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NBM-550 is part of the NBM-500 instrument family. It delivers extremely accurate results for electromagnetic field strength measurements. NBM-550 handles applications from a few Hertz through to long wave and on up to high frequency microwave radiation using a selection of interchangeable probes for electric and magnetic fields.

The field strengths are captured with flat frequency response probes or probes with shaped frequency response, allowing the measurement values to be assessed against an environmental or occupational safety standard. The calibration factors for each probe are stored in the probe itself and are read out and taken into account automatically by the measuring set.

Frequency response weighted probes for convenient testing.

There are different personal safety limits at different frequencies. “Shaped probes” take care of the frequency issues for you, providing an easy-to-read display as a % of standard. You don’t have to deal with the actual field strength limits or frequencies, enabling quick and simple measurements even under complex ambient conditions. Narda Safety Test Solutions is the only supplier for shaped probes. Why? We hold the patent for this feature.

What is a shaped probe?

The traditionally-used flat frequency response probes have been developed with the aim of providing a probe having as constant sensitivity to magnetic field strength as possible over the usable frequency range. In contrast, Narda’s patented Shaped Probes are constructed in a completely different way. The sensitivity of these probes is designed to match a particular directive or standard. The sensitivity versus frequency (frequency response) of the probe is as closely as possible in inverse proportion to the limit value curve. The measured values are not displayed in V/m or W/m2, but are shown as “% of standard” instead. This makes it very easy to assess the results, particularly in multi-frequency environments as there is no need to worry about the predominant frequencies in the field. A result of less than 100% always means that the limit values are not exceeded anywhere within the entire frequency range of the probe. The “% of standard” display is referred to the power density of the electromagnetic field. The high bandwidth of 300 kHz to 50 GHz of a Narda “Shaped Probe” is unique.

What’s the reason for the extremely wide bandwidth of Narda’s shaped probes?

When compared with conventional broadband probes, Narda’s Shaped Probes have a much wider frequency range (e.g. 300 kHz – 50 GHz). The reason for this is the use of a diode-based probe section for the lower frequency range (approx. 300 kHz – 2 GHz) and a thermocouple probe section for the upper frequency range (approx. 300 MHz – 50 GHz). Both parts of the probe have suitable frequency responses which are superimposed after adjustment of the sensitivity and which correspond as closely as possible to the limit value curve of a particular safety standard (e.g. ICNIRP).
Although the transition region is continuous, Shaped Probes can be considered simply as diode probes below 1.5 GHz and as thermocouple probes above 1.5 GHz.

What’s the difference between thermocouple and diode-based probes?

Both types of probe use dipoles to detect the electric field. The dipoles in the thermocouple probes are formed by thermocouples connected in series, which generate a DC voltage proportional to the power density. In the diode-based probes, the dipoles are formed by two equal lengths of wire with a detector diode as rectifier between them. Both these techniques can be used to develop broadband sensors. 

Ask your reseller for sets suitable for your application.