Hanna Instruments HI7640-58, Instruction Manual

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Main Features 4
Principle of Operation
The method is based on the principle of fluorescence quenching and features an immobilized Pt- based
luminophore that is excited by the light of a blue LED and emits a red light. Dissolved oxygen quenches this
excitation. When there is no oxygen present, the lifetime of the signal is the greatest; as oxygen hits the sensing
surface, the lifetime becomes shorter.
The intensity and lifetime are inversely proportional to the amount of oxygen present; as oxygen interacts with
the luminophore it reduces the intensity and lifetime of the luminescence. The lifetime of the luminescence is
measured by a
photodetector , and is used to calculate the dissolved oxygen concentration. This is, in turn,
reported by the HI510 controller as % saturation or mg/L of dissolved oxygen.
Over time, the sensor’s optical components can age but are compensated for by using the reference signal to
compensate the measuring path. As a result, the sensor provides accurate dissolved oxygen measurements over
long periods of time without the need for frequent calibrations.
4. MAIN FEATURES
• Factory calibrated Smart Cap for data storage
•
3/4
” NPT external thread at both ends
• Built-in temperature sensor for measurement
• Digital probe stores model, firmware, serial number, calibration information and Smart Cap data
(serial number, installation date)
• Minimum maintenance (no electrolyte refill or membrane replacement)
• Measurement reliability independent of flow rate
• Reduced response time
• Stable readings even when oxygen concentration is low
5. SERIES CONFIGURATION
HI7640 –
5 8
z z
5 Optical DO sensor
8 Smart probe with RS485 connection
zz
00 supplied with DIN connector (without cable)*
05 , 10 , 15 , 25 , 50 fixed cable length (in meters)
* See Accessories section for patch cable ordering codes.