Ultraviolet, visible and infrared light radiation of all wavelengths impinge on the input Aperture at the tip of the PALM Probe Light Guide. The light is directed down the Light Guide to the base of the Probe body where the UV filter passes the UV light at interest to the photodetector. The photodetector converts the light energy to a current that is proportional to its intensity. The signal is conditioned, digitized, processed and displayed on the LCD of the PALM Probe.
The Light Guide is constructed out of steel alloy and coated with a non-conductive ceramic coating to insulate and protect the user from accidental shock while taking measurements. The Light Guide is further isolated from the Probe Body by a non-conductive Delrin block. The Probe Body contains the optics, electronics, battery and display functions of the unit. The Probe Body can be held either with an "over" or "under" hand type of grip. The raised membrane switches are easy to operate with either hand.
The PALM Probe has a very wide dynamic range that automatically adjusts itself for the user. For example, the PALM Probe can measure light from approximately 100 microwatts/cm2( µW/cm2) up to 10 Watts/cm2 (W/cm2). The decimal point in the LCD "floats" over three places to cover the wide dynamic range on the unit. The PALM Probe display allows the user to alternate between Watts-Joules-Seconds during data collection and after a reading or run has been made. The SELECT button allows the user to toggle between the values.
When collecting irradiance data with the PALM Probe, the display will change as the Probe changes position under the UV source. As the aperture opening moves into the focused peak irradiance area of the UV source, the reading will increase. Variations in irradiance may also be seen when the PALM Probe is moved along the length of a UV bulb. The LCD display will automatically scale and adjust as the PALM Probe takes readings. Pressing the RUN/STOP button will stop the collection of data and the highest irradiance value measured during the collection of data will be displayed. Most users will find that the Irradiance value (W/cm2) displayed is the most important value collected by the PALM Probe when it comes to process control for a particular application.
UV Energy Density or Dose incorporates time into the irradiance measurement. The PALM Probe displays the Energy Density or Dose value in Joules (J/cm2) on the LCD.
The dose is an integration of the area under the irradiance curve. The dose reading increases as the reading continues. The speed at which the dose increases depends on the irradiance value. Switching to the built in timer in the PALM Probe will help monitor the "time component" of the dose reading for more consistent results. Placement of the PALM Probe in the same location is important in order to get consistent and repeatable irradiance values to calculate dose readings. |