JPS62298726A - Electronic balance - Google Patents

Abstract

PURPOSE:To prevent load data from missing during the reading of temperature information by counting the output of a load sensor by two counters for high- order and low-order digits and changing over and inputting the output of a temperature sensor to the counter for the high-order digit. CONSTITUTION:When a changeover switch 5 driven by a command from a microcomputer 6 has been changed over to the side of a first counter 3a, since a second counter 3b counts up only when the first counter 3a for counting frequency signals from a load sensor 1 overflows, the values of both the counters represent load data. Then, when the changeover switch 5 is changed over to the side of a temperature sensor 4, the values of the counter 2b represent temperature data. In this case, since the high-order digit of the load data that has been represented by the counter 2b does not change unless a load sharply changes, the load data can be obtained from the value of the counter 3b before the changeover switch 4 is operated and the present value of the counter 3a.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an electronic balance, and more particularly to an electronic balance having a temperature compensation function.

<Prior Art> Generally, the sensitivity of an electronic balance ε changes depending on the temperature due to the temperature characteristics of its load sensor. In order to perform this compensation, a temperature sensor is usually disposed near the load sensor, and its output is used to correct the load value detected by the load sensor.

FIG. 4 shows a block diagram of a conventional electronic balance.

The load W acting on the load sensor 111141a is converted into, for example, an analog signal by the load sensor 41, and the pulse train converter 4 is configured with a V-F converter or a double integration circuit.
2a and a counter 42b that counts the number of output pulses.
is digitized by an A-D converter 42 consisting of
It is incorporated into the CPU 43. On the other hand, the analog output of a temperature sensor 44 disposed near the load sensor 41 is configured to be inputted to an A-D converter 42 for the load sensor 41 via a switch 45, and at a predetermined period. By driving this switch 45, the 111 force of the temperature sensor 44 is digitized and input to the CPLJ 43.

The CPU 43 averages or digitally filters the load data that is taken every moment to obtain a measured value, and at the same time performs temperature compensation calculations using the temperature data that is taken at a predetermined period during this period. The tolerance value is displayed on the display 46.

With the above configuration, the A-D converter 42 is connected to the load sensor 41.
and temperature sensor 44,
Efforts are being made to reduce costs.

<Problems to be Solved by the Invention> In the conventional electronic balance shown in Fig. 4, however, reading of load information is interrupted while reading temperature information, and as a result, the interval between the display of weighing values is shortened. This may be temporarily delayed and may cause discomfort or discomfort to the person taking the measurement. In addition, with high-precision electronic balances, temperature compensation cannot be performed adequately unless temperature information is read once every 1 to 2 seconds, which means that there are always gaps in load data and disturbances. In some cases, there is a problem in that normal disturbance removal cannot be performed even if averaging or digital filter processing is performed.

In order to eliminate loss of load data, separate A-D converters may be connected to each of the load sensor and the temperature sensor, but in this case, the cost i/amp becomes large.

The present invention has been made in view of the above, and an object of the present invention is to provide an electronic balance in which load data is not lost even when temperature information is being read, and the cost does not increase significantly.

<Means for Solving the Problems> The configuration for achieving the above object will be explained with reference to FIG. 1 corresponding to the embodiment. A counter for counting the frequency in order to convert it into a digital value is composed of two counters (first and second counters 3a and 3b) that respectively handle the upper and lower digits. Further, the upper digit counter (second counter 3b) is configured so that a frequency signal based on the output of the temperature sensor 4 can be inputted at a predetermined period via a changeover switch 5.

A frequency signal based on the output of the load sensor 1 is transmitted to two counters (first and second counters 3a.

3h), load data is obtained from the count values of both counters, and a frequency signal based on the output of the temperature sensor 4 is input to the counter for the upper digit (second counter 3h). In this state, temperature data is obtained from the count value of the counter for the lower digits, and load data is obtained from the count value of the counter for the lower digits and the count value of the counter for the upper digits immediately before this state is reached. Configure to obtain. It is characterized by the above.

<Function> When the frequency signal based on the output of the temperature sensor 4 is not input to the counter 3b for upper digits, the load sensor 1
The frequency signal based on the output of the lower digit counter 3a
When the count exceeds the counter capacity and overflows, the least significant digit of the -digit digit counter 3b increases by one count. Therefore, the count values of both counters 3a and 3b represent the digitally converted value of the load data. Further, in this case, the contents of the counter 3b for the upper digits do not change unless there is a significant load change such as when loading and unloading the load onto the plate la.

When the selector switch 5 is activated and a frequency signal based on the output of the temperature sensor 4 is input to the upper digit counter 3b,
The count value of the high-order digit counter 2b represents the digital conversion value of the temperature data. At this time, a frequency signal based on the 111 force of the load sensor 1 is input to the lower digit counter 3a, and the count value represents a lower predetermined digit of the digitally converted value of the load data.

° In this case, as mentioned above, the contents of the upper digit counter 3b do not change unless there is a significant change in the load, so the count value of the upper digit counter 3b before actuating the changeover switch 5 is used as is. Then, the data conversion value of the load data is obtained by using this value and the count value of the counter 3a for the lower digits, so that the load information is not lost even when reading the temperature information.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

The output of the load sensor 1, which generates an analog signal of a magnitude corresponding to the load on the plate 1a, is input to the pulse train converter 2. The pulse train converter 2 is constituted by, for example, a double integration circuit, and outputs a pulse signal having a frequency corresponding to the magnitude of the input signal. The output signal of this pulse train converter 2 is input to the first counter 3a. This first counter 3a has a small capacity, for example, 8 old t, and overflows during normal measurement. This overflow provides an input signal to the second counter 3b via the changeover switch 5. That is, when the first counter 3a overflows, the second counter 3b counts a pulse signal obtained by frequency-dividing the pulse signal from the pulse train converter 2 by 1/256 (8 bits). Therefore, the frequency signal from the pulse train converter 2 is
The first counter 3a counts the lower digits, and the 20th counter 3b counts the upper digits.
A digital conversion value of the output of the load sensor 1 is obtained from these count values. This first and second counter 3a
The count values of 3b and 3b are respectively input into the microcomputer 6 separately.

Each counter 3a, 3b has its count value cleared to 0 by a clear signal from the microcomputer 6 every time a count value is taken. The capacity of the second counter 3b may be the maximum count value required for digitizing the load data minus the capacity of the tenth counter 3a.

A temperature sensor 4 is provided near the load sensor 1 . This temperature sensor 4 is either a frequency output type sensor itself, or an analog output type converting it into a frequency and outputting it. An example of a circuit configuration of an output type temperature sensor is shown in FIG. 3, and an example of a circuit configuration of a frequency conversion type temperature sensor using a thermistor or a temperature sensitive resistor 31 as a sensor is shown in FIG.

The output frequency signal from the temperature sensor 4 as shown below is
It can be input to the second counter 3b via the changeover switch 5.

The changeover switch 5 is driven at a predetermined period according to a command from the microcomputer 6. That is, the microcomputer 6 turns the changeover switch 5 toward the temperature sensor 4 once every time the load data is read a predetermined number of times, and causes the second counter 3b to count the output frequency signal. Here, since the temperature information is for compensation, its resolution does not need to be as high as that of the load information, and the number of effective digits as data may be small, so the second
The capacity of the counter 3b is sufficient for digitization.

Therefore, the output signal from the temperature sensor 4 is digitally converted by the count value of the second counter 3b, and the microcomputer 6 takes in the force count value of the second counter 3b as temperature data.

When taking in this temperature data, the frequency signal from the load sensor 1 is input only to the first force counter 3a, so complete load data cannot be obtained;
Data for t is taken into the microcomputer 6. Here, in general measurements, the digital value of the upper digit part by the second counter 3b does not change except when there is a large load change such as when loading and unloading a sample.
The load data can be formed from the current count value of the first counter 3a by using the value immediately before reading the temperature data for the minus digit part.

As a result of the above, the microcomputer 6 can substantially read load information even within the reading width of temperature information, and a series of load data will not be missing. From this load data and temperature data, a measured value after temperature compensation is calculated and displayed on the display 7.

In addition, the load sensor should be a frequency output type, such as a tuning fork,
A system that extracts string vibration, crystal, or capacitance change as a frequency change can be used. In this case, in the embodiment shown in FIG. 1, the pulse train converter 2 is not required, making it more cost-effective. becomes.

<Effects of the Invention> As explained above, according to the present invention, the frequency signal based on the output of the load sensor is counted by two force counters that each share the lower and upper digits, and the The digit counter is configured so that a frequency signal based on the output of the temperature sensor can also be inputted via a changeover switch, and when the temperature information is not being read, it is 211!
Load data is obtained from the count value of the counter i1, and when reading temperature information, the load data is obtained using the count value of the counter for the lower digits and the count value of the load signal from the force counter for the upper digits just before that. Therefore, there is no loss of load data due to temperature data collection.

As a result, the measurement display interval is not prolonged, the measurer does not feel strange, and normal processing is possible even when disturbances occur. Furthermore, since an A-D converter cannot be provided for each sensor, there is no significant cost increase. If a frequency output type load sensor is used, the cost reduction effect will be even greater. Incidentally, the counters for the lower digits and the upper digits may be built-in counters of a single-chip CPU, and further simplification of the configuration can be expected.

[Brief explanation of the drawing]

Fig. 1 is a program diagram showing the configuration of an embodiment of the present invention;
3 and 3 are diagrams showing an example of the circuit configuration of the temperature sensor 4, respectively, and FIG. 4 is a block diagram showing the configuration of a conventional electronic balance. ■ = Load sensor 1a - Plate 2 - Pulse train converter 3a - First counter 3b - Second counter 4 - Temperature sensor 5 - Changeover switch low - Microcomputer Patent applicant Representative of Shimadzu Corporation
Patent Attorney Nishi 1) New Figure 4

Claims (3)

[Claims] (1) A load sensor that converts the applied load into an electrical signal, a temperature sensor that compensates for the temperature characteristics of the load sensor, and temperature-compensated load detection by reading digital conversion data from the load sensor and temperature sensor. In a balance equipped with an arithmetic unit that calculates a value, a counter that counts the frequency signal based on the output of the load sensor in order to convert the frequency signal into a digital value is configured with two counters each responsible for the upper and lower digits. With,
The upper digit counter is configured so that a frequency signal based on the output of the temperature sensor can be input at a predetermined period via a changeover switch, and a frequency signal based on the output of the load sensor is inputted to the two counters. When counting is in progress, the load data is obtained from the count values of both counters, and when the frequency signal based on the output of the temperature sensor is input to the counter for the upper digit, the load data for the upper digit is obtained. An electronic device characterized in that the temperature data is obtained from the count value of the counter, and the load data is obtained from the count value of the counter for the lower digits and the count value of the counter for the upper digits immediately before the state is reached. Balance. (2) The electronic balance according to claim 1, wherein the load sensor is a frequency output type sensor. (3) The electronic balance according to claim 1 or 2, wherein the temperature sensor is a frequency output type sensor.