Signal test

The most important and substantial, by the time and volume of work required, are those tests where the determination of main metrological characteristics, at which the evaluation of the influence of various external factors on the sensor s sensitivity is performed, should be done. A aoss-sensitivity test to other gases, impact of the presence of humidity on the sensor output signal test at different temperatures, a vibration test, a thermoshock test, and other tests imitating the extreme working conditions of the sensor will follow afterwards. 

In addition, the sensor principle permits a complete self-test of the sensor, including the rotary oscillator (BITE = built in test). For the self-test, the rotary oscillator is deflected electrostatically via additional electrodes between the oscillator and the substrate. The sensor structure reacts to this in precisely the same way as if a turning movement has occurred the sensor detects a turning-rate signal. Testing is also possible during operation and thus permits a permanent function monitoring. 

Interference immunity testing, SRECS should, wherever practicable, be loaded with a typical application program, and all the peripheral lines are subjected to standard noise signals. Testing for immunity to EM-interference need not be performed where adequate immunity of the SRECS for its intended application can be shown by analysis. 

The connections of the capillary to the detector, injector and the insert are additional and frequent trouble spots. Injeetion of 2 mL of dichloromethane into the closed oven is a useful overall leak test. A rapid response of the detector (10-20 s) indicates a leak near the detector, a signal delayed by the residence time in the column (eg., 60s for a 30m column length) indicates a leak near the injector. The more specific signal test is then applied as discussed above. Ferrules for the capillary are frequent sources of problems with some equipment. Graphite or vespel ferrules must have a 0.5 mm bore for a 0.32 mm i.d. column. 

IEEE Standard 1149.4-1999, Standard for a Mixed-Signal Test Bus, IEEE Inc., 345 E. 47th St., New... 

At these tests was parallel to vibrations observation discovered acoustic response of balls contact with sample surface. Characteristic courses of total number of AE signal counts (in all observed levels) dependence on time are shown on Fig.6. 

At contact fatigue tests of different steel and cast iron types was used the acoustic emission technique. Processed records from the AE analyser show importance of acoustic response of tested surface continuous sensing. In graphs are obvious characteristic types of summation curves, or may be from significant changes of AE signal course identified even phases of the wear process. 

Mechanical stretch tests were made with the speed of (0,3-3,0) 10" m/s and with the simultaneous registration of the AE signals. Number of the AE impulses (Nl ) and AE amplitude (A) were selected as the measurable parameters of the AE. 

For clutter suppression, the test statistic used by the noncoherent detector has been proposed as an interesting output signal [1], This was motivated by the fact that, provided that transient and noise models are valid, the test statistic reflects the likelihood that a transient is present. 

The technique presented above has been extensively evaluated experimentally using ultrasonic data acquired from a test block made of cast stainless steel with cotirse material structure. Here we briefly present selected results obtained using two pressure wave transducers, with refraction angles of 45° and 0°. The -lOdB frequency ranges of the transducers were 1.4-2.8 MHz and 0.7-1.4 MHz, respectively. The ultrasonic response signals were sampled at a rate of 40 MHz, with a resolution of 8 bits, prior to computer processing. 

Fokker Bond Tester. An ultrasonic inspection technique commonly used for aircraft structures is based on ultrasonic spectroscopy [2]. Commercially available instruments (bond testers) used for this test operate on the principle of mechanical resonance in a multi-layer structure. A piezoelectric probe shown in Figure 3b, excited by a variable frequency sine signal is placed on the surface of the inspected structure. A frequency spectrum in the range of some tens of kHz to several MHz is acquired by the instrument, see Figure 3a. 

The ultrasonic testing of anisotropic austenitic steel welds is a commonly used method in nondestructive testing. Nevertheless, it is often a problem to analyze the received signals in a satisfactory way. Computer simulation of ultrasonics has turned out to be a very helpful tool to gather information and to improve the physical understanding of complicated wave phenomena inside the samples. 

Signal Processing Algorithms in Mechanised Ultrasonic Testing. 

The operation is quite simple One sets the frequency to the lowest value, adjusts the gain and phase to the desired sensitivity using a special calibration standard discussed below and performs a zero-compensation on a defect free zone of the standard. Now one is ready to test. As one slides the probe across the surface of an aluminum structure, a signal response will be indicative of the presence of corrosion or of the presence of a subsurface edge. 

---