Ac milligauss meter - model UHS
This meter is designed to do precise measurements of AC magnetic field in a wide frequency range of 13 Hz to 75 kHz (75,000 hz). The frequencies include most ELF (that is, frequencies below 1 KHz) and VLF (above 1 KHZ) magnetic fields.
The meter measures the true 3-axis magnitude of the AC field. Two other more specialized measurements can also be performed: 3 axis VLF- only (1kHz - 75 kHz) to measure the strength of higher frequency fields, and 1 axis full bandwidth (13 Hz - 75kHz) to determine the principal direction of the AC magnetic field. These specialized measurements are selected by the knob labelled "TYPE OF MEASUREMENT". A "RANGE" knob allows a wide range of field strengths to be measured - from .01 to 1999 milligauss.
Most measurements will be performed with both knobs turned to the
leftmost position. This setting is for measurement of true magnitude
of magnetic field at the widest range of frequencies (ELF + VLF) up
to a strength of 19.99 milligauss.
|Accuracy: This meter has a typical error of +/-3% of the reading in
the frequency range 45 Hz to 5kHz. At certain measurement angles and
certain frequencies in the 3-AXIS modes, the error may be as high as
+/-7%. That is, a reading of 10.00 milligauss means the field is as high
as 10.70 or as low as 9.30, but most of the time the actual field will
be between 10.30 and 9.0 (this is in RMS units). Note that this accuracy
specification is for sine waves in the very wide frequency range of 45
Hz to 5 kHz. Other manufacturers of digital 3-axis meters only specify
the accuracy for 60 Hz sine waves. (Those types of meter will generally
have significant additional error above 100 Hz. Because of advanced high
frequency detection circuitry, the model UHS does not have this problem).
The meter works by measuring the absolute value of the AC field strength
in 3 axes (or 1 axis), and then finding the time-average of that absolute
value. That time average is then scaled so that a sine wave reads in
RMS units. Sensitivity is down to ½ at the frequency limits 13
Hz and 75 kHz. In the 3-AXIS 1 kHz - 75 multiplier in the lower right
of the table) if the wave is actually 50 kHz. Also, if you're measuring
pure 60 Hz, and it reads 13.62 milligauss on the ELF + VLF, then it will
only read .0025 x 13.62 = .03 milligauss on the VLF only setting. These
calculations require that you know the frequency.
The alkaline 9v battery lasts about 20 hours. "LOW BATTERY" will appear on the display when approximately one hour of battery life remains. To replace the battery, press down on the back door (near the centre of the back of the meter) and slide this door outward (downward) to separate it from the meter body. Then change the battery.
Warranty for this meter is one year.