The impact of humidity on GTD
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The impact of humidity on GTD

The impact of humidity on GTD

The influence of the humidity of the environment manifests itself in the form of water, rain, water vapor, drops, splashes, etc. Under the influence of moisture, metals are corroded, and dielectrics reduce their surface resistance. When testing the electronic controller for moisture resistance, the test regulator is placed in a humidity chamber in which the temperature is set according to the specifications, and then the humidity is raised to 95%. .98%. The regulator is maintained under these conditions for 2-10 days. Water permeability of the electronic regulator is determined by means of water falling on it (pouring or as a spray).

Mechanical effects. The impact of vibration, which is a periodic mechanical vibration, is especially dangerous when their frequency coincides with the frequency of the natural vibrations of the elements of the electronic regulator. Under certain conditions, mechanical resonance may occur, which usually leads to destruction of the equipment. The moment of occurrence of a resonance is determined with the help of strain gauges installed at the most critical points of the structure. An electronic regulator located on the engine must withstand sinusoidal vibrations with an acceleration amplitude of 20g in the 5 frequency range. .2000 Hz.

Impacts in the form of mechanical shocks occur with a sharp change in acceleration and are characterized by acceleration and duration. Blows occur under normal operating conditions YES during landing, taxiing or when YES unexpectedly collides with gusts of wind in flight. The purpose of the tests is to determine the stability of the equipment for impacts that occur when the landing is forced. When the electronic regulator is located on the motor, mechanical single and multiple impact loads are possible. The peak acceleration of a single shock load can reach 15g (duration 15 ms). With shock loads of multiple action, the peak acceleration reaches 8g (duration 20 ms).

The acoustic effects are kind of mechanical effects occurring at YES mainly because of the noise generated by the engines. Quantitatively, the acoustic noise is characterized by sound pressure and frequency range of sound vibrations. Acoustic noise in the installation of electronic regulator on the engine can reach a sound pressure level 150 dB (in the frequency range 0,1. 10 kHz).

In addition to climatic and mechanical testing of electronic control were tested for exposure to sand and dust, fungal formations, salt spray, and other hazardous liquids. The requirements for the stability of the equipment under the influence of external factors determined in accordance with specific standards.

Tests to confirm the reliability of

Reduce the number of defects associated with the climatic, mechanical and other types of impacts on the electronic controller allows full and thorough study of its design, the use of a special element base, efficient incoming inspection of purchased products of microelectronics and electrical engineering, the use of different types of training (thermal, mechanical and electrical) elements, circuit boards, components and blocks and ensure comfortable conditions electronic controller.

Cause of failure is the effect of temperature, vibration and humidity, and the place of manifestation of failure - connectors, electronic components and elements of the solder joints.

In the course of designing, manufacturing and testing of the electronic unit can not be avoided and engineering defects and errors in manufacturing. As a result, the actual MTBF prototype electronic device is significantly different from the settlement. This difference indirectly characterizes the design, technological and production level of the company. The tests focused on proactive identification of structural and technological defects electronic controller.

Prior to the operation to be confirmed MTBF actual HIL tests on the motor and the stands of two or more samples.

It is allowed to use accelerated equivalent-cyclic tests (UETCI). Modern methods of UECI are built on the basis of the use of forced regimes, which accelerate the physicochemical processes in the materials and structural elements of the tested electronic regulators, which contributes to the faster development of failures in them. Such conditions can be created by changing the nominal operating conditions of the electronic unit to more stringent temperature, vibration, humidity, supply voltage, implementing combined effects, as well as cyclic changes in external influences with increased frequency. The use of UECI makes it possible to accelerate the test several times.

5.4 Information and measuring systems for test benches for ACS

The information in the process of bench tests were prepared by ACS information-measuring system (IMS). The need to perform these functions in the transitional modes -

One of the main features of IIS in experimental studies of ACS. Depending on the objectives of the test units and systems GTD can be divided into three frequency ranges of measurement parameters:

(1) up to several hertz - for steady-state modes;

(2) to tens-hundreds of hertz - for transients;

(3) tens of kilohertz - for rapidly changing processes.

Thus, in determining the pressure and cavitation characteristics of the fuel pumping units of measurement are performed in the first frequency band in the control parameters for pick-up and verification of the accuracy of regulation - in the second, and the measurement of pressure pulsation and vibration in the diagnosis of buildings - in the third.

Means of measuring

When choosing the measuring instruments, the physical nature of the measured parameters, the range of their variation, the required accuracy in "statics" and "dynamics" are taken into account. In the ACS tests, the speed of rotation n, the pressure pb and the air temperature tB, the flow rate GT, the pressure pT and the fuel temperature tT, the displacement a of the controls, etc. are measured. The requirements for the measuring instruments also depend on the type of the test bench, the type of testing, the characteristics of the device under test. The measurement error can be estimated with respect to the parameter IV. For example, the range of the change in speed n is 0%. 110% with an allowable error of ± 0,1% .0,15% IV.

When testing machines and systems on non-motorized (laboratory, HIL) stands for selection of measurement criteria of accuracy is dependent on the tolerance D on the deviation of the measured parameter X according to the relationship:

Information-measuring system is a set of hardware and software, which can be made of concentrated or distributed scheme. The bench test complex IMS is one of the subsystems of a multi-level process control system testing.

The information-measuring system of a concentrated type has a centralized calculator and measuring channels (IR) of physical quantities, which, using a communication device with an object of the USO, are connected to a bench computer equipped with visualization and data storage devices. The measuring channel contains sensors D of the corresponding physical quantities with an output electrical signal, secondary transforming VIs and forming devices and communication lines J1C. To calibrate the sensors, special devices are used to automatically set the A3 of reference physical signals. Automatic switches can be used to ensure the operation of multi-range meters, etc.

The low-power signal output from the sensor is amplified in the VI and provides a normalized form: DC voltage, for example, ± 5, frequency 5. 500 Hz, amperage 4. 20 mA or converted into a digital signal.

The normalized output signal of the EP via J1C transferred to the USO. To receive the measurement signals of ODR has inputs from

sponding nomenclature, which via a multiplexer connected to the measuring device. The analog signals are converted to digital form by the ADC, the frequency - the number of counters by pulses.

The main characteristics of the ADC is the conversion, the number of effective bits of the conversion, the signal / noise ratio, differential and integral nonlinearity, and others. In order to measure signals in the first frequency band used as a rule, 14-24-bit, in the second - 12-14-bit in the third - 10-12-bit ADC. The latter frequency conversion reaches 0,5. 1 MHz.

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