Angle of rotation sensor having a counting arrangement with at least two pulser-wire motion sensors providing electrical energy used as a voltage supply

An angle of rotation sensor for measuring the angular position of a rotary shaft during more than one revolution consists of a fine angle of rotation sensor linked to the rotary shaft and of a counter. The revolutions of the shaft are all counted without mechanical gears, without an outer voltage supply and without supply batteries, with a simple and economical design. Pulse wire movement sensors supply voltage pulses depending on the rotation of the shaft. The number of voltage pulses is stored in a non-volatile read/write memory.

BACKGROUND OF THE INVENTION 
The subject of the invention is an angle of rotation sensor for measurement 
of an angular position of a rotary shaft over more than one revolution. 
From DE 41 37 092 A1 there is a known angle of rotation sensor in which an 
angle encoder, which can be a scanned coded disc, registers the angular 
position of a rotary shaft for a single revolution. A potentiometer 
subsequent to the coded disc registers the absolute angular position of 
the rotary shaft over several revolutions. A subsequent evaluation circuit 
combines the position of the coded disc together with the number of 
revolutions, under consideration of the gear-train play and measurement 
tolerance of the potentiometer. Angle of rotation sensors of this type 
always supply the absolute angle of rotation over several revolutions 
independently of any intermediate interruptions of the power supply. 
Disadvantages are the high production costs for the gear-train and sensor 
elements, as well as the limited durability because of the many mechanical 
moving parts. The number of revolutions which can be registered is limited 
by nature of the mechanical construction. 
From DE 37 29 949 A1 there is an angle of rotation sensor known with a 
counting arrangement Z, several pulse-wire motion sensors S1 to S6 
arranged around the circumference, and several magnets M. The outputs of 
the pulse-wire motion sensors are so applied to the counting arrangement 
that the count in the counting arrangement represents the angular position 
of an input wheel attached to the rotary shaft. The disadvantage of this 
arrangement is that the counting arrangement ceases to function with loss 
of power supply, such that rotation of the shaft can no longer be 
registered and the actual count is lost. 
A known angular position sensor of this type is the product CE 100 from the 
company T+R, Trossingen. A fine sensor element registers the angular 
position of the shaft over one revolution, the measured values repeating 
periodically with each revolution. One or more coarse sensors are coupled 
subsequent to the fine sensor by means of gearing. The absolute 
measurement value is the result of a suitable combination of the 
measurements from the fine and the coarse sensor elements. Angular 
position sensors of this type supply the absolute angle of rotation over a 
large number of revolutions, independently of any intermediate 
interruption of the power supply. Disadvantages are the high production 
costs for the gear-train and the sensor elements, as well as the limited 
durability because of the many mechanical moving parts. The number of 
revolutions which can be registered is limited by the nature of the 
mechanical construction. 
A further angle of rotation sensor of the stated type is known from the 
product OAM-74-11/24 bit-LPS-5V (TS5778N10) from the Tamagawa Seiko 
Company, Tokio. A measurement arrangement registers the angular movement 
of a rotary shaft. By means of a counter, incremental shaft movements are 
summed over several rotations under consideration of the direction of 
rotation to provide an absolute value. On loss of supply voltage, the 
operation of the angle of rotation sensor is maintained by means of a 
buffer battery. Long interruptions in the voltage supply during stoppages 
also have to be bridged by the buffer battery. The cost of realising this 
form of sensor is less than that for gear-coupled angle sensor elements. 
The disadvantage of this arrangement is the limited life of the buffer 
batteries. These need to be replaced at regular intervals. A further 
disadvantage is the necessity to supply the sensor element from a buffer 
battery and the associated additional battery load. Under extreme 
environmental conditions such as high or low temperature batteries cannot 
be used. 
SUMMARY OF THE INVENTION 
As opposed to these arrangements, the invention has the goal of further 
developing the type of angle of rotation sensor presented initially such 
that with simple construction and low cost, when the external supply of 
voltage fails, the shaft rotations continue to be counted without resource 
to mechanical gears or the supply of power from batteries. 
To solve this task, the invention makes use of the characteristics wherein 
the counting arrangement comprises at least two pulse-wire motion sensors 
fixed on an arc segment, at least one permanent magnetic, a non-volatile 
read/write memory, and an electronic countercircuit. Accordingly, 
pulse-wire motion sensors give out voltage pulses, the quantity of which 
is placed into a non-volatile read/write memory. A pulse forming circuit 
produces a voltage from the pulses given out by the pulse-wire motion 
sensors which is used to supply a control circuit, the non-volatile 
read/write memory and an up/down counter, such that advantageously without 
an external supply of power or without the use of voltage stored in 
batteries, the number of shaft revolutions can be counted. This and 
further advantageous developments of an invention-worthy angle of rotation 
sensor are noted in the subtitles.

DETAILED DESCRIPTION OF THE DRAWINGS 
The angle of rotation sensor 1 displayed in FIG. 1 consists of a rotary 
shaft 2, a fine angle of rotation sensor connected to the shaft which 
measures angle of rotation over one revolution, and a counting arrangement 
4 to count the total number of revolutions of the rotary shaft. The 
counting arrangement of this embodiment has pulse-wire motion sensors 
6,7,8, permanent magnets 10,11,12 attached to the shaft, and an electronic 
counting circuit 13. The counter is supplied with voltage pulses 28,29,30 
from the motion sensors, and via conductor 59 with the measurement value 
from the fine angular position sensor. The fine angle of rotation sensor 
is provided by a known element, e.g. as an optical encoder or resolver. 
The counter circuit is connected to a supervisory unit 15 via an interface 
with connections 14 and a voltage supply via connection 15. 
FIG. 1, FIG. 3 and FIG. 4 show various principle forms of arrangement of 
pulse-wire motion sensors, permanent magnets and pole-pieces. The voltage 
pulses from the motion sensors are assigned to particular angular 
positions of the rotary shaft 2. Under consideration of past rotation 
states by making use of voltage pulses which have occurred in the past it 
is possible to: 
register every full rotation of the rotary shaft 2, 
take into consideration the direction of rotation of the rotary shaft, 
take into consideration the characteristic position differences between the 
set and reset action of Wiegand sensors, 
unequivocally associate the voltage pulses from the motion sensors with the 
number of revolutions of the rotary shaft through a combination of the 
rotation state as given by the voltage pulses and the position given by 
the fine angle sensor, also for mechanically or magnetically produced 
tolerances in the angular position of the voltage pulses. 
FIG. 2 shows an arrangement with three unipolar pulse-wire motion sensors 
6,7,8, fixed on arc-segments with a spacing of 120 degrees, a switching 
permanent magnet 10 attached to the rotary shaft 2, and two reset magnets 
11, 12, attached to the rotary shaft. The pulse-wire motion sensors, also 
known as Wiegand sensors, are realised in this arrangement in a know 
manner with pulse-wire segments wound with sensing coils. Set and reset 
magnets are so arranged that they pass the motion sensors on rotation of 
the shaft such that the magnetic fields of the set and reset magnets 
permeate the impulse-wire of the sensors with a corresponding change of 
polarity. When the switching magnet 10 passes any of the motion sensors, 
then these produce from the sensing coils in a known manner through the 
simultaneous change of magnetisation of all magnetic domains (Wei.beta. 
regions) in the pulse-wire, short voltage pulses of a defined amplitude 
and duration. The passing of a reset permanent magnet 11, 12 sets the 
magnetic state of the motion sensor back again. 
Unipolar functioning pulse-wire motion sensors, as known, supply a voltage 
pulse only on the switching action, not on the reset action. Pulse length 
and amplitude are not dependent on the speed of motion of the switching 
and reset magnets. Switching and reset magnets are so arranged on the 
rotor such that after the switching magnet has passed, a reset magnet will 
always pass a motion sensor before the switching magnet passes either of 
the other two motion sensors. The advantage of the arrangement according 
to FIG. 2 is the high voltage amplitude produced by unipolar operating 
pulse-wire motion sensors. 
FIG. 3 shows a design form with two fixed bipolar pulse-wire motion sensors 
70, 71 positioned on an arc with 90 degree separation and a permanent 
magnet 72 attached to the rotary shaft 2. As opposed to unipolar sensors, 
bipolar pulse-wire motion sensors provide a voltage pulse on both the 
switching and the reset action. The advantage of this arrangement is the 
realisation with a minimum quantity of motion sensors. 
FIG. 4 shows a design form with two fixed bipolar pulse-wire motion sensors 
positioned on an arc with 180 degree separation, consisting of two sensing 
coils 90, 91, two permanent magnets 92, 93 acting on sensing coil 90, two 
permanent magnets 94, 95 acting on sensing coil 91 and a pulse-wire motion 
sensor 96 attached to the rotary shaft 2. As opposed to the previous 
examples according to FIG. 2 and FIG. 3 the sensing coil of the pulse-wire 
motion sensor is, in a known manner, separated from the pulse-wire and 
positioned between two permanent magnets. 
When rotation of the shaft causes the pulse-wire to pass both the magnets 
and the sensing coil, two magnetisations of the pulse-wire occur, only one 
of which, due to the geometrical arrangement so influences the magnetic 
field in the sensing coil such that a voltage pulse is induced. This 
arrangement supplies voltage pulses whose polarity indicates the sense of 
rotation. 
FIG. 5 shows a mechanical arrangement of three motion sensors 73, 74, 75, a 
permanent switching magnet 77 and two reset permanent magnets 76, 78. The 
effective magnetic axes of the motion sensors and the permanent magnets 
are positioned radially to the axis of the rotary shaft 2. The permanent 
magnets which are attached to the shaft are embedded in a part of the 
shaft constructed of material non-conductive to magnetic fields in order 
that the forming of magnetic fields is not influenced by the material of 
the shaft. An arrangement in this form allows the construction of an angle 
of rotation sensor conforming to the invention with a small outside 
diameter. 
FIG. 6 shows a mechanical arrangement of three motion sensors 73, 74, 75 
consisting of units each made in a known manner from a bipolar functioning 
pulse-wire motion sensor and two permanent magnets, are arranged as shown 
in FIG. 5. The magnetisation of the motion sensors is carried out by a 
moving pole-piece 80, attached to the rotary shaft. The magnetic flux from 
both permanent magnets permeates the motion sensor (pulse-wire and the 
sensing coil wound around it) in opposite directions via air-gaps. When an 
air-gap is bridged by the proximity of the moving pole-piece 80, the 
magnetic flux from one magnet is magnified and the motion sensor is 
re-magnetised in an opposite sense. Similarly, the motion sensor is 
remagnetised in the opposite sense when the pole-piece is in the proximity 
of the other air-gap. The advantage of this arrangement rests on the 
particularly simple realisation of the parts of the arrangement which are 
in motion. 
FIG. 7 shows a further mechanical arrangement of three motion sensors 80', 
81, 82, a switching permanent magnet 83 and two reset permanent magnets 
84, 85. The effective magnetic axes of the motion sensors and the 
permanent magnets are positioned parallel to the axis of the rotary shaft 
2. The permanent magnets which are attached to the shaft are embedded in a 
part of the shaft constructed of material non-conductive to magnetic 
fields in order that the forming of magnetic fields is not influenced by 
the material of the shaft. An arrangement in this form allows the 
construction of an angle of rotation sensor conforming to the invention 
with a particularly short length. 
FIG. 8 shows a mechanical arrangement of three motion sensors 80', 81, 82, 
consisting of units made in a known manner from a unipolar functioning 
pulse-wire motion sensor (see FIG. 6) and two permanent magnets, are 
arranged as shown in FIG. 7. The magnetisation of the motion sensors is 
carried out by two moving pole-pieces 87, 88 which are attached to the 
rotary shaft, as described in FIG. 6. The advantage of this arrangement, 
apart from the particularly simple realisation of the parts which are in 
motion, lies in the short length of the construction. 
FIG. 9 shows the arrangement of an electronic circuit 13 consisting of 
three pulse forming circuits 16, 17, 18, a control circuit 19, a settable 
up/down counter 22, a non-volatile read/write memory 21 and a 
computing/interface circuit 20. Each of the pulse forming circuits 
consists of a diode 23, a charging capacitor 24, a discharge resistor 25, 
an electronic switch 26 and a diode 27. The voltage pulses U1, U2, U3 
produced by the motion sensors 6, 7, 8, are applied to the three pulse 
forming circuits 16, 17, 18. A voltage pulse passes diode 23 in the 
conductive direction and charges capacitor 24. 
The voltage on the charging capacitor, as an impulse voltage vector Y=[Y1, 
Y2, Y3] consisting of the analogue signals Y1, Y2, Y3, 28, 29, 30, is 
passed to the control circuit 19. The capacitor voltage is applied to the 
circuit consisting of an electronic switch 26 and discharge capacitor 25. 
Logic signals "discharge charging capacitor" 32, 32, 33 to discharge the 
charging capacitors are supplied to the electronic switches from the 
control circuit 19. An auxiliary voltage supply is obtained from the 
charging capacitor via diode 27 in the conducting direction and applied to 
conductor 34. The auxiliary voltage supply is supplied to the power supply 
inputs of the control circuit 19, the up/down counter 22 and the 
non-volatile memory 21. The auxiliary voltage supply and the external 
voltage supply via conductor 34 are connected together by means of diode 
60 in a conducting direction. 
Thus under normal operating conditions with an external source of voltage 
the control circuit, the up/down counter and the non-volatile memory are 
supplied with operating power externally. Should the external source of 
power fail, then the fine angle of rotation sensor, the computing and the 
interface circuits are no longer supplied with a source of operating 
voltage and the counting of shaft revolutions is carried out utilising the 
auxiliary voltage supply obtained from the pulse forming circuit. The 
control circuit 19 provides a logic-signal "output ready" 36 to control 
the transfer of the value of the number of revolutions to the computing 
and interface circuit 20 and the logic signals "write to non-volatile 
memory" 37 and "read from non-volatile memory" 38 to control the operation 
of the non-volatile memory. Further, the control circuit is connected to 
the non-volatile memory via the logic signal "counter direction" 42 and 
the condition vector "last revolution state" Z=[Z1, Z2, Z3] consisting of 
the logic signals Z1, Z2, Z3, 43, 44, 45. Further, the control circuit 
provides the logic signals "clock" 39, "up/down" 40 and "set counter" 41 
to the up/down counter. 
The up/down counter is connected to the non-volatile memory by the data 
word "revolutions", consisting of the data bits D0, D1, . . . Dn 46, 47, 
48, . . . 49 by means of which the revolution count can be loaded and 
returned. The non-volatile memory is connected to the computing and 
interface circuit 20 via logic signal "count direction output" 50 and a 
condition vector "last revolution condition output" Z'=[Z1',Z2',Z3'] 
consisting of the logic signals Z1',Z2',Z3', 51, 52, 53, and via data word 
"revolutions output", consisting of the data bits D0', D1', . . . Dn' 54, 
55, 56, . . . 57. The non-volatile memory is realised using ferro-electric 
storage technology. It contains a data word, split for example into twelve 
bits for the revolution count, three bits as storage for the condition 
vector "last revolution condition" Z and one bit for "count direction" 42. 
Storage elements in ferro-electric technology are characterised by 
particularly low power consumption and by fast read and write modes. The 
storage element in ferro-electric storage technology is an electrical 
crystal dipole. Similarly to a ferro-magnetic dipole, this changes its 
direction under the influence of an electrical field, and maintains this 
direction in the absence of a supply of power. In another form of 
realisation according to subtitle 7, the non-volatile read/write memory 
uses a static semiconductor element in CMOS technology with a buffer 
battery or a buffer capacitor. Since the motion sensors do not require a 
source of power, this form of realisation requires an advantageously low 
supply current for the operation of the non-volatile memory, such that the 
buffer battery remains useable over a long lifetime. 
FIG. 10 shows as an example the voltage pulses produced by the three 
pulse-wire sensors 6, 7, 8, and their correspondence to the absolute 
rotation angle of the rotary shaft 2: 
EQU WA=WF+N.times.360.degree. 
where 
N: number of revolutions of the shaft 
WA: absolute angle of rotation 
WF: angle of rotation over one revolution 
By means of the voltage pulses U1, U2, U3 a single revolution of the shaft 
is divided into three sectors I, II, III. The occurrence of voltage pulse 
U1 indicates for an anti-clockwise rotation the transition from sector III 
to sector I and for clockwise rotation the transition from sector I to 
sector III. A similar condition applies to the voltage pulses U2, U3. The 
angular position of the rotary shaft can thus be determined to be within 
either sectors I, II or III by evaluating the state of the voltage pulses 
U1, U2, U3 taking into consideration the previous states U1 (-1), U2(-1), 
U3(-1). The number of shaft revolutions can be determined by the 
evaluation of the voltage pulses as follows. 
The following is a description of one arrangement showing the operation of 
the motion sensors 6, 7, 8, the electronic counter 13, the pulse forming 
circuits 16, 17, 18, the control circuit 19, the settable up/down counter 
22, the non-volatile memory 21 and the computing and interface circuit 20 
by means of logical relationships and control sequences. 
The "pulse voltage vector" Y=[Y1, Y2, Y3] assumes the values Y=[100], 
Y=[010], Y=[001], with the following meaning: 
Y=[100]: actual switching magnet position in arc segment I or III 
Y=[010]: actual switching magnet position in arc segment I or II 
Y=[001]: actual switching magnet position in arc segment II or III 
The condition vector "last rotation condition" Z=[Z1, Z2, Z3] assumes the 
values Z=[100], Z=[010], Z=[001], with the following meaning: 
Z=[100]: last switching magnet position in arc segment I or III 
Z=[010]: last switching magnet position in arc segment I or II 
Z=[001]: last switching magnet position in arc segment II or III 
The logic signal "count direction" has the following meaning 
RB=0: clockwise rotation, count down 
RB=1: anticlockwise rotation, count up 
The condition vector "last rotation condition" Z and the logic signal 
"count direction" are stored in the non-volatile memory. 
After the build-up of the auxiliary supply voltage UV' as the result of a 
voltage pulse from one of the motion sensors, the control circuit works 
through the following control sequence: 
Step 1: wait for voltage pulse, then continue with step 2 
Step 2: load the up/down counter from the non-volatile memory, read pulse 
voltage vector Y=[Y1, Y2, Y3 ], load "last revolution condition" Z=[Z1, 
Z2, Z3 ] from non-volatile memory 
Step 3: increment, decrement or leave the up/down counter unchanged based 
on the evaluation of "count direction", voltage pulse vector Y and 
condition vector "last revolution condition", using the logic signals 
"clock", "up/down" and "set counter" 
Step 4: determine new direction of rotation, set the count direction bit 
accordingly 
Step 5: write the contents of the up/down counter 22, the voltage pulse 
vector Y as condition vector "last revolution condition" Z, and direction 
bit RB into the non-volatile memory 21. 
Step 6: if the external supply of power is present, transfer the contents 
of the non-volatile memory 21 to the computing and interface circuit 20 
using the logic signal "output ready". 
Step 7: discharge the charging capacitor by operating the electronic 
switch. Continue with step 1. 
This control sequence ensures that the up/down counter is loaded with the 
contents of the non-volatile memory, is either incremented or decremented 
depending on the pulse voltage vector Y, the condition vector "last 
revolution condition" Z and the count direction bit RB and the result 
returned to the non-volatile memory. 
The count direction bit RB is set according to the logical evaluation of 
the equations (G1) to (G9): 
______________________________________ 
If Z = [100] AND Y = [001] then RB = 0 (down) 
(G1) 
If Z = [100] AND Y = [010] then RB = 1 (up) 
(G2) 
If Z = [100] AND Y = [100] then RB is not changed 
(G3) 
If Z = [010] AND Y = [100] then RB = 0 (down) 
(G4) 
If Z = [010] AND Y = [001] then RB = 1 (up) 
(G5) 
If Z = [010] AND Y = [010] then RB is not changed 
(G6) 
If Z = [001] AND Y = [010] then RB = 0 (down) 
(G7) 
If Z = [001] AND Y = [100] then RB = 1 (up) 
(G8) 
If Z = [001] AND Y = [001] then RB is not changed 
(G9) 
______________________________________ 
Changing the up/down counter is dependent on the pulse voltage vector Y, 
condition vector "last rotation condition" Z and count direction bit RB 
according to the following logical conditions: 
______________________________________ 
If Z = [001] AND Y = [100] AND RB = 1 then N = N + 1 
(G10) 
If Z = [010] AND Y = [100] AND RB = 0 then N = N - 1 
(G11) 
If Z = [100] AND Y = [010] AND RB = 0 then N = N + 1 
(G12) 
If Z = [100] AND Y = [001] AND RB = 1 then N = N - 1 
(G13) 
For all other conditions N = N 
(G14) 
______________________________________ 
The equations (G10) and (G11) indicate that for each pulse U1 from the 
motion sensor 6 for monotonic rotation of the rotary shaft in clockwise or 
anticlockwise direction respectively, the up/down counter will be 
respectively incremented or decremented by the value "1". The equations 
(G12) and (G13) indicate that after a change in the direction of rotation 
the pulses U2, U3 from the motion sensors 7 and 8 will accordingly be used 
to increment or decrement the rotation counter. 
The computing and interface circuit 20 combines together the measurement 
value from the fine angle of rotation sensor and the value from the 
rotation counter stored in non-volatile memory to provide an absolute 
value for the angle of rotation. Since the positions of the voltage 
generating motion sensors 6, 7, 8 relative to the position of the fine 
angle of rotation sensor depends on manufacturing and component 
tolerances, then to establish the absolute angular position WA of the 
rotary shaft, the value from the fine angle of rotation sensor 3, the 
count stored in the non-volatile memory 21, the condition vector "last 
revolution condition" Z and the count direction bit must be evaluated. 
This evaluation also takes into consideration the transitional condition 
which occurs with a change of rotational direction, according to equations 
(G12) and (G13), and synchronises information from the revolutions counter 
with the angle position given by the fine angle of rotation angle sensor. 
The result is a corrected counter condition N' which is a function of the 
angular position of the fine angle of rotation sensor, the condition 
vector "last revolution condition" Z and "count direction" RB. The 
evaluation is made according to the following algorithm: 
______________________________________ 
If RB = 1 AND Z = [100] AND WF &lt; 180.degree. then N' = N 
(G19) 
If RB = 1 AND Z = [100] AND WF &gt; 180.degree. then N' = N 
(G20) 
If RB = 0 AND Z = [100] AND WF &lt; 180.degree. then N' = N 
(G21) 
If RB = 0 AND Z = [100] AND WF &gt; 180.degree. then N' = N 
(G22) 
If RB = 1 AND Z = [010] AND WF &lt; 300.degree. then N' = N 
(G23) 
If RB = 1 AND Z = [010] AND WF &gt; 300.degree. then N' = N 
(G24) 
If RB = 0 AND Z = [010] AND WF &lt; 300.degree. then N' = N 
(G25) 
If RB = 0 AND Z = [010] AND WF &gt; 300.degree. then N' = N 
(G26) 
If RB = 1 AND Z = [001] AND WF &lt; 60.degree. then N' = N 
(G27) 
If RB = 1 AND Z = [001] AND WF &gt; 60.degree. then N' = N 
(G28) 
If RB = 0 AND Z = [001] AND WF &lt; 60.degree. then N' = N 
(G29) 
If RB = 0 AND Z = [001] AND WF &gt; 60.degree. then N' = N 
(G30) 
______________________________________ 
where: 
RB: count direction 
WF: angular position measured by the fine angle of rotation sensor 
N: number of revolutions stored in the nonvolatile memory 21 
N': corrected number of revolutions 
The absolute angular position WA of the rotary shaft 2 after several 
revolutions is given by the combination of the angle measurement WF from 
the fine-wire angle of rotation sensor 3 and the corrected counter value 
N'. This is carried out by the computing and interface circuit 20: 
EQU WA=WF+N'.times.360.degree. 
with 
WA: absolute angle of the shaft over several revolutions 
WF: absolute angle of the shaft over a single revolution 
N': corrected number of revolutions 
The absolute value is transmitted from the computing and interface circuit 
20 via data-interface with conductors 14 to the supervisory unit 15. Since 
for most practical purposes the counter has to be set to a specific value 
then the transmission of a counter value from the supervisory unit 15 to 
the non-volatile memory of the angular rotation sensor is also provided. 
FIG. 11 shows an alternative graphical presentation of the logical 
conditions from equations G1 to G14 describing the counting of the shaft 
revolutions in the form of a state diagram. Accordingly, the motion of the 
shaft is represented by four logic states S(1L) 100, S(1R) 101, S(2) 102, 
S(3) 103 and ten state transitions corresponding to the shaft rotation in 
clockwise or anticlockwise direction. 
The interpretation of the states 
S(1L): actual switching magnet position in arc-segment I or III last count 
direction "up" 
S(1R): actual switching magnet position in arc-segment I or III last count 
direction "down" 
S(2): actual switching magnet position in arc-segment I or II 
S(3): actual switching magnet position in arc-segment II or III 
The following transitions between states are possible, the change of count 
N in the revolution counter and/or the change in direction bit RB are 
shown in the following table. 
______________________________________ 
S(1L) =&gt; S(2): 
-- RB = 1, Transition 107 
S(1R) =&gt; S(2): 
N = N + 1 RB = 1, Transition 109 
S(1L) =&gt; S(3): 
N = N - 1 RB = 0, Transition 105 
S(1R) =&gt; S(3): 
-- RB = 0, Transition 106 
S(3) =&gt; S(1L): 
N = N + 1 RB = 1, Transition 104 
S(2) =&gt; S(1R): 
N = N - 1 RB = 0, Transition 108 
S(2) =&gt; S(1L): 
-- RB = 1, Transition 110 
S(3) =&gt; S(1L): 
-- RB = 0, Transition 111 
S(1R) =&gt; S(1R): 
-- -- Transition 112 
S(1L) =&gt; S(1L): 
-- -- Transition 113 
______________________________________ 
For monotonic anticlockwise rotation of the shaft, with transition states 
104, 107, 110, incrementation of the up/down counter is given on 
transition 104. For monotonic clockwise rotation of the shaft, with 
transition states 106, 108, 111, decrementation of the up/down counter is 
given on transition 108. For reversal of rotation within the sectors I and 
II, transition states 112 and 113 occur without influencing either counter 
or count direction bit. For a change of rotation from anticlockwise to 
clockwise and passing out of sectors I and III, transition 105 occurs and 
the counter is decremented. For a change of rotation from clockwise to 
anticlockwise and passing out of sectors I and III, transition 109 occurs 
and the counter is incremented. The count direction bit is set to logic 
"1" on transitions 107, 109, 110, 104, and set to logic "0" on transitions 
105, 106, 108, 111. The evaluation of the count direction bit occurs 
before each state transition, the update occurs after.