Description
The SMARTS II detects all types of electromagnetic fields from 400 MHz to 100 GHz. The monitor uses a dual sensor design. The microwave portion of each sensor employs thermocouple detectors so that radar signals are accurately converted to true RMS values while the diode design used for the lower frequencies provides RMS detection even in very complex, multisignal environments. The output of the high frequency sensors is combined and fed to a low-noise amplifier circuit. Similarly, the output of the low frequency sensors is combined and fed to another low-noise amplifier. The output of these two amplifier circuits is scaled in terms of percent of the respective safety standard. The sum of these two amplifier levels is used to determine whether the monitor is above or below the alarm threshold that has been selected by the user. SMARTS II monitors respond equally to all polarizations and cover almost a hemisphere. The SMARTS II operates from a 9-volt lithium Ultralife battery (U9VL) or a +12 V to +24 V DC supply. Every monitor has an audible and visual alarm indication. An alarm condition causes both a voltage transition to occur and, in the case of DC supply operation, a SPDT relay to operate. Either the voltage transition (+4 V/-4 V) signal or the relay contacts can be used to provide remote alarms, a record of alarm conditions, and/or automatic shutoff of equipment.
Applications
The SMARTS II performs measurements for human safety purposes, particularly in workplace environments where high electric or magnetic field strengths are likely. The SMARTS II is an area monitor that can be installed on ceilings and walls, with automatic frequency response evaluation according to a selected safety standard. SMARTS II emits warning sounds if user settable thresholds are exceeded. SMARTS II is ideal for security installations in aircraft hangars or military facilities, thanks to its frequency range from 400 MHz to 100 GHz and measurement range of up to 3000% of the limit value of the chosen safety standard.
Operation
SMARTS II monitors operate like common household smoke detectors. When operating normally, the alarm LED flashes approximately every 40 seconds. If operating under battery power and the battery needs replacement, a “chirp” accompanies the LED flash. The SMARTS II goes into alarm mode if the battery drops below a critical level. A continuous audible alarm and a LED flash every second occurs when the SMARTS II detects RF radiation at its preset level or higher. Both an electronic signal and, in the case of DC supply operation, a relay closure are provided during alarm conditions. Either of these indications can be used to activate various usersupplied remote circuitry and systems. Operation can be verified at any time by depressing the TEST button that activates a full-system test. For battery operation that means an audible and visual alarm and an electronic signal and, at DC supply operation an additional relay activation. The ENABLE input can be used in situations where the standard operating procedure produces RF field levels in excess of the threshold and exposure to people is possible (e.g., in an anechoic chamber or on the deck of a ship). The ENABLE input can be tied to a motion sensor or an interlock switch. Under these conditions, the SMARTS II activates its alarms only when two conditions are satisfied: (1) high levels of RF are present and (2) motion is detected or a door is open. The alarm threshold is field adjustable from 10% of standard to 50% of standard. The user can easily switch from battery operation to an external, low voltage DC supply.
