JP2641569B2 - Electronic balance with calibration weight circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic balance having a calibration weight circuit and a digital signal processing unit for automatically controlling the calibration weight circuit.

An electronic balance of this kind is known from DE 36 39 521 A1.

However, the result of the automatic calibration is only reliable when no operation is performed on the balance during the calibration process and, for example, no disturbances due to air flow occur. Accordingly, West German Patent Application Publication No. 3714540 has already proposed the following. That is, it has been proposed that, when monitoring the measurement result of the balance, it is based on the assumption that weighing will not be performed in a subsequent time unless a load change is detected for a predetermined time. But this assumption is very uncertain.

The problem to be solved by the invention is to improve a scale of the type described at the outset,
The structure is to ensure that the obstacles of automatic calibration are eliminated.

Means for Solving the Problems This problem is solved by the means according to claim 1. By incorporating a proximity sensor, the operator can be early detected when approaching the scale, and before the operator places the weighing object on the load pan, it is necessary to prevent the start of calibration or to perform normal calibration. Can be terminated.

The digital signal processing unit preferably has a storage element, in which the output signal of the proximity sensor is continuously stored, so that the automatic calibration is not started in a short measuring phase, and the output signal of the proximity sensor is stored again after a predetermined time. Will be erased. Automatic control of the calibration weight circuit is prevented when the response of the proximity sensor is stored in the storage element.

If the balance does not have a "standby" switching position, the proximity sensor is advantageously shut off when in this switching position,
Automatic control of the calibration weight circuit is always possible. By selecting the switching position "standby", the operator indicates that he or she does not intend to carry out the hit weighing.

In the case of a scale with a motorized windshield, the proximity sensor is also advantageously used for controlling the windshield. To this end, the proximity sensor has two switching thresholds, which prevents automatic control of the calibration weight circuit when the first switching threshold is exceeded, and that when the second switching threshold is exceeded, the operator: When in very close proximity-control the movable windshield with the motor.

If the digital signal processing unit attempts to control the calibration weight circuit, but is prevented by the output signal of the proximity sensor, the symbol is advantageously controlled in the display area,
This allows the operator to manually initiate the calibration if he considers it necessary.

It is generally known that there are various embodiments for proximity sensors. Vibration sensors are also suitable for the purposes described here. This is because the movement of the operator always accompanies the vibration of the place where the scale is installed. At that time, the measuring system of the balance can be directly used as a vibration sensor by evaluating the AC component of the measurement signal.

Embodiment The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic perspective view of the balance, showing a lower part 35 and an upper part 34.
, A weighing dish 3, a weighing result display unit 19,
Shown are a tare key 30, a Cal key 31 for manual activation of the calibration process, a symbol 32 in the form of a weight unit, and a capacitive proximity sensor 45 '. The function of the individual components will be explained in more detail in connection with FIG.

FIG. 2 shows a vertical section of the weighing system of the scale of FIG. 1 and a block circuit diagram of the associated electronics. The casing of the balance and the voltage supply of the electronic circuit are not important to the invention and have been omitted for clarity. The weighing system has a system support 1 fixed to a casing, on which a load detector 2 is mounted movably in the vertical direction via two levers 4 and 5 having joint points 6. The load detector 2 carries a load pan for storing the weighed object on its upper part, and transmits a force corresponding to the weight of the weighed object to the load arm of the conversion lever 7 via the coupling member 9. The conversion lever 7 is supported on the system support 1 by a cross spring joint 8. A coil body having a coil 11 is attached and fixed to a compensation arm of the conversion lever 7. The coil 11 is in the gap of the permanent magnet device 10 and generates a compensating force. At this time, the magnitude of the compensation current flowing through the coil 11 is controlled by the position sensor 16 and the control amplifier 14 as described below. That is,
The balance is controlled so as to balance between the weight of the weighed object and the compensating force generated electromagnetically. Compensation current is measured resistance 15
Forms a measurement voltage, and the measurement voltage is supplied to an analog / digital converter 17. The digitized result is transferred to a digital signal processing unit 18 and displayed on a display unit 19 in digital. Furthermore, a temperature sensor 26 is provided, which converts the temperature of the measurement value detector into a digital signal and supplies it via a line 29 to the digital signal processing unit 18. Thereby, the digital signal processing unit 18 can correct the temperature error of the measurement value detector.

The load arm of the conversion lever 7 extends beyond the point of attachment of the coupling member 9 (12) and terminates in a downwardly cranked portion 22. Three center pins that stand in the vertical direction are attached and fixed to the portion 22. Only two of the center pins 24 and 25 are shown in FIG. This center pin supports the calibration weight 13. The calibration weight has a hole 29 from below. The hole terminates in a conical surface 23. This hole passes exactly through the center of gravity of the calibration weight, so that the conical surface lies vertically above the center of gravity of the calibration weight.

FIG. 2 also shows a stroke device for the calibration weight, which has a pin 20. The pin is movably guided in the sleeve 21 fixed to the casing in the vertical direction. The device for moving the pin is shown only by the eccentric 28 and the electric motor 41. The pin 20 extends through a hole 27 in the part 22 to a hole 29 in the calibration weight 13. In the position shown, the calibration weight is on the center pin and therefore the conversion levers 7, 12, 2
2 and the pin 20 is densely terminated below the conical surface 23 with its conical tip. When the pin is lifted by the eccentric 28, it comes into contact with the conical surface 23, lifting the calibration weight 13 from the conversion lever and pressing it against the projection 39 fixed to the casing. This is the normal position (weighing position) of the calibration weight. On the other hand, the sunken position shown in FIG. 2 is only taken for the calibration process. The center of gravity of the calibration weight 13 can be shifted slightly by means of the screw 38 so that fine adjustments can be made.

When the digital signal processing unit 18 identifies that calibration should be performed based on the program, e.g., the temperature of the temperature sensor 26 has changed significantly since the last calibration, the digital signal processing unit switches to line 36. And 37
Via gate (with gate 42 open)
Start 40. The progress control unit 40 starts the motor 41 and, after the conversion levers 7, 12, and 22 of the calibration weight 13 are mounted, the digital signal processing unit 18 notifies the stable state (stationary state) of the measured value via the line 46. Until the calibration weight is again lifted to the weighing position by the motor. The digital signal processing unit 18 then calculates and stores the new calibration coefficients.

The above-mentioned parts of the balance are known in the prior art, so their construction and function are only briefly described.

The electronic balance of FIG. 2 further has a proximity sensor 45. The proximity sensor controls the gate 42 via the inverter 44. Proximity sensor 45 responds to the approach of a person or object by an output signal on line 47. Various configurations of proximity sensors are known. For example, there are a capacitive proximity sensor, a distributed optical proximity sensor, and a proximity sensor using electromagnetic waves or ultrasonic waves, and need not be described here. The proximity sensor in FIG.
Shown as a capacitive proximity sensor with 5 '.

When the proximity sensor reports that no one is nearby,
The signal on line 47 is zero, and inverter 44 opens gate 42 with a logic "1" on its output. This causes the calibration command to pass from line 36 to line 37. But proximity sensor
When 45 responds, the gate 42 is shut off and the progress control 40 cannot be activated by the digital signal processing unit. If the digital signal processing unit 18 requests calibration, the calibration does not start. Gate 43 and tracks instead
The symbol 32 is controlled via 48. The operator thereby receives information that the calibration is indeed appropriate.
Thus, if the operator wishes to calibrate, he or she can manually trigger the calibration by operating the operation key 31 or abort the response of the proximity sensor, i.e. the calibration shutdown, by leaving the balance.

To illustrate the function of FIG. 2, gates 42 and 43,
Inverter 44 and progress control unit 40 have been shown and described as discrete components. Of course, this range can also be realized as a part of the digital signal processing unit 18 by software. This is indicated by the dotted line in FIG.

In an advantageous development of the invention, an electrical storage element is interposed between the output of the proximity sensor 45 and the input of the inverter 44 in FIG. The storage element stores a positive output signal of the proximity sensor 45 for a predetermined time. Thereby, the gate 42 is also shut off for a predetermined time after the proximity sensor 45 finally responds. In the case of integrated software means, the storage can be realized by a storage area 33 configured as, for example, a circular shift register.

If the balance has a switching position "standby", the proximity sensor 45 is advantageously switched off in this switching position. Thus, calibration is always possible while in this switching position. Surveillance of the surroundings is unnecessary. This is because the selection of the switching position "standby" by the operator identifies that no weighing is to be performed.

A vibration sensor may be used as the proximity sensor 45. In that case, the measurement system of the electronic balance can be directly used as a vibration sensor. The vibration acts as an AC voltage component in the measurement signal, which should be pure DC at constant load. Thereby, the digital signal processing unit 18 can also perform the function of the proximity sensor 45 in the form of a vibration sensor. This is indicated by the dotted line in FIG.

FIG. 3 shows a second embodiment of the electronic balance. The scale has a casing 51 with a lower part 51, a pouch 52 for the display 53 and the operating element 58, a weighing pan and draft shields 54 to 57 for protecting the weighed material thereon from airflow. The windshield is composed of a frame 59, a front plate 54, two movable side doors 55 and a movable ceiling member. By shifting one of the side doors 55,
The weighing chamber can be opened by a motor (not shown), and the weighing pan 59 can be inserted. In this embodiment, an ultrasonic transceiver 50 is provided as a proximity sensor. The ultrasound transceiver emits short ultrasound pulses and subsequently receives echoes in some cases. A corresponding proximity sensor is arranged on the other side wall of the scale. The echo signals successive to the transmission pulse are compared with each other, and if significantly different, a signal is output. Additionally, in this embodiment, the ultrasonic proximity sensor can act to electrically open the windshield side plate 55. If a particularly strong echo is generated in the ultrasound receiver in a short time interval with respect to the transmitted pulse, this means, for example, that the operator's hand approaches the corresponding side door 55 of the windshield, and the proximity sensor detects this side. Causes the door to open.

Advantageous Effects of the Invention The present invention eliminates obstacles in performing automatic calibration.

[Brief description of the drawings]

1 is a perspective view of a balance, FIG. 2 is a vertical sectional view of a scale system of the balance according to the present invention, and a block circuit diagram of an associated electronic circuit;
FIG. 3 is a perspective view showing another embodiment of a scale having a windshield movable by a motor. 18 Digital signal processing unit 33 Memory device
45,50… Proximity sensor

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Christian Oldendorf Getztingen Tool Akerai, Germany 31 (56) References JP-A-57-61919 (JP, A) JP-A-60-13223 (JP) , A) JP-A-62-69124 (JP, A)

Claims (7)

(57) [Claims] An electronic balance having a calibration weight circuit (13/20/28/41/40) and a digital signal processing unit (18) for automatic control of the calibration weight circuit. 45, 50) is incorporated in the balance, and the automatic control of the calibration weight circuit by the digital signal processing unit (18) is interrupted by the output signal of the proximity sensor (45, 50). . 2. The digital signal processing unit (18) has a storage element (33) in which an output signal of the proximity sensor (45) is continuously stored and erased again after a predetermined time,
The automatic control of the calibration weight circuit (13/20/28/41/40) is interrupted also when the response of the proximity sensor (45) is stored in the storage element (33). Electronic scales. 3. An electronic balance having a "standby" -switching position according to claim 1, wherein the proximity sensor (45, 50) is shut off in the switching position "standby". 4. The proximity sensor (50) has two switching thresholds, and when the first switching threshold is exceeded, the calibration weight circuit (13/2).
Automatic control of 0/28/41/40) is interrupted by the digital signal processing unit (18) and a windshield (55) drivable by a motor is controlled when the second switching threshold is exceeded. An electronic balance having a windshield drivable by the motor according to any one of the above. 5. The control is interrupted when the digital signal processing unit (18) controls the calibration weight circuit (13/20/28/41/40) and by the output signal of the proximity sensor (44,50). The electronic balance according to any one of claims 1 to 4, wherein the symbol (32) is controlled in the display area. 6. The electronic balance according to claim 1, wherein a vibration sensor is used as the proximity sensor. 7. The electronic balance according to claim 6, wherein the measuring system of the balance is used as a vibration sensor by evaluating an AC voltage component of the measurement signal as a vibration signal.