GB 15631-1995 Performance requirements and test methods for point-type infrared flame detectors
Some standard content:
National Standard of the People's Republic of China
Performance requirements and test methodsfor point infrared flame detectors1 Subject content and scope of application
1.1 Subject content
GB 15631—1995
This standard specifies the performance requirements, test methods and markings for point infrared flame detectors (hereinafter referred to as detectors) with a wavelength greater than 850nm.
1.2 Scope of application
This standard applies to point infrared flame detectors installed in general industrial and civil buildings. For detectors with special performance installed in special environments, this standard shall also be implemented unless the special performance requirements are separately specified by relevant standards. 2 Reference standards
GB12791 Performance requirements and test methods for point-type ultraviolet flame detectorsGB12978 Inspection rules for fire alarm equipment
GB2423.1 Basic environmental test procedures for electric and electronic productsTest A: Low temperature test method Basic environmental test procedures for electric and electronic productsTest A: Low temperature test method GB 2423.1
Basic environmental test procedures for electric and electronic productsTest B: High temperature test method GB 2423.2
GB2423.3 Basic environmental test procedures for electric and electronic products Test Ca: Steady-state damp heat test method GB2423.10 Basic environmental test procedures for electric and electronic products Test Fc: Vibration (sinusoidal) test method GB2423.19 Basic environmental test procedures for electric and electronic products Test Kc: Sulfur dioxide test method for contact points and connectors 3 Performance requirements
3.1 When a fire occurs in the monitored area and the fire parameters reach the specified value, the detector should output a fire alarm signal and start the detector's alarm confirmation light or other display with the same function. 3.2 The detector should withstand the tests specified in Chapter 4 of this standard and meet all the requirements of this standard. 4 Test methods
4.1 General requirements for tests
4.1.1 Test the detector according to the provisions of Appendix A. Eight detectors are required for each test. 4.1.2 The application documents to be submitted for testing shall comply with the provisions of Article 4.1.4 of GB12978. 4.1.3 The detector shall be inspected for appearance before testing. The test can be carried out only when it meets the following requirements: a. There is no corrosion, coating peeling, blistering, obvious scratches, burrs or other mechanical damage on the surface; b. The text symbols and signs are clear and the structure is not loose. Approved by the State Administration of Technical Supervision on July 19, 1995 36
Implemented on February 1, 1996
GB15631-1995
4.1.4 If there is no explanation in the relevant clauses, all tests shall be carried out under the following normal atmospheric conditions: temperature: 15~35℃; relative humidity: 45%~75%; pressure: 86~106 kPa.
4.1.5 If there is no explanation in the relevant clauses, the tolerance of each test data is ±5%. 4.1.6 If the detector is required to be powered on during the test, the detector should be powered on according to the requirements of the manufacturer. 4.1.7 If the sensitivity of the detector depends on the judgment of the fire alarm controller, the fire alarm controller shall set the maximum and minimum limit values of the sensitivity of the detector for testing, and the test results shall meet the requirements of Article 4.21. 4.1.8 The following tests specified in this standard are type inspections. 4.2 Response threshold test
4.2.1 Purpose
Test the response threshold of the detector.
4.2.2 Equipment
The detector response threshold detection device is a special device (as shown in Figure 1). It consists of an optical track, an infrared light source, an infrared dimming film, a modulator, an aperture, a detector mounting bracket and other relevant test and recording equipment. The device shall meet the test requirements of Articles 4.2, 4.4, 4.5, 4.6, 4.7 and 4.8.
Figure 1 Infrared flame detector detection device
1 Optical track; 2-photomultiplier tube; 3-carrying stop light reduction film: 4-cooling chamber; 5 light source; 6-shutter: 7-IR filter; 8-aperture; 9-detector; 10 reader 4.2.2.1 Optical track
Main technical parameters
Length 2: 2000mm2
Straightness: less than 0.04mm
4.2.2.2 Infrared light source
The infrared light source uses the flame generated by the combustion of gasoline gasification gas. During the entire test process, the change in its radiation energy measured by a radiometer at a distance of 1500mm from the light source should not be greater than 20%. During the test, the light source should always remain stable. In order to avoid the flickering of the flame itself caused by the fluctuation of the surrounding air, a special gasoline gasification burner is used, and its combustion chamber is not affected by the airflow outside. The combustion chamber is cooled by water circulation to avoid the influence of thermal radiation from the combustion chamber during the combustion process. 37
4.2.2.3 Infrared dimmer
GB15631—1995
The infrared dimmer plays the role of attenuating infrared radiation. This detection device uses a neutral infrared dimmer, which can pass infrared radiation with a wavelength greater than 850nm. Its transmittance depends on the specific test conditions. 4.2.2.4 Modulator
The modulator consists of a chopper and a DC motor. The chopper driven by the DC motor rotates at a basic frequency of 12.5Hz in front of the aperture and the dimmer to modulate the infrared radiation generated by the combustion (as shown in Figure 2). 4.2.2.5 Aperture
The aperture plays the role of attenuating the radiation of the standard flame. Its aperture range is 4 to 10mm. The aperture itself should be blackened and the surface should not reflect light.
New Optical Device
Figure 2 Schematic diagram of modulator
4.2.2.6 Mounting bracket
The mounting bracket can be installed with detectors of different models of bases and can slide along the optical track. Its height is adjustable and it can rotate 180° with the vertical line of the axis of the optical track as the axis. The bracket itself should be blackened and no light reflection should occur on the surface. 4.2.3 Test method
Before the test, the detector is installed on the mounting bracket of the test device so that it is on the same horizontal axis as the standard light source and can receive the radiation of the infrared light source to the maximum extent. It is connected to the control or indication equipment to keep it in a normal monitoring state and remain stable. Use a radiometer to measure the radiation energy of the light source at a distance of 1500mm from the light source and observe its changes. Move the mounting bracket of the detector to a distance of 1500mm from the light source. 4.2.3.1 Try to find the detector response point
Repeatedly move the detector mounting bracket along the optical track to determine the maximum distance D at which the detector can reliably respond within 30 seconds. The point corresponding to this distance on the optical track is the detector response point. According to the optical principle, the square of the distance D between the detector response point and the light source is inversely proportional to the effective power S radiated by the light source to the detector sensing surface, that is:
where K is the transformation constant.
GB15631-1995
For detectors with random response characteristics, the response threshold must be repeatedly measured at least 6 times until the change in the next response threshold does not exceed 10% of the average value of the response threshold values measured in the previous few times. For detectors with frequency band characteristics, the modulator must be adjusted to the flicker frequency given by the manufacturer (including 0). 4.2.3.2 Calculation of response threshold ratio
When the measured radiation energy of the light source changes by more than 5% but less than 20%, the response threshold ratio Smax:Smin of the detector should be calculated by multiplying or dividing by the correction factor P1/P2.
PI: Radiant energy measured in the first test; P2: Radiant energy measured in the second test. 4.3 Power-on test
4.3.1 Purpose
To test the stability of the detector under normal atmospheric conditions. 4.3.2 Method
Test the D value of the detector response point in accordance with the provisions of 4.2.3. Allow it to run continuously for 7 days under normal monitoring conditions. After the operation is completed, measure the D value of the detector response point in the same measurement direction as before the operation in accordance with the provisions of 4.2.3, and compare it with the D value in the consistency test of the detector to determine Dmax and Dmin, and calculate the response threshold ratio Smax:Smin. 4.3.3 Test equipment
Infrared flame detector detection device.
4.3.4 Requirements
a. During the test, the detector should not send out a fault or fire alarm signal; b. The response threshold ratio Smax:Smin should not be greater than 1.3. 4.4 Repeatability test
4.4.1 Purpose
Test the repeatability of the detector response value. 4.4.2 Method
According to 4.2.3 stipulates that the response threshold is measured 6 times continuously at any position of the detector's normal working position. The maximum value of the 6 response thresholds is represented by Dmax, and the minimum value is represented by Dmin. Finally, the response threshold ratio Smax:Smin is calculated. 4.4.3 requires that the response threshold ratio Smx:Smin should not be greater than 1.3. 4.4.4 Test equipment
Infrared flame detector detection device.
4.5 Azimuth test
4.5.1 Purpose
To test the response performance of the detector in different viewing angles, so as to determine the "viewing cone angle range" of the detector. 4.5.2 Method
To test the D value of the detector response point according to the method specified in Article 4.2.3. Each time the detector is measured, the detector is rotated by an angle so that the angles between the axis of the detector viewing cone angle and the optical axis are 0°, 15°, 30°, and 45° respectively. If the viewing angle range specified by the manufacturer's technical standard is greater than 45°, the rotation angle shall be carried out according to the manufacturer's regulations).
4.5.3 Requirements
The response threshold ratio Smax:Smin should not be greater than 2.0. 39
4.5.4 Test equipment
Infrared flame detector detection device.
4.6 Consistency test
4.6.1 Purpose
To test the consistency of the detector response threshold. GB15631—1 995
4.6.2 Method
Test the D values of the detector response points of the eight detectors according to the provisions of Table A1 in the Appendix and the method specified in Article 4.2.3, and determine Dmax and Dmin from them, and calculate the response threshold ratio Smax:Smin. 4.6.3 Requirements
The response threshold ratio Smax:Smin should not be greater than 2.0. 4.6.4 Test equipment
Infrared flame detector detection device.
4.7 Voltage fluctuation test
4.7.1 Purpose
To test the adaptability of the detector to work under the condition of rated working voltage fluctuation. 4.7.2 Method
According to Article 4.2.3, the rated working voltage is reduced by 15% and increased by 10% to measure the response threshold. Compared with the response threshold of the detector in the consistency test, the Dmax and Dmin values are determined from the three, and the response threshold ratio Smax is calculated. : Smin.
4.7.3 Requirements
The response value ratio Smax:Smin should not be greater than 1.6.4.7.4 Test equipment
Infrared flame detector detection device.
4.8 Ambient light test
4.8.1 Purpose
To test the stability of the performance of the detector under the action of ambient light. 4.8.2 Method
Fix the detector on the fixing surface of the mounting bracket in the normal working position, and turn on the control and indicating equipment to put it in the normal monitoring state.
Before the test, install the ambient light interference simulation device (referred to as the light interference device, as shown in Figure 3) between the infrared standard light source and the detector, and make the distance between it and the detector 200mm. 40
Test steps:
GB 15631—1995
Figure 3 Ambient light interference test devicewwW.bzxz.Net
1—Incandescent lamp 2—Ring fluorescent lamp 3—Detector Irradiate with two 25W incandescent lamps (color temperature is 2850±100K) for 1h; irradiate with a 308mm diameter, 30W ring fluorescent lamp (color temperature is about 4900K) for 1h; irradiate with two 25W incandescent lamps and a 308mm diameter, 30W ring fluorescent lamp for 1h at the same time; make the interference light sources of the above three light interference devices be energized for 1s and de-energized for 1s at the same time and repeat ten times. d.
After the above test, test the D value of the detector response point according to the method specified in Article 4.2.3, and compare it with the D value of the detector in the consistency test, determine the Dmax and Dmin values, and calculate the response threshold ratio Smax:Smin. 4.8.3 Requirements
a. The detector should not send out a fault or fire alarm signal during the test; b. The response threshold ratio SmaxSmin should not be greater than 1.3. 4.8.4 Test equipment
Infrared flame detector detection device.
4.9 High temperature test
4.9.1 Purpose
To test the adaptability of the detector under high temperature conditions. 4.9.2 Method
Place the detector and its base in a high temperature test chamber, and connect the control and indicating equipment to put it in a normal monitoring state. Under the condition of 23±5℃, at a heating rate of no more than 0.5℃/min. Raise the temperature to 55±2℃ and keep it under this condition for 2h. Take out the detector and place it under normal atmospheric conditions for 1h. Then test the response point D value according to the method specified in Article 4.2.3, and compare it with the D value of the detector in the consistency test, determine the Dmax and Dmin values, and calculate the response threshold ratio Smax:Smin. 4.9.3 Requirements
The detector should not send out fault or fire alarm signals during the test; the response threshold ratio Smax:Smin should not be greater than 1.3. b.
4.9.4 Test equipment
The test equipment (high temperature test chamber) should comply with the provisions of Chapter 4 of the national standard GB2423.2. 41
4.10 Low temperature test
4.10.1 Purpose
GB15631-1995
To test the adaptability of the detector for use in low temperature environments. 4.10.2 Method
Place the detector and its base in the low temperature test chamber, and connect the control and indicating equipment to put it in normal monitoring state. Keep the temperature at 15-20℃ and relative humidity not more than 70% for 1 hour, then reduce the temperature to -10℃ at a cooling rate not more than 0.5℃/min, and stabilize under this condition for 2 hours (the detector should not be frozen in the test chamber). After the low-temperature stabilization period, turn off the control and indicating equipment, take out the detector, and restore it in an environment with a temperature of 15-25℃ and a relative humidity of not more than 70% for 1-2 hours, then test its response point D value according to the method specified in Article 4.2.3, and compare it with the D value of the detector in the consistency test, determine the Dmax and Dtmin values, and calculate the response threshold ratio Smax:Smin. 4.10.3 Requirements
a. The detector should not send out a fault or fire alarm signal during the test; b. The detector should not have any damage to the coating and corrosion after the test; C. The response threshold ratio Smax:Smin should not be greater than 1.3.4.10.4 Test equipment
The test equipment (low temperature test chamber) should comply with the provisions of Chapter 4 of the national standard GB2423.1. 4.11 Impact test
4.11.1 Purpose
To test the adaptability of the detector to non-multiple repetitive mechanical impacts and the integrity of its structure. 4.11.2 Method
Install the detector and the base in the center of the bottom surface of the wooden beam of the impact test equipment (as shown in Figure 4) according to their normal working positions, and turn on the control and indication equipment to put it in a normal monitoring state. Adjust the test equipment, and drop a cylindrical steel block with a mass of 1kg vertically from a height of 700mm along the guide device to the center of the top surface of the wooden beam. The impact area is 18cm2±10%, and the drop is 1 time. After the test, the D value of the response point shall be tested according to the method specified in Article 4.2.3, and compared with the D value of the detector in the consistency test, the Dmax and Dmin values shall be determined, and the response threshold ratio Smax: Smin shall be calculated. 4.11.3 Requirements
The detector shall not send out fault or fire alarm signals during the test; a.
b. The detector shall not have mechanical damage and loose fastening parts after the test; the response threshold ratio Smx: Smin shall not be greater than 1.3. c.
4.11.4 Test equipment
The main body of the test equipment (see Figure 4) is a wooden beam support device. The wooden beam is made of pine wood and has a cross-sectional size of 100mm×50mm. The narrow side of the wooden beam is fixed on two pine wood legs with a width of 50mm. The legs are placed on a flat cement floor and have sufficient height so that the detector does not touch the ground. The legs are at right angles to the longitudinal axis of the wooden beam, and the center distance between the two legs is 900mm. 42
4.12 Impact test
4.12.1 Purpose
GB15631--1995
Figure 4 Impact test equipment diagram
This distance should ensure
the detector does not touch the floor
a—1 kg steel block; b—guide rod; c—wooden beam; d—nut and gasket; e—wooden support foot; f detector to test the adaptability of the detector to withstand mechanical impact. 4.12.2 Methods
Install the detector and base on the rigid horizontal mounting plate of the collision test equipment in their normal working positions (as shown in Figure 5), and turn on the control and indication equipment to put it in normal monitoring state. Adjust the collision test equipment so that the center of the hammer impact surface can hit the detector from the horizontal direction and align it with the part of the detector that is most vulnerable to damage. Then, hit the detector with a hammer speed of 1.5±0.125m/s and a collision kinetic energy of 1.9±0.1J. After the collision, test the D value of its response point according to the method specified in Article 4.2.3, and compare it with the D value of the detector in the consistency test to determine the Dmax and Dmin values, and calculate the response threshold ratio Smax:Smin
4.12.3 requirements
The detector should not send out a fault or fire alarm signal during the test; after the test, there should be no loosening or displacement between the detector and the base, and between the base and the mounting plate; b.
The response threshold ratio Smax:Smin should not be greater than 1.3. c.
4.12.4 Test equipment
The main body of the test equipment (see Figure 5) is a pendulum mechanism. The hammer of the pendulum is made of hard aluminum alloy AlCu4SiMg (solid solution and aging treatment), and its shape is a hexahedron with an inclined collision surface. The hammer pendulum is fixed on a steel wheel hub with a ball bearing, and the ball bearing is installed on a fixed steel shaft of a hard steel frame. The structure of the hard steel frame should ensure that the pendulum can rotate freely when the detector is not installed. The overall dimensions of the hammer are 94mm long, 76mm wide and 50mm high. The angle between the chamfered surface of the hammer and the longitudinal axis of the hammer is 60°±1°, the outer diameter of the pendulum of the hammer is 25±0.1mm, and the wall thickness is 1.6±0.1mm. The radial distance between the longitudinal axis of the hammer and the axis of rotation is 305mm, and the axis of the pendulum of the hammer must be perpendicular to the axis of rotation. The steel wheel hub with an outer diameter of 102mm and a length of 200mm is concentrically assembled on a steel shaft with a diameter of 25mm. The accuracy of the diameter of the steel shaft depends on the tolerance of the bearing size used.
Two steel counterweight arms with an outer diameter of 20mm and a length of 185mm are installed on the steel wheel hub in the direction opposite to the swing rod, and their extended length is 150mm. An adjustable counterweight block is installed on the two counterweight arms to balance the hammer head with the counterweight arm. An aluminum alloy pulley with a thickness of 12mm and a diameter of 150mm is installed at one end of the steel wheel hub. A cable is wound around the pulley. One end of the cable is fixed to the pulley, and the other end is tied to the working hammer.
GB15631—1995
Figure 5 Collision test equipment diagram
a—mounting plate; b—detector; c—hammer; d—pendulum rod re steel wheel hub, f—ball bearing ig—rotate 270°h—working weight; —counterweight, k—counterweight arm; l—pulley The horizontal mounting plate of the detector is supported by a steel frame, and the mounting plate can be adjusted up and down so that the center of the collision surface of the hammer head hits the detector from the horizontal direction. When using the test equipment, first adjust the position of the detector and the mounting plate. After adjustment, fasten the mounting plate to the steel frame, then remove the working weight, and balance the pendulum mechanism by adjusting the counterweight. After adjusting the balance, pull the pendulum rod to a horizontal position and tie the working weight. When the pendulum mechanism is released, the working weight will cause the hammer head to rotate rad to hit the detector.
The mass of the working weight is:
Where: r—effective radius of the pulley m. When r is 75mm, the mass of the working weight is about 0.55kg, and the mass of the hammer head is about 0.79kg.
4.13 Vibration test
4.13.1 Purpose
To test the adaptability of the detector to withstand vibration and the integrity of its structure. 4.13.2 Method
Install the detector and the base on the vibration table in their normal working positions and put them in normal monitoring state. Perform a frequency sweep cycle on three mutually perpendicular axes in the frequency cycle range of 10～150~～10Hz, with an acceleration amplitude of 9.81m/s2 and a sweep rate of 1 octave/min to check for dangerous frequencies. If there is a dangerous frequency, the detector shall be subjected to a fixed-frequency vibration test with an acceleration amplitude of 9.81m/s and a duration of 90±1min at each dangerous frequency on three mutually perpendicular axes; if there is no dangerous frequency, the detector shall be subjected to a fixed-frequency vibration test with a frequency of 150Hz, an acceleration amplitude of 9.81m/s2 and a duration of 90±1min on three mutually perpendicular axes.
Then, test the D value of the response point according to the method specified in Article 4.2.3, and compare it with the D value of the detector in the consistency test to determine Dmax and Dmin, and calculate the response value ratio Smax:Smin. 4.13.3 Requirements
GB15631—1995
: The detector shall not send out a fault or fire alarm signal during the test; b. After the test, the detector shall have no mechanical damage and loose fastening parts; the response threshold ratio Smax:Smin shall not be greater than 1.3. C
4.13.4 Test equipment
The test equipment (vibration table and fixture) shall comply with the provisions of Article 3.1 of GB2423.10. 4.14 Electrostatic discharge test
4.14.1 Purpose
To test the resistance of the detector to electrostatic discharge caused by contact with live personnel and objects. 4.14.2 Method
Place the detector and the base on the test grounding plate, and the distance from the edge of the grounding plate shall not be less than 100mm. Turn on the control and indicating equipment to put it in normal monitoring state. Adjust the output voltage of the electrostatic discharge generator to 8000V, charge the electrostatic discharge probe connected to the 150pF energy storage capacitor and the 1502 resistor to 8000V, and discharge the detector through the 150Q resistor. After each charge, the electrostatic discharge probe should be immediately touched to a test point on the detector housing. Regardless of whether arc discharge occurs, the probe tip must be in solid contact with the test point. Electrostatic discharge shall be conducted 10 times at different test points of the detector housing (bottom surface and measuring surface), with the time interval between each discharge being at least 1s.
After the test, the D value of the response point shall be tested according to the method specified in Article 4.2.3, and compared with the D value of the detector in the consistency test, to determine Dmax and Dmin, and calculate the response threshold ratio Smax: Smin. 4.14.3 Requirements
a. The detector shall not issue a fault or fire alarm signal during the test; b. The response value ratio Smax: Smin shall not be greater than 1.3. 4.14.4 Test equipment
4.14.4.1 Electrostatic generator: output voltage 8000V ± 10%, its electrical schematic diagram is shown in Figure 6, and the output current waveform is shown in Figure 7. 4.14.4.2 Electrostatic discharge probe: the discharge end is a $8 sphere, and the connector and the rear hemisphere are covered with insulating material. 4.14.4.3 Grounding wire: The grounding wire of the DC power supply and the electrostatic discharge probe used in the electrostatic discharge test must be connected to the grounding wire of the power plug together with the grounding plate.
=150pF
Figure 6 Schematic diagram of electrostatic discharge generator
. Discharge probe
Safety grounding wire
4.15 Radiated electromagnetic field test
4.15.1 Purpose
GB156311995
5ns±30%
30ns±30%
Figure 7 Output current waveform of electrostatic generator
To test the adaptability of the detector to work in the radiated electromagnetic field environment. 4.15.2 Method
Place the detector and the base on the insulation test bench, turn on the control and indicating equipment, and put it in normal monitoring state. Connect the test equipment as shown in Figure 8, place the transmitting antenna in the middle, and place the detector and the electromagnetic interference meter antenna 1m on both sides of the transmitting antenna. Adjust the output of the 1~500MHz power signal generator so that the reading of the electromagnetic interference meter is 10V/m. During the test, the frequency should change slowly at a rate not greater than 0.005 octave/s within the frequency range of 1~500MHz. At the same time, the detector should be rotated to observe and record the working conditions of the detector. If the transmitting antenna used is directional, the transmitting antenna should be aligned with the electromagnetic interference meter antenna first, and the output of the power signal generator should be adjusted to 10V/m. Then, the position of the transmitting antenna should be reversed and aligned with the detector for testing. Within the frequency range of 1~500MHz, the test should be carried out with the horizontal polarization and vertical polarization of the antenna respectively. The test should be carried out in a shielded room. To avoid large measurement errors, the position of the antenna should meet the requirements of Figure 9. After the test, test the D value of the response point according to the method specified in Article 4.2.3, and compare it with the D value of the detector in the consistency test to determine Dmax and Dmin, and calculate the response threshold ratio SmaxSmin. 4.15.3 Requirements: The detector should not send out fault or fire alarm signals during the test; the response threshold ratio Smax:Smin should not be greater than 1.3.1m
Electromagnetic interference measuring instrument
Power signal generator
Detector
Transmitting antenna
Figure 8 Layout of test equipment
4.15.4 Test equipment
Obstacles or screen wallsIndoor walls
GB 15631--1995
Tested instrument
Transmitting line
Electromagnetic interference
Measurement instrument antenna
Figure 9 Antenna position diagram
4.15.4.1 Power signal generator (or signal generator and power amplifier) a.
Frequency range: 1～500MHz;
Output power: Should be able to provide sufficient power to meet the requirement of generating 10V/m electromagnetic field 1m away from the transmitting antenna, and the output b.
Power is adjustable;
Sweep frequency rate: less than 0.005 octave/s. c.
4.15.4.2 Electromagnetic interference measurement instrument: Should meet the technical requirements of GB6113 "Electromagnetic interference measurement instrument". 4.15.4.3 Transmitting antenna
1～30 MHz
20~~200 MHz
Long-wire antenna;
Biconical antenna;
200~500MHz
Helical antenna:
Other antennas that meet the test requirements may also be used. 4.16 Electrical transient test
4.16.1 Purpose
To test the adaptability of the detector to work under the interference conditions caused by electrical transients. 4.16.2 Method
Connect the detector to the control and indicating equipment to put it in normal monitoring state. Carry out the following tests on each external connection line of the detector: a.
Apply a positive and negative polarity transient voltage of 1000V±10% and a frequency of 5kHz±20% (see waveform in Figure 10); apply a transient pulse of 15ms every 300ms (see Figure 11); b.
Test time is 2min.
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