tr = 2Pi
Isat = VOC / RS
A typical value (SiC photodiode) for VOC is 2.0 V and for RS = 5 Ohm. This calculates: Isat = 2.0 V / 5 Ohm = 0.4 A = 400 mA.
The saturation radiant intensity z calculates by the below formula: z = Isat / (S * A)
Where S is the radiant sensitivity of a photodiode and A is the active area. A typical value for S is 0.13 A/W and A = 0.06 mm² (valid for SG01S). This calculates: zsat = 0.4 A / (0.130 A/W * 6 * 10-8 m² ) = 51.28 MW/m² = 5.13 kW/cm²
Detailed further information is provided by the Hamamatsu „Chapter 2 of Handbook of Si Photodiodes“ to be downloaded from the Hamamatsu website.
AMPLIFIED UV PHOTODIODES (TOCON series)
Customers are especially cautioned to AVOID SATURATION conditions. Saturation is when Signal voltage equals Power Supply Voltage (normally 5V). Saturation will not damage the TOCON but it can lead to PERSONAL SAFETY PROBLEMS or other DAMAGE due to unknown and potentially excess UV exposure levels.
As-delivered the TOCON is sensitive in the specified range. Example: A TOCON_ABC6 is sensitive between 180 nW/cm² and 1.8 mW/cm².
This means that the TOCON will saturate (output voltage = input voltage) at approx. 1.8 mW/cm². At the lower end a radiation of 180 nW/cm² will still output a couple of mV. While selecting a TOCON, the most important thing to consider is to not illuminate the TOCON until saturation level. A saturation will not damage the TOCON but likely the voltage output will no longer be linear to the radiation input because any increase of radiation above / below the saturation point will not further increase the output voltage.
The TOCON is stable for capacitive loads up to 30 pF under all circumstances. If more capacitive loading can not be avoided a series resistor of 10 Ohms … 100 Ohms may be required to ensure stability up to few hundred nF.
DATALOGGER, DISPLAYS and CONTROLLER
A typical calibration certificate is given here (link). It contains the following information et al:
– Reference irradiation measured by a traceable-calibrated (spectro-) radiometer
– Calibration object signal
– Calibration factor [Signal]/[W/m²]
200 – 249 nm 13%
250 – 299 nm 7%
300 – 399 nm 5%
400 – 430 nm 4%