18 Annex A
210 SRM-3006 Narda
18.2 Matrix method (precision measurement)
Measurement setup
The antenna is fitted to a tripod and connected to the Basic Unit via a long
cable (see Fitting a Narda antenna on a tripod on page 33).
Defining the matrix
For this measurement, the volume to be measured is sampled at fixed
points arranged in a matrix.
Assuming that the emission affects the whole body evenly, the volume to be
measured could be defined as being e.g. a cylinder of height approximately
2 m and diameter approximately 1 m, corresponding roughly to the size of
the human body.
Various measurement heights are specified within this cylinder volume. The
resulting field strength is determined at each height. The spacing of the
measurement points should reflect the sensitivity of the corresponding body
parts and organs to radiation.
Antenna positioning
The antenna is mounted on a tripod so that it can be positioned exactly in
the matrix of measurement points.
Only one component of the field strength can be determined at a time using
a single axis antenna. For this reason, the antenna must be rotated to each
of the three orthogonal directions at every measurement point and the result
determined for each direction. The equivalent field strength used for the
assessment is derived from the vector sum of the three orthogonal field
strength values. The SRM supports this type of sequential measurement.
To ensure precise orthogonal alignment of the antenna axis, an antenna
positioning device is available in addition to the tripod for making
measurements with a single axis antenna.
Procedure
1. Fit the antenna with the antenna holder on the tripod.
2. Place the tripod at the first position to be measured.
3. Set the tripod to the first height to be measured.
4. Perform the sequential measurement at this position.
5. Save the isotropic result that is determined for this position.
6. Repeat steps 2 through 5 for each further measurement height.
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