art for transmitting digital information power may be sent to the das board through pins 32 and sockets 38 or through a separate connection to the das board fig5 illustrates an instrument capable of detecting gases remote from the main instrument circuitry the instrument 50 has a handheld unit 51 equipped with a lcd display 53 alarm devices 54 and operating buttons 55 all connected to the main instrument board not shown the instrument has a retractable probe 58 with a sensor 60 on the opposite end the sensor 60 is mounted in a protective housing 62 which allows the sensor to expose to gas through an opening 63 the sensor includes a das board not shown connected to the main instrument board by a cable not shown placed inside retractable tubing 65 which may extend several feet from the main instrument body in applications not requiring remote sensing or when the instrument is not in use the probe 58 is retracted such that the sensor assembly rests in recess 66 in the instrument case the das board may be assembled in several ways for example the active and passive components may be in standard packages which may be readily obtained from the shelf the disadvantage the area required for mounting the individual components on the printed circuit board since the intent is to attach the das directly to a small sensor considerable effort is required to keep the das board size approximately.