JPH02243921A - Load cell type scale - Google Patents

Abstract

PURPOSE:To correct a load cell output automatically by generating weight data based on a counted value corrected by a temperature correcting means. CONSTITUTION:The weight value of a reference weight is measured first under the environment of reference temperature and the environment of different temperature from the reference temperature and counted values outputted from an A/D converter 3 at this time are detected. A keyboard 7 is operated to set the counted value at the time of the reference value in the 1st counted value memory of a ROM 5 and also set the counted value at the time of the different temperature in a 2nd counted value memory. Then coefficient arithmetic processing is performed periodically and a temperature correction coefficient C is calculated from the current temperature under the used environment which is measured by a temperature sensor 10. When the measurement of weight is taken by a load cell 1 in this state, the current actual counted value is temperature-corrected with the coefficient C and weight data is generated based upon the counted value after the temperature variation to display the weight on a display device 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a load cell scale that can correct variations in output due to temperature fluctuations.

[Prior Art] In general, load cell scales obtain weight data by signal processing a voltage signal generated on the output side of a bridge resistor when the bridge resistor loses its balance due to a load applied to the load cell. Since the resistance value of the bridge resistor changes depending on the temperature, variations in the temperature of the usage environment cause variations in its output. For this reason, conventional load cell scales are equipped with a resistor for temperature compensation.
For example, weight data is actually monitored under two different temperature environments (for example, 0° C. and 40° C.) at the time of shipment, and if the variation is outside the allowable range, the resistance value of the temperature compensation resistor is adjusted. In this way, the weight data is repeatedly measured under two types of temperature environments and the temperature compensation resistor is adjusted, and if the weight data falls within an allowable range, the load cell scale is shipped.

Problems to be Solved by the Invention] As mentioned above, in conventional load cell scales, in order to correct variations in load cell output due to temperature fluctuations, weight data under two types of temperature environments are It was necessary to repeatedly perform maintenance work and adjustment work for the temperature compensation resistor.

Therefore, the present invention proposes a load cell type scale that can suppress variations by automatically correcting the load cell output according to the temperature of the usage environment and eliminates the need for 711 measurement work and adjustment work for variation correction. That is.

[Means for Solving the Problems] The load cell scale of the present invention includes a temperature sensor that measures temperature, and a load cell that measures all reference weights at the reference temperature.
a reference count value memory that stores the count value output from the analog/digital converter; a count value calculation means that calculates the count value corresponding to the reference weight at the current temperature measured by the temperature sensor; coefficient calculating means for calculating a temperature correction coefficient by dividing the count value in the reference count memory by the count value calculated by the means; The weight data is created based on the count value corrected by the temperature correction means.

[Function] In the present invention having such a configuration, when the load cell is used for weighing, a count value corresponding to the load is output from the analog/digital converter, and a coefficient calculated by the coefficient calculation means is added to the count value. (always) corrected to the output under k-type temperature. Since weight data is created using this corrected count value, variations in load cell output due to temperature fluctuations are automatically suppressed and output.

C Embodiment One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. In the figure, 1 is a load cell that outputs a voltage signal according to the load, 2 is an amplifier that amplifies this load cell output, and 3
inputs the voltage signal output from this amplifier 2 and converts it into a digital count value.
A converter 4 (hereinafter abbreviated as A/D) is a CPU (central processing unit) which processes the data taken in by interrupting the count value from the A/D converter 3 at a predetermined cycle.

The CPU 4 has a ROM in which program data is stored.
5. RA with various memories used for data processing
A keyboard/display controller 9 for controlling M6, a keyboard 7, and a display 8 is connected to a human-powered boat 11 that takes in 7 items (transmission via river 71 from +1) via a pass line.

The temperature sensor 10 is provided near the load cell 1,
The temperature of the environment in which this load cell 1 is placed can be measured.

As shown in FIG. 2, the RAM 5 includes a first count value memory 51, a second count value memory 52, and a coefficient memory 5.
3, a work memory 54, etc. are formed.

The first count value memory 51 is a so-called reference count value memory that stores the count value A output from the A/D converter 3 when the reference weight is measured by the load cell 1 at the reference temperature T1. The second count value memory 52 is a memory that stores the count value B output from the A/D converter 3 when the reference weight is measured by the load cell 1 at a temperature T2 different from the reference temperature T1. Required data is set in both memories 51 and 52 by manual keystrokes from the keyboard 7.

Here, in this example, the load cell 1 having the weight/count value characteristics shown in FIG. 3 is used, the reference weight is 30 kg, the reference temperature T1 is 0°C, and the temperature T2 is 40 kg.
The temperature shall be 0°C. Therefore, as can be seen from Figure 3, the first
The count value A of the count value memory 51 is 3100.
0 count (Ct) is set, and the count value B of the second count value memory 52 is 31040 counts (ct).
) is set.

The coefficient memory 53 stores the temperature correction coefficient C calculated by the coefficient calculation process shown in FIG.

This coefficient calculation process is a process that the CPU 4 periodically executes at a preset cycle. That is, CPU4
starts the flowchart every time a certain period of time elapses, and first, the count value A (=3100Oc) of the first count value memory 51 is
t) and the count value B (=3
104Oct) and find the difference (B-A-4Oct),
This difference is calculated between the reference temperature TI (-0℃) and the temperature T2 (-4℃).
0℃) and the difference (T2-Tl-40℃), the count value change amount Δ(-1et/"C
) is calculated. Next, the CPU 4 receives the currently measured temperature T of the temperature sensor 10 via the input port 11. Then, the measured temperature T
The count value K of the reference weight for the measured temperature T is calculated by multiplying the product by the count value A in the first count value memory 51 (count value calculation means).

Now, assuming that the temperature T measured by the temperature sensor 10 is, for example, 20° C., the count value is 3102 Oct.

Next, the first count value memory 5 is set to the above count value.
Calculate the temperature correction coefficient C (-0,99936) by dividing the count value A within 1 (coefficient calculation means)
. The calculated temperature correction coefficient C is then stored in the coefficient memory 53, and this process is ended.

Further, the CPU 4 interrupts data from the A/D converter 3, that is, the load cell 1, at a predetermined cycle.
The program is set so that the data processing shown in FIG. 5 is executed when an electric signal is inputted through the amplifier 2 and an actual count value converted into a digital count value is input manually. That is, when the actual count value is taken in, the actual count value is multiplied by the temperature correction coefficient C in the coefficient memory 53 to perform temperature correction on the count value (temperature correction means).

Now, assuming that the temperature correction coefficient C is 0.99936 and the actual count value is 31020, the count value after temperature correction is 31000ct.

Next, this temperature-corrected count value is subjected to data processing and converted into weight data. Here, since the count value 31,000 ct after temperature correction corresponds to the case where the temperature is 0° C., weight data of 30 kg corresponding to the count value 31,000 ct is obtained as shown in FIG. Thereafter, the weight data is rounded for display and displayed on the display 8 via the keyboard/display controller 9, and this processing is completed.

As described above, in this embodiment, the weight of the reference weight is first measured (in an environment at the reference temperature and in an environment at a temperature different from this reference temperature), and the weight is measured from the A/D converter 3 at that time. Detect each count value.

Then, by operating keys on the keyboard 7, the count value when the temperature is at the reference temperature is set in the first count value memory 51 of the RAM 5, and the count value when the temperature is different from the reference temperature is set in the second count value memory 52. . Then, the coefficient calculation process is periodically executed, and the temperature correction coefficient C is calculated based on the current temperature in the usage environment measured by the temperature sensor 10. When weight is measured using the load cell 1 in this state, the actual count value at that time is temperature corrected by the temperature correction coefficient C, weight data is created from the count value after this temperature correction, and the weight is displayed on the display 9. Ru.

Therefore, for example, the first count value memory 51
By determining and setting the value A of the second count value memory 52 and the value B of the second count value memory 52 in advance, variations in the output that occur in the load cell 1 due to temperature fluctuations in the constantly used environment are automatically corrected thereafter. The weight will be displayed. Therefore, it is not necessary to repeatedly measure the load cell output under two types of temperature environments and adjust the temperature compensation resistor to ensure the accuracy of the load cell 1 as in the past, and it is also necessary to make adjustments for temperature compensation. A highly reliable and easy-to-use load cell scale can be obtained.

In addition, in the above example, the temperature correction coefficient C was determined by setting the reference weight to 30 kg, the reference temperature to 0°C, and the temperature different from this reference temperature to 40°C, but everyone is not limited to this example. Of course.

[Effects of the Invention] As described in detail above, according to the present invention, the load cell output can be automatically corrected according to the temperature in the constantly used environment, and Ap1 regular work and adjustment work for correcting variations are not required.
It is possible to provide a load cell scale that is highly reliable and easy to use.

[Brief explanation of drawings]

The figures are diagrams showing an embodiment of the present invention, in which Fig. 1 is a block diagram showing the overall configuration of a load cell type scale, and Fig. 2 is a block diagram showing an RA
Figure 3 is a diagram showing an example of the weight count value characteristics of the load cell, Figure 4 is a flowchart showing the CPU's coefficient calculation process, and Figure 5 is the CPU's actual count value input process. FIG. 1...Load cell, 3...Analog/digital (
A/D) converter, 4-CPU, 10-...temperature sensor,
51...First count value memory, 52...Second count value memory, 53...Coefficient memory. Applicant's agent Patent attorney Takehiko Suzue ↓ Figure 2 Figure 1! L child figure 3 0kg Kema 5J figure figure 5

Claims (1)

[Claims] A temperature sensor that measures temperature in a load cell scale that outputs a voltage signal in response to a load and converts the voltage signal from the load cell into a digital count value using an analog/digital converter, and creates weight data from the count value. a reference count value memory that measures a reference weight with the load cell at a reference temperature and stores the count value output from the analog/digital converter; count value calculation means for calculating a corresponding count value;
coefficient calculation means for calculating a temperature correction coefficient by dividing the count value in the reference count memory by the count value calculated by the calculation means; 1. A load cell scale, comprising: temperature correction means for multiplying a count value outputted from the weigher; and generating weight data based on the count value corrected by the temperature correction means.