FAQ - SITA CleanoSpector
How does ambient light affect the measurement?
The SITA CleanoSpector automatically compensates for the ambient light by measuring both the ambient light and the radiation emitted by the fluorescence. Excessive ambient light can result in an overload of the detector diode (Warning on device: Ambient light!). Fast changes in the light conditions, for example by switching on ceiling lights or fluctuating shade during a measurement can cause measurement deviations. Fast changes in light during a measurement should therefore be avoided. If the SITA CleanoSpector detects a change in the ambient light it will output the warning “Ambient light fluctuation”. In this case, it is recommended that you improve the measuring conditions and/or ambient light conditions (steady light conditions or shading) and repeat the measurement.
What effect does the measuring distance have on the result?
The optimal measuring distance is decisive for a correct measurement. You can easily set the measuring distance by placing the sensor with a spacer on the part or by measuring with a stand and target pointer. Deviations from the optimal measuring distance result in lower measured RFU values. The influence of the distance depends on the optic version of the sensor.
Why does the measured value drop to the same level during a multiple measurement?
This is due to the photo bleaching effect. Photo bleaching is a dynamic process in which the contamination is photo-chemically destroyed by the UV excitation, which reduces its ability to fluoresce. The intensity of the photo bleaching effect depends on the material. In practice, the photo bleaching effect is of secondary importance in the cleanliness inspection of parts. A multiple measurement of the same spot is not practical. Instead, one should measure on several different spots in order to obtain an average, which then makes it possible to assess the cleanliness of the part. We recommend conducting a measuring system analysis with multiple measurements using the SITA Calibration Standards to eliminate adverse effects from photo bleaching and positioning.
Why do the measuring values differ so much depending on the measured point?
Filmic contaminations are generally distributed unevenly on the surface. They are dependent on the geometry of the part, as well as the machining and cleaning process. Typically, heavier contamination is distributed more unevenly. The cleaner the surface, the lower the RFU values and also the absolute divergence of the measuring values.
Does the sensor head have to be in a vertical position to the surface in a contact-free measurement?
No, the sensor head does not necessarily have to be perpendicular to the surface. Deviations of ±15° around the perpendicular will not cause significant changes of the measured fluorescence intensity. Depending on the application, higher angles are also permissible. If the angle of the measurement is always the same, such as 45°, the measured values are comparable with each other (45° with 45°), not however with measured values of 0°.
What effect does the surface roughness have on the measurement?
The surface roughness has only a secondary influence on the measurement, because the meas-urement does not detect the reflected UV radiation, but rather the emitted fluorescence of the contamination. As a point light source the fluorescent light radiates in all directions. However, the surface roughness does influence the cleanliness of the part itself, because rough surfaces are generally harder to clean.
How does the base material of the part influence the measurement?
The base material can influence the measurement. One influencing factor is the basic fluorescence of the part material. Metal and ceramic surfaces do not fluoresce. In the case of glass surfaces, fluorescence is possible due to contamination in the amorphous structure. Other materials such as paper, textiles and plastics tend to fluoresce more strongly due to their complex structure of organic molecules. In the case of fluorescent base materials, it must be determined whether a reliable cleanliness inspection of these parts with a fluorescence measurement is possible.
Another influencing factor is the property of the basic material to absorb and reflect light in different wavelength ranges. The same coating thickness of a particular material can provide different RFU values on copper and on stainless steel. In practice, however, this is of secondary importance, since limit values for sufficient cleanliness of parts should always be defined for the specific process. In addition to the quantity of contamination, the limit value is affected by the type of contamination, the follow-up process, and the influence of the basic material on the follow-up process (Limit values for sufficient cleanliness of parts).
How often should the SITA CleanoSpector be calibrated?
We recommend a regular inspection with the included Calibration Standards. In the default setting, the SITA CleanoSpector issues the warning “Check required” 40 days after the last check. In addition, as part of your regular monitoring of measuring equipment, we recommend servicing and adjustment of the SITA CleanoSpector and the corresponding Calibration Standards by the manufacturer every 1-2 years.
Can the measurement with the SITA CleanoSpector be automated?
The SITA CleanoSpector is designed as a hand-held measuring device. The fluorescence measurement technology SITA clean line CI is used for inline measurements or for scanning surfaces. Due to the adjustment with the SITA Calibration Standards, the measuring results (RFU value) of all hand-held measuring devices SITA CleanoSpector are comparable to each other as well as to the inline sensors SITA clean line CI (if the same optic version is used).
What types of contamination can be detected/cannot be detected with the SITA CleanoSpector?
Processing aids such as oils, greases, cooling lubricants and release agents are technical liquids that also contain numerous additives, which can likewise contribute to fluorescence. Measuring procedures. Whether a contamination fluoresces sufficiently depends on the particular application and can be assessed by a simple fluorescence test. Whether a contamination can be detected in the quantities that are disruptive for your process can easily be determined based on parts from your process. This should be checked with uncleaned as well as with well cleaned and poorly cleaned parts.
What has to be taken into account in a measuring system analysis?
A measuring system analysis must always take into account the photo bleaching effect as well as the uneven distribution of contamination on a surface. In a first step, we therefore recommend conducting the measurement system analysis with the SITA Calibration Standards; these effects do not occur. Further measuring system analyses that also examine the influences of the tester and the test specimen should take into account the influence of uneven distribution of the contamination as well as the photo bleaching effect.