EMF

DC-1kHz low frequency magnetic field measurements

The HP-01 & NBM-550 is a powerful combination of magnetometer probe and hand-held field meter that offers a complete, portable solution for taking safety measurements in workplaces where personnel are at risk from the effects of strong magnetic fields.

The hand-held meter is a more rugged and portable alternative to a laptop and also provides immunity to high electromagnetic fields – fields that could easily disrupt the operation of a standard laptop. The two Narda units together are ideal for taking measurements to ensure compliance with the Control of Electromagnetic Fields at Work Regulations 2016, which are the transposition into UK law of EU Directive 2013/35/EU. In particular, the equipment will help to avoid hazards due to the indirect effects of strong magnetic fields, such as projectile risk or interference with active implanted or body-worn medical devices. Potentially vulnerable personnel include those working in hospitals’ MRI facilities, railway workers in the vicinity of electric trains’ DC motors, and industrial employees involved in processes using large magnetic stirrers, strong permanent magnets or electrolysis.

The HP-01 offers an extremely wide measurement range of 10µT to 10T, a dynamic range of 120dB, and is capable of measuring time-varying fields with frequencies up to 1kHz. Its three mutually orthogonal Hall-effect sensors enable the field to be determined with a single measurement in any direction – unlike single-axis Hall-effect probes, which are generally unsuitable for safety applications as they require three separate readings and subsequent calculations to achieve an accurate measurement. Another key feature of the HP-01 device is its powerful built-in FFT analyser, which allows detailed, highly accurate signal analysis in both time and frequency domains. Also, since the limit values in safety standards are usually specified for static fields and time-varying fields with frequencies up to 1Hz, the HP-01 facilitates compliance measurements by incorporating a finite impulse response (FIR) filter that captures only frequency components in the 0Hz to 1Hz range.

The NBM-550 instrument, meanwhile, includes a hold button to ‘freeze’ measurements for easy readout and has the capacity to store up to 5000 results, with each one automatically timestamped. It can be operated with one hand by anyone – left-handed or right-handed – and its large backlit monochrome LCD graphic display is easy to read even in darkness or sunlight. There is also a keypad lock to prevent inadvertent operation of control keys and a fully automatic zeroing function to eliminate the effects of temperature on the results. Optional features include a GPS receiver for adding location data to each measurement and a facility for recording voice comments, which are stored with the corresponding measured values. All data can be transferred to a PC for further analysis using the software supplied.

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