JPH0132930B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zero tracking device for compensating for zero point shift caused by load cell creep phenomenon in electronic weighing machines. Appropriate tracking can be applied to zero point fluctuations in both cases: long static zero point fluctuations and dynamic zero point fluctuations with short change periods caused by wind and vibrations. Our aim is to provide what we can.

A conventional electronic weighing machine with a zero tracking device is constructed as shown in FIG. 1 is a load cell that converts the load G into an analog signal, 2 is an amplifier,
3 is an analog-to-digital converter that digitally converts the output signal of the load cell 1 via the amplifier 2; 4 is a memory for storing correction values; and 5 is a memory for storing weighed raw data Wo from the output of the analog-to-digital converter 3.
A calculation unit 6 subtracts the correction value of the calculation unit 5, and 6 instructs the memory 4 to update the memory when the digital value W output from the calculation unit 5 is below a predetermined value [predetermined range] N and this state continues for a predetermined period or more. A zero-tracking determination section 7 outputs P, and a weight display section 7 displays a digital value W as a weight display.

In this way, conventionally, the contents of the memory 4 are updated to the weighing raw data Wo, so normal zero tracking operation can be expected against the above-mentioned static zero point fluctuations, but dynamic zero point fluctuations If the temperature is high, the value in the memory 4 may be updated to the data in the transition period from a temporary large change until returning to the stable position. There are cases where the digital value W at that time exceeds a predetermined value, and in this case, there is a problem that the weight is no longer in the weight range where zero tracking is applied, and no tracking is applied after that. .

The present invention provides a processing circuit that calculates a moving average value using raw weighing data obtained by digitally converting a weighing signal as input data, a memory that uses the moving average value calculated by the processing circuit as input data, and the memory. an arithmetic unit that uses the contents of the moving average value as a subtractive number, and a tracking determination unit that monitors a deviation between the weighted raw data and the content of the memory to determine whether or not a zero tracking condition is satisfied. The memory is configured to update its contents when the tracking determination section determines that the zero tracking condition is satisfied, and corrects the static and dynamic data using the moving average value of the weighed raw data. Appropriate tracking is applied to both zero point fluctuations,
An embodiment of the present invention will be described below with reference to FIG. Components having the same functions as those in FIG. 1 are given the same reference numerals and their explanations will be omitted.

8 is a processing circuit that calculates the moving average value W′o of the latest past n conversion values of the analog-to-digital converter 3; 9 is a memory that receives the moving average value W′o as input data; 10 is a moving average value Memory 9 with W′o as minuend
The first calculating section 11 uses the content of the weighted raw data Wo as the minuend, and the second calculating section 11 calculates the deviation between the two using the weighted raw data Wo as the minuend and the contents of the memory 9 as the subtractive.
The contents of the memory 9 are updated in response to a memory update instruction P from the tracking determination section 6 which uses the digital value output from the second calculation section 11 as input data.

Because of this configuration, if static zero point fluctuation occurs, the weighing raw data Wo and the moving average value
W′o changes in almost the same way, and the contents of the memory 9 are almost the same as the contents of the memory 4 of the conventional zero tracking device, so that appropriate tracking can be expected. In addition, when a dynamic zero point fluctuation occurs, even if the weighing raw data Wo temporarily changes significantly, this change will appear as a 1/n fluctuation in the moving average value W′o, and the moving average value W The change in ′o follows the change in the weight raw data Wo with a slight delay. Therefore,
Even if the tracking determination unit 6 detects a slow and large change in the weighing raw data Wo through the second calculation unit 11 and issues a memory update instruction P, the correction value input to the memory 9 will not be the same as the weighing raw data. It does not change as much as Wo changes, and can be tracked when it returns to a stable position.

As explained above, according to the zero tracking device of the present invention, it is possible to perform better zero tracking than before, not only for static zero point fluctuations but also for dynamic zero point fluctuations, and for electronic weighing machines. This greatly contributes to improving the operability of the system.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electronic weighing machine equipped with a conventional zero tracking device, and FIG. 2 is a block diagram of an electronic weighing machine equipped with a zero tracking device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Load cell, 3... Analog-digital converter, 6... Tracking judgment part, 8... Processing circuit, 9
...memory, 10, 11...first and second calculation units,
Wo...Weight raw data, W'o...Moving average value, P...Memory update instruction.

Claims (1)

[Claims] 1. A processing circuit that calculates a moving average value using raw weighing data obtained by digitally converting a weighing signal as input data, a memory that uses the moving average value calculated by this processing circuit as input data, and a memory that stores the contents of this memory. a calculation unit that uses the moving average value as a subtractive; and a tracking determination unit that monitors a deviation between the weighted raw data and the content of the memory to determine whether a zero tracking condition is satisfied; The content of the memory is updated when the tracking determination unit determines that a zero tracking condition is satisfied;
A zero tracking device that outputs a digital value of the arithmetic unit output as a correction signal for the weighed raw data.