Application

Summary:
Decreasing irradiance requires increasing chip active area. If the irradiance to be measured is unknown, an L-chip photodiode should be used for prototypes.

Detailed answer:
The active area of the chip determines how many photons can be collected by a photodetector. Semiconductor detectors, such as SiC UV photodiodes, convert photons into an electrical current, the photocurrent I. This photocurrent increases linearly with the irradiance and the active area of the chip. Since the price of the detector increases with the active area, the choice of area is essentially a compromise between cost and photocurrent. If you know the minimum and maximum irradiance you wish to measure with the UV photodiode, the following simplified formula gives a rough estimate of the photocurrent I for a given chip active area AChip. I=Achip *Eλ *1000 where I is the photocurrent in nA, A is the active chip area in mm² (enter values of 0.06 or 0.2 or 0.5 or 1 or 1.82 or 7.6 or 36) and Eλ is the spectral irradiance of the UV light source you like to measure in mW/cm². The minimum current (photodiode output at the lowest irradiance to be measured) should not be less than 500pA. If you do not know Eλ, the L-chip (1.00mm²) type photodiode should be used for a first evaluation step.

Summary:
For UV measurement, unfiltered broadband SiC is used by default

Detailed answer:
By default, unfiltered broadband SiC is used for UV measurements. If a UV source also emits radiation that must not contribute to the sensor’s signal (e.g. UV medium pressure lamps used for water or air purification that also emit non-germicidal UV radiation), a filtered SiC detector (UVC, UVB+C or UVA only) should be selected.

Summary:
Our SiC-VUV photodiodes are used here.

Detailed answer:
Our standard SiC photodiodes only have a low sensitivity below 220nm. Below approx. 200nm they have they no longer have any sensitivity. For applications where radiation below 220nm needs to be measured, our VUV (“vaccum UV”) photodiodes are used. Typical applications are the destruction (cracking) of organic carbons in fat or in water (TOC) at 185nm or the matting of paints at 172nm. VUV photodiodes are also used to monitor PFAS photolysis.

Summary:
Yes, but we do not recommend their use.

Detailed answer:
Yes, we manufacture 3535 SMD type photodiodes (ceramic package), but we recommend the use of metal TO photodiodes. The packaging and hermetic sealing of photodiode chips in metal TO housings with a fused glass window is a mature and extremely reliable process that has been in use for more than 50 years. A TO-packaged sglux SiC UV photodiode is usually the most reliable and durable component in a product, even when exposed to very high UV radiation or operated at high temperature levels. However, recent progress in the development of long life UV LEDs, also in the UVC range, allow UV low pressure tubes to be replaced by these LEDs, resulting in a significant potential reduction in product dimensions. The miniaturization of products such as UV transmittance measurement modules or point-of-use LED UVC disinfection modules allows our customers to move into new areas of application. Sometimes our TO-packaged UV photodiodes are considered too bulky. Our SiC SMD photodiode range is designed for these applications. The package consists of a ceramic body with a mineral window glass to make these SMD photodiodes as reliable as possible. However, TO type photodiodes remain the best choice in terms of durability, reliability and price.

Summary:
By default, 2-pin photodiodes are used.

Detailed answer:
By default, 2-pin photodiodes are used. One pin is connected to the metal body of the photodiode and to the anode. The other pin is isolated and connected to the cathode. A 3-pin photodiode is characterized by two isolated pins (connected to the anode and cathode) and one pin connected to the metal case. The 3-pin photodiode is used if the photodiode package is in contact with metal components of the customer's product.

Summary:
The response time is about 190ps (FWHM).

Detailed answer:
At the Helmholtz-Zentrum Berlin, investigations were carried out on pulse excitation with 266 nm fs laser pulses. The response time of the measured SiC photodiodes is determined by a decay constant of 7 ns at 0 V BIAS voltage. At a maximum BIAS voltage of -160 V, this converges in an exponential relationship towards 3.5 ns. The rise time could not be measured precisely with the available setup, but is faster than 80 ps (sigma), i.e. approx. 190 ps (FWHM).

Summary:
An S-chip type photodiode saturates at around 4.2 kW/cm². Such a high irradiance is very unusual.
Detailed answer:
The saturation current Isat of a photodiode is determined by its open circuit voltage VOC and its series resistance RS according to the formula: Isat = VOC / RS A typical value (SiC photodiode) for VOC is 2.0 V and for RS = 5 Ohm. This gives Isat = 2.0 V / 5 Ohm = 0.4 A = 400 mA. The saturation radiant intensity z is calculated using the formula below: z = Isat / (S * A) Where S is the sensitivity of a photodiode and A is the active area. A typical value for S is 0.16 A/W and A = 0.06 mm² (valid for SG01S). This gives: zsat = 0.4 A / (0.160 A/W * 6 * 10-8 m²) = approx. 42 MW/m² = 4.2 kW/cm². Such a high irradiance is very unusual. However, some laser measurement applications can reach such irradiance levels for short periods of time. This may affect the output current of the photodiode. Please contact us for further information.

Summary:
Yes.

Detailed answer:
Yes, the photodiode is hermetically sealed and, accordingly, water pressure proof. However, the rear side contact pins must not get in contact with water our moisture. This will influence the photodiode’s output current.

A TOCON is a UV photodetector that contains a SiC or a GaP detector chip and an amplifier circuit that outputs a voltage of 0 to 5 V. This output voltage is linear in proportion to the UV radiation intensity reaching the chip.

Compared with a bare UV photodiode the TOCON’s big advantage is the amplifier’s position inside the TO5 metal housing and its close proximity to the detector. This construction protects the usually very low current levels generated by the detector chip from electromagnetic interference and also from moisture and pollution induced disturbances. A point to be considered of the TOCON is the lower dynamic range (approx. 3 orders of magnitude) compared with a SiC UV photodiode (10 orders of magnitude). To overdome this disadvantage we offer each TOCON type in many different amplification levels to avoid saturation and too low voltage output levels for nearly all applications.

A TOCON is smaller and much less expensive than a sensor probe. Additionally a TOCON is water pressure proof and hermetically sealed. A point to be considered is that at the presence of strong electromagnetic interferences or in case of excess voltage a sensor probe could be of a better performance. The reason is that a sensor probe contains more space that is needed for components that avoid problems caused by ESD or excess voltage.

No, the TOCON is not calibrated. If required, the sglux calibration laboratory offers an individual calibration service including a calibration certificate. This document assigns the voltage output of one specific TOCON to the irradiation of a specific UV radiation source. 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 below the saturation point will not further increase the output voltage.

The theoretical maximum signal output is always a little less (approx. 5%) than the supply voltage.

No, no additional amplifier is required.

Please use a standard voltmeter to read out the signal. Caution! Wrong wiring of power supply can lead to immediate destruction of the device. Please refer to our application note delivered with the device.

A TOCON is a sophisticated product with many internal components. Many of these internal components, and especially the quantum efficiency of the UV-sensing SiC chip and the gain resistor value, have sample to sample scatter (variation). TOCONs are designed for a total scatter of +/-20% in signal and some devices will show greater variance. It is recommended that that when choosing a TOCON model for production, the TOCON should be chosen so that the 5V saturation level is TWICE the expected signal from the device under normal conditions and that under normal/design conditions, output voltage is about 2.5V. 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.

The TOCON can drive resistive loads as low as 2 kOhms, but we recommend not to stress this limit unnecessarily. In normal environments an input impedance of >= 100 kOhm is recommended for the readout circuitry. In very harsh (EMI/EMC/noisy) surroundings impedances of >= 10 kOhm can be considered taking into account a slight reduction in output swing. 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.

No, the sensor is not calibrated. If required, the sglux calibration laboratory offers an individual calibration service including a calibration certificate. This document assigns the voltage output or the current value of one specific sensor to the irradiation of a specific UV radiation source. As-delivered the sensor is sensitive in the specified range. Please find further details at the sglux website’s calibration section.

All sglux sensors are supplied with shielded cables. The shield must be earthed by the user on the measuring device side. On the sensor side, the shield is not connected to the sensor housing in order to avoid ground loops in the event of contact with a system housing with a different potential than the measuring device.

All our PTFE sensors (UV-Cosine, UV-Water-PTFE and UV-Radial) are generally suitable for this purpose and are supplied with a special cable gland.

Our standard stainless steel is 1.4404, but we can also manufacture our sensors in other steel grades on request.

All stainless steel sensors can also be used at higher temperatures. These must then be configured with a photocurrent output, which is connected to an external amplifier such as the RADIKON_simple.

By default our sensors do have a large time constant because most applications measure slowly changing signals. The time constant depends on the sensitivity of the device and ranges between 50ms and 200ms. For detection of Xenon flash light or pantograph arc detection according to EN 50317 we produce special solutions with application adapted time constants. If for other applications a shorter time constant than 50 ms … 200 ms is needed we are happy to produce a customized version. Time constant reduction is possible down to 100 µs depending on the irradiance level of the application (gain value).

We offer our UV-Cosine sensor for outdoor measurements. The housing is waterproof IP68 at window side, stain repellent and on request submersible.

sglux offers the UV transmitter, a solar-powered network node with a connection to the mobile phone network or the UVMicrolog data logger. Both devices can be equipped with different sensors and different calibrations.

sglux is specialized in in-line monitoring, i.e. the continuous monitoring of emitters using permanently installed sensors. By using the radiation-hard semiconductor material SiC, this is also possible at very high irradiation. If the design of the system does not permit in-line monitoring, the uvLink or the UVMicrolog can move across the conveyor belt.

sglux offers the UVRRM reference radiometer, which is approved for many years. If more than one or special calibrations are required (e.g. LED), the UV Radiometer SXL 55 or the UVTOUCH should be used.

The current consumption of a Multiboard is between 4 mA and 20 mA, depending on the amount and type of operating voltage (uni / bipolar) as well as the load at the output (multimeter = no load).