JPH0564284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an electronic balance with a built-in span calibration weight.

(b) Prior art High-precision electronic balances require frequent calibration in order to maintain their accuracy due to the temperature dependence of component parts, aging, etc.
It has a built-in weight with a known mass, and updates the coefficient (span coefficient) for converting the output of the load detection unit into mass based on the output when that weight is loaded on the load detection unit and the known mass. It has become common to have a so-called span calibration function.

However, it is dangerous to absolutely trust such span calibration. That is, the calibration mass may differ from the original value due to changes in mass over time due to wear, oxidation, reduction, etc. of the built-in weight, or due to adhesion of dust, for example. In such a case, the measurement value after span calibration will include all errors, but for the user, it is important to note that the measurement value immediately after span calibration is performed on an electronic balance with a built-in weight and span calibration function. It is generally difficult to imagine that such an error would occur in the values, and it is becoming a problem.

(c) Purpose The present invention has been made in view of the above, and is capable of automatically detecting when there is a possibility that the calibration will not be performed correctly due to the causes mentioned above during span calibration. The purpose of the present invention is to provide an electronic balance with a built-in calibration weight that can prohibit calibration operations and issue a warning to that effect, thereby always guaranteeing calibration operations.

(d) Configuration The configuration for achieving the above object will be explained with reference to the functional block diagram shown in FIG. a, a span coefficient storage means b for storing a span coefficient, and a calculation using the contents of the span coefficient storage means b, the load detection part b
mass conversion means c for converting the output from
, a built-in weight addition/removal mechanism e that loads the built-in weight d to the load detection section a when a calibration command is generated, a weight mass storage means f in which the mass of the built-in weight d that has been accurately measured in advance is written; In a balance equipped with a built-in span calibration calculation means g that calculates a span coefficient from the output of the load detection section a when the weight d is loaded and the contents of the weight mass storage means f, and updates the contents of the span coefficient storage means b. Comparison means h for comparing the actual mass value measured by the balance when the weight d is loaded and the contents of the weight mass storage means f;
The span calibration calculation means g includes an alarm means i that issues an alarm when the measured mass value is within the allowable range with respect to the contents of the weight mass storage means f based on the comparison result, and the span calibration calculation means g The present invention is characterized in that the span coefficient is calculated only when the measured mass value is within the permissible range based on the above.

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

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

The load detection unit 1 generates an electric signal corresponding to the load on the weighing pan 1a or when the built-in weight 3 is loaded by the weight addition/removal device 2 consisting of a cam 2a, a lever 2b, a motor 2c, etc. A
- It is supplied to the control unit 5 via the D converter 4.

The control unit 5 is composed of a microcomputer, and includes a CPU 5a that executes various calculations and programs and controls each peripheral device, a ROM that stores programs to be described later, and stores calculation results, etc.
It is equipped with a memory section 5b consisting of a RAM, a nonvolatile weight mass memory for storing the true value of the mass of the built-in weight 3, and an interface circuit 5c for connecting the control section 5 with external equipment. There is.

A display 6 for displaying a weighed value and an alarm device 7 for issuing an alarm are connected to the control unit 5. Further, a drive command signal for the motor 2c of the weight adding/removing device 2 is also supplied from the control section 5.

In the normal measurement mode, the digital conversion data w of the electrical signal corresponding to the load on the weighing pan 1a from the load detection unit 1 is calculated as follows (1) using the span coefficient K stored in the storage unit 5b. ) is converted into mass W by the formula and displayed on the display 6.

W=K·w... (1) When the power is turned on or when the calibration command switch is operated, the span calibration mode is executed. The operation at this time will be explained based on the flowchart shown in FIG. Note that the weight mass memory in the storage unit 5b stores the following information at the time of shipment of the electronic balance, etc.
Built-in weight 3 using a reference weight with guaranteed mass.
Measure the true mass of and memorize its value W ₀ . Furthermore, the allowable range of the mass of this built-in weight 3 is ±〓
Set. For example, the value of ±〓 becomes ±3 mg when the accuracy of the electronic balance is ±3 mg.

Now, when a span calibration command is issued, first, after collecting the digital conversion data w ₁ from the load detection section 1 before the built-in weight 3 is loaded (ST1), a drive signal is issued to the motor 2c to convert the built-in weight 3 (ST2). Next, the data w ₂ after the loading is collected (ST3), and the measured mass Ws of the built-in weight 3 is determined using the difference ws between w ₂ and w ₁ (ST4), ST5). It is determined whether the measured mass Ws is within the allowable range (W ₀ ±〓) for the original true mass of the built-in weight 3 (ST6), and if it is within the allowable range, the span is determined by the following equation (2). The coefficient is calculated and its value K' is replaced with the conventional span coefficient K (ST7, ST8) to perform so-called span calibration.

K'=W ₀ /ws... (2) If the measured mass Ws is outside the range of Wo±〓, if the mass of the built-in weight 3 changes for some reason as described above, or if there is a problem with the weight addition/removal device 2. , or the weighed value cannot be guaranteed due to a malfunction of the load detection section 1, etc., so an alarm is issued to notify that fact (ST9), and span calibration is not performed.

In addition, in the above embodiment, the actual measured mass Ws was obtained by loading the built-in weight 3 once, but the actual measured mass Ws was obtained by repeating the addition and subtraction multiple times and using the average value.
You can also use it as Furthermore, the actual measured mass is calculated by taking the average value of the multiple measured values excluding the maximum and minimum values.
Ws may be used, and in these cases, more accurate determination can be made. Furthermore, if you calculate the standard deviation〓 from the actual measured values multiple times, compare Ws±〓 and Wo±α, and issue a warning even if there is a possibility that the tolerance range is exceeded, it will be statistically better. Accurate judgment can be made.

(f) Effects As explained above, according to the present invention, in an electronic balance with a span calibration function that includes a built-in calibration weight, the actual measured mass value when the built-in weight is loaded is accurately measured in advance. The weight mass value is compared with the written memory contents, and a span calibration operation is performed only when the measured mass value is within a predetermined tolerance with respect to the memory contents; Since the alarm is issued without executing the span calibration operation, there is no risk of incorrect span calibration being performed due to changes in the mass of the built-in weight over time or the adhesion of dust. As a result, the user can always obtain a weighed value with guaranteed accuracy, and can immediately send the balance for repair after knowing that there is a problem with the balance.

[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, and FIG. 3 is a flowchart showing a program in the span calibration mode. DESCRIPTION OF SYMBOLS 1...Load detection part, 1a...Weighing pan, 2...Weight addition/removal device, 3...Built-in weight, 5...Control unit, 6
...Indicator, 7...Alarm device.

Claims (1)

[Scope of Claims] 1. A load detection unit that converts the applied load into an electrical signal, a span coefficient storage unit that stores a span coefficient, and a calculation using the contents of the span coefficient storage unit, the load detection unit A mass conversion means for converting the output from the 2000 into a mass value, a built-in weight addition/extraction mechanism that loads the built-in weight against the load detection section when a calibration command is generated, and a built-in weight addition/extraction mechanism that loads the built-in weight against the load detection section when a calibration command is generated. a span calibration calculation for updating the contents of the span coefficient storage means by calculating the span coefficient from the output of the load detection section when the built-in weight is loaded and the contents of the weight mass storage means; A comparison means for comparing the actual mass value measured by the balance when the built-in weight is loaded with the content of the weight mass storage means, and a comparison means for comparing the actual mass value stored in the weight mass storage means based on the comparison result. The span calibration calculation means has an alarm means that issues an alarm when the content of the means is outside the permissible range, and the span calibration calculation means is configured to issue an alarm when the measured mass value is within the permissible range based on the comparison result by the comparison means. An electronic balance characterized in that it is configured to calculate a span coefficient. 2. The electronic balance according to claim 1, wherein the measured mass value is an average value of measured mass values obtained by loading a plurality of times. 3 The standard deviation of each of the measured mass values of the plurality of loads is determined, and when the standard deviation exceeds a preset tolerance value, an alarm is issued. An electronic balance according to scope 2.