DE4317917A1 - Tare compensation method for weighing passenger lift suspension load - measuring load on cage suspension and digitising difference between load and tare compensation signals and moving cage accordingly - Google Patents

Abstract

The method involves preparing an analogue load signal representing the load on the cage suspension, a tare compensation signal and a compensated analogue load signal according to the difference between the load and compensation signals and digitising the compensated signal. The digitised signal is stored. A useful load signal is produced according to the difference between the stored digitised load signal and the digitised load signal. The elevator cage is moved according to the useful load signal. USE/ADVANTAGE - For compensating empty weight of passenger lift cage. Weight on suspension is measured without use of calibration weight.

Description

The invention relates to weighing an elevator suspension load and recalibrating a system for weighing the load of an elevator hanging.

An elevator car has the option of closing the suspension load weigh, it is suspended by means of ropes, which are held by two crossheads sluggish and run through holes in a suspension plate. The car sits on a shelf support that connects two side supports, hers are connected to the crosshead beams. When passengers in the Entering the car, the tension in the ropes increases and causes that the suspension plate acts against the crosshead beams. An one Individual load cell can be between the suspension plate and the Crosshead carriers can be arranged to carry out the weighing of the load men. Such an arrangement for weighing a suspension load is shown in pending U.S. patent application SN 07 / 792,978, filed on May 5, November 1991. There the load cell provides an analog Load signal to an analog / digital converter (ADU), which ana loge load voltage is converted into a digital voltage by a Elevator calculator can be processed.

The tare is the weight of an empty container, which is from the Total weight is subtracted to get the net weight. A The problem with weighing the suspension load is that the Tare is a dynamic value and as a function of the car position varies, because the weight of the treadmill and Compensation cables with the up and down movement of the Car increased or decreased. The tare is on the lowest floor (the static tare) is not the same as the tare on the top floor. The difference in tare between the lower and upper end of the Elevator shaft can be relatively large in relation to the car  weight and weight of passengers. To compensate for tare, one solution is to convert the analog load signal into a To compensate digital signal and the digital signal for the tare. This is "Digital Scale" in U.S. Patent 4,181,946 and U.S. Patent 4,630,696 "Apparatus and Method for Automatic System Calibration to Provide Enhanced Resolution in Computerized Weighing Systems ".

In addition, numerous elevator cars are equipped with sensors, which load signals deliver to the elevator control, which are characteristic for the weight of the elevator car. The measured weight can be used by the controller before loosening the Brake to precisely preset the motor with a torque in order to Realizing allocation strategies, for example driving past Bullets from which a hall call was made if the car is full, or displaying an overload condition. To walk past Call hall calls or to indicate an overload condition is the load signal compared with a predetermined load value, which in the up train control is stored.

Numerous sensor systems are subject to long-term drift phenomena, what calibration is required. In connection with weighing an elevator car load can cause the sensor drift to jerky Start moving if the engine is not correct in its torque is preset. Furthermore, there may be an inadequate Realization of the allocation strategies takes place, for example Drive the car past a floor sending a hall call, whether even the car is not fully loaded.

The usual procedure for calibrating the load sensors is for the Maintenance personnel in getting a calibration weight to the building fen and the sensor signals under different load conditions measure up. This procedure requires the massive calibration load weight onto a truck that is usually on the carpet the entrance hall is pushed to the elevator car. This leads to wear of the carpet as well as the mechanics, which is used to recalibrate the load weighing system.  

For the calibration not only load carts are needed, which is bad mer is, they are also required for recalibration. The need Recalibration may occur if the Car runs back or forwards. A passenger inside the vehicle korbs can watch a runback when he sees that the Car just moved before closing the doors. The backward fen takes place when the car goes in one direction, that of the trip direction to the next floor stop is opposite. A lead takes place when the car lurches in the same direction that the car moves to the next floor. Both Phenomena are caused by incorrect presetting of the torque caused (pretorquing) of the engine. Usually the Motor preset in its torque so that when loosening the The car does not brake. But for the right anchor To be able to supply current, the weight of the car be known. If not, it will either be too much or too much little torque preset, so that the rewind or the Leading takes place.

One way to recalibrate without recreating the Calibration weight to the location of the elevator is the weight leave there after calibration. This is in U.S. Patent 4,674,605 "Automatic Elevator Load Sensor Calibration System" described. There an empty elevator car is caused, a predetermined calibration weight to be transported, which is above the normal car Running route is located above the top floor. The exit signal from the car load sensor before and after lifting the calibration device weight is calculated together with the known values for the weight of the empty car and the calibration weight used to carry the load to recalibrate against the signal function. During this system obtaining a calibration weight from outside the building ver into the building to calibrate the load weighing system avoids, it requires a calibration weight for each well, as well Space above the normal driving distance, which is the calibration weight records.

It is an object of the present invention, the tare at a Lastmes solution on the suspension of an elevator car.

Another object of the invention is to provide a system for weighing the load calibrate an elevator suspension without calibration weight.

The invention is based on the finding that conventional methods for Compensate for the tare to have a resolution that is too bad to the weight of a passenger versus the thousands of pounds of To extract the total load. For example, if the load of empty driving basket in the elevator shaft is 13,500 pounds and an eight bits full ADC is used, the resolution is 117 pounds per bit. So it is a value that is large enough for it a person can step into the car and not lose their weight the load measuring system is detected.

The invention is further based on the observation that the calibration of a weighing system for an elevator load is usually manual Introduction of calibration weights into the car and the renewed Introducing calibration weights into the car of a new potassium necessary, but when weighing the suspension load the dynamic tare can be used as a recalibration standard.

According to the invention, in a weighing arrangement for an elevator suspension load the tare partially before the implementation of the analog load signal into a digital load signal while a residual tare subtractor the tare remaining in the digital load signal is eliminated and a benefit signal delivers.

According to the invention, the dynamic tare is measured and used to to recalibrate a weighing system for an elevator suspension load.

The advantage of the present invention is that most of the Tare is eliminated during a load measurement before implementing a  Analog signal takes place in a digital signal, so that a greater resolution is obtained for the passenger load.

An advantage of the invention is that when the load weighing system is recalibrated, no one can bring a calibration weight into the building must. Instead, the elevator system itself is used for calibration of his own truck system.

In the following, exemplary embodiments of the invention are described with reference to the Drawings explained in more detail. Show it:

Fig. 1 is a front view of a weighing system for an elevator suspension load with a the invention, illustrative block diagram;

Fig. 2 is a logical diagram illustrating the determination of a rule for the partial compensation of the tare ver;

Fig. 3 is a graphical representation of the elevator positions compared to the tare;

Figure 4 is a logic diagram illustrating tare compensation according to the rule described in Figure 2;

Fig. 5 different transfer functions for the ADC 20 corresponding to different values of Vref;

Fig. 6 is a graphical representation of floor positions versus tare and digital load signal, and at the same time floor positions versus a digital tare compensation signal (DTCS);

Fig. 7 is a logic diagram illustrating the construction of a residual table;

Fig. 8 is a residual tare table;

Fig. 9 is a logic diagram illustrating the digital subtracting a stored load signal from a digital load signal;

. FIG. 10 is a flow chart showing the weighing system, the calibration of the load according to Figure 1 also illustrates the determination of a Neukalibrierungsstandards for calibrating the loadweighing system of FIG. 1; and

FIG. 11 is a flow diagram illustrating the recalibration of the truck weighing system of FIG. 1.

Tare compensation

The tare can take three values. The static tare is the tare during a load measurement that takes place when a car 2 is located on the first floor. The dynamic tare is the tare in a load measurement at any other point. The tare that changes when the ascending or descending car carries an increasing / decreasing amount of running cable and compensation rope is called the dynamic tare. Residual tare is the tare that remains in a compensated load signal on a line 18 after a first pass to subtract tare from the load measurement by a partial tare compensator 24 .

Fig. 2 shows a car 2 in the elevator shaft. 4 A compensation rope 6 hangs from the car 2 . Energy is supplied to the car 2 via a running cable 8 . A load measuring cell 10 supplies an analog load signal (ALS) on a line 11 to a summer 12 , in which an analog tare compensation signal (ATCS) provided by a digital / analog converter (DAU) 14 on a line 16 is added, so that a compensated load signal (CLS) is given to the ADC 20 on a line 18 . The ADC 20 supplies a digital load signal (DLS) to a partial tare compensator 24 , a residual tare subtractor 26 and a residual tare table 28 . Partial tare compensator 24 performs a first pass in removing or subtracting tare and partially eliminates it from the load signal prior to analog-to-digital (A / D) conversion, while residual tare subtractor 26 performs a second pass, eliminating the tare that remained after the A / D conversion. The partial tare compensator 24 is responsive to the digital load signal and car position provided by an elevator shaft position transmitter 29 to provide a digital tare compensation signal (DTCS) to the DAU 14 . The Restta rasubtrahierer 26 responds to the position of the car 2 , the Digi tal load signal, a stored floor and a digital stored load signal to provide a payload. The residual tare table 28 is responsive to the digital load signal and car position and stores the digital load signal on each floor. The partial tare compensator 24 contains two blocks: "fetch tare compensation rule" and "partial compensate tare", both of which are shown in detail in the logic diagrams of FIGS . 2 and 4, respectively. Similarly, the residual tare subtractor 26 contains two blocks: "Form a Table" and "Subtract Residual Tare", which are shown in the logic diagrams of Figures 8 and 10, respectively. The routines according to FIGS. 2 and 4 form a first run in the compensation of tare, which provides a partial compensation of the tare. The routines of Figs. 8 and 10 form a second pass in compensating for the tare, and the remaining sub trahieren after execution of the routines of FIGS. 2 and 4 Resttara.

The partial tare compensator 24 and the residual tare subtractor 26 form secondary functions which serve to eliminate an electronic offset which is due to inaccuracies in the switching of the load weighing system. The electronic offset may originate from the load cell if it provides a non-zero analog signal, although no load is applied to it. Similarly, summer 16 may provide a non-zero sum depending on analog load and analog tare compensation signals corresponding to a value of zero.

Partial tare compensator 24 eliminates most of this electronic offset, and residual tare subtractor 26 eliminates what remains of offset.

The ADC 20 responds to an analog reference voltage Vref, which is supplied by a second DAU 30 , which itself responds to a digital reference voltage Vdref. Vdref is provided by a calibration section in the computer 31 . The computer 31 includes three software sections: an original calibration section 32 , a re-calibration standard section 34 and a re-calibration section 36 . The purpose of the original calibration section 32 is to calibrate the truck system of FIG. 1 when the elevator car 2 is installed, using a calibration weight 38 as the standard of origin by means of which the truck system of FIG. 1 is calibrated. The purpose of the recalibration standard section is to create a standard to calibrate the load weighing system in the future. The purpose of the recalibration section is to recalibrate the truck weighing system of Figure 1 using the future standard. The original calibration standard section 32 , the recalibration standard section and the recalibration section are explained below with reference to FIGS. 10 and 11, respectively.

FIG. 2 shows a logic diagram which can be carried out in the computer 31 and is called "fetch tare compensation rule". Empirical studies have shown that the relationship between the tare and the car position is linear. Therefore the rule is the equation for a straight line. A straight line is determined by two points. A first pass through the elevator shaft from the bottom floor to the top floor ( FIG. 2) takes place with an empty car 2 . For the routi ne according to FIGS . 2, 7, 10 and 11, the car 2 must be empty. In the routines according to FIGS. 4, 9, the car 2 can travel with passengers as normal.

After the START in step 50 , the static tare, here an intersection with the y-axis for the straight line, is determined. This includes running an empty car 2 to the floor of the elevator shaft 4 (step 52 ) in order to obtain an estimated residual tare and the digital load signal (step 54 ), and increasing the DTCS via the partial tariff compensator 24 until the digital Load signal from ADC 20 is one bit smaller than the estimated residual tare (steps 56 , 58 ). Since the car 2 is empty, the digital load signal means the following tare: (a) on the first floor and before the execution of the routine according to FIG. 4, there is the static tare, (b) everywhere else and before the execution of the routine after Fig. 4 indicates the digital load signal the dynamic tare, and (c) after executing the routine of Fig. 4, the Digi tal load signal indicates the residual tare. The estimated residual tare is determined empirically and forms an approximation to the absolute value of waveform B in FIG. 6.

A second point is required to define the straight line. The car position on the bottom floor is measured in millimeters and the DTCS is saved (step 60 ). Next, the car is moved to a second floor at the top of the elevator shaft (step 61 ). The digital load signal and the estimated residual tare are determined (step 62 ). The DTCS is increased until the digital load signal is less than the estimated residual tare (steps 64 , 66 ). In step 68 , the car position and the DTCS are stored.

Then the car position on the bottom floor is subtracted from the car position on the top floor (step 70 ). The difference is the length of the elevator shaft. Next, the bottom floor DTCS is subtracted from the top floor DTCS, thereby obtaining a digital tare difference (step 72 ). Then the digital tare difference is divided by the length (step 74 ). The quotient defines an incline.

Fig. 3 shows the tare shown as a function of the car position. The slope, multiplied by the car position, plus the DCTS for the static tare, results in a rule for the tare compensation, namely the equation of the waveform A according to FIGS . 3, 6 (step 76 ).

A second logic diagram with the designation "partial compensation of the tare" in FIG. 4 begins when the elevator car 2 is located in the elevator shaft 4 . The logic diagram makes use of the logic diagram of FIG. 2 and requires determining the car position (step 80 ), determining the lowest floor DTCS, determining the slope (step 82 ) and inserting these values into the rule to determine of DTCS (step 84 ) before returning to START ( Fig. 2). The DTCS value is continuously provided by the partial tare compensator 24 ( FIG. 1) as the car 2 moves up and down in the elevator shaft, and an analog tare compensation signal is subtracted from the analog load signal in the summer 12 .

If the car 2 is empty and moves again from the bottom up while the tare is compensated according to the above rule, the tare is compensated, but only in discontinuous increments (increments), and not smoothly. There remains an uncompensated tare between the DTCS increments when the car 2 starts up, and between decrements (reduction steps) when the car 2 goes down. FIG. 6 shows a graphical representation of the tare as a function of the car position in waveform B. Waveform A from FIG. 3 is also shown. As can be seen on the first floor, after the partial tare compensator 24 makes a first pass in compensating for the tare, the digital load signal indicative of the tare has a non-zero value for a given DTCS. Compare point "a" of curve A. When car 2 starts up and the tare compensation rule is followed, the DTCS increases and the digital load signal for the empty car returns to zero (e.g. between floors 1 and 2 ). Thereafter, the tare is only partially compensated until the DTCS is increased next.

Between the increases and decreases in DTCS are the Slopes of waveforms A and B are the same. The digital load Signal values for the empty car "a", b, c, d, e, f and g are the  Ordinate values for points "a", b, c, d, e, f, and g on curve B on one floor.

Figure 6 shows the DTCS as a function of floor location. Wave form C represents the DTCS. X is the value of the DTCS on the first floor. The tare is completely compensated. Only at the moment of increasing or decreasing DTCS ("TARE IS COMPLETELY COMPENSATED").

Instead of partial, it is desirable to fully compensate for the tare on the floors where passengers get on and off and where the accuracy of weighing the load is of paramount importance. The way to accomplish this is to find out the tare that remains after the partial tare compensator 24 does its job during a second pass of the well and then subtract that value from the digital load signal during normal operation. Figure 7 shows a routine for obtaining the residual tare on each floor during an empty car run from top to bottom and storing this value in a residual tare table. Figure 8 shows the residual tare table. Fig. 9 gives an overview of the method for subtracting the residual tare during normal operation on each Ge lap.

Step 86 after the routine of FIG. 7 ensures that the tare is found which remains after the operation of the partial tare compensator 24 ( FIG. 1) in the routine of FIG. 4, the digital load signal for the upper floor is saved in the residual tare table. The empty car 2 moves from the top floor to the bottom floor (step 88 ) and on each floor the digital load signal is read and stored in the tare table (steps 90 , 91 ). The points a, b, c, d, e, f, g according to FIG. 6 are those points at which the digital load signal is measured. After the rest of the tare table is complete (step 94 in Fig. 7), during normal operation the digital load signal is read (step 96 in Fig. 9) on a floor (step 28 ) and the digital stored load signal which corresponds to this floor, is read out and the payload is calculated as the difference between the digital load signal and the digital stored load signal. In step 104 , a car 2 can then be moved depending on the payload signal. Then return to START ( Fig. 2).

In this way, the requirements for the dynamic range of the ADC when weighing the suspension load are reduced by providing tare compensation as a function of the elevator position. The tare remaining after the correction by the routine of FIG. 4 is eliminated by measuring and subtracting it from the digital load signal.

calibration

Now that the tare of the load weight has been fully compensated, the load weighing system must be calibrated. Fig. 10, the software displays the Ursprungskalibrierabschnitts 32nd After START (step 120 ) the static tare is determined. This requires moving the car 2 empty to the floor of the elevator shaft 4 (step 122 ) to obtain an estimated residual tare and the digital load signal (step 124 ), and increasing the DTCS via the partial tare compensator 24 until the digital load signal from ADC 20 is one bit smaller than the estimated residual tare (steps 126 , 128 ). In step 129 the static tare is saved. Next, in step 130 the car 20 is loaded with a calibration weight by hand in order to calibrate the truck system according to FIG. 1. Then, in step 132, the value Vref is increased until the digital load signal indicates the size of the weight of the car 2 . A person can perform step 132 by placing the digital load signal on a digital display, comparing the digital load signal to a correct digital load signal, and increasing the Vdref value until the digital load signal indicates the calibration weight. The correct digital load signal read from the display is 127% of the maximum payload, for example expressed in pounds divided by the total number of ADU bits multiplied by the calibration weight (pounds). In step 136 , the value Vref is stored in order to be available when determining the recalibration standard, ie as a result for the dynamic tare.

Following step 136 , steps 140 to 146 determine a standard for the future calibration. The aim of this recalibration plan is to use the weight of the elevator ropes and the running cable as well as other elements that form the dynamic tare as the recalibration standard. Therefore, in step 140 the value DTCS is defined as the static tare and is not defined as in step 84 ( FIG. 4). Next, the car 2 is freed from the calibration weights (step 141 ) and moved to a second floor, which is located on the top of the elevator shaft (step 142 ). The digital load signal is read and stored to be used as the recalibration standard (step 144 ). In step 146 , the value DTCS is redefined as in step 84 ( FIG. 1). The dynamic tare is now available for use as a recalibration standard.

The routine of FIG. 11 is executed when the load weighing system of FIG. 1 needs to be recalibrated. The need can be indicated by a backward or forward run. After the START (step 148 ), the static tare is obtained in step 150 when the elevator car 2 is empty, as was explained in connection with FIGS. 2 and 10. Because the weight of the lifting ropes and the running cable and other elements that make up the dynamic tare is to be used as the recalibration standard, DTCS is defined as the static tare. In step 152 , the empty elevator car 2 is moved to the same floor as in step 142 in FIG. 10. Vref is then set until the value is as large as the value of the digital load signal that was stored in step 144 of FIG. 10 (step 156 ). Vref is stored to apply ADC 20 (step 158 ) and DTCS is redefined as in step 84 ( FIG. 4).

At this point the load weighing system has been recalibrated without the need for a calibration weight. The routine of FIG. 11 can be called again each time the load weighing system of FIG. 1 needs to be recalibrated.

While the steps of FIG. 10 are performed separately from those of FIG. 2, they could also be carried out simultaneously with the steps of FIG. 2. For example, the routine could FIG. 2 cause all that ge through the routine of Fig. 10 and Fig. 2 is jointly achieved when (a) is loaded after the step 61 in FIG. 2, the car with calibration and Vref extent is adjusted until the digital load signal indicates the calibration weight and this value of Vref is stored before the calibration weights are removed, and (b) after step 66 the value of the digital load signal is stored for use as a recalibration standard.

Claims (12)

1. A method for moving an elevator car ( 2 ), comprising the steps:

• - Providing an analog load signal, which indicates a weight on a car suspension;
• - Providing an analog tare compensation signal;
• - Providing a compensated analog load signal depending on the difference between the analog tare compensation signal and the analog load signal;
• - Converting the compensated analog load signal into a digital load signal;
• - Providing a digital, stored load signal;
• - Providing a payload signal depending on the difference between the digital, stored load signal and the digital load signal; and
• - Moving the elevator car ( 2 ) depending on the useful signal.

2. The method of claim 1, wherein the step of providing a digital, stored load signal comprises:

• - Moving the empty elevator from one end of the elevator shaft to the other end depending on the analog tare compensation signal; and
• - Measuring the amount of the digital load signal on each Ge along the elevator shaft and storing the Digi tal load signal in a tare table, and providing a digital, stored load signal, the value of which comes from the tare table.

3. A method of compensating for the tare in an elevator load weighing signal, comprising:

• - Providing an analog load signal, which is characteristic for the weight on a car suspension;
• - Providing an analog tare compensation signal; and
• - Providing a compensated analog load signal depending on the difference between the analog tare compensation signal and the analog load signal.

4. The method of claim 3, wherein the step of providing the analog tare compensation signal comprises:

• - measuring a static tare;
• Providing an incline that describes a relationship between an elevator position and the tare;
• Multiplying the slope by the static tare to form a product; and
• - Summing the product with the elevator position to obtain the analog tare compensation signal.

5. The method according to claim 3, characterized by:

• - Converting the compensated analog load signal into a digital load signal;
• - Providing a digital, stored load signal; and
• - Providing a payload signal depending on the difference between the digital stored load signal and the digital load signal.

6. A method for tare compensation in an elevator load weighing signal, comprising:

• - Providing an analog load signal, which is characteristic of the weight on a car suspension;
• - Providing an analog tare compensation signal, comprising the steps:
• - measuring a static tare;
• Determining an incline that describes a linear relationship between the car position and the tare, including:
• - Moving an empty car to a first floor along the elevator shaft;
• - measuring the digital load signal;
• - Compensating the digital load signal with an estimated residual tare and adjusting the amount of a digital tare compensation signal until the amount of the digital load signal is less than the estimated residual tare;
• - Measuring and storing a digital tare compensation signal for a first floor;
• - Moving the empty elevator to a second Ge along the elevator shaft;
• Measuring the digital load signal while the car is at the top of the elevator shaft;
• Comparing the digital load signal with an estimated residual tare and adjusting the amount of a digital tare compensation signal until the amount of the digital load signal is less than the estimated residual tare while the car is at the top of the elevator shaft;
• - Measuring and storing a digital tare compensation signal for a second floor; and
• - dividing an elevator shaft length by the difference between the digital tare compensation signal for the first floor and the digital tare compensation signal for the second floor;
• Multiplying the slope by the elevator position to obtain a product;
• Summing the product with the elevator position to obtain the analog tare compensation signal; and
• - Providing a compensated analog load signal depending on the difference between the analog tare compensation signal and the analog load signal.

7. A method for tare compensation of an elevator load weighing signal, comprising:

• - Providing a representative of the weight on a car suspension analog load signal;
• - Providing an analog tare compensation signal; and
• - Providing a compensated analog load signal depending on the difference between the analog tare compensation signal and the analog load signal;
• - Converting the compensated analog load signal into a digital load signal;
• - Providing a digital, stored load signal, comprising:
• - Moving the empty elevator from one end of the elevator shaft to the other end depending on the analog tare compensation signal; and
• - measuring the amount of the digital load signal on each floor along the elevator shaft and storing the digital load signal in a residual tare table, and providing a digital stored load signal, the value of which comes from the residual tare table;
• - Providing a payload signal depending on the difference between the digital, stored load signal and the digital load signal.

8. An elevator load weighing device comprising:

• - a summer ( 12 ) which provides a compensated load signal in response to an analog load signal representative of the weight on a car suspension and an analog tare compensation signal;
• - An analog / digital converter ( 20 ) which responds to the compensated load signal to deliver a digital load signal (DLS);
• - A tare compensator responsive to the digital load signal and an elevator position signal to provide a digital tare compensation signal; and
• - A digital / analog converter ( 14 ) which responds to the digital tare compensation signal (DTCS) to provide an analogue tare compensation signal (ATCS).

9. The device of claim 8, further comprising:

• a residual tare table for storing the digital load signal and the elevator position signal on each floor; and
• - A residual tare subtractor ( 26 ) which responds to the digital ge stored signal and the stored elevator position and an elevator position signal to subtract the digital stored signal from the digital signal on each Ge.

10. The apparatus of claim 8, wherein the digital tarakom compensation signal depends linearly on the elevator position. 11. A method for recalibrating a weighing system for weighing the elevator suspension load, comprising the steps:

• - measuring the dynamic tare;
• - Calibrate the load weighing system with an analog reference voltage depending on the dynamic tare since by that the analog reference voltage is adjusted until a characteristic digital load signal for the weight on the suspension equals the dynamic tare.

12. The method of claim 11, wherein the step of measuring the dynamic tare comprises:

• Moving an empty car to a first floor along an elevator shaft;
• - measuring the digital load signal;
• - Comparing the digital load signal with an estimated residual tare and adjusting the amount of the digital tare compensation signal until the amount of the digital load signal is smaller than the estimated residual tare;
• - Measuring and storing a digital tare compensation signal for a first floor;
• - Moving an empty car to a second floor Ge, which is above the first floor; and
• - Measuring a digital load signal, which is characteristic of the weight on the suspension of the weighing system.