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66 -- ANALOG PORTION OF EMAT MEASUREMENT SYSTEM AND EMAT PORTION OF PORTABLE EMAT MEASUREMENT SYSTEM SOL NB85303258MAB POC Michelle Bernal, Purchasing Agent, (303) 497-3983 or FAX (303) 497-3163 E-MAIL: NOAA; MASC Acquisition Management, Joyce.J.Mills@noaa.gov. The National Institute of Standards & Technology (NIST) requires the analog portion of portable EMAT measuring system and the EMAT portion of portable EMAT measurement system. The analog portion of a Portable EMAT Measurement System and operating software for field thickness gaging and residual and applied stress determinations. (The complete measurement system will comprise of the analog portion, remote EMAT, operating software, and portable personal computer with internal analog-to-digital converter.) The system is intended primarily for time-of-flight applications using shear-wave EMATs operating a 2 MHz, assuming tone-burst excitation with typically 10 cycles per burst. The analog portion of the system must be capable of delivering at least 10 kWatts electrical peak power at 2 MHz to an EMAT load with 3-ohm resistance and 20-microHenry inductance. The single- shot time resolution of the system should be at least 2 ns when measuring time delay between multiple reverberations that typically existin a plate-like geometry. Typically, this performance level should be achieved in ferritic-steel plates 10 mm in thickness. Since the system is intended for real-time applications, digital signal averaging methods should not be used to improve the time resolution of the system. Although the nominal frequency of operation will be 2 MHz, the analog portion of the system should be capable of operating in the 500 kHz -5 MHz frequency region. All of the functions (frequency of operation, power and gain settings, and the like) should be externally settable using a standard personal computer operating under a Windows 95, or later, operating system. The personal computer, which will be supplied by NIST, will incorporate an 8- bit, 10 Ms/s digital-to-analog converter. It is desirable that the total package dimensions, including the personal computer, not exceed 12x12x18 inches. The documentation of the operating software should contain sufficient detail to enable NIST personnel to incorporate alternative time-measurement algorithms. Also, the documentation of the analog portion of the system should be sufficiently complete to enable NIST personnel to interface a range of EMAT probes and portable computers. The EMAT portion of the system should be a small, hand-held probe capable of generating and detecting 2-MHz shear waves propagating along the surface normal in a plate-like specimen. Since the probe will be used for pulse-echo birefringence-type measurements, it must contain two coaxial EMAT coils, each equipped with a preamplifier and a means for protecting the preamplifier circuitry from the high-power electrical driving signal. It is desirable that the preamplifier provide at least 40 dB of voltage gain and exhibit sufficiently-low noise characteristics to facilitate single-shot time of flight measurements with a resolution of 2ns, or better. A means for protecting the EMAT from mechanical damage (wear plate) must be incorporated in the design. The EMAT probe must be capable of a first-return, signal-to-noise performance of at least 30 dB at 2MHz when driven by a 10-cycle burst and operated on a ferritic steel plate 50mm in thickness. The documentation package must include sufficient detail to enable NIST personnel to model the ultrasonic signals generated and detected by the EMAT and describe the physical construction of the EMAT in technical reports and publications. Both items must be received 8 weeks after contract award date. There is no formal RFQ. Interested sources may submit a bid by fax or mail but it must be received on or before July 31, 1997. See Note 1***** (0195)

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