JPH0115007B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides bridge balance adjustment and zero point temperature compensation in a load cell having two or three beams and four strain gauges forming a bridge circuit disposed on the beams. This article relates to a method for easily performing the following.

As a mechanism for converting the magnitude of the load into an electrical signal, as shown in FIG. 4 strain gauges C
There is a bending beam type load cell 5 to which T-1, T-1, C-2, and T-2 are attached. This load cell 5 has four strain gauges C-1, T-1,
C-2 and T-2 are connected to a bridge circuit as shown in Fig. 2, and a constant voltage is supplied between a pair of opposing connection points A and B through a power supply resistor Ni, and the load receiving part of the load cell 5 is connected to the bridge circuit. Apply a load to 2. Then, strain corresponding to the magnitude of this load occurs in the beams 3 and 4, causing each strain gauge C-1, T-1, C-2,
The resistance value of T-2 changes, thereby generating a potential difference between the other connection points C and D of the bridge circuit. By taking this out from the output lead lines G and B, the magnitude of the load is detected.

Thus, this type of load cell 5 undergoes bridge balance adjustment and zero point temperature compensation after assembly. This adjustment measures the output of the load cell 5 with no load, checks whether this measured value is within the allowable error range with respect to the reference value, and if the deviation is outside the range, connect the compensation lead wire to the This was done by inserting and connecting in series to the strain gauges on each side of the bridge circuit depending on the positive or negative direction. For example, if the bridge balance shifts to the + side, insert and connect the compensating constantan wire 6 in series with the strain gauge C-2 as shown in Figure 3, and if the shift due to the temperature at the zero point shifts to the - side. If there is a deviation, insert and connect the compensating thin copper wire 7 in series to the strain gauge T-2 as shown in FIG. Specifically, for example, this adjustment is carried out by attaching a terminal plate 8 for connection to the load cell 5, and connecting lead wires from each strain gauge and external lead wires R, G, B, and W for input and output to the load cell 5.
This is done by connecting the compensation constantan wire 6 and the compensation copper thin wire 7, and changing the connection method. Examples of this connection are shown in FIGS. 5 to 8. The wiring example shown in Figure 5 is for compensating when the bridge balance shifts to the + side and the shift due to the temperature of the zero point shifts to the + side. The thin compensation copper wire 7 is inserted and connected in series to the strain gauge C-1. The wiring example shown in Fig. 6 is for compensating when the bridge balance shifts to the negative side and the shift due to the temperature of the zero point shifts to the positive side. -1 and the compensating copper fine wire 7 is inserted and connected in series to the strain gauge C-1. In addition, in the connection example shown in Figure 7, the bridge balance shifts to the + side,
This is to compensate when the deviation due to the temperature of the zero point is shifted to the negative side, and the constantan wire 6 for compensation is inserted and connected in series with the strain gauge C-2, and the fine copper wire 7 for compensation is connected to the strain gauge. T-
Two devices are inserted and connected in series. The wiring example shown in Fig. 8 is for compensating when the bridge balance shifts to the negative side and the deviation due to the temperature of the zero point shifts to the negative side, and the compensation constantan wire 6 is connected to the strain gauge. The strain gauge T-1 is inserted and connected in series, and the compensating copper thin wire 7 is inserted and connected in series to the strain gauge T-2. In addition, if the deviation of the bridge balance or the deviation due to the temperature of the zero point is within the allowable error range, directly insert each strain gauge C-1 without inserting the compensation constantan wire 6 or the compensation copper thin wire 7, respectively. ,T-1,
Of course, C-2 and T-2 can be connected to external lead lines R, G, B, and W.

By the way, when compensating the load cell 5 by such means, each strain gauge C-1,
T-1, C-2, T-2 directly to external lead line R,
Connect G, B, and W, and check the bridge balance and the direction and magnitude of the deviation due to temperature at the zero point from the measurement results when no load is applied. Based on this,
Determine the wiring connection method for compensation, remove the lead wires of each strain gauge C-1, T-1, C-2, and T-2 from the brazed locations of the terminal plate 8 by melting the brazing material, and then The compensation constantan wire 6 or the compensation copper thin wire 7 must be inserted and connected by brazing. However, this has to be done in a narrow space inside the assembled load cell 5, which is very inefficient and leads to incorrect attachment of lead wires.

In view of the above-mentioned drawbacks, the present invention has been developed to improve and eliminate these drawbacks, and examples thereof will be described below.

In this invention, for example, as shown in FIG. 9, there are 3 One set of individual terminals is provided, and the output side lead wires G and B are connected to the central terminals a and a, respectively.
Connect strain gauges C-1, T-1, C-2, T- to terminals b, b, c, c on both sides of each set.
Connect the ends of the lead wires from No.2. Further, short-circuiting lead wires 9, 9 are connected in advance between the center terminals a, a and the terminals b, b, c, c on both sides thereof before each of them is assembled into the load cell. In this state, these are assembled at each position on the beams 3 and 4 to manufacture a load cell, and measurements are taken under no load to adjust the balance. In the initial connection state shown in Figure 9, the shorting lead wire 9 is connected to each strain gauge C-1, T.
-1, C-2, and T-2 are connected to the output side external lead wires G and B. By performing measurements in this state, it is possible to know the bridge balance and the magnitude of the deviation due to temperature at the zero point. If they are out of the allowable error range with respect to the reference value, the position at which the compensating lead wire should be inserted and connected can be determined based on the positive and negative directions of the deviation. Then, the shorting lead wire 9 at that position is cut, and the compensation constantan wire 6 or the compensation copper thin wire 7 is inserted and connected in place of the cut shorting lead wire 9, and the balance adjustment of the bridge circuit of the load cell 5 is completed. do. That is, for example, if the bridge balance has shifted to the + side, the compensating constantan wire 6 is inserted and connected between both terminals a and c on the strain gauge C-2 side as shown in Fig. 10, and the zero If the deviation due to the temperature at the point is on the negative side, the compensating copper thin wire 7 is inserted and connected between both terminals a and c on the strain gauge T-2 side as shown in the figure.

Next, an example of a specific wiring circuit in which the method of the present invention is implemented will be described.

In FIG. 11, 10a and 10b are intermediate terminal boards for connecting the lead wires of strain gauges C-1, T-1, C-2, and T-2. 11...11 and their connections 12 are formed. Also 1
3 is a terminal board for external extraction, and terminals 1 for connection with the intermediate terminal boards 10a and 10b are provided on the printed circuit board.
4, 14...14, external input/output line connection terminals 15, 15, 15, 15, constantan wire for compensation 6 or fine copper wire for compensation 7, and lead wire for short circuit 9
Terminals a, b, and c for connecting the two terminals, as well as their connections 6, are formed. These intermediate terminal plates 1
0a, 10b and the terminal plate 13 for external extraction are fixed to the load cell as shown in FIG. 12, for example.

That is, in this embodiment, the intermediate terminal plates 10a,
10b is a strain gauge C-1, T-1 and C-2, T-2 on each beam 3, 4 of the load cell.
The external drawer terminal plate 13 is placed at an intermediate position.
is fixed inside the fixed part 1 of the load cell 5. Adjustment work involves measuring the output of the load cell 5 with no load in this assembled state, and using the measured values to determine the deviation from the reference values for bridge balance and zero point temperature compensation, and if compensation is required. It is sufficient to cut at most two short-circuiting lead wires 9 at the corresponding positions, and insert and connect a compensating constantan wire 6 or a compensating thin copper wire 7 in place of the cut short-circuiting lead wires 9, 9. In other words, this adjustment work is extremely simplified.

In the above embodiment, the shorting lead wires 9 are once inserted and connected in series to all the strain gauges on each side of the bridge circuit, and the connection is made by providing three terminals on each side at the output extraction position of the bridge circuit. I'm going. However, it goes without saying that the embodiments of the present invention are not limited to this. In short, this invention inserts and connects the short-circuit lead wire 9 in series with the strain gauge at one or more locations, and cuts the short-circuit lead wire 9 as necessary based on the measurement results for balance adjustment. Instead of the shorting lead wire 9, a compensating constantan wire 6 or a compensating fine copper wire 7 is inserted and connected. For example, if the bridge balance shift or shift direction due to zero point temperature is likely to occur only in one direction,
By inserting and connecting the shorting lead wires 9 only at the corresponding locations, manufacturing costs can be minimized.

As explained above, the present invention arranges strain gauges at multiple locations on a beam, connects each strain gauge to form a bridge circuit, supplies input from between a pair of opposing connection points, and supplies input from the other pair of connection points. In a load cell that outputs a potential difference according to the strain of the beam between the connection points, assemble the shorting lead wires by inserting and connecting them in series in advance to the strain gauges that make up the sides of the bridge circuit. After assembly, inspect the direction and extent of the bridge balance shift when no load is applied and the shift due to temperature at the zero point. Based on the inspection results, determine whether compensation is necessary. If compensation is necessary, After deciding which position to insert the compensation resistor, cut the short-circuit lead wire at the corresponding position, and insert and connect the compensation lead wire that is the compensation resistor in its place to make the adjustment. It is possible to test the direction and degree of the bridge balance deviation during no load of the later load cell and the deviation with respect to the temperature of the zero point without a compensation resistor. For example, there is no need to insert and connect a compensation resistor, and if it is outside the tolerance range, it is possible to accurately detect where on the bridge to insert the compensation resistor, cut the shorting lead wire at the corresponding position, and connect it instead. The adjustment work is completed by inserting and connecting the compensation lead wire, which is a compensation resistor, so the work is simple, inexpensive, and does not take up much space. This serves as a mark for the insertion/connection position of the lead wire for use, eliminating any wiring errors, and greatly improving the workability of adjusting the output balance of this type of load cell.

[Brief explanation of drawings]

Figure 1 is a perspective view showing an example of a load cell, Figure 2 is a perspective view showing an example of a load cell.
The figure is a bridge circuit diagram composed of a strain gauge, Figures 3 and 4 are explanatory diagrams of conventional adjustment methods for bridge circuits, and Figures 5 to 8 are explanations of different specific examples of the conventional adjustment methods. 9 and 10 are explanatory diagrams of the principle of the bridge circuit adjustment method of the present invention, FIG. 11 is an explanatory diagram of a specific embodiment thereof, and FIG. 12 is a perspective view showing the state in which it is incorporated into a load cell. It is a diagram. 1... Fixed part, 2... Load receiving part, 3, 4... Beam, 5... Load cell, 6... Constantan wire for compensation, 7... Thin copper wire for compensation, 9... Lead wire for short circuit, 10a , 10b... intermediate terminal board, 13...
...Terminal board for external drawer, C-1, T-1, C-2,
T-2...Strain gauge, R, G, B, W...
...External lead wire, Ni...Power supply resistance.

Claims (1)

[Claims] 1 Strain gauges are arranged at multiple locations on a beam, each strain gauge is connected to form a bridge circuit, and input is supplied from between a pair of opposing connection points, and input is supplied from between a pair of opposing connection points. In a load cell that outputs a potential difference according to the strain of the beam from between the bridge circuits, the short-circuit lead wires are assembled in advance by inserting and connecting them in series to the strain gauges that make up the sides of the bridge circuit. After assembly, inspect the direction and degree of bridge balance deviation under no load and deviation due to temperature at the zero point. Based on the inspection results, determine whether or not compensation is necessary. If compensation is necessary, at what position? The invention is characterized in that it is determined whether to insert a compensating resistor at the position, the short-circuiting lead wire at the relevant position is cut, and a compensating lead wire, which is a compensating resistor, is inserted and connected in its place to perform adjustment. How to adjust load cell output balance.