Electronic weighing apparatus

An analog voltage representing the weight of an article being weighed is provided by a strain-gage type load cell. The analog voltage is converted into digital weight value data by means of an analog/digital converter. If the weight value data which are provided after the lapse of a predetermined time period following the turning on of a power supply, are within a predetermined range, the weight value data are stored in a memory as an offset value. The data stored in the memory are used for subtraction from further weight value data are displayed in digital manner by a display. If the weight value data provided after the lapse of a predetermined time period is off the predetermined range, a renewal setting of the offset value in the memory is prevented.

BACKGROUND OF THE INVENTION 
1. Field of the Invention; 
The present invention relates to an electronic weighing apparatus. More 
specifically, the present invention relates to an electronic weighing 
apparatus wherein an analog voltage provided by a load converter such as a 
strain-gage type load cell is converted into a digital value, whereby the 
magnitude of the load is displayed in a digital manner. 
2. Description of the Prior Art 
Conventionally a strain-gage type load cell has been used as a load 
converter. One example of an electronic weighing apparatus employing a 
conventional strain-gage type load cell is shown in FIG. 1. Referring to 
FIG. 1, a weighing pan, not shown, for placing an article being weighed is 
coupled to a strain-gage type load cell 1. The load cell 1 comprises an 
energizing voltage source 3, a fine adjustment variable resistor 5 and a 
rough adjustment variable resistor 7. As is well known, such load cell 1 
provides an analog signal of the magnitude which is proportional to the 
weight of an article placed on the weighing pan and the analog signal is 
applied to an amplifier 9. The amplified analog voltage provided by the 
amplifier 9 is applied to an analog/digital converter 11. The 
analog/digital converter 11 may comprise an integrated circuit 
"ICL8052/ICL71C03" manufactured by Intersil Incorporated, U.S.A. for 
example. The analog/digital converter 11 serves to convert a given analog 
voltage into a corresponding digital signal, which is applied to a display 
control 13 through a terminal T1. The display control 13 is responsive to 
a signal representing the sign of plus or minus of the given weight value 
provided by the terminal T2 as well as the given digital signal from the 
terminal T1 of the analog/digital converter 11 to cause a well-known 
digital display 15 to display the weight value. 
In such conventional electronic weighing apparatus, it has been a common 
practice to make sure that the zero point of the load cell 1 and the 
display zero point in the display 15 coincide with each other. 
Accordingly, a fine adjustment is required for that purpose and such fine 
adjustment is accomplished by a variable resistor 5. Such variable 
resistor is liable to exhibit a poor temperature coefficient 
characteristic and is hence not necessarily stable with respect to a 
temperature variation. Accordingly, fine adjustment is required from time 
to time in accordance with a variation of an ambient temperature and it is 
difficult to display accurate weight data. Furthermore, the digital output 
obtained from the analog/digital converter 11 exhibits a stepwise 
variation, as shown in FIG. 2, for example, which requres that no output 
change occurs just at the zero point. More specifically, although a 
conventional weighing apparatus requires zero point adjustment to preclude 
an output change at the zero point, as shown in FIG. 2, the higher the 
resolution the more difficult is such zero point adjustment. Accordingly, 
a conventional electronic weighing apparatus as shown in FIG. 1 has made 
it impossible to enhance the resolution of an analog/digital converter. 
In order to avoid the above described problem, it has been proposed that an 
offset value is in advance set so that the zero point of a load cell and 
the zero point of a display may deviate from each other, thereby to 
simplify a manual operation of an electronic weighing apparatus. As such 
an offset value, a value of approximately five percent of the full range 
of the scale, for example, is selected and such offset value is set in 
response to initiation of an operation of the apparatus upon turning on of 
a power supply, for example. On the occasion of weight measurement, the 
offset value, which is preset in advance or stored, is used for 
subtraction from an analog/digital converter output and the difference 
value is displayed as a weighed value. Thus, an electronic weighing 
apparatus of a type for setting an offset value avoids precise fine 
adjustment and accordingly can simplify a manufacturing process of the 
apparatus. More specifically, by setting such an offset value, any 
influence on a display exerted by a variation of the weight value of a 
placing pan for placement of an article is avoided, if such variation of 
the weight of a placing pan is within the range of the offset value. Hence 
a fine adjustment becomes unnecessary. Furthermore, since such weighing 
pan can be exchanged with relative freedom without precise adjustment, 
maintenance of the apparatus is also facilitated. 
Thus, in an electronic weighing apparatus of a type for setting an offset 
value, such an offset value is stored in a memory. The timing for storing 
such offset value in a memory is selected to be responsive to initiation 
of an operation of the apparatus, so that the output of an analog/digital 
converter may be stored in a memory after a predetermined time period, say 
five to ten seconds, following turning on of a power supply, for example. 
Thus, the apparatus is structured such that the content in the memory is 
again applied to the output of an analog/digital converter each time when 
the power supply is turned on without regard to the magnitude of the 
weighed value at that time. In other words, even if the output from the 
analog/digital converter at the time of storing an offset value in a 
memory is relatively large, such value is stored in the memory as an 
offset value. 
On the other hand, a load cell for use in such an electronic weighing 
apparatus and a structure for supporting such load cell are not 
necessarily designed to have a surplus mechanical strength. Accordingly, 
the output from such load cell exhibits a linearity characteristic only 
within a given limited range. Therefore, the linear portion of the output 
from an analog/digital converter receiving such output from a load cell is 
also limited to a certain restricted range. In other words, although the 
output of a load cell and thus the output from an analog/digital converter 
exhibits a linear change characteristic with respect to a variation of the 
weight in a given predetermined range which is inherent in an apparatus, 
the output does not necessarily exhibit such a linear change when the 
output exceeds such range. Accordingly, if and when an offset value being 
set in advance immediately before a weighing operation is too large and a 
weight value of an article being weighed is added thereto, the sum value 
could exceed the above described linearity range. In such a case, the 
weighing accuracy may not necessarily be satisfactory. 
Meanwhile, in such apparatus for setting an offset value described above, 
it has been a common practice that a display is controlled to display "0" 
until such offset value is set. Furthermore, in a case where an offset 
value is stored in a memory in response to turning on of a power supply, 
the display is controlled to display "0" until after the lapse of a 
predetermined time period and therefore an operator cannot check the range 
or the magnitude of the offset value. In other words, in such a 
conventional apparatus, an operator cannot observe the magnitude of an 
offset value being stored in a memory when the weighed value is displayed. 
Accordingly, it is a disadvantage that the weight measurement is made 
without knowing whether a large change of such an offset value has 
occurred which would reduce the weighing accuracy. 
In an apparatus in which an offset value is not stored in a memory in 
response with turning on of a power supply but an offset value is renewed 
manually, such offset value can be checked by looking at a display. 
However, when an apparatus is structured such that an offset value may be 
manually set in a memory, an offset value is renewed after an operator 
himself checks the magnitude of such offset value. Accordingly, in the 
case where such offset value is set through manual operation, it may 
occur, unless the range of an offset value inherent in the apparatus is 
known, that an erroneous judgement and accordingly an erroneous offset 
value renewal is made. Such a situation also reduces the operating 
facility of such an apparatus and deteriorates the weighing precision of 
the apparatus. 
SUMMARY OF THE INVENTION 
Briefly described, the present invention relates to an electronic weighing 
apparatus comprising a storage means for storing an offset value being 
preset and is adapted for correcting weighed value data based on the data 
stored in the storage means. The present weighing apparatus is 
characterized in that storing of such an offset value in the storage means 
is prevented if the offset value being preset in the storage means is 
outside a predetermined range. 
According to the present invention, since an offset value exceeding the 
predetermined range is not preset, a weighing outside the linearity range 
of the apparatus caused by too large an offset value, which occurred 
conventionally, is avoided. In other words, weighing in the range where a 
weighing accuracy is degraded, is avoided. Accordingly, once an offset 
value is set, an accurate weighing is assured. In the case where an offset 
value is off or outside a predetermined range, such offset value is 
prevented from being set for renewal. Thus, it may occur that the zero 
point of the apparatus deviates substantially. Accordingly, based on 
whether an offset value can be set or not, it can be determined whether 
the apparatus is in a normal state or in an abnormal state. By noting down 
when an offset value cannot be renewed, it is easier for an operator to 
make the above described determination. 
In a preferred embodiment of the present invention, a strain-gage type load 
cell is employed as a load converter and the output thereof is converted 
into a digital value by means of an analog/digital converter. The 
converted digital value is applied to a microcomputer or a microprocessor. 
At that time an interrupt signal is applied to the microcomputer from the 
analog/digital converter upon completion of the conversion, so that a 
microcomputer is responsive to an interrupt signal to read thereafter the 
digital value from the analog/digital converter. In a further preferred 
embodiment of the present invention, the analog/digital converter and the 
microcomputer are adapted to be operable in synchronism and accordingly a 
particular input/output register conventionally required, is not needed. 
Even in an apparatus employing a microcomputer, it is determined whether 
the above described offset value is within a predetermined range. If the 
offset value exceeds the above described range, the renewal setting of the 
offset value is prevented to avoid an inaccurate weighing. 
Accordingly a principal object of the present invention is to provide an 
electronic weighing apparatus which is capable of preventing a reduction 
in the accuracy that otherwise could be caused by an offset value set in 
advance. 
Another object of the present invention is to provide an electronic 
weighing apparatus wherein it is determined whether an offset value or a 
weight value is within a predetermined range, whereupon setting of such 
offset value is determined. 
A further object of the present invention is to provide an electronic 
weighing apparatus wherein the setting of an offset value is prevented 
when a weight value or an offset value exceeds a predetermined range. 
Still another obejct of the present invention is to provide an electronic 
weighing apparatus which provides to the operator an indication whether or 
not an offset value has been set. 
Still a further object of the present invention is to provide an improved 
electronic weighing apparatus employing a microcomputer or a 
microprocessor. 
These objects and other objects, features, aspects and advantages of the 
present invention will become more apparent from the following detailed 
description of the present invention when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS: 
FIG. 3 is a block diagram showing one embodiment of the present invention. 
The embodiment shown comprises a strain-gage type load cell 1 which 
comprises an energizing voltage source 3 and an adjustment variable 
resistor 7. The adjustment variable resistor 7 is connected to one side of 
a strain-gage constituting the load cell 1, so that the same serves to 
cancel "ineffective graduations" caused by a placing pan for placement of 
an article being weighed and other means, not shown, associated therewith. 
The output analog signal obtained from the strain-gage or load cell 1 is 
amplified by an amplifier 9 and is then applied to an analog/digital 
converter 11. By adjusting the amplification degree of the amplifier 9, it 
is possible to make a range adjustment. The analog/digital converter 11 
may be implemented by the previously described integrated circuit, i.e. 
the integrated circuit model No. ICL8052/ICL71C03 manufactured by Intersil 
Incorporated, U.S.A. The analog/digital converter 11 has two output 
terminals T1 and T2. The output terminal T1 serves as a data output 
terminal for providing a digital signal of a binary coded decimal code 
associated with the magnitude of the output analog voltage obtained from 
the amplifier 9. On the other hand, the output terminal T2 serves as a 
polarity signal output terminal which provides a signal representing the 
polarity of the above described analog voltage which assumes the low level 
or the logic "zero" when the polarity is plus and which assumes the high 
level or the logic "one" when the polarity is minus. The data in the form 
of a digital signal obtained from the data output terminal T1 of the 
analog/digital converter 11 are applied to a comparator 29, a memory 33 
and to a subtractor 35 as a minuend. The signal obtained from the polarity 
signal output terminal T2 of the analog/digital converter 11 is applied to 
a display control 13 to be described below. 
A power supply turning on detecting circuit 17 comprises an integrating 
circuit means 19 incuding a series connection of a resistor and a 
capacitor. The integration circuit 19 is responsive to a voltage V.sub.DD 
when the power supply, not shown, is turned on and integrates the voltage 
in accordance with a predetermined integration time constant. The output 
of the integration circuit 19 is applied to a level detector 21 such as a 
Schmidt circuit. The level detector 21 is responsive to the output voltage 
of the integration circuit 19 to provide a signal which assumes the high 
level if the output voltage of the integration circuit 19 exceeds a 
predetermined value. The output of the level detector 21 is applied to a 
differentiation circuit 23 which is responsive to the rising or leading 
edge of the output of the level detector 21 to provide one differentiated 
pulse output to a determining portion 25. 
The determining portion 25 comprises a data setter 27, a comparator 29 and 
an AND gate 31. One input of the AND gate 31 is connected to receive the 
differentiation pulse output from the above described differentiation 
circuit 23. The comparator 29 is connected to receive at one input thereof 
a digital signal obtained from the analog/digital converter 11 and to 
receive at the other input thereof an output from the data setter 27. The 
data setter 27 sets data representing a range of an offset value suitable 
for the particular type of weighing appartus. More specifically, the data 
setter 27 is used to set a weight value data corresponding to 
approximately four to five percent of the full scale or full range of the 
apparatus. The data setter 27 may be provided with a predetermined circuit 
arrangement or alternatively may be implemented by a discrete structure 
such as a pinboard matrix or a digital switch such as a thumb rotary 
switch. The comparator 29 is connected to receive as an input A the 
digital signal obtained from the analog/digital converter 11 and as an 
input B the output obtained from the data setter 27. The comparator 29 is 
adapted such that if the input A is smaller than the input B (i.e. A&lt;B) 
the output of the high level or the logic "one" is provided, but when the 
input A is larger than the input B (i.e. A.gtoreq.B) the output of the low 
level or the logic zero is provided. The output of the comparator 29 is 
applied to the other input of the AND gate 31. The output from the AND 
gate 31 is applied to a memory 33 as a write enable signal. More 
specifically, when the output from the AND gate 31 is the high level or 
the logic "one", the data in the memory 33 are renewed, whereas, when the 
output of the AND gate 31 is the low level or the logic "zero", data 
renewal in the memory 33 is inhibited. The memory 33 is used for storing 
an offset value and the output is applied to the subtractor 35 as a 
subtrahend. 
The subtractor 35 evaluates a difference between the minuend i.e. the 
digital signal obtained from the analog/digital converter 11 and the 
subtrahend i.e. the digital signal obtained from the memory 33, for 
providing the subtraction result to the display control 13. The display 
control 13 is responsive to the signal received from the polarity signal 
output terminal T2 of the analog/digital converter 11 and the subtraction 
result (a digital signal) obtained from the subtractor 35 to digitally 
display a weighed value by means of the display 15 in accordance with the 
received digital signal when the signal obtained from the terminal T2 is 
the low level or the logic "zero". On the other hand, when the polarity 
signal is the high level or the logic "one", the display 15 is caused to 
make a predetermined display without regard to the input digital signal 
received from the subtractor 35. 
Meanwhile, the display control 13 may be structured to receive the signal 
from the level detector 21 included in the power supply turning on 
detecting portion 17. The display control 13 causes the display 15 to make 
another predetermined display until the high level signal is received from 
the level detector 21. The display control 13 will be described below in 
more detail with reference to FIGS. 5 and 6. 
The weight value data being set in the data setter 27 correspond to a point 
"a" shown in FIG. 4 and corresponds to approximately four to five percent 
of the full scale range of the electronic weighing apparatus shown. 
Referring to FIG. 4, the lines b and b' representing the output show that 
the output changes in accordance with an adjustment of the variable 
resistor 7 shown in FIG. 3. 
The just described apparatus operates as follows. Upon turning on of the 
power supply, the integration circuit 19 initiates the integration, as 
shown at (A) in FIG. 3A, so that the output gradually increases. When the 
output voltage of the integration circuit 19 reaches a predetermined 
value, the high level signal is obtained at that time from the level 
detector 21, as shown at (B) in FIG. 3A. Accordingly, the differentiation 
circuit 23 provides a differentiated pulse at that time, as shown at (C) 
in FIG. 3A. 
On the other hand, upon turning on of the power supply, an analog signal 
representing the load at that time is obtained from the strain-gage type 
load cell 1 and accordingly a digital signal representing the load is 
provided by the analog/digital converter 11 through its output terminal 
T1. The comparator 29 provides the output of the logic "one" or the high 
level if the received digital data signal (A) is smaller than the digital 
data signal (B) provided from the data setter 27. The AND gate 31 is 
responsive to the logical product of the output of the high level obtained 
from the comparator 29 and the pulse obtained from the differentiation 
circuit 23 to provide a write enable signal to the memory 33. More 
specifically, during a time period after turning on of the power supply 
until the pulse is obtained from the differentiation circuit 23, i.e. 
after the lapse of a time period t in FIG. 3A, the determining portion 25 
determines whether the data obtained from the analog/digital converter 11 
is within the predetermined weight value data at that time. More 
specifically, the determining portion 25 determines whether an offset 
value being set after the lapse of a time period t0 after turning on the 
power supply, is within the predetermined range, i.e. a range where a 
linearity of the apparatus is not degraded. If the offset value (A) is 
smaller than a predetermined weight value (B), i.e. if the data (A) is 
within the point "a" shown in FIG. 4, the memory 33 is enabled to set the 
data given at that time in a renewal manner as an offset value. On the 
other hand, the data set in the memory 33 is applied to the subtractor 35. 
However, at that time it is supposed that the two inputs of the minuend 
and of the subtrahend of the subtractor 35 are of the same value and 
accordingly, the display 15 is caused to display "0" as a weighed value. 
At the time when the time period t has lapsed and if the given data (A) 
exceeds the preset weight value data (B), the comparator 29 provides at 
its output the low level or the logic "zero". Accordingly, the AND gate 31 
blocks the pulse obtained from the differentiation circuit 23 and thereby 
disables the memory 33 to renew the data. Therefore, a renewed setting of 
an offset value in the memory 33 is prevented. In other words, in such a 
case the memory 33 is not loaded with any offset value. 
The variable resistor 7 for canceling "ineffective graduations" is adjusted 
so that the output voltage obtained from the amplifier 9 comes to a midway 
point c below the point "a" shown in FIG. 4 if no article is placed on the 
apparatus. An adjustment to such midway point "c" is made as follows. 
After turning on the power supply, the weighing pan, not shown, is 
slightly raised, so that the ineffective graduation component exerted on 
the load cell 1 may be decreased. Then the display value immediately 
before the indication by the display 15 changes to "0" is read and the 
read display value is compared with a standard value which is known in 
advance. If there is a deviation between the read display value and the 
known standard value, again the variable resistor 7 is adjusted to make 
both coincide with each other. Through the above described operation, 
setting to the midway point c can be made with ease. 
Now referring to FIGS. 5 and 6, the display control 13 and a display manner 
by the display 15 responsive thereto will be described. As shown in FIG. 
5, the display control 13 comprises a decoder 131 connected to receive the 
digital data of a binary coded decimal code obtained from the subtractor 
35, for example. The decoder 131 decodes the received digital data of the 
binary coded decimal code to form segment selection signals corresponding 
to seven segments "a to g" of each digit position of the display 15. The 
outputs A to G correspond to the segments a to g, respectively, of each 
digit position of the display 15. The outputs A to F from the segment 
decoder 131 are applied to the corresponding inhibit gates 132a to 132f, 
respectively. The inhibit gates 132a to 132f receive at the respective 
inhibit inputs a polarity signal obtained from the analog/digital 
converter 11 through the output terminal T2. The outputs of the inhibit 
gates 132a to 132f are applied to one input of each of the corresponding 
OR gates 133a to 133f. The OR gates 133a to 133f receive, at the other 
input thereof, the output Q of a flip-flop 136. The signal obtained from 
the output G of the segment decoder 131 is applied to one input of the 
corresponding OR gate 133g. The OR gate 133g is also connected to receive 
the above described polarity signal and the output Q of the flip-flop 136. 
The outputs of the OR gates 133a to 133g are applied through the 
respective corresponding drivers 137a to 137g to energize the respective 
segments a to g of the display 15. In the display 15 the corresponding 
segments of each of the digits, in the embodiment shown, five digits, are 
connected, so that the corresponding segments are driven by the output of 
the corresponding drivers. Digit signals D1 to D5 have a timing relation 
as shown in FIG. 6, so that the respective digits G1 to G5 of the display 
15 may be driven by the corresponding drivers 138a to 138e. 
The set input S of the flip-flop 136 is connected to receive the output of 
the differentiation circuit 135 and the reset input R of the flip-flop 136 
is connected to receive the output of the AND gate 31 included in the 
determining portion 27. The differentiation circuit 135 provides one 
differentiated pulse when the power supply is turned on, for example. 
Accordingly, the flip-flop 136 is responsive to turning on of the power 
supply to cause the output Q to assume the high level. 
In operation, first the display of a positive weighed value will be 
described. In such a case any inhibit inputs are applied to the inhibit 
gates 132a to 132f and accordingly the respective outputs A to F obtained 
from the segment decoder are applied as such through the OR gates 133a to 
133f to the drivers 137a to 137f. The output G of the segment decoder 131 
is applied as such through the OR gate 133g to the corresponding driver 
137g. On the other hand, since the digit signals D1 to D5 are provided in 
succession in a cyclic manner as shown in FIG. 6, the display 15 is 
responsive to the segment selecting signals for displaying the data in a 
digital manner in accordance with a well-known dynamic driving system. 
Now a case where the voltage from the amplifier 9 is minus will be 
described. In such a case, the output of the high level or the logic "one" 
is obtained from the terminal T2 (FIG. 3) of the analog/digital converter 
11. Therefore, the inhibit gates 132a to 132f are inhibited from providing 
the data signal. Accordingly, the outputs A to F obtained from the segment 
decoder 131 are inhibited by the corresponding inhibit gates 132a to 132f. 
However, only the output G is applied through the OR gate 133g to the 
driver 137g. Accordingly, the display 15 is responsive to the respective 
digit selecting signals D1 to D5 to display by the segment G of the 
corresponding digits G1 to G5. Therefore, an indication by the display 
becomes "- - - - -", thereby to indicate that the weighed value is minus. 
When the power supply is turned on, the flip-flop 136 is set to respond to 
the output from the differentiation circuit 135, whereby the output Q of 
the flip-flop 136 assumes the high level. Therefore, the outputs obtained 
from the OR gates 133a to 133g and are applied to the corresponding 
drivers 137a to 137g. Accordingly, all the segments "a to g" of the 
respective digits G1 to G5 in the display 15 are energized, thereby to 
display an "8" in all of the digits. Thereafter, when a pulse is obtained 
from the AND gate 31 shown in FIG. 3, i.e. after the lapse of a 
predetermined time period t (FIG. 3A) after turning on of the power 
supply, the flip-flop 136 is reset and if the weight value data (offset 
value) at that time does not exceed the predetermined range, the output Q 
is reversed to the low level. Accordingly, in such a case the display 15 
continues to display an "8" in all of the digits until after the lapse of 
the time period t following turning on of a power supply. After the lapse 
of the time period t the display 15 shows a digital display associated 
with the output obtained from the segment decoder 131. While displaying an 
"8" in all the digits, such display may be made to blink by repeatedly 
turning the power supply of the display 15 on or off, for example. In the 
absence of a pulse from the AND gate 31 even after the lapse of a time 
period t following the turning on of the power supply, i.e. when the data 
(offset value) obtained from the analog/digital converter 11 exceeds the 
predetermined range after the lapse of a time period t (the point "a" in 
FIG. 4), the flip-flop 136 is not reset and accordingly the indication of 
"8" at the respective digits in the display 15 continues without 
resetting. As a result, an operator knows that the apparatus is in some 
serious trouble for some reason, so that the zero point of the apparatus 
has largely deviated from its correct position. Under the just described 
circumstances the operator also knows that a weighing measurement does not 
necessarily provide an accurate weighed value. Since the apparatus is 
adapted such that when a weighed value becomes minus in the case where the 
weighing pan, not shown, is raised for some reason, an indication of "-" 
is made in the respective digits in the display 15 as described 
previously, such situation can also be confirmed with ease. 
FIG. 7 is a block diagram showing another embodiment of the present 
invention. The FIG. 7 embodiment is substantially the same as the FIG. 3 
embodiment, except in the following respects. Therefore, a detailed 
description of the same portions in the FIG. 7 as those in the FIG. 3 will 
be omitted. The FIG. 7 embodiment comprises a push button switch 37 which 
may be considered to correspond to the power supply turning on detecting 
portion 17 in FIG. 3. More specifically, in FIG. 7, upon operating the 
push button switch 37, one input of the AND gate 31 assumes the high level 
and a write operation of the memory 33 is controlled in response to the 
output from the comparator 29 at that time. More specifically, although in 
FIG. 3 a write operation of an offset value in the memory 33 was 
automatically controlled in response to turning on of a power supply, in 
FIG. 7 such writing operation may be controlled as desired at the desired 
timing by operating the manual switch 37. By doing so, the determining 
portion 25 can be made effective and, as described above, if and when the 
output of the analog/digital converter 11 at that time is outside the 
range of the preset weight value data, i.e. the offset value as preset is 
outside the predetermined range, the offset value is not set in a renewal 
manner in the memory 33 even if the manual switch 37 is operated at that 
time. 
In although the above described embodiments an indication "- - - - -" was 
made in the display 15 in response to the polarity signal obtained from 
the analog/digital converter 11, thereby to give notice of an abnormality 
of the placing pan. However, such notifying means may be implemented by a 
separate display element without relying upon the display 15. 
Alternatively, such notifying means may comprise a sound alarm means such 
as a buzzer. 
FIG. 8 is a block diagram showing a further embodiment of the present 
invention, implemented as a price scale employing a microcomputer 41. To 
that end, the microcomputer 41 is connected to receive data from a unit 
price data setter 45 as well as the output from the analog/digital 
converter 11. In the FIG. 8 embodiment the load cell 1 is implemented as a 
strain-gage type and the analog/digital converter 11 may be implemented by 
the previously described integrated circuit. The microcomputer 41 may 
comprise model No. "6500 series" manufactured by Rockwell International 
Corporation, U.S.A. The unit price data setter 45 is used to set a unit 
price of the commodities, such as a price per 100 g. Accordingly, the 
microcomputer 41 is responsive to the given weight value data and the unit 
price data to calculate the price of the commodity and display the same on 
the display 15. Since a structure of such price scale is well-known to 
those skilled in the art, a more detailed description thereof will be 
omitted. 
As is well-known, the microcomputer 41 comprises a read only memory for 
storing a system program for the apparatus, and a random access memory 
having a register for temporarily storing the digital data obtained from 
the analog/digital converter 11 and regions for storing other data. The 
read only memory and the random access memory, not shown, are controlled 
by an arithmetic logical unit. The microcomputer 41 further comprises an 
input/output interface, so that the signal from the analog/digital 
converter 11 is applied through the input/output interface, not shown, to 
the arithmetic logical unit, not shown, and the signal from the arithmetic 
logical unit is applied through the input/output interface to the 
analog/digital converter 11 and the display 15. The analog/digital 
converter 11 is responsive to the clock signal obtained from a first clock 
source 39 to convert the analog voltage into a digital signal. The 
microcomputer 41 is also responsive to a clock signal obtained from a 
second clock source 43. The clock pulse signal obtained from the first 
clock source 39 is selected to be, for example, in the range of 200 to 500 
kHz, whereas the clock pulse signal obtained from the second clock source 
43 is selected to be, for example, in the range of 1 to 2 MHz. The signal 
applied from the microcomputer 41 to the input terminal T3 of the 
analog/digital converter 11 is a conversion enable signal (C/S). The 
signal provided from the output terminal T3 of the analog/digital 
converter 11 to the microcomputer 41 is a strobe signal. The microcomputer 
41 is connected to receive the strobe signal as an interrupt signal input. 
Referring to FIG. 9, a read operation of the data from the analog/digital 
converter 11 into the microcomputer 41 in the FIG. 8 embodiment will be 
described. The microcomputer 41 provides a conversion enable signal from 
the terminal C/S to the terminal T3 of the analog/digital converter 11 at 
a predetermined cycle determinable based on the clock pulse obtained from 
the second clock source 43. The conversion enable signal is shown as (A) 
in FIG. 9. The analog/digital converter 11 is responsive to the conversion 
enable signal to convert the analog voltage obtained from the amplifier 9 
into digital data as a function of the clock pulse obtained from the first 
clock source 39. The analog/digital converter 11 is responsive to the 
completion of the converting operation to provide the strobe signal 
(interrupt signal) to the microcomputer 41 from the output terminal T4. At 
the same time, the converted digital data of the binary coded decimal code 
is supplied to the data output terminal T1. Accordingly, the microcomputer 
41 is responsive to the interrupt signal, i.e. the strobe signal to read 
from the data output terminal T1 the data provided to the input/output 
terminal, as shown as (C) in FIG. 9. Then the microcomputer 41 calculates 
the price of the commodity based on the unit price obtained from the unit 
price data setter 45 and based on the newest weighed data, whereupon the 
result is displayed by the display 15. After such one cycle operation or 
control processing is completed, the microcomputer 41 provides again the 
conversion enable signal C/S to the analog/digital converter 11. 
Therefore, the analog/digital converter 11 is operable in synchronism with 
the processing operation by the microcomputer 41 in a common cycle. 
Therefore, if the load on the load cell 1 changes, the display value by 
the display 15 is displayed in a renewal manner in response to each 
conversion enable signal C/S obtained from the microcomputer 41. Thus, 
since the microcomputer 41 is responsive to the strobe signal or the 
interrupt signal obtained from the analog/digital converter 11 to read the 
data as shown as (C) in FIG. 9, an FIFO register (a first-in-first-out 
register) which was conventionally required in this type of microcomputer 
can be dispensed with. 
Now referring to FIGS. 10 and 11, the operation of the FIG. 8 embodiment 
will be described. 
FIG. 10 is a flow diagram for explaining the operation of the FIG. 8 
embodiment when the power supply is turned on. More specifically, when a 
power supply, not shown, is turned on in the FIG. 8 embodiment, a routine 
shown in FIG. 10 is started and the microcomputer 11 initiates the system 
program at the first step 101. Then the microcomputer receives the output 
from the power supply turning on detecting means such as a differentiation 
circuit as shown in FIG. 5, for example, whereby an initial flag is set at 
the step 103. Such initial flag is formed in a portion of the regions in 
the random access memory, not shown. Then at the step 105 a command for a 
display manner described above in conjunction with the FIG. 5 embodiment 
is provided. More specifically, in the FIG. 5 embodiment, an indication 
"8" was made in all of the digits G1 and G5 in the display 15 when the 
power supply is switched on. Preferably such indication was made in a 
blinking manner. Therefore, in FIG. 8 the microcomputer 41 is also adapted 
for providing an instruction for a blinking "8" display in each of the 
respective digits in the display 15 when the power supply is turned on. In 
the following step 107 a timer for a predetermined time period (t) is set. 
Such timer function can also be implemented using a portion of the regions 
in the random access memory, not shown. Then in the step 105 the 
microcomputer 41 determines whether the predetermined time period (t) has 
lapsed, i.e. whether the timer, not shown, is reset. If it is determined 
in the step 109 that the timer is reset, i.e. the preset time period (t) 
has lapsed, the microcomputer 41 determines in the step 111 whether the 
initial flag has been reset. If the initial flag has been reset, then the 
instruction for a blinking indication of "8" in each of the respective 
digits in the display 15 is turned off. Meanwhile, the initial flag is 
reset in the routine shown in FIG. 11. Thus, the microcomputer 41 causes 
an indication "8" to be made in a blinking manner in each of the 
respective digits in the display 15 at the beginning of turning on after a 
power supply at least for the above described predetermined time period 
(t). As a result, the operator knows that a weighing cannot be made during 
that time period. 
FIG. 11 is a flow diagram for explaining the operation when an interrupt 
signal is provided from the analog/digital converter 11 to the 
microcomputer 41. More specifically, if the strobe signal or the interrupt 
signal is provided by the analog/digital converter 11, the microcomputer 
41 receives at the first step 121 the data from the analog/digital 
converter 11, i.e. the data provided from the input/output interface. 
These data are received as described above with reference to FIG. 9. Then 
in the following step 123 the microcomputer 41 provides the conversion 
enable signal (the signal from the terminal C/S) to the analog/digital 
converter 11, thereby to trigger the analog/digital converter 11. Then in 
the step 125 the microcomputer 41 determines whether the initial flag has 
been set. As described above, at the beginning of turning on of a power 
supply, the initial flag has been set. If and when the initial flag has 
been set, then in the following step 127 it is determined whether the data 
from the analog/digital converter 11 is "plus", if so, it is determined in 
the step 129 whether the data is within a predetermined range, (the range 
from zero to "a" in FIG. 4, for example). If the data is within that 
range, then the microcomputer 41 determines in the step 131 whether such 
weighed value data is in a stabilized state. The determination as to 
whether the data is in a stabilized state can be made based on whether the 
data items being received in succession are the same. For example, in a 
situation where the placing pan, not shown, is vibrating, the previous 
data item and the present data item do not coincide with each other, 
whereas if the placing pan is in a stabilized state it is supposed that 
the previous data item and the present data item coincide with each other 
in such a situation. Accordingly, by comparing the previous data item and 
the present data item, it may be determined whether the data is in a 
stabilized state. If it is determined in the step 131 that the data has 
reached a stabilized state, the microcomputer 41 stores the stabilized 
data obtained form the analog/digital converter 11 in a temporary storing 
register, not shown. Such temporary storing register can also be 
implemented by using a portion of the random access memory, not shown, and 
corresponds to the memory 33 in FIG. 3. After the microcomputer 41 has 
stored the data obtained from the analog/digital converter 11, the 
microcomputer 41 resets in the step 135 the initial flag which was set 
when a power supply was turned on. 
If the decision in any one of the previously described steps 125, 127, 129 
and 131 is "NO", the microcomputer 41 shifts to the following step 137. 
Accordingly, if it is determined in the step 129 that the data obtained 
from the analog/digital converter 11 exceeds a predetermined range, namely 
a range of an offset value allowed in advance in accordance with the type 
of scale involved, the microcomputer 41 then determines in the step 139 
whether the blinking indication by the display 15 at the beginning of 
turning on of a power supply described above in conjunction with FIG. 10, 
is in an on state. If it is determined in the step 139 that the blinking 
indication by the display 15 is continuing, then in the step 141 such 
blinking indication is continued. As a result, an operator knows that the 
offset value being stored at that time is outside the allowed range and in 
such a situation the offset value cannot be set. 
If the decision in the step 127 is "NO", i.e. if the data as received is 
"minus", the microcomputer 41 shifts through the steps 139 and 143 to the 
step 145, where an indication "-" is displayed at each of the respective 
digits in the display 15, thereby to indicate that the weighed data is 
"minus". 
In a weighing operation after the offset value is set and if the initial 
flag has been reset in the previous step 135, the decision in the step 125 
is "NO" and the microcomputer 41 shifts to the step 137. In the step 137 a 
difference between the weighed value data obtained from the analog/digital 
converter 11 and the data previously stored in the temporary storing 
register, i.e. the offset value is calculated and the difference is 
displayed by the display 15. Thereafter the microcomputer 41 shifts 
through the steps 139 and 143 to the step 147 and in the step 137 the 
evaluated weighed value data is displayed by the display 15. 
Although the present invention has been described and illustrated in 
detail, it is to be understood that the same is by way of illustration and 
example only and is not to be taken by way of limitation, the spirit and 
scope of the present invention being limited only by the terms of the 
appended claims.