FAQ UV Photodiodes

1. What is the detector speed?
The detector risetime / falltime is calculated by that formula: tr/f = 2 Pi RC
Example = a typical value of R is 50 Ohm and the C value for a SG01S photodiode is 15pF. This
with R = internal resistance of the amplifier and C = capacitance of the photodiode
tr/f = 2Pi * 50 Ohm * 21 * 10-12 F = 6,59 * 10-9 s = 6,59 ns
2. What is the saturation of a photodiode?
The saturation current Isat of a photodiode is determined by its open circuit voltage VOC and its serial
resistance RS following the formula:
Isat = VOC / RS
A typical value (SiC photodiode) for VOC is 2,0V and for RS = 5Ohm. This calculates: I sat = 2.0 V / 5
Ohm = 0,4 A = 400mA.
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 = 0,055 mm2 (valid for SG01S). This calculates: zsat = 0,4 A / (0,130 A/W * 5,5 * 10-8 m2 ) =
55,94 MW/m2 = 5,59 kW/cm2
3. What are typical rise and fall time of different UV photodiodes?
Capacitance C
tr = 2Pi
(R = 50 Ohm)
15 pF
4,7 ns
50 pF
15,7 ns
250 pF
78,5 ns
4. Is your UVC photodiode compliant to DVGW W294 (2006)?
Yes, f1,Z < 0,25
5. What is the lowest pressure that the photodiode can withstand?
Our UV photodiodes are hermetically sealed. Thus, a use under vaccum is possible, theoretically down to
0 Pa.
6. When is a filtered UV photodiode needed?
Our four filtered versions of the UV photodiode lead to a tighter sensitivity range.
7. What is the maximum signal output of a TOCON?
The theoretic maximum signal output is always a little less (approx. 5%) than the supply voltage.
8. Do I need an external amplifier?
No, no additional amplifier is required.
9. How can I use my TOCON?
Please use a standard voltmeter to read out the signal. Caution! Wrong wiring leads to immediate
destruction of the device. Please see our application note delivered with the device.
10. What about the TOCON scatter?
A TOCON is a sophisticated product where a lot of different components create the TOCONs function. All
of these components properties, e.g. the efficiency of the UV-sensing SiC chip or the gain resistors value
scatter within a certain range. This results the TOCONs total scatter of +-35%. This means, if you buy a
certain quantity of TOCONs it could happen that one TOCON e.g. outputs a voltage of 1000mV at a
certain radiation. The less sensitive TOCON within the batch may output 1000mV minus 30% = 700mV
and the most sensitive TOCON may output 1.300mV. At most cases this scatter does not cause problems
if suited analogue or digital output voltage analysing components are used. However, one very important
thing is to be considered: The TOCON must never saturate while illuminated with UV radiation.
Saturation means that the TOCONs voltage output Vout equals to the input (=power supply) voltage Vin.
Saturation will not damage the TOCON but saturation means that the output value most likely is wrong =
too low compared to the radiation to be measured. This information is quite important for developers
who purchased a certain sample quantity or just one TOCON and consider to order a volume quantity. To
make sure that not a single TOCON of this volume quantity will saturate in use you should make sure
that the sample(s) do not output a voltage higher than 50% of the input voltage while illuminated with
the maximum radiation to be measured (e.g. the radiation of a new lamp). If Vout is higher than 0,5 Vin
one may try to increase the distance to the UV source or to purchase a less sensitive TOCON (see table
below). This +-35% scatter is a default value. If this causes problems, please contact us. By means of
binning processes we feel able to reduce the scatter of the batch. However, please consider that also a
reduced scatter still requires an individual calibration of each TOCON. Thus, usually scatter reduction
does not create a technical benefit.
11. Do you offer an UV sensor for outdoor measurements?
We can offer our UV-Cosine sensor for outdoor measurements. The housing is waterproof IP68 at window
side, stain repellent and on request submersible.
12. Which products can be connected to the Sensor Monitor?
Photodiodes or UV sensors with voltage output (TOCON series, UV probes).
13. Is the Sensor Monitor calibrated?
By default, the units input terminals are NIST traceable calibrated looking at the displayed voltage
(Sensor connected) and current (Photodiode connected). If the Sensor Monitor is delivered in a bundle
with an UV sensor, the Sensor Monitor will come calibrated. A calibration certificate is available on
14. Do you offer a waterproof datalogger?
Our UVMICROLOG can be configured to be waterproof.
15. What is the power input of a Multiboard?
The current consumption of a Multiboard is between 4mA and 20mA, depending on the amount and type
of operating voltage (uni / bipolar) as well as the load at the output (multimeter = no load).
16. Do you offer NIST calibration?
sglux offers PTB-traceable (Physikalisch Technische Bundesantalt) calibration.
17. Which information is shown on the calibration certificate?
The data coming from the calibration is a concrete value that states while using one specific lamp a value
of xxx mV equals to yyy mW/cm2 @ zzz nm.