ISCEV has published guidelines for calibration. All ISCEV standards can be found at https://iscev.wildapricot.org/standards . The calibration guideline article from ISCEV is attached at the bottom of this article.
Re calibration is recommended for ganzfeld type stimulators on an annual basis; a calibration file is created at the time of manufacture. Ganzfeld stimulators are the Colordome and handheld Colorburst. It is up to the end user to decide if they wish to order a recalibration service. Please see article titled "Check Calibration Status" to determine the current status of your Ganzfeld stimulator's calibration.
The dome should be recalibrated before the ratio of INI / Counts values reach 1.5. You may continue to operate the stimulator up to that point. In general a recalibration will be performed every 12-15 months to allow for Diagnosys to be able to offer a recalibration service, either by onsite visit if possible, or by shipping the stimulator to Diagnosys for an in-house calibration.
The reason a calibration needs to be redone is due to the degradation of the light source inside. These light sources degrade over time due to temperature and usage. There are a few types of light sources in the Colordome. LED's are found in all colordomes, and are used for most all protocols. Xenon bulbs are found in some colordomes, and emit a short white flash. UV type diodes are used for colordomes in some research settings.
Diagnosys does not provide usage hours like many TV manufacturers provide. Unlike TV's, which are run at consistant lumanaces, Colordome's are run at a variety of flash intensities. The LED's will degrade variably based on how the end user operates their Colordome. Any color of light, at luminances ranging from 10^-9 cd/m2 all the way up to 10^3. Due to variable usage, a standard number of usage hours before recalibration is needed can not determined.
When making a generating new calibration data during a recalibration service, the new data is expected to be different than the original calibration at the time of manufacturing. This is due to aging of the LED's, Xenon tube
A calibration process requires removing the ColorDome or ColorBurst from your facility and shipping it to Diagnosys. Diagnosys will have the stimulator for about 2 days before sending it back. With shipping time on either end, the total calibration process lasts about 1 week.