All Sensirion sensors are calibrated before they are shipped out. Some of the sensors such as carbon dioxide sensors are sensitive and can come under mechanical stress during handling and can offset the sensor. To offset this, apply the Forced Recalibration (FRC) or Automatic Self Calibration (ASC). Ideally, a sensor calibration is performed after sensor installation, to compensate for potential mechanical stress during installation.
Calibration certificates can be found in the Download Center.
Below are some questions Sensirion has received on the calibration of their sensors.
What do you suggest the time interval should be to test that the device is still calibrated and whether adjustments need to be made?
Sensirion does not suggest a time interval to test the device as it depends on too many external factors. If any regulations for your product demand verification on a certain time base, it might be advisable to make the sensor exchangeable in case it requires replacement.
What is the device-to-device variation of the SGP sensors?
All SGP sensor are calibrated individually during the production process. Therefore, the device-to-device variation of the SGP is very low. See datasheet, accuracy specifications for more details. Examples of the D2D observed in field measurements are shown e.g. in the app note AN_SGP_Testing_Guide.
Does Sensirion offer a recalibration service for its Liquid Flow Sensors?
No, Sensirion does not offer a recalibration service. Our sensor technology allows for a design without any moving parts and thus without wear and tear. The sensor therefore has a good long term stability, rendering a fixed e.g. annual, verification unnecessary from a technical perspective. However, we do recommend setting up an application specific maintenance schedule, where the sensor performance is regularly checked within the application. Due to the application specificity of such a schedule, your application specialists is responsible for its definition.
Can the liquid flow meter be used to monitor liquids it has not originally been calibrated for by Sensirion?
Yes, this is in principle possible. Select the standard calibration field that best matches your fluid’s chemical composition. For example, the water calibration can be used for saline solutions or the hydrocarbon calibration can be used for lubricant oils. A matching calibration field increases the possibility of a linear response from the sensor. A good rule of thumb is to use the IPA calibration for all liquids that do not contain any water.
Regardless of the fluid, your liquid flow meter is capable of a high repeatability. Typical values for repeatability range from 0.8% to 1.5% for all media, depending on the liquid flow meter at hand. This allows you to use the sensor as a very precise relative gauge when liquid flow is required to stay within an acceptable range. In such a case, the sensor’s output can be compared to set maximum and minimum flow rates and used as upper and lower thresholds for reference. The liquid flow meter can then monitor process repeatability within verified acceptable limits. Since absolute values may vary from sensor to sensor, this tolerance band must be newly set for each individual flow meter.
What is the impact on accuracy when the operating conditions alter from the calibration conditions?
Sensirion MFCs directly measure the number of gas molecules (or gas mass) flowing past the sensor and thus show only very minor dependency on deviations in pressure and temperature from the calibration conditions. The respective temperature and pressure coefficients can be gathered from the datasheets. A change in gas temperature induces both a zero point and a span error. By contrast, a deviation in pressure causes only a span error.
Does Sensirion offer multigas/multirange calibrations?
Sensirion can calibrate MFC/MFMs both with multiple calibrations of different gases (multigas) and with multiple full-scale flow ranges of the same gas (multirange).
The following precondition must be fulfilled to provide a multigas option with optimal calibration performance:
N2 equivalent FS flow ranges of the specified gases must be close to each other.
Multigas/multirange calibration is available with both real gas and gas conversion calibrations.