gskin Instruction Manual for gskin Radiation Sensors
2 / 14 gskin Radiation Sensors: Instruction Manual CONTENT 1. SHORT USER GUIDE... 4 2. gskin RADIATION SENSOR INTRODUCTION... 5 3. FUNCTIONALITY TEST... 6 3.1. Checking electrical resistance of the sensor... 6 3.2. Checking sensor behavior between a temperature difference... 6 4. INSTALLATION OF A gskin RADIATION SENSOR... 7 4.1. Mounting substance... 7 4.2. Mounting... 8 5. SENSOR READ-OUT... 9 5.1. gskin DLOG Data Logger... 9 5.2. Voltmeter as read-out device... 9 5.3. 3 rd party read out devices... 10 6. DATA ANALYSIS... 11 6.1. Radiation measurement... 11 6.2. Temperature corrected sensitivity... 11 7. MAINTENANCE OF THE SENSOR... 12 7.1. Removing a sensor from a measurement setup... 12 7.2. Cleaning the sensor... 12 7.3. Storage... 12 8. GENERAL CONSIDERATIONS... 13 8.1. Cable extension... 13 8.2. Electromagnetic interference... 13 8.3. Trouble shooting electrical problems... 13 8.4. Application in temperatures outside of the operating temperature range... 13 8.5. Use in fluids... 13 9. LIST OF SYMBOLS... 14
3 / 14 gskin Radiation Sensors: Instruction Manual Preface gskin Radiation Sensors are Radiation Sensors of high quality. For taking benefit of their outstanding performance some precautions must be taken during storage, assembly and packaging. Therefore, please read the following instructions carefully. The exposure to volatile organic compounds requires special care, i.e. high concentration and long exposure time to specific chemicals shall be avoided. Such critical conditions are known to occur in manufacturing environment and/or at storage. Therefore, the handling and the choice of housing and packaging materials are crucial. Ambient conditions, however, do not affect the performance of the gskin sensors. Applicability This document is applicable to all gskin Radiation Sensors supplied by greenteg AG. This document is specifically applicable to gskin -XE 43 9R, gskin -XE 44 9R, gskin -XE 43 8R, gskin -XE 44 8R, gskin -XK 43 9R, and gskin -XK 44 9R.
4 / 14 gskin Radiation Sensors: Instruction Manual 1. SHORT USER GUIDE About the gskin Radiation Sensors The gskin Radiation Sensors measure the radiation power incident on its surface. It is based on the conversion of radiation into heat upon absorption. The high sensitivity of the thermopile modules coupled with the thin design and low thermal resistance ensures fast measurements with high precision. Prepare your measurement Procure a mounting substance (i.e. thermally conductive tape, past, or glue) to mount the sensor in your setup. Procure a read-out device (i.e. gskin DLOG Data Logger, voltmeter, or 3 rd party read out devices) Mounting the sensor Before attaching the sensor, the sensor must be tested as described in section 2. Once the sensor s functionality has been verified, the mounting surface has to be prepared. Figure 1: Schematic graph of gskin Radiation Sensor mounting and functionality. Ensure that the mounting surface is flat, dry, and free of dust and grease. Clean the backside sensor surface with ethanol or isopropanol. Do not use acids or bases for cleaning the sensor. Never clean an absorptive coating with any liquid. Mount the sensor using a mounting substance. A detailed description of the sensor mounting is given in section 4. How to calculate the incident power The power of the radiation incident to the sensor surface is proportional to the voltage output of the sensor. Its unit is W, and it is calculated using the following formula: Ф = U / Z [W] where U is the sensor output voltage, in V; and Z is the radiant sensitivity of the sensor, in mv/w.
5 / 14 gskin Radiation Sensors: Instruction Manual 2. gskin RADIATION SENSOR INTRODUCTION gskin Heat Flux Sensors without plug Absorptive side of the gskin Sensor gskin Heat Flux Sensors with plug Absorptive side of the gskin Sensor Figure 2: Absorptive side of the gskin -XE 43 9R sensor. Figure 3: Absorptive side of the gskin -XE 44 9R sensor. Positive and negative side of the gskin Radiation Sensor The gskin Radiation Sensor should be mounted with the absorptive side of the sensor in the direction of the expected incoming radiation. The radiation is transformed into heat in the absorber layer and leads to a heat flux through the sensor. A positive voltage signal is observed. However, the gskin Radiation Sensors detect heat flux signals bi-directionally: If the direction of the heat flux is reversed (e.g. because no radiation is present but substrate is warm compared to environment), the sign of the sensor voltage output changes (i.e. from positive to negative).
6 / 14 gskin Radiation Sensors: Instruction Manual 3. FUNCTIONALITY TEST All gskin Radiation Sensors are produced adhering to high manufacturing standards. Before shipping, the performance of every gskin Radiation Sensor is individually checked. However, external factors (e.g. transportation, prior use), might affect the functionality of the sensor module. Before permanent installation, the sensor functionality must be tested. This section describes the necessary steps to perform the functionality test. 3.1. Checking electrical resistance of the sensor Electrical resistance testing is performed using a standard multimeter. The resistance measurement must be done without any applied temperature gradient (e.g. with the sensor hanging in air). It is possible to measure the resistance under operating conditions, but it is not recommended. The resistance should be in the range specified in the datasheet. These values include the resistance of cables. While a resistance below 0.5 ohm indicates a short circuit, a resistance more than the value stated in the datasheet indicates physical wearout of the sensor or its cables. In both cases, the sensor is not functional and must be replaced. 3.2. Checking sensor behavior between a temperature difference Connect the sensor to a voltmeter (resolution preferably in the μv range). Place the sensor with the backside on a metallic surface at room temperature. Make sure, the contacts are not short-circuited via the metallic surface. When touching the sensor with a warm finger on the upper surface, you should get a signal in the mv range. Use the delivered protective foil or a thin polymer foil for protecting the absorptive side of the sensor when applying pressure. If the sensor signal does not increase significantly upon heat input on one side, a short circuit might be the reason. Check the electrical resistance again. If the signal randomly fluctuates between a positive and negative signal, or the voltages are in the saturation range of your multimeter, the electric contact is interrupted leading to an open circuit. Check the connection of your electrical probes. If they are in good contact with the cables and the signal show one of the three described features, the sensor is not functional and has to be replaced.
7 / 14 gskin Radiation Sensors: Instruction Manual 4. INSTALLATION OF A gskin RADIATION SENSOR This section describes the recommended mounting methods for the gskin Radiation Sensors. The application notes describe additional mounting options for specific measurement tasks. All application notes are available at www.. 4.1. Mounting substance In order to get meaningful measurement data, the gskin Radiation Sensor has to be mounted with adequate mounting substances. Adequate mounting substances feature high thermal conductivity and low thickness. Three types of mounting substance are suitable: thermally conductive tape, thermally conductive paste, and thermally conductive glue. greenteg offers a product for each of these three categories. The mounting substance should be chosen based on the measurement setup. Thermally conductive tape Thermally conductive tape should be used for simple tasks, where quick setup is crucial and the thermal coupling is of secondary importance. Clean the surface, where you want to measure radiation, and apply the tape to the backside of the sensor. Mount the sensor onto the surface by applying gentle pressure to establish the adhesion. Use a force below 2 kg/cm 2. Leave the protective foil on the sensor or place some polymer foil for protection of the absorber coating when applying pressure. Thermally conductive paste Thermally conductive paste is recommended for applications where gentle pressure is used to fix the gskin Radiation Sensor in the measurement setup. It generates a very strong thermal coupling as the paste adapts to surface inhomogeneities in the surface. Clean the surface, where you want to measure radiation, and spread a thin layer of paste onto the backside of the sensor. Then press the sensor gently onto the surface. Use a force below 2 kg/cm 2. Leave the protective foil on the sensor or place some polymer foil for protection of the absorber coating when applying pressure. You might need to hold the sensor in place with tape across the electric cables. Thermally conductive glue Thermally conductive glue is suitable for applications where additional mechanical stability is required. Like the thermal paste, it generates a strong thermal coupling and adapts to surface inhomogeneities. Clean the surface, where you want to measure radiation, and spread a thin layer of thermal glue onto the backside of the sensor. Then press the sensor onto the surface and follow the curing instructions of the glue. Use a force below 2 kg/cm 2. Leave the protective foil on the sensor or place some polymer foil for protection of the absorber coating when applying pressure. Removal of the mounting substance To remove the different mounting substances, refer to the respective manufacturer s instruction manual. If no instructions are available, contact the supplier. Isopropanol and ethanol can be used as cleaning agents whereas acids and bases must be avoided. Rub the surface gently with a soaked tissue to remove residues of the mounting substance.
8 / 14 gskin Radiation Sensors: Instruction Manual 4.2. Mounting The sensor responds to all three types of heat transfer: radiation, conduction, and convection. An instruction of how to minimize the influence of conductive and convective heat flux onto the radiation measurement is described in the radiation-specific application notes at www.. The following instructions explain how to obtain highly precise measurements for the radiation part. The scenario introduced here, can be adapted to suit other measurement situations. Figure 3: gskin Radiation Sensor mounted on a solid surface. Mounting instructions: 1. Select a suitable thermal stabilizer onto which the sensor can be mounted. The size of this stabilizer depends on the incident power you expect during the measurement. Further details can be found in the radiation specific application note, which can be found on www.. 2. Ensure that the surface of the stabilizer is flat, dry, and free of dust and grease. Clean the sensor backside surface with ethanol or isopropanol. Do not use acids or bases for cleaning the sensor. Leave the protective foil on the sensor or place some polymer foil for protection of the absorber coating when applying pressure. Apply the sensor using any of the above described mounting substances. When mounting the sensor, make sure no air is trapped between the surface and the sensor. Air gaps are thermally insulating and distort the measurement results strongly. 3. Mount the sensor with the absorptive side of the sensor in the direction of the incident radiation (as shown in Figure 3 4. Make sure that the contacts are not electrically short-circuited by the stabilizer surface. To avoid such an electric contact, you can place a small sheet of insulating material (e.g. scotch tape) below the crimp contacts. 5. Leave the protective foil on the sensor or place some polymer foil for protection of the absorber coating when applying pressure. Use a force below 2 kg/cm 2. 6. In order to ensure meaningful results, we recommend protecting the sensor from any convection. This is best achieved by placing a black coated cylinder around the sensor with its axis in the direction of the incoming beam. Alternatively, a glass slide or a lucent housing can be placed on top of the sensor. The absorption characteristics of such a cover have to be taken into account, however. 7. Bending the crimp contacts: For fitting the sensor in narrow locations, it might be necessary to bend the crimp contacts. Do not bend the contacts in an angle larger than +/- 15, and do not bend them repeatedly.
9 / 14 gskin Radiation Sensors: Instruction Manual 5. SENSOR READ-OUT The gskin Radiation Sensors output is an analog voltage signal. Depending on the measurement task, the voltage signal is in the µv to mv range. To read-out the sensor signal, three options are available: the gskin datalogger. The following section describes each option separately. DLOG Data Logger, a voltmeter, or a 5.1. gskin DLOG Data Logger The gskin DLOG Data Loggers are specifically developed for fast and straightforward radiation measurements with all gskin Sensors. The gskin DLOG Data Logger works as a complete solution and includes PC software. The gskin DLOG can be set to either measure the analog voltage signal (in V), or radiation signal (in W or W/m 2 ). Optionally, the gskin DLOG Data Loggers can be equipped with up to 2 temperature sensors. Detailed information is available at greenteg s webshop www.shop.. Applicability The gskin DLOG Data Logger is compatible with the gskin -XE 44 9R, gskin -XE 44 8R, and gskin -XK 44 9R. 5.2. Voltmeter as read-out device Voltmeters are used for simple measurement tasks and/or for sensor functionality tests. In order to read the output voltage of the sensor with high accuracy, you need a voltmeter with high resolution. The resolution of the radiation measurement is limited by the voltmeter resolution and noise. Table 1 demonstrates the importance of the voltmeter resolution. Voltmeter resolution of 1 mv Voltmeter resolution = 1 µv Radiation resolution [mw] 38.0 0.038 Table 1: Radiation resolution of a gskin -XE 43 9R Radiation Sensor with a sensitivity of 26.3 mv/w. The voltmeter resolution is the most critical feature when choosing the optimal device. Due to the low electrical resistance of the sensor, there are no special requirements regarding the input resistance of the voltmeter. The gskin Radiation Sensors can be used bi-directionally: If the direction of the radiation is reversed, the sign of the sensor voltage output changes (i.e. from positive to negative). The gskin Radiation Sensor should be mounted with the absorptive side (black side) of the sensor in the direction of the incident radiation. As the sensitivity of the sensor does not depend on the direction of the incoming radiation, the measurement of the reversed radiation has the same accuracy. However, on some voltmeters the measurement of negative voltages may not be possible or may be less accurate than the measurement of positive voltages. Applicability Voltmeters are compatible with the gskin -XE 43 9R, gskin -XE 43 8R, and gskin -XK 43 9R.
10 / 14 gskin Radiation Sensors: Instruction Manual 5.3. 3 rd party read out devices A data logger is highly recommended for the detection of time-dependent variations of the sensor signal. For the choice of the suitable device, the same considerations as for the voltmeter apply. Applicability Data loggers are compatible with the gskin -XE 43 9R, gskin -XE 43 8R, and gskin -XK 43 9R.
11 / 14 gskin Radiation Sensors: Instruction Manual 6. DATA ANALYSIS This section contains the basic analysis methods needed to interpret data from the gskin Radiation Sensors. More advanced methods are available in radiation-specific application notes at www.. 6.1. Radiation measurement The power of the radiation incident to the sensor surface is proportional to the voltage output of the sensor. Its unit is W, and it is calculated using the following formula: Ф = U / Z [W] where U is the sensor output voltage, in V; and Z is the radiant sensitivity of the sensor, in mv/w. 6.2. Temperature corrected sensitivity The sensitivity of the gskin Radiation Sensors depends on the temperature level at which they are used. The temperature-corrected sensitivity of the sensor is calculated using the following formula: Z = Zo + (T To) * Zc [mv/w] where Zo is the radiant sensitivity at calibration temperature, in mv/w; Zc is the linear correction factor for the radiant sensitivity, in (mv/w)/ C; To is the calibration temperature, in C; and T is the mean sensor temperature level, in C. Values Zo, Zc, and To are sensor specific calibration values. For uncalibrated sensors, the values Zo, Zc, and To are not provided. T can be determined by the following formula: T = (Th + Tc) / 2 [ C] where Th and Tc are the temperature of the absorptive side and the backside of the sensor, in C, respectively. If Th cannot be measured exactly, T is best approximated by using an estimate for the incoming radiation Ф and calculating T = Tc + (Ф * K)/2 [ C] where Ф is the expected power of the incoming radiation, in W; and K is the thermal resistance of the gskin Sensor, in K/W
12 / 14 gskin Radiation Sensors: Instruction Manual 7. MAINTENANCE OF THE SENSOR 7.1. Removing a sensor from a measurement setup If the gskin Heat Flux Sensor has been mounted using thermally conductive tape or paste, it can be easily removed without destroying the sensor. greenteg s thermally conductive tape and thermally conductive paste can be removed following the instructions mentioned in section 4.1. 7.2. Cleaning the sensor Cleaning is only necessary before mounting the sensor. Clean the sensor backside surface with ethanol or isopropanol. Once the sensor is mounted, no further cleaning is necessary. 7.3. Storage Store the unused gskin Radiation Sensors at ambient temperatures in a clean and dry place. In order to protect the absorber surface, put it back into the shipping package (wrap the sensor in the polymer foam). No further care is required.
13 / 14 gskin Radiation Sensors: Instruction Manual 8. GENERAL CONSIDERATIONS 8.1. Cable extension gskin Radiation Sensor with a plug (i.e. gskin -XE 44 9R, gskin -XE 44 8R, and gskin -XK 44 9R) gskin Radiation Sensors with a plug can easily be extended using the provided extension cable options. gskin Radiation Sensor without a plug (i.e. gskin -XE 43 9R, gskin -XE 43 8R, and gskin -XK 43 9R) gskin Radiation Sensors without a plug may be extended by any standard extension method (barrier strips, soldering, connectors, crimping etc). For noise suppression, we recommend using shielded cables. Make sure not to produce any short circuits. 8.2. Electromagnetic interference Due to the low electrical resistance of the sensor and the aluminum coating, the output signal is resistant to electromagnetic interference. In most cases, no countermeasures are necessary. If electromagnetic interference is a problem within an application, the typical countermeasures (e.g. shielded cables, grounding) have to be taken. 8.3. Trouble shooting electrical problems In case of electrical problems: check all connections and cables. Check for loose ends and/or short circuits in the leads. In some cases, corroded cables are the issue. If the problem cannot be located in the leads/cables, the sensor may be broken and has to be replaced. 8.4. Application in temperatures outside of the operating temperature range The operating temperature range of the gskin Radiation Sensors is stated in the respective data sheets. Outside of this range, the output voltage signal might take unexact values. 8.5. Use in fluids The sensor may be exposed to moisture or clean neutral water at temperatures less than 50 C (323.15 K) for a short time by insulating the connection between the wire and the measurement device properly. This may be done by sealing with lacquer, silicone rubber or similar materials. In these environments, it is recommended to mount the sensor with thermally conductive glue. However, long term exposure to wet ambient conditions is not recommended as this may corrode the metallic leads. However, long term exposure to wet ambient conditions is not recommended as this may corrode the metallic leads. In any case, do not expose the sensor to strong acids and bases.
14 / 14 gskin Radiation Sensors: Instruction Manual 9. LIST OF SYMBOLS Name Symbol Unit Radiation power Φ W Sensor output voltage (measured) U V Temperature corrected radiant sensitivity Z mv/w Radiant sensitivity at calibration temperature Zo mv/w Correction factor for radiant sensitivity Zc (mv/w)/ C Absolute thermal resistance K K/W Electrical resistance R Ohm Temperature of the hot side Th C Temperature of the cold side Tc C Calibration temperature To C Sensor temperature T C Sensor area A m 2 Sensor thickness d µm Disclaimer The above given restrictions, recommendations, materials, etc. do not cover all possible cases and items. This document is not to be considered to be complete and it is subject to change without prior notice. Revision History Date Revision Changes 12. November 2013 0.1 (preliminary) Initial revision