Electronic angle indicator

An electronic angle indicator providing a digital indication for a desired angle comprises a pivotally suspended gravity responding pendulum retaining a ring magnet, a reference angle dial retaining a ring magnet and two magnetic field sensors, one for sensing magnetic field change of said pendulum and the other one for sensing magnetic field change of said reference angle dial. The output of said pendulum magnetic field sensor is compared with the output of said reference angle dial magnetic field sensor and causes the indicators display attainment of a desired angle orientation selected by said reference angle dial, or greater or lesser angle than the angle orientation selected by said reference angle dial.

This invention relates to angle indicators and specifically to improved 
angle sensing and measuring mechanism for an angle indicator. 
Heretofore, there have been many prior art on electrical indicators. These 
prior art adapted a light emitting and light detecting technique to 
indicate an object angle orientation by detecting either a vial air bubble 
or a rotor slot position. Two pair of light sources and detectors are 
positioned such that one end of the vial bubble or the rotor slot is 
positioned in between one of the light sources and one of the light 
detectors, and the other end of vial bubble or the rotor slot is 
positioned in between the other light source and detector when an 
inherently predetermined angle orientation, either horizental or vertical 
angle, is found, these cause to display one indicator for a correct angle, 
and another indicator for greater angle and another indicator for lesser 
angle than one of the inherently predetermined angles. 
These type of devices, however, have a problem obtaining an accurate angle 
measurement caused by the angle sensing technique and mechanism, and lose 
reliability as the light sources age and the power source is slightly 
lower or higher than a predetermined value. These prior art, moreover, 
have limitations being measured since only the inherently predetermined 
angles are recognized, and lose practicality since the devices are complex 
in structure and bulky in size. 
Accordingly, several objects of my invention are; 
a. to provide accuracy of angle measurement by adapting magnetic field 
sensing mechanism; 
b. to eliminate the inherent limitation on measuring angle orientations of 
various objects; 
c. to improve the reliability caused by aging of the angle sensing 
mechanism; 
d. to improve the dependance on power source; 
e. to provide simplicity in structure; and 
f. to provide small in size and compactness. 
Further objects and advantages of my invention will become apparent from a 
consideration of the drawings and ensuring description thereof.

DESCRIPTION 
Refering to the drawings and more particularly FIG. 1, it can be seen an 
improved electronic angle indicator 10 having a rugged principle body 11, 
which is made of a durable plastic or the like. 
The casing 11 is comprised of a flat contacting surface 11a to make contact 
with objects to measure their angle orientations, a side wall 11b having 
non-protruding rotatable angle dial 17, two circular display windows 
14a,15a which pass through light beam generated by LED's 14,15 
respectively, a top cover 12 having two circular display windows 14b,15b 
which pass through the light beam generated by LED's 14,15 respectively 
and an electrical power ON-OFF slide switch 13, a battery compartment 
cover 16 which is used to replace a battery 25, a side wall 11c, and both 
sides of symetrical top surfaces 11d,11e having curvacious surfaces as 
shown in FIG. 1. 
A gravity responding pendulum assembly 20 is consisted of two pivots 20a, 
20b in the center of front and back side of the pendulum assembly 20 
respectively, a weight 20c on the bottom of the back side of the pendulum 
assembly 20 and a ring magnet holder 20d which retains a ring magnet 21 as 
shown in FIG. 2. The ring magnet 21 is composed of a north pole 21c in the 
first quadrant, a south pole 21d in the second quadrant, a north pole 21a 
in the third quadrant and a south pole 21b in the fourth quadrant as shown 
in FIG. 5. 
The ring magnet 21 is mounted in the magnetic holder 20d such that the 
boundary line 21e of the north pole 21a and the south pole 21b is 
coinsided with the line between the center of the pivot and the center of 
mass of the pendulum assembly 20. The ring magnet 21 has a dimension of 
0.125 inch in inner diameter, 0.25 inch in outer diameter and 0.125 inch 
in thickness or the like and is made of ALNICO V magnet or the like. Pivot 
holders 11g,11h are designed to maximize responding sensitivity of the 
pendulum assembly 20 to gravity field. 
A magnetic sensor 22 is mounted on the lower front side of the pendulum 
assembly 20 with a predetermined distance and on the center of the 
boundary line 21e of the north and the south pole 21a,21b so that the 
minimum magnetic field strength is applied to the magnetic sensor 22 when 
the contacting surface 11a is placed on an object having one of multiple 
angle orientations of 90 degrees which are 0, 90, 180 and 270 degrees with 
respect to gravity field, and the maximum magnetic field strength on an 
object of 45,135,225 and 315 degrees of angle orientations with respect to 
gravity field. 
A reference angle dial 17 which rotatablely selects a desired angle is 
consisted of a cross shaped groove 17a which provides a means to rotate 
the reference angle dial 17, and a hair line 17b which provides a means 
aligning with angle indicia 11f. The reference angle dial 17 also retains 
a multi-pole ring magnet 18 which is identical to said multi-pole ring 
magnet 21 and is mounted in the reference angle dial 17 in the same way as 
the way said multi-pole ring magnet 21 is mounted. A reference angle dial 
retainer 11i provides holding and supporting means to the reference angle 
dial 17 and provides a desired reference angle position latching means for 
the multiple angle orientations of 90 degrees and angle position holding 
means for angles other than the multiple angle orientations of 90 degrees. 
A magnetic sensor 19 is identical to the magnetic sensor 22 and is mounted 
in the reference angle dial retainer 11i in the same way as the way as the 
magnetic sensor 22 is mounted. A magnet shield 24 is employed to prevent a 
possible magnetic interference between the ring magnet 21 in the pendulum 
assembly 20 and the ring magnet 18 in the reference angle dial 17. An 
electronic circuit board 23 is mounted in the cavity of the principle body 
11 to provide means of electronic circuit implementation. 
In FIG. 6, a typical schematic diagram of the electronic angle indicator 10 
is schematically illustrated. 
Comparators 27a,27b, such as LM119 device supplied by National 
Semiconductor Corporation, form a limit comparator 27 and drive the LED's 
14,15 of the angle electronic indicator 10. 
The output of the magnetic sensor 22, such as UGN-3501T device supplied by 
Sprague Electronic Company, is connected to a negative terminal of the 
comparator 27b and to one end of a resistor R1. The other end of the 
resistor R1 is connected to a positive terminal of the comparator 27a and 
one end of a resistor R2, and the other end of the resistor R2 is 
connected to the ground. 
The output of the magnetic sensor 19 is connected to the negative terminal 
of the comparator 27a and one end of a resistor R3. The other end of the 
resistor R3 is connected to the positive terminal of the comparator 27b 
and one end of a resistor R4, and the other end of the resistor R4 is 
connected to the ground. The output of the comparator 27a is connected to 
the cathode terminal of the LED 15, and the output of the comparator 27b 
is connected to the cathode terminal of the LED 14. The anodes of the 
LED's 14,15 are connected through resistors R5,R6 respectively to the 
power source 25, such as 9 v dry cell battery. A set of typical values of 
the resistors R1, R2, R3, R4, R5 and R6 are respectively 100, 20,000, 100, 
20,000, 330 and 330 ohms. 
The reference angle dial 17 provides a means to select a desired relative 
reference angle by aligning the hair line 17b with the angle indicia 11f. 
The 0 degree scale of the angle indicia 11f is used to measure the 
multiple angle orientations of 90 degrees of an object. The positive 
indicia scales other than the 0 degree scale is used to select a desired 
reference angle of counter clockwise inclinations up to +45 degrees from 
the multiple angle orientations of 90 degrees of an object. The negative 
indicia scales are used to select a desired reference angle of clockwise 
inclinations up to -45 degrees from the multiple angle orientations of 90 
degrees of an object. 
The magnetic sensor 19 senses change in magnetic field intensity and 
converts the magnetic field intensity to electrical signal on the output 
of the magnetic sensor 19, which is a DC anolog signal, when the reference 
angle dial 17 changes its position. The electrical signal so produced by 
the magnetic sensor 19 establishes an upper limit to the limit comparator 
27 and a lower limit, which is generated from the upper limit by a voltage 
devider comprised of the resistors R3, R4, to the limit comparator 27. The 
output of the magnetic sensor 19 is adapted to reference the upper and 
lower limit to improve the accuracy of the electronic angle indicator 10 
to compensate aging problem and the dependance on the power source. 
As the contacting surface 11a of the electronic angle indicator 10 is 
tilted to counter clockwise or clockwise direction from the multiple angle 
orientations of 90 degrees of an object, the gravity responding pendulum 
assembly 20 seeks for the gravity field and provides the magnetic sensor 
22 positive or negative magnetic field, respectively. The magnetic sensor 
22 converts the positive or negative magnetic field intensity, 
respectively to more or less positive electrical signal at the sensor 
output, which is a DC anolog signal. The sensor output so converted is 
compared with the lower limit of the limit comparator 27. 
The LED 14 is lit when the sensor output is higher than the lower limit and 
is extinguished when the sensor output is lower than the lower limit of 
the limit comparator 27. The sensor output is attenuated by the voltage 
divider comprised of the resistors R1, R2, and the divider output signal 
is compared with the upper limit of the window comparator 27. The LED 15 
is lit when the sensor output is lower than the upper limit and is 
extinguished when the sensor output is higher than the upper limit of the 
limit comparator 27. Both of the LED's 14, 15 are lit with the sensor 
output is lower than the upper limit and higher than the lower limit of 
the limit comparator 27. 
Summerizing the operation of this invention, the LED 14 is lit when an 
angle orientation of an object being measured has an angle displacement 
lying in the counter clockwise direction with respect to an angle selected 
by the reference angle dial 17. The LED 15 is lit when an angle 
orientation of the object being measured has an angle displacement lying 
in the counter clockwise direction with respect to the angle selected by 
the reference angle dial 17. Both of the LED's 14,15 are lit when an angle 
orientation of the object being measured has the same angle orientation as 
the angle selected by the reference angle dial 17. 
While the above description contains many specificities, these shall not 
construed as limitations on the scope of the invention, but rather as an 
exemplification of one preferred embodiment thereof. Many other variations 
are possible, for example; instead of using as a desired angle indication 
means, a direct angle readout means of an object being measured may be 
used simply by adapted an anolog to digital conversion means and 
displaying the angle in digits as shown in FIG. 8; instead of utilizing 
one axis pendulum mechanism, two axis pendulum mechanism 26 as shown in 
FIG. 7 may be adapted to provide capability to compensate for severe tilt 
against the pendulum pivot axis 20a,20b, when measuring horizental angle 
orientation for a special application, by mounting pivots 26a,26b of the 
two axis pendulum mechanism 26 orthogonally in place of the pendulum 
assembly 20 in FIG. 2; to provide variety of applications of present 
invention, especially for a larger scale application, an extender 28 shown 
in FIG. 9 may be used. 
Accordingly, the scope of the invention should be determined not by the 
embodiment illustrated, but by the appended claims and their legal 
equivalents.