BS EN 61786-1-2014 pdf download.Measurement of DC magnetic, AC magnetic and AC electric fields from 1 Hz to 100 kHz with regard to exposure of human beings Part 1: Requirements for measuring instruments.
The various types of instrumentation available for characterizing quasi-static magnetic fields are described in Clause 0.1,
The various types of instrumentation available for characterizing static magnetic fields are described in Clause D.3
Several types of magnetic field meters are in common use, e.g. field meters with coil probes. meters with Hall-effect probes, and meters that combine two coils with a ferromagnetic core as in a fluxgate magnetometer.
NOTE 2 Hall effect probes respond to static as well as time-varying magnetic flux densities. Due to limited sensitivity and saturation problems sometimes encountered when attempting to measure small power frequency flux densities in the presence of the substantial static geomagnetic flux of the earth, Hall-effect probes have seldom been used to measure magnetic fields of ac, power lines.
The various types of instrumentation available for characterizing quasi-static electric fields are described in Clause E.1. The following two types of electric field meters are considered in this standard:
a) the free-body meter;
b) the ground reference meter.
Sufficient information shall be provided with the instrumentation, including instrument specifications and a clearly written instruction manual, to enable users to determine compliance with this standard, to aid them in the proper operation of the field meter, and to assess the usefulness of the device for the user’s application. The instrument specifications that shall be provided and/or satisfied are given below.
5.2 Measurement uncertainty
The measurement uncertainty of the measuring instrument shall be specified by the manufacturer of the instrument. The measurement uncertainty shall be determined following the ISOIIEC Guide 98-3. The uncertainty shall be specified as an extended measurement uncertainty using a coverage factor of 2. The uncertainty is valid after available correction factors are applied. The uncertainty shall contain all components which are relevant when the instrument is used in a nearly uniform field. Such components may be calibration uncertainty. frequency response, deviations of the gain in different measurement range settings, isotropy of the probe, internal noise sources, non-linearity, stability, temperature response and humidity response. The uncertainty of the instrument does not include effects due to the handling of the instrument like positioning the probe in a non-uniform field or the influence of the measuring person on the field to be measured. Such components must be taken into account as additional uncertainties in the measurement report.
NOTE 1 At power frequency. the uncertainty of measuring instrument is usually 10 % or better
5.4 Pass-band
Broadband measuring instruments in the AC range always have a lower and an upper cut off frequency, which define a pass band. Normally the pass band limits are defined by the minus 3 dB point of the frequency response. The nominal frequency response of an instrument can be described as the frequency response of a system with a high pass filter and a low pass filter connected in series. The filter types and the filter orders should be specified (e.g. 3rd order Butterworth high pass and 51h order Butterworth low pass). The nominal frequency response of the instrument is normally not treated as a source of measurement uncertainty because the band limiting effect of the filters is a desired property of the instrument if broadband measurements are made. In frequency selective measurements (e.g. FFT) the band limiting effect of the filters is not desired and the nominal frequency response should be automatically corrected, The measurement uncertainty of an instrument due to manufacturing tolerances is normally greater at the band limits compared to medium frequencies. Therefore the measurement uncertainty of an instrument is often specified also and sometimes only in a restricted frequency range. This range is not as broad as the pass band but should be still broad enough to cover all frequencies of interest. In the restricted frequency range the influence of the nominal frequency response shall be negligible.
5.5 OperatIng temperature and humidity ranges
The temperature and relative humidity ranges over which the instrument operates within the specified uncertainty shall be at least -10 °C to 45 °C and 5 % to 95 %. respectively. Sudden temperature changes that can lead to condensation in the instrument should be avoided.
Electric field measurement may be perturbed If the relative humidity is more than 70 % due to condensation effect on the probe and support (2) 1, Since the effect of humidity depends on the field meter, the ability of the field meter to work correctly under those conditions should be checked before measurement (see Annex F).
5.6 Power supplies
The use of measurement equipment that is operating on Internal battery power is recommended.
If batteries are used, provision should be made to indicate whether the battery condition is adequate for proper operation of the field meter. Instruments used to record personal exposure should be capable of at least 8 h operation within their rated uncertainty before replacement or recharging of the batteries becomes necessary.
If rechargeable batteries are used it is recommended that the instrumentation is not operated while connected to the charging station. When such connections are necessary, it should be demonstrated that stray fields from the battery charger. conducted disturbances from the mains voltage and electromagnetic coupling via the connecting leads (to the battery charger) do not affect the measurement (see 5.9).BS EN 61786-1-2014 pdf download.
BS EN 61786-1-2014 pdf download
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