Electrometer with low common mode interference

Abstract

The utility model discloses a low common mode interference electrometer, and belongs to the technical field of electrometers. Comprising an electrometer, and the input end of the electrometer is provided with an anti-interference module; the anti-interference module comprises a circuit board, an operational amplifier, a wire A and a wire B are arranged on the circuit board, the wire A and the wire B are connected with different pins of the operational amplifier, and an input signal and an input signal ground are directly bridged on the circuit board through the wire A and the wire B; the wire A and the wire B have the same model and length and are parallel to each other. According to the utility model, the parallel input signal ground leads with the same length and the same model are bridged on the edge of the input signal lead. The same common-mode interference can be generated on the input signal wire and the output signal ground wire, and the influence of the common-mode interference on the signals is reduced by utilizing the extremely high rejection ratio of the operational amplifier to the common-mode signals, so that the stability of the electrometer is improved.

Description

Technical Field

[0001] This utility model relates to the field of electrometer technology, and in particular to a low common-mode interference electrometer. Background Technology

[0002] An electrometer is primarily used to measure minute and weak electrical signals. It uses a high-impedance resistor or capacitor to perform an I / V conversion on the weak current, generating a measurable voltage signal. Because the electrometer's output signal can reach the fA level, leakage current on the circuit board itself can cause fatal interference to this fA-level weak current. Simultaneously, since the input signal is transmitted through wires, common-mode interference can couple onto the signal transmission line. Because it is a single-ended signal, it is easily affected by common-mode interference, further impacting the electrometer's performance. Utility Model Content

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low common-mode interference electrometer.

[0004] The purpose of this utility model is achieved through the following technical solution: a low common-mode interference electrometer, comprising an electrometer, wherein the input end of the electrometer is provided with an anti-interference module; the anti-interference module comprises a circuit board, wherein an operational amplifier, wire A and wire B are provided on the circuit board, wire A and wire B are connected to different pins of the operational amplifier, and the input signal and the input signal ground are directly connected across the circuit board through wire A and wire B; the wire A and wire B are of the same type and length and are parallel to each other.

[0005] Preferably, the wires A and B are fixed by a support post.

[0006] The beneficial effects of this utility model are:

[0007] 1) By bridging the input signal conductor with parallel input signal ground conductors of equal length and type, the same common-mode interference is generated on both the input signal conductor and the output signal ground conductor. The operational amplifier's extremely high common-mode rejection ratio reduces the impact of common-mode interference on the signal, thus improving the stability of the electrometer. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the anti-interference module structure. Detailed Implementation

[0009] The technical solutions of the present application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative effort are within the scope of the present application.

[0010] Referring to Figure 1 The present application provides a technical solution: a low common-mode interference electrometer, comprising an electrometer, an anti-interference module is arranged at the input end of the electrometer; the anti-interference module comprises a circuit board, an operational amplifier, a wire A and a wire B are arranged on the circuit board, the wire A and the wire B are connected to different pins of the operational amplifier, and the input signal and the input signal ground are directly connected across the circuit board through the wire A and the wire B; the wire A and the wire B are of the same model and length and are parallel to each other.

[0011] In the present embodiment, the influence of the leakage current and the space common-mode interference on the input signal on the circuit board is reduced, and the insulation resistance of the input signal to the circuit board needs to be improved, and two input signals with the same common-mode interference signal need to be generated, and then the influence of the common-mode signal on the signal is reduced and the signal-to-noise ratio of the electrometer is improved through the operational amplifier with a large common-mode signal rejection ratio.

[0012] As Figure 1 shown, the schematic diagram includes a circuit board, an operational amplifier, a wire A (input signal), a wire B (input signal ground), and a support. The input signal is transmitted through the wire A, and the input signal ground is transmitted through the wire B. In order to improve the insulation resistance of the input signal to the circuit board, the input signal and the input signal ground are not transmitted through the wires on the circuit board, but are directly connected across the circuit board through the wire A and the wire B, and are fixed through the support and are directly welded with the pins of the operational amplifier; the input signal of the wire A and the input signal ground of the wire B are both interfered by the common-mode signal; in order to ensure that the common-mode signals on the wire A and the wire B are basically consistent, the wire A and the wire B need to be the same type of wire, and the wire A and the wire B need to be the same length and parallel to each other; the operational amplifier has a very high common-mode rejection ratio, and the common-mode interference generated by the wire A and the wire B is suppressed by the operational amplifier, further reducing the influence of the common-mode interference on the performance of the electrometer.

[0013] In some embodiments, the wire A and the wire B are fixed through the support.

[0014] The above merely describes preferred embodiments of the present application, and it should be understood that the present application is not limited to the forms disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concepts described herein, by the above teachings or related art or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the claims of the present application.

Claims

1. A low common-mode interference electrometer, characterized in that: The device includes an electrometer, the input terminal of which is equipped with an anti-interference module. The anti-interference module includes a circuit board on which an operational amplifier, wire A, and wire B are provided. Wire A and wire B are connected to different pins of the operational amplifier, and the input signal and the input signal ground are directly connected across the circuit board through wires A and B. Wires A and B are of the same type and length and are parallel to each other.

2. The low common-mode interference electrometer according to claim 1, characterized in that: The wires A and B are fixed by a support post.

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