Personal Monitors are used to warn users when field strength is starting to become significant with regard to a permissible exposure level.
Because permissible levels vary with frequency the Nardalert S3 and RadMan 2LT & XTLT & XT have shaped alarm thresholds; the units alarm at a set percentage of a given safety guideline, typically 50% for a first stage alarm, irrespective of frequency. This means the user does not have to identify different types of equipment or constantly re-set the monitors alarm level.
The Nardalert S3 has a wide frequency range covering LF radio & with a thermocouple sensor high frequency applications like radar or 5G. The RadMan 2LT is a low cost unit covering a reduced frequency range and the RadMan 2XT covers a wider frequency range (but without a thermocouple sensor).
Unlike cheap imitations units can respond accurately to different polarisations, different modulations and operate across a wide temperature range ensuring you don't have to deal with costly false alarms. Conversely Narda personal monitors will provide an accurate indication when field strengths are truly high - remember it's a safety device so it's nice that specifications are underwritten by Narda, the byword for EMF safety for over 50 years.