15
Broadband Field Strength Probe for a Multimeter
3M
™
ScanEM-QC Electromagnetic
Near-Field Probe provides DC
voltage that is a function of field
strength. Connect ScanEM-QC
Probe to the multimeter set to Volts
DC (typical scale of 2V). You
will need BNC to Banana Plug
adapter. Set the
Level
dial to 0 (left-
most position). In absence of the
electromagnetic field the multimeter
should show 0V. Should the multimeter display any other voltage reading,
use it as the correction factor to any further field measurements. You can
characterize ScanEM-QC’s Probe output using GTEM cell, etc. and then
convert ScanEM-QC’s output into absolute values of the field strength.
When using ScanEM-QC Probe with a multimeter, avoid touching the tip
of ScanEM-QC Probe with your hand — it may induce a feedback between
typically non-shielded circuitry in a multimeter and the ScanEM-QC Probe
antenna that just got many times bigger by virtue of your touching it.
A typical transfer function of 3M
™
ScanEM-EQC Probe is shown in the
figure to the left. This figure is given for reference only. All specifications
are subject to change without notice.
Know What You are Measuring
Î
A word of caution: Avoid misleading numerical readings of the field strength by
understanding what you are actually measuring. ScanEM-QC Probe measures
the field strength at its tip. In the near field the field strength fluctuates
dramatically depending on the distance from the source. Slight repositioning
of the tip of ScanEM-QC Probe may result in different readings.
ScanEM-EQC DC Response
(typical)
1
10
100
1000
10000
0
500
1000
1500
2000
2500
3000
3500
F ield S trength, m V /m
D C O utput, m V
3M
™
Scan EM-EQC Probe DC Response
(typical)
