination
with the RS-485 two wire communication software option. This can be used to record events like
calibration and diagnostic messages, and to update configuration of the converter remotely.
The DO402G accepts inputs from galvanic, polarographic and optical sensors. Percent
saturation, mg oxygen/L water, and ppm DO can be displayed and transmitted. Compensation
for atmospheric pressure altitude, salinity and temperature are included for the best accuracy of
measurement.
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Features
• Simple 3 level operation
• Display mg/L, ppm, % saturation
• Air calibration or saturated water calibration
• Chloride concentration compensation can be programmed
• Automatic temperature compensation
• Built-in barometric air pressure compensation
• “Hold” function enables fixed output signal during maintenance
• Two separate mA output signals
• Wide flexibility incorporating free programmable range settings, selection of output signals
and alarm functions
• Analog output with adjustable damping time
• Password protection for each programming level
• Built-in wash timer with remote start possibility
• IP65 weather protection
• Universal mounting possibilities
• Sensor diagnostics
• RS-485 bi-directional communication
• Logbook via RS-485 link
• PI control on mA and pulsed contact controls
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Method of operation
The EXA DO30 operates on a galvanic cell principle.
The sensor contains a measuring cell consisting of a silver cathode and a lead anode. The
voltage generated by this electrode pair is sufficient to generate a spontaneous reduction of
oxygen at the cathode, so no external voltage source for this reaction is required. The electrodes
are immersed in an electrolyte containing potassium hydroxide. Oxygen molecules can pass
through a permeable membrane into the cell. The output current of the cell is directly related to
the partial pressure of oxygen at the sample side.
In the sensor a thermistor is integrated to be able to correct for temperature changes. Both
signals are used in the converter to ensure an automatically compensated value for dissolved
oxygen. Calibration is worked out by simple air calibration to make sure that the performance of
the instrument will be maintained.
9th Edition: Aug. 05, 2015-00