Wearable monitors for detection of non-ionizing radiation (NIR) are essential for those working in areas of high electromagnetic (EM) radiation. The first such NIR monitor was introduced two decades ago by Narda Microwave. The company has refined its technology since then, and the results are clear to see in its latest model.

The Nardalert S3 (Fig. 1) measures electric field strengths from 100 kHz to 50 GHz. It features a removable sensor pack to eliminate calibration downtime. It can be worn on the body or operated remotely for fixed-area monitoring via a fiber-optic connection. It also features a liquid-crystal display (LCD) screen that is backlit by light-emitting diodes (LEDs), and supported by audible and vibration alerts.

The Nardalert S3 is a major enhancement over its predecessor, the Nardalert XT, which integrated its sensors as part of the instrument mainframe. As a result, the entire monitor had to be returned to the factory for calibration every two years. The Nardalert S3 incorporates radial field, diode-dipole, and thermocouple array sensors in a removable pack, so only the pack needs to be sent for the two-year calibration. A spare sensor can be installed to continue operating the Nardalert S3.

Current sensors operate in compliance with standards from the Federal Communications Commission (100 kHz to 50 GHz), Radiation Protection Bureau of Health Canada (Safety Code 6), IEEE (C95.1, 3 MHz to 50 GHz), and International Commission on Nonionizing Radiation Protection (ICNIRP). Others will be offered for lower (ELF/VLF) frequency ranges and additional standards. the instrument has a monitor range of 5 to 200% of a standard's levels.

The Nardalert S3 provides information by means of its top-mounted, 1.1 x 1.4 in., white-LED-backlit color LCD display. It shows function status, signal strength bar graphs, the spectral region where radiation is present, total signal strength, and battery and sensor status. An option adds logged data and exposure and alert history. It has alarms for 50 and 200% of standard-based radiation levels and will perform without degradation in areas with ELF field strengths as high as 6 kV/m.

The fiber-optic interface makes the Nardalert s3 a dual-function instrument, since as many as eight monitors can be used for fixed-area monitoring, sending their real-time data to 50 m away (plastic cable, longer with glass) to a new product called the NBM-580 (Fig. 2). this unit aggregates the data, controls each unit, and under software control sends data and alerts locally via Ethernet or anywhere over the Internet. The Nardalert S3 stores as many as 62,000 events over 4.3 h to 43 days.

The instrument has mini-USB 2.0 and fiber-optic interfaces. Adapters are included for North American, Australian, European, and UK power-line voltages and plug configurations. The unit operates about 25 h on its rechargeable RCR123 lithium battery or standard CR123 lithium battery. The Nardalert S3 is accompanied by Narda NS3-TS Windows software. Data can be exported to other programs and displayed in text or graphical form.

The Nardalert S3 measures 4.61 x 3.25 x 1.25 in. and weighs 8 oz. with sensor. It has a rugged plastic housing with a protective silicon skin. It is supplied with lithium rechargeable battery; carrying case for the monitor; charger and accessories; 5-VDC/100 to 240 VAC power supply; belt clip and lanyard; USB cable; and ns3-ts software.