JPS6361902A - Load cell type balance - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to improvements in load cell scales.

[Conventional Search Technique] As shown in FIG. 3, conventional load cell scales include a load cell 1 that outputs a voltage signal according to the load, and an amplifier 2 that amplifies the voltage signal from the load cell 1 and outputs it as a voltage Va. It is known that there is a Note that the amplifier 2 is composed of a pair of operational amplifiers 21 and 22, and the output V+ of the amplifier 2 is converted from analog to digital in a subsequent stage, processed as a digital signal, and displayed.

When this type of load cell scale is grounded in an environment with strong radio waves, the amplifier is particularly affected, causing measurement errors. To prevent this, conventionally, the amplifier 2 was covered with a shielding case 3 to prevent it from being influenced by external radio waves, as shown by the dotted line in the figure.

[Problems to be Solved by the Invention] However, in the case where the shielding case is used for shielding, there is a problem that the device becomes large because the entire circuit section is covered with the case.

This invention has been made to solve such problems, and an object of the present invention is to provide a load cell scale that can reliably prevent amplifiers from being adversely affected by radio waves and can be made smaller. .

[Means for Solving the Problems] The present invention provides a load cell type weighing machine equipped with a load cell that generates a voltage signal corresponding to a load and an amplifier that amplifies and outputs the voltage signal from the load cell.
consisting of a pair of operational amplifiers, the non-inverting input terminal of each operational amplifier is connected to each output terminal of the load cell, and a capacitor is connected between the non-inverting input terminal and the inverting input terminal of each operational amplifier, Further, a capacitor is connected between the inverting input terminal of each operational amplifier and the ground, and a high frequency filter or a capacitor is connected between the non-inverting input terminal of each operational amplifier and the ground.

[Operations] In the present invention having such a configuration, the radio waves carried on the signal line from the load cell to the amplifier are cut off by the connected capacitors and high frequency filters, and there is no risk of them being input to the amplifier.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 11 is a load cell that outputs a voltage signal according to the load, and 12 is a pair of operational amplifiers 121 and 122, which amplify the voltage signal from the load cell 11 and send out an output Va.

One of the output terminals of the load cell 11 is connected to the non-inverting input terminal (+) of the operational amplifier 121, and the other is connected to the non-inverting input terminal (+) of the operational amplifier 122. And from the load cell 11 to the operational amplifier 121,1
High frequency filters 13 and 14 such as EMIFIL are inserted in the input line to 22.

A capacitor 15 is connected between the non-inverting input terminal (10) and the inverting input terminal (=) of the operational amplifier 121, and a capacitor 15 is connected between the non-inverting input terminal (+) and the inverting input terminal (-) of the operational amplifier 122. A capacitor 16 is connected between the inverting input terminal (-) of the operational amplifier 121 and the grounding point, and a capacitor 17 is connected between the inverting input terminal (-) of the operational amplifier 122 and the grounding point. 18 are connected. Each of the high frequency filters 13 and 14
A part of it is grounded.

A resistor 19 is connected between the inverting input terminal and the output terminal of the operational amplifier 121, and a resistor 20 is connected between the inverting input terminal and the output terminal of the operational amplifier 122. A resistor 21 is connected in series between the resistors 19, 20, and 20, and a reference voltage E is applied to both ends of the series circuit of each resistor 19, 20, and 21 to obtain an output Vo.

In this embodiment with such a configuration, even if external radio waves enter the input line from the load cell 11 to the input terminal of each operational amplifier 121, 122, they will be transmitted through the high frequency filter 13, 14 and the capacitor 15, 16, 17. Since the signal is cut by .18, there is no possibility that the operational amplifiers 121 and 122 will be adversely affected by the radio waves. In other words, the same effect as being shielded by a shield case can be obtained.

In this way, the high frequency filters 13, 14 and the capacitors 15, 16, 17, 18 can prevent harmful effects from external radio waves without using a shield case. Moreover, since a shield case is not used in this way, the device can be made smaller.

Next, another embodiment of the invention will be described with reference to the drawings.

Note that the same parts as in the above embodiment are given the same reference numerals and detailed explanations will be omitted.

As shown in FIG.
It is inserted between the non-inverting input terminal (+) of No. 22 and the ground point.

Even with such a configuration, the electromagnetic waves from the outside can be cut off by each of the capacitors 15 to 18, 22, and 23, so that the same effect as in the embodiment described above can be obtained.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a load cell scale that can reliably prevent an amplifier from being adversely affected by radio waves and can be downsized.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a circuit diagram showing another embodiment of the invention, and FIG. 3 is a circuit diagram showing a conventional example. 11...Load cell, 12...Amplifier, 121゜1
22... Operational amplifier, 13.14... High frequency filter, 15.16.17, 18.22.23... Capacitor. Applicant's agent Patent attorney Takehiko Suzue Figure 3

Claims (1)

[Claims] In a load cell type weigher equipped with a load cell that generates a voltage signal corresponding to a load and an amplifier that amplifies and outputs the voltage signal from the load cell, the amplifier is composed of a pair of operational amplifiers, and the amplifier is composed of a pair of operational amplifiers. The inverting input terminal is connected to each output terminal of the load cell, and a capacitor is connected between the non-inverting input terminal and the inverting input terminal of each operational amplifier, and the inverting input terminal of each operational amplifier is connected to ground. A load cell type weigher, characterized in that a capacitor is connected between each of the operational amplifiers, and a high frequency filter or a capacitor is connected between the non-inverting input terminal of each operational amplifier and ground.