AlphaLab GM1-HS User manual

DC Gaussmeter Model GM1
This magnetometer (gaussmeter) measures DC magnetic field (with polarity) up to + or
Operation:
Turn the meter on by pressing “Power” for at least 1 second Note that the last few millimeters at the (black) end of the
probe has a square bulge on one side; the other side is flat
from the tip The brass is on the “flat” side
The center of that square bulge is the location of the Hall
is very small (0 2 x 0 2 mm)
Place the flat side of the probe’s end (not the square bulge side) against the surface to be
measured A ne
gative sign indicates that the probe is touching the south pole of a magnetized object; in contrast, a north
pole will read positive (“positive” is indicated by the
sensor is 1 1mm above
the flat surface or 1 0mm below the top of the square bulge) and is centered in the center of the
square bulge
Below 10 gauss, only three digits (such as “
-
stronger than +/-
799 99 gauss, the extreme left digit will display
about one hour of battery life remaining
Remove the soft bumper or “boot” if present, and then slide off the battery door
on the back side Replace with a common 9
-
be removed by holding the meter so that the battery can fall out, and then tapping the meter on a table
7ma and the LO BATT reads if bat
tery voltage remains below 7V for at least one minute
battery voltage of 5 8V) You may need to press “Power” twice the first time with a new battery MAKE SURE THE
METER TURNS ON AFTER REPLACING THE BATTERY
Offset
Adjustment (only necessary if measuring weak fields):
The offset controls
allow you to add or subtract
you are holding the sensor in a certain orientation in space, and you want
field is present
Press “Auto Zero” to do this
equivalent of adjusting the “tare” weight of a weight scale, because there may be an a
want to subtract out When turned on
, the display will read approximately zero in zero field, but you can more precisely
adjust the offset to zero if you do one of two things, either:
1) Place the sensor in a “zero
gauss chamber” (not supplied with this meter, but see www trifield com) and
Zero
2) Place the sensor end flat on a non-
magnetic table or desk with the square bulge facing up
will read the upward-pointi
ng component of the magnetic field
should then read a negative number )
Note the number on the display
down This 2
nd
reading should be the
negative
should be 0 40 (gauss)
If the two readings are not the negative of each other, then the
a zero reading in zero field For example
, if the 1
gauss (the average of the two readings)
Adjust the
of opposite sign Offset is adjusted by pres
sing the “+” or “
DC Gaussmeter Model GM1
HS Instructions
This magnetometer (gaussmeter) measures DC magnetic field (with polarity) up to + or
Turn the meter on by pressing “Power” for at least 1 second Note that the last few millimeters at the (black) end of the
probe has a square bulge on one side; the other side is flat
Note also that a small section of brass is visible about 15mm
The center of that square bulge is the location of the Hall
Place the flat side of the probe’s end (not the square bulge side) against the surface to be
gative sign indicates that the probe is touching the south pole of a magnetized object; in contrast, a north
pole will read positive (“positive” is indicated by the
absence of a polarity sign on the display)
The actual center of the
the flat surface or 1 0mm below the top of the square bulge) and is centered in the center of the
-
0 37”) will be displayed
For stronger fields, more digits will appear
799 99 gauss, the extreme left digit will display
(It is a “1”)
If the display reads “LO BATT”, there is
Remove the soft bumper or “boot” if present, and then slide off the battery door
-
volt rectangular battery Alkaline is preferred
The old battery can most easily
be removed by holding the meter so that the battery can fall out, and then tapping the meter on a table
tery voltage remains below 7V for at least one minute
(Accuracy errors will occur below
battery voltage of 5 8V) You may need to press “Power” twice the first time with a new battery MAKE SURE THE
METER TURNS ON AFTER REPLACING THE BATTERY
Adjustment (only necessary if measuring weak fields):
allow you to add or subtract
any field
to or from the displayed number of gauss
you are holding the sensor in a certain orientation in space, and you want
the display to show “zero”, even though some
Press “Auto Zero” to do this
Then you can bring in a magnetized object to measure
equivalent of adjusting the “tare” weight of a weight scale, because there may be an a
mbient magnetic field that you’ll
, the display will read approximately zero in zero field, but you can more precisely
adjust the offset to zero if you do one of two things, either:
gauss chamber” (not supplied with this meter, but see www trifield com) and
magnetic table or desk with the square bulge facing up
In this orientation, the meter
ng component of the magnetic field
(If the field is instead downward-
pointing there, the meter
Note the number on the display
Then flip the sensor so the square bulge is facing
negative
of the 1
st
reading That is, if the 1
st
reading was –
0 40 (gauss), then the 2
If the two readings are not the negative of each other, then the
offset
is not adjusted perfectly for
, if the 1
st
reading is 1 00, and the 2
nd
reading is 0 00, then the
Adjust the
offset knob so that the 1
st
and 2
nd
readings are the same number but
sing the “+” or “
-
” buttons If you hold one button down, the offset amount will
This magnetometer (gaussmeter) measures DC magnetic field (with polarity) up to + or
- 799 99 gauss
Turn the meter on by pressing “Power” for at least 1 second Note that the last few millimeters at the (black) end of the
Note also that a small section of brass is visible about 15mm
The center of that square bulge is the location of the Hall
-Effect sensor, which
Place the flat side of the probe’s end (not the square bulge side) against the surface to be
gative sign indicates that the probe is touching the south pole of a magnetized object; in contrast, a north
The actual center of the
the flat surface or 1 0mm below the top of the square bulge) and is centered in the center of the
For stronger fields, more digits will appear
For fields
If the display reads “LO BATT”, there is
Remove the soft bumper or “boot” if present, and then slide off the battery door
The old battery can most easily
be removed by holding the meter so that the battery can fall out, and then tapping the meter on a table
Current drain is
(Accuracy errors will occur below
battery voltage of 5 8V) You may need to press “Power” twice the first time with a new battery MAKE SURE THE
to or from the displayed number of gauss
This feature is used if
the display to show “zero”, even though some
Then you can bring in a magnetized object to measure
This is the magnetic
mbient magnetic field that you’ll
, the display will read approximately zero in zero field, but you can more precisely
gauss chamber” (not supplied with this meter, but see www trifield com) and
then press Auto
In this orientation, the meter
pointing there, the meter
Then flip the sensor so the square bulge is facing
0 40 (gauss), then the 2
nd
is not adjusted perfectly for
reading is 0 00, then the
offset is off by 0 50
readings are the same number but
” buttons If you hold one button down, the offset amount will

count up or down faster The meter offset will return to factory reset when power is turned off You can change the
factory reset by removing the 4 screws in back and taking off the front cover Turn the small round potentiometer below
(nearest the battery) that says “internal offset”
Measurements:
This type of meter is often used to check residual (accidental) magnetization of parts In general, this accidental
magnetization is perpendicular to the surface of the part, so the probe can be placed flat against the part, and this is the
correct direction for detection of that field You may need to scan the probe across the surface to find the highest
number This highest reading is usually found at the ends or sharpest points of the part
There are some peculiarities of measuring residual magnetization Long, thin steel parts will often “amplify” the Earth field
by a factor of 10 or so, at the ends of the part If the long-axis of the part is pointed east-west, or perpendicular to the local
indoor field, this is not a problem The strength of the Earth field is about 0 5 gauss, so you may see up to about +/-5
gauss at the end of a properly demagnetized steel rod if the rod is pointed in the direction of the Earth field The north pole
of the earth is not horizontal in most locations In most of Asia the magnetic field direction is within about +/-20° of
horizontal In North America if you face north and then look downward from horizontal 20° (Central Mexico) to 55°
(Northern US) to as much as 90° down in parts of Canada, that is the direction of magnetic north You can detect the field
strength and direction with the meter Note that with the bulge in the probe pointing toward the Earth north, you will read a
negative number, because it's pointing toward the south pole of a magnet If you flip the sensor 180° so that the bulge is
facing Earth north, you will read a positive number
When scanning the surface of parts, if you want to measure with a resolution of less than five gauss, it’s recommended
that you keep the probe end stationary with its thin axis (magnetic sensitivity direction) pointed perpendicular to the local
magnetic field direction, and with OFFSET adjusted so the display instantly reads zero You’ll know it’s correctly zeroed
and perpendicular to the local field direction if when you flip the probe end 180°, the display continues to read zero Then
scan the part along the flat surface of the probe and look for the highest number (either positive or negative)
SPECIFICATIONS: 1
axis DC Gaussmeter GM1
HS
Range/Resolution:
799 99 G/0 01 G; with polarity indicator
Accuracy:
+/- 1% of reading (16° to 29°C); +/- 2% (-4° to 65°C)
Offset:
Auto Zero Also fine offset (0 01 gauss resolution)
Probe (non
detachable):
2 1 (thick) x 4 3 x 24 mm
Size:
5 2 x 3 6 x 1 6 inches; 132 x 91 x 41 mm
Weigh
t:
8 oz
Battery:
9 volt alkaline (~ 20 hour life)/ "Low Battery" indicator
The warranty period for this meter is one year from the date of delivery.
Manufactured in the USA by AlphaLab, Inc. 3005 South 300 West Salt Lake City, Utah 84115 USA www.trifield.com [e-mail] [phone]