JPH0349052B2 - - Google Patents

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to electronic balances.

(b) Prior art In high-precision electronic balances, the ratio between the weighing capacity and the reading limit reaches 1/1.6 million to 1/2 million (0.5 PPM). However, electronic components and other components have relatively large temperature dependencies and changes over time. For example, among the components, permanent magnets have a temperature dependence of 200
It has ~400PPM/℃ and aging rate of 10PPM/month. Therefore, even if various design measures and strict adjustments are made during manufacturing, the temperature dependence of the span cannot be reduced to 1 or more.
The limit is to keep it within 2PPM/℃, and even if the ambient temperature at the time of measurement changes by only 1℃, the reading limit will be 2 to 4 when measuring near the weighing level.
This will result in a count error. Therefore,
Such high-precision electronic balances cannot perform reliable measurements unless they are kept in a constant temperature room, and the span must be calibrated almost every day to produce errors due to aging. The drawback was that it was extremely difficult to use.

Here, no matter how high precision an electronic balance is, there are some ways of using it that do not require that level of precision. Therefore, if a span change occurs to the extent that the accuracy of the balance cannot be guaranteed, simply detecting this and automatically performing span calibration will not work, for example, if the command is issued while measuring a sample. Even though the balance user does not require much precision, problems arise such as having to take the sample down from the pan and take measurements again after span calibration. Rather, the automatic span calibration function described above becomes a nuisance.

(C) Purpose The present invention has been made in view of the above, and it is possible to maintain the span of a balance without any error by using parts that are relatively temperature-dependent and without making very strict adjustments. An electronic balance that can always perform highly accurate measurements without having to take measurements in a constant temperature room, etc., or without worrying about errors caused by aging, and which does not suffer from the above-mentioned problems. The purpose is to provide.

(d) Configuration The configuration of the present invention will be explained based on the functional block diagram shown in FIG.

The load detection section a converts the loaded load into an electrical signal. The signal is converted into mass by the mass conversion means b using the conversion coefficient stored in the conversion coefficient storage means c, and is displayed on the display means d.

When the span calibration command is issued, the weight addition/removal mechanism e places a built-in weight of a predetermined mass on the load detection section a, and the output of the load detection section a at that time is taken into the conversion factor calculation means f. The conversion coefficient calculation means f calculates a new conversion coefficient based on the output value and the mass of the weight, and updates the conversion coefficient by replacing the value with the contents of the conversion coefficient storage means c.

In the electronic balance as described above, the present invention is characterized by providing the following means.

That is, the temperature change determining means g determines whether the ambient temperature detected by the temperature detecting means h has changed by a preset temperature or more compared to the temperature at the previous span calibration.

Further, the measurement/non-measurement determining means i determines whether or not the sample is being measured in the load detection section a based on the magnitude of the output signal of the load detection section a.

Then, the span calibration command generating means j determines, based on the determination results by the temperature change determining means g and the measurement/non-measurement determining means i, that there has been a temperature change of more than a predetermined temperature since the previous span calibration, and that measurement is not being performed. Automatically generates span calibration commands in certain cases.

On the other hand, the notification means k similarly gives notification that span calibration is necessary when there is a temperature change of more than a predetermined temperature since the previous span calibration based on the determination result by the temperature change determination means g.

(e) Examples Embodiments of the present invention will be described based on the drawings.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

The load detection unit 11 detects the load on the weighing scale 11a with the load sensor 11b, outputs an analog electrical signal corresponding to the load, and the signal is sent to the switch 1.
The signal is introduced into the A-D converter 13 via 2, converted into a digital signal, and then input into the control section 14. The control unit 14 is composed of a microcomputer, and includes a CPU 14a that executes various calculations and programs and controls each peripheral device, a memory 14b that has an area for storing programs to be described later, conversion coefficients, etc., and external peripheral devices. and an interface circuit 14c for connecting the control unit 14.
It is composed of etc. The digital conversion input from the load detection section 11 is configured to be converted into mass by the control section 14 and displayed on the display 15 as described later.

The load detection unit 11 is provided with a temperature sensor 16 adjacent to the load sensor 11b, and this temperature sensor 16 detects the temperature near the temperature sensor 16 and outputs an analog electrical signal corresponding to the temperature. do. The signal is passed through the switch 12 from A to D.
The signal is introduced into the converter 13, converted into a digital signal, and then input to the control unit 14.

The switch 12 switches the input signal to the A-D converter 13 to the signal from the load detection section 11 or the signal from the temperature sensor 16, based on a command from the control section 14.

The weight addition/removal mechanism 17 includes a motor 17a driven based on a command from the control unit 14, and a motor 1
The controller 1 is composed of an eccentric cam 17b that is rotated by an eccentric cam 7a, and a lever 17c that is displaced about a fulcrum 17c' by the rotation of the eccentric cam 17b.
4, the calibration weight 18 can be loaded onto or unloaded from the load sensor 11b.

Next, we will discuss the effect.

FIG. 3 is a flowchart showing a data processing program written in the memory 14b according to the embodiment of the present invention.

First, a command is issued to the switch 12 to make the input signal to the A-D converter 13 the signal from the temperature sensor 16, and the digital conversion data t is taken in (ST
1, ST2). When the data t does not differ by more than a preset temperature T (for example, 0.5°C) from the temperature data t ₀ at the time of the previous span calibration, which will be described later, the switch 12 switches the data to the A-D converter 13. The input signal is the signal from the load detection section 11, and the digital conversion data w is taken in (ST3, ST
4, ST5). Then, the data w is converted to mass W as follows using the conversion factor K currently stored in the memory 14b, W=K・w...(1) General procedures such as tare subtraction and zero point correction The measurement display value is determined by performing arithmetic processing and displayed on the display 15 (ST6, ST7, ST8). Such a measurement routine is normally executed.

If the load sensor 1
When the temperature near 1b changes by more than the above temperature, at a certain period, in this example, every time the weighing value is displayed,
Since the data t from the temperature sensor 16 has been read, the span calibration routine from ST9 to ST9 is executed immediately from ST3. In this routine, the detected temperature data t is stored as t ₀ and used as the reference temperature for the next span calibration (at the next span calibration, it becomes "temperature data t ₀ from the previous span calibration"), and the switching Load sensor 11b by device 12
Input the output to the A-D converter 13 and collect the digital conversion data w (ST10, ST1
1). If the value is not within the specified value near zero load, it is determined that there is a sample on the weighing pan 11a, that is, measurement is in progress, and unless an alarm is issued and calibration is performed, the measured value will not be reliable. It notifies you that the sample cannot be obtained and prompts you to remove the sample from the weighing pan 11a (ST
12, ST13). If it falls within the above range,
The data w is stored as _w0 (ST14), the motor 17a of the weight adjustment mechanism 17 is driven to rotate the biasing cam 17b by a predetermined angle, and the lever 17
c is displaced downward to load the calibration weight 18 onto the load sensor 11b (ST15), and the load sensor 11
After waiting for a predetermined period of time based on the response characteristics of b and waiting for data w to become stable, data w is taken in (ST16, ST17). Then, the conversion coefficient K (or S) is calculated using the data w due to the load of the calibration weight 18, the data _w0 at the time of no load mentioned above, and the mass P of the calibration weight 18, K=P/(w- w ₀ ) ...(2) (or S=(w-w ₀ )/P ...(2)', and update the conversion factor K by replacing the value with the value stored up to then. (ST1
8). Next, the motor 17a is driven to cause the weight adjustment mechanism 17 to move the calibration weight 18 to the load sensor 11b.
Remove the load on (ST19), proceed to ST5, and return to the normal measurement routine. Note that when S shown in (2)' is used as a conversion factor, the conversion formula (1) in ST6 is changed to (1)' below.

W=w/S …(1)′ Also, data at no load during span calibration
Regarding the collection of w ₀ and the data w when the calibration weight 18 is loaded, it is desirable to specifically average a large number of digitally converted data from the load sensor 11b to obtain an accurate conversion count. Note that since the temperature changes slowly, it is not necessary to check the temperature t every time the display is performed. For example, as shown in FIG. 5, after ST8, ST20,
ST21 may be provided to check t every Q times of display. Note that the temperature sensor 16
In order to compensate for the temperature coefficient, a normally provided temperature sensor (provided near the magnet) may be used in common.

Next, as another embodiment of the present invention, an example will be described in which, in addition to the calibration for each fixed temperature change, the calibration can also be performed for each fixed period of time. In this case, ST3 and ST in the flowchart of the above embodiment
4, ST3' shown in FIG. 4 may be inserted. As a result, the calibration routine is executed when the temperature changes by a predetermined temperature or more from the temperature at the previous span calibration, or when a predetermined time or more has elapsed since the previous span calibration, whichever comes first. be done. Even if time-based calibration is performed, the process proceeds from ST3' to ST9 and the temperature at that point is stored as t ₀ , so there is no need to immediately perform temperature change-based calibration after time-based calibration. . The means for measuring elapsed time is
There is no need to separately install hardware such as a clock function, and it can be easily determined by the number of cycles of the program. For example, a step may be provided between ST7 and ST8 that counts up the contents of a register each time the routine passes, and a step that resets the contents when the calibration routine is executed.
For example, it may be provided at the next stage of ST19.

Furthermore, it would be more complete if the calibration routine was executed unconditionally once when the power was turned on, and then the calibration was performed over temperature changes and over time.

In the above embodiment, the output of the temperature sensor 16 is
A-D for digitizing the load sensor 11b output
Although we have described the example of introducing it into the converter 13 at a predetermined period,
A small bit number A-D converter dedicated to the temperature sensor 16 may be provided separately. Furthermore, if a crystal oscillation temperature sensor whose oscillation frequency changes depending on the temperature is used, direct control is possible without A-D conversion. can be incorporated into the department.

(f) Effects As explained above, according to the present invention, it is constantly monitored whether or not the ambient temperature change since the previous span calibration has exceeded a certain amount, and whether or not the sample is being measured. There is a temperature change over a certain amount,
In addition, since span calibration is automatically executed when the sample is not being measured, the measured value is always within a certain error, allowing the user to obtain highly reliable measured values. There is no need to prepare a special room such as a constant temperature room for measurements. Furthermore, since the temperature dependence of the span of the balance can be made 3 to 10 times rougher than when the present invention is not adopted, component parts can be made cheaper and adjustment work can be made easier, reducing costs. I can do it.

Furthermore, even if the ambient temperature changes above a certain level, span calibration will not be forcibly executed while the sample is being measured, and the balance user will only be notified that span calibration is required. Depending on the purpose of use, the balance user may perform span calibration by removing the sample being measured from the pan when performing measurements that require high accuracy, or perform span calibration when performing measurements with relatively rough accuracy. It is now possible to select any action, such as continuing measurement if the situation is satisfactory.
There is no problem such as a decrease in work efficiency due to unnecessary span calibration being forcibly performed when rough measurements are being made.

Further, if the calibration is configured to be automatically performed every time a certain period of time passes, there is no need to worry about changes over time, which is even more effective.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.
Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a flowchart showing the data processing program, and Figs. 4 and 5 show main parts of the data processing program of other embodiments of the present invention. This is a flowchart. 11...Load detection section, 11a...Weighing plate, 11b
...Load sensor, 12...Switcher, 13...A-
D converter, 14...control unit, 14a...CPU,
14b...Memory, 14c...Interface circuit, 15...Display device, 16...Temperature sensor, 17
... Weight adjustment mechanism, 17a ... Motor, 17c...
...Lever, 18...Calibration weight.

Claims (1)

[Claims] 1. An output signal from a load detection unit that converts a placed load into an electrical signal is converted into mass using a stored conversion coefficient and displayed, and a span calibration command is given. In an electronic balance, a built-in weight of a predetermined mass is placed on the load detection section, and the conversion factor is updated using the output signal from the load detection section at that time and the mass of the weight. means for detecting temperature; temperature change determining means for determining whether or not the detected temperature has changed by more than a preset temperature with respect to the temperature at the time of the previous span calibration; Measurement/non-measurement discrimination means that determines whether the sample is being measured based on the magnitude of the output signal, and based on the discrimination results of the above-mentioned discrimination means, there is a temperature change of more than the above-mentioned certain temperature and the sample is not being measured. Based on the determination result by the span calibration command generation means that generates the span calibration command when An electronic balance characterized by being equipped with a notification means. 2. The span calibration command means is based on the determination results of the temperature change determination means and the measurement/non-measurement determination means, and the notification means is based on the determination results of the temperature change determination means, and the span calibration command means is based on the determination results of the temperature change determination means. 2. The electronic balance according to claim 1, wherein the electronic balance is configured to issue the span calibration command every predetermined period of time after span calibration, and to issue the notification. 3 The means for detecting the temperature is a temperature sensor that outputs an analog signal, and the output signal of the temperature sensor is sent at a predetermined period to an A-D converter for digitizing the output signal of the load detection section. The electronic balance according to claim 1 or 2, characterized in that the electronic balance is configured to be inputted by being switched.