Brian,
I perform this calibration without automated positioning equipment with
only 32 probe position changes covering both vert and horiz polarizations.
This data is usable for generating uniform field levels from 1 to 20 V/m
at ANY level desired. The trick is to follow the 61000-4-3 par. 6.2
procedures, calibrating at 10% steps using a level in the range of 3-10 V/m
(no leveling required). You should record fwd. pwr. delivered to the
transmit antenna, rather than sig. gen. output power. Record data for each
frequency step, before changing probe position. Once all the data is
recorded, use the relationship between fwd. pwr. and field strength to
determine the forward power required to get at least 12 of the 16 locations
in the required range for each frequency step. This relationship is: E2 =
E1 * (FP2)1/2 / (FP1)1/2 where E = field strength in V/m and FP = fwd.
pwr. in mW
Use of spreadsheet software will greatly simplify your data calculations.
Additionally, once you determine the appropriate fwd. power levels (for
(12/16 position field uniformity) for, say 10V/m; using the above
relationship with FP as the variable, you can calculate the appropriate
forward power level for a uniform field strength at any V/m level! Good
luck.
Doug Frazee
Lead Compliance Engineer
Windermere Military/Commercial Compliance Laboratory
Annapolis, MD
USA
dfra...@windermeregroup.com
-Original Message-
From: brian_ku...@leco.com [SMTP:brian_ku...@leco.com]
Sent: Wednesday, December 02, 1998 11:42 AM
To: emc-pstc
Subject:EN61000-4-3 Hints and Tips
It's that time of year again where our lab must perform the dreaded
"Calibration
of Field" test for the EN61000-4-3 standard "Radiated Immunity". If you
performed the test as explained in the standard (section 6) moving the
Field
Probe to each of the 16 positions for each frequency for both vertical and
horizontal and for us at 3V/m and 10V/m power levels, you have to go inside
the
chamber over 17,000 times.
Because this is not practical, I assume that most labs measure all
frequencies
at each of the 16 positions. This reduces the number of trips into the
chamber
to only 64, but you still have to deal with over 17,000 pieces of data.
What we currently do is level at each frequency to the desired field
strength
(lets say 3V/m) and store the output level of the Signal Generator. Repeat
this
for all 16 positions. Then for each frequency throw away the 4 highest
values
and keep the fifth. This is the data that we will use during the test.
This
will take us anywhere from 3-5 days to gather and calculate all the data.
There is got to be a better way, hopefully easier and quicker. I'm very
interested in how other labs perform this annual procedure. Any hints or
Tips
would be most appreciated.
Thanks in advance,
Brian
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