Modelo O2S-D       
(enterrado)        

SENSOR DE OXIGENO
(Modelos O2S-F y O2S-D)                  

Miden la cantidad de Gas Oxígeno (O₂) en el Aire                                                                             Ver más imágenes...

Los modelos O2S-F y O2S-D son sensores de tipo célula galvánica. This differs from a polargraphic oxygen sensor in that a galvanic type sensor does not require a power supply as a polargraphic sensor does. It has a lead anode, a gold cathode, an acid electrolyte and a Teflon membrane. The current flow between the electrodes is proportional to the oxygen concentration being measured. An internal bridge resistor is used to provide a mV output.

The mV output responds to the partial pressure of oxygen in air. The standard units for partial pressure are kPa. However, gas sensors that respond to partial pressure are typically calibrated to read out in mole fraction of the gas in air, which has units of moles of oxygen per mole of air. These units can be directly converted to % O₂ in air or ppm O₂ in air.

Gas sensors read out in percent because this value does not change with temperature or pressure. The concentration of oxygen in our atmosphere is 20.95%, and this value, to 4 significant digits, has not changed for decades. This means that we are surrounded by calibration gas for this sensor (provided you are not breathing on the sensor when it is being calibrated. Our exhaled breath is about 17% oxygen).

Model O2S-F comes with our flow-through head design suitable for use with an in-line application. 

Model O2S-D comes with our new diffusion head that creates a pocket of air space and is thus suitable for soil applications. 

Both models now are built with a type-k thermocouple to monitor changes in temperature and and internal micro-heater to prevent condensation on the sensing membrane.

MEDIDOR DE OXIGENO CON SENSOR SEPARADO
(Modelo O2M-F ó O2M-D)

Mide la cantidad Instantánea de Gas Oxígeno (O₂) en el Aire.

Esto combina el sensor mencionado más arriba con un medidor

de mano dedicado (la compensación de temperatura no está disponible con esta unidad).

Modelo O2M-F ó Modelo O2M-D

Modelo O2M-FD  (con cabezas intercambiables)
 

FRACCION MOLAR Y PRESION PARCIAL

" FRACCION MOLAR Y PRESION PARCIAL: Understanding the two ways to express the amount of oxygen in air."

SENSIBILIDAD EN TEMPERATURA

In a constant oxygen atmosphere, the mV output of the sensor would change in proportion to a change in the absolute temperature. Since room temperature is about 300 K, a 3 degree Celsius temperature change would change the output by 1% (from 20.9 to 20.7%). However, this unit has a temperature compensation circuit that corrects for about half of the temperature effect.   For exact measurements, the sensor has a type-K thermocouple inside that can be used to more precisely correct for the effect of temperature.

CAMBIOS DE PRESION

The sensor is not pressure compensated so changes in barometric pressure change the mV output of the sensor. Barometric pressure changes are relatively small and they do not occur rapidly so it is not always necessary to measure and correct for pressure. At sea level, the pressure averages 101.3 kPa and ranges ± 2%. The pressure extremes are uncommon. Barometric pressure varies less than +/- 1% on about 90% of the days of the year. When the sensor is in air the reading could change from about 20.7 to 21.2 % over a period of several weeks, assuming typical pressure changes.
 

SALIDA

The output signal of the sensor is approximately 11 mV in ambient air, or 0.5 mV per 1% O2. The user must calibrate the sensor at their location, at their pressure, to establish the exact multiplier to convert the mV reading to % O2. If the output was exactly 11.0 mV the multiplier would be 1.905 (20.95 / 11.0).
 

PRECISION

Absolute accuracy of the sensor depends on how often it is calibrated. To achieve the best accuracy, automated calibration with ambient air at least once each day is recommended. Typical drift rates are less than 0.05% in 24 hours.
 

OFFSET DE CERO

The mV output in ultra-pure nitrogen gas (0.000 % oxygen) is typically ± 0.05%. Precise measurements of hypoxic and anaerobic conditions can be made by making a periodic zero calibration of the sensor with ultra-pure nitrogen gas. The zero offset for each sensor is highly reproducible and should be entered into the software after a zero-test.
 

VIDA DEL SENSOR Y TEMPERATURA DE ALMACENAMIENTO

VIDA DEL SENSOR. The life expectancy of the sensor is expressed in %-hours as follows:
     [Oxygen Concentration (%) x Exposure Time (hours)]

Accordingly, the life of the Apogee Oxygen Sensor is 900,000 %-hours or approximately 5 years of continuous use (at 21% oxygen at 20^oC).

STORAGE TEMPERATURE. The life of the sensor can be extended by storage at a lower temperature. For example a sensor stored at 0^oC will have a life expectancy approximately twice that of a sensor stored at 20^oC. The absolute minimum storage temperature is -20^oC. Below that temperature the electrolyte will freeze. Maximum storage temperature is 60^oC.
 

INFLUENCIA DE VARIOS GASES

The sensor is unaffected by CO, H₂, and various acidic gases such as CO₂, H₂S, NO_x, SO_x. However, the Teflon membrane used in the sensor may be damaged by ozone.
 

DEPENDENCIA DE LA HUMEDAD

The graph at the right shows an example of humidity dependency.

The sensor is not influenced by humidity, but its output decreases

as O₂ is displaced by water vapor molecules in the air.
 

SHOCK, VIBRACION Y ORIENTACION

The sensor is resistant to 2.7 G of shock. Vibration may influence the sensitivity characteristics of the sensor and should be minimized.

For the most stable reading, the sensor should be used with the sensor opening facing down. This facilitates the best contact of the electrolyte with the O₂ sensing elements.
 

USO DEL SENSOR

1. Conectar los cables a un voltímetro de calidad o registrador de datos.

DESDE EL SENSOR:
             Cable rojo es positivo / high
             Cable negro es negativo / low
             Cable desnudo/transparente esla pantalla (tierra)
             Cable verde es alimentación +12 V  - positivo
             Cable blanco es alimentación -12 V - negativo
CABLE DEL TERMOPAR - Typo K (funda marrón)
             Cable amarillo es positivo
             Cable rojo es negativo

2. Measure the mV output of the sensor in a well ventilated area to insure that the O₂ concentration is 20.95%. Do not breathe on the sensor as exhaled breath is 16 to 17% oxygen.

3. Divide 20.95 by the mV output value. This is the multiplier to convert mV to % O₂. This multiplier will be correct for your elevation, current barometric pressure, and current humidity.

For model O2S # _________, the approximate multiplier value at sea level is _________. This number is intended as a general reference only. It was obtained in Logan, UT (elevation 1.6 km above sea level) and adjusted to predict the mV output at sea level. Most locations are a few hundred feet above sea level so calibration at the location of use is necessary.

4. Install multiplier value in your datalogger program.

5. Recalibrate as needed when changes in pressure or humidity occur.
 

ESPECIFICACIONES DEL SENSOR DE OXIGENO

ENTORNO OPERATIVO

5 a 40 °C;  0% a 100% oxígeno

SALIDA

Aprox. 12 mV a 20.95% O₂ a nivel del mar
He de ser calibrado por el usuario

DIMENSIONES

2.37" largo, 1.25" diámetro con una punta roscada de 1/2" x 20

PESO

175 g

RANGO

0 a 100% oxígeno

CABLE

2 metros de cable par trenzado y apantallado (total de 5 cables)
2 metros de cable Termopar typo-K

DESDE EL SENSOR:
             Cable rojo es positivo / high
             Cable negro es negativo / low
             Cable desnudo/transparente esla pantalla (tierra)
             Cable verde es alimentación +12 V  - positivo
             Cable blanco es alimentación -12 V - negativo
CABLE DEL TERMOPAR - Typo K (funda marrón)
             Cable amarillo es positivo
             Cable rojo es negativo

REPRODUCIBILIDAD

+/- 0.2% O₂ (típicamente +/- 1% O₂)

GARANTIA

1 year parts and labor