How to Measure?





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"On-Line" Monitors

On-line monitoring of the production process allows users to measure the radiant energy from the lamp and/or the reflector, noting any change that may occur. The sensors are most often mounted in a fixed location in the system.

On-Line monitors and sensors can be used to:

On-line monitors can be simple sensors, multiple-wavelength detectors and even spectroradiometers. In most UV curing systems, the sensors cannot be located to duplicate UV arriving at the cure surface, and therefore measure irradiance indirectly or on a relative basis. Sensors that are installed in a UV system need to be durable and resistant to avoid changes (solarization) induced by constant exposure to the UV source. Mounting location is important and some systems may use a shutter to reduce these effects.

Each UV system usually requires an individual sensor. Multiple lamp systems usually require multiple sensors. Often times it is best to place a sensor in the part of the system that is first expected to change - the extreme end of an arc lamp for example that tends to blacken as it ages.

The values reported are a relative measurement. With a newly-installed or newly-refurbished lamp system, or after a thorough cleaning of the reflector and bulb, the monitor is usually given a relative “intensity” of 100% or specific output value (volts or amps). This is the baseline and subsequent measurements are compared to the initial reading. As the percentage or output value decreases, it alerts the operator that a change has occurred in the curing system, and can use this as an indicator to establish a set point to take corrective action.

The advantage of on-line monitoring is that it is simple and automatic. It is not necessary to include a large number of parameters – in fact; one or two is usually adequate. This type of monitoring is best used to detect serious changes in key exposure parameters, and to indicate the need for maintenance before the process is affected. Periodic correlation with a calibrated radiometer is recommended.

Online Sensor Behind Reflector

Online Sensor Mounted

Compact Sensor

If readings can also be made with an absolute reading radiometer you should be able to make comparisons between different production lines.

The readings from on-line monitors can also be coordinated with absolute reading radiometers.