How can I choose the most suitable sensor for my application?
We offer compatible sensors as replacement for almost any application. In order to choose the corresponding item, please provide our sales department with following necessary information:
- manufacturer and/or name of device the sensor has been used for
- manufacturer and/or part number P/N of the sensor you want to replace
- if not available, photos with several views or even an exhausted sensor will
help us to identify the item.
In addition to our standard program, which can be seen on this website, we offer customized solutions. Please, contact our Sales Department for further help. As a little help to design your specific cell, please use this inquiry form sheet
What are the recommended storage conditions for gas sensors of IT Gambert?
Please, refer to our Product Specification of the according sensor. We recommend to stock sensor not longer than 3 months, since warranty time counts from shipping date. As a rule of thumb we mostly recommend storage temperatures between 5°C - 30°C.
Temperature has an effect on output signal of the sensor. Though, please note, that sensor and instrument must come to an equilibrium prior to calibration procedure. Otherwise calibration procedure will fail or the reading of the instrument will be incorrect.
Based on which functional principle do your sensors work?
Please, find detailed explanation on Sensor Basics under Technology.
What materials are your sensors made of?
Please, refer to Product Specification of each item.
How and how often should a sensor be calibrated?
In calibrating a given gas analyser, it is best to use a calibration of reference gas whose content is near or equal to the full scale reading.
In most cases the ambient conditions under which sensor and instrument, as a whole, will be calibrated are of great importance. The best result will be achieved if calibration will be performed equal to the subsequent real operating conditions of pressure, temperature and relative humidity.
The calibration interval depends amongst others on the required degree of precision. The more often the measuring instrument along with a sensor has been calibrated, the better its accuracy. Substantial changes of the ambient atmosphere (pressure, temperature, relative humidity) will systematically require a recalibration of the cell.
Do your sensors require warm-up time?
The sensor's warm-up time will depend on its storage conditions. As far as Vol.% oxygen sensors are concerned, some of them will require short-cut along their storage period.
In general 30 minutes will be required before the sensor reaches its full performance. In all cases, care should be taken, that the sensor and the measuring instrument have the same temperature; otherwise the warm-up time will be prolonged by the time required to equalize the temperature difference.
Toxic gas cells without on-board potentiostate will require run-in time which mainly depends on how long the sensors have been stored without being hooked-up to any external potentiostate (the longer the storage-, the longer the run-in time).
What is the best moment to replace a sensor?
The nominal lifetime of oxygen sensors expressed in %Vol. O2 per hour is a theoretically calculated value given in the oxygen sensors specification. There is no fixed date given when an oxygen sensor should be replaced.
Depending on pressure, temperature and gas concentration each sensor will have a different expiry date. In general, the best moment to replace a sensor is when it reaches only 50% of it's original output signal, or if the instrument indicates "sensor failure".
The lifetime of toxic gases sensors that come with potentiostate will depend predominantly on the lifetime of its on-board battery (2-3 years), whereas the lifetime of cells featuring no potentiostate will mainly depend on their operating conditions (temperature, relative humidity, pressure).
Which factors affecting the lifetime of an oxygen sensor?
The most important factor is the amount of O2 partial pressure. This is due to the sensors amount of lead anode material available and the rate of oxygen being consumed. This rate is governed by the average oxygen concentration the sensor is exposed to across its lifetime. As a first approximation, there is a direct inversely proportional relationship between decrease of sensor life, resulting in a drop of electrical output, and increase of oxygen concentration.
Assuming a sensor is specified for 250 000 Vol.% hours nominal, which is approx. 1.4 years at ambient air. The same cell will last approx. 1/5 of the time if it is continuously exposed to 100 Vol.% of oxygen.
Other life limiting factors are humidity, temperature and in some cases cross-interfering gases.
Which impact has temperature on a sensor?
Within the recommended temperature range IT's oxgen sensors that have on-board temperature compensation feature a very low temperature-related measurement error usually not more than 1%/°K. Outside the recommended range the measurement error will increase >1%/°K.
In general, very low (-20°C) or high (60°C) temperature may lead to sensor damage. Temperatures above 60°C risk to melt the plastic housing and membranes which could ultimately lead to leakages.
In case you have a special request on higher operating temperatures, please ask our sales department for further information.
Which impact has humidity on a sensor?
Relative humidity (RH) has an effect on the output signal of oxygen sensors. A shift in the humidity level will change the O2 partial pressure and thus change the sensor’s output signal.
We recommend a minimum relative humidity level of about 50%. Lower RH could lead to the drying out of the sensors electrolyte. However, IT also offers sensors specially designed to work in extremely dry environments.
The sensors should not be submerged! Even diving sensors, featuring an extra water-repellent head space are not suitable for under-water analysis, the sensible part being the connectors.
What is the pressure dependence of the sensor?
Membrane types of electrochemical gas sensors give an output signal that is
proportional to the partial pressure of the measured gas. Ignoring other minor
gas contributions ambient air consist of nitrogen and oxygen only and to simplify
matters Dalton's law can be written as:
P(total) = P(oxygen) + P(nitrogen)
P(oxygen) and P(nitrogen) partial pressures of each constituent.
P(total) is the absolute ambient air pressure at a certain point with regard
to weather condition.
For example, P(total) at sea level is 1 atmospheres. The partial pressure
of oxygen is then 0.209 atmospheres and that of nitrogen 0.791 atmospheres. It
is evident that when the total (absolute) pressure halves the partial pressure
of all constituent gases will halve as well. This has to be taken into consideration
when applying an oxygen analyser where the total pressure will vary, a readout
in partial pressure units should be employed.
The differential pressure is the difference in absolute pressure between two
points of measurement in a system P(differential) = |P1| - |P2|. This value is
to be taken into consideration while conceiving the sampling system for a sensor;
the difference of pressures applied to different parts of the sensor should not
exceed 1.7 bar, otherwise it could lead to instability and leakages. For optimal
performance the entire sensor should be exposed to the same pressure within the
range specified in the technical data of each sensor.