CN202975122U

CN202975122U - Buffering and isolation function-equipped current signal collection circuit for electric fire monitor

Info

Publication number: CN202975122U
Application number: CN 201220678932
Authority: CN
Inventors: 李晨阳
Original assignee: BEIJING BURTON ELECTRIC Co Ltd
Current assignee: BEIJING BURTON ELECTRIC Co Ltd
Priority date: 2012-12-10
Filing date: 2012-12-10
Publication date: 2013-06-05
Anticipated expiration: 2022-12-10

Abstract

Disclosed in the utility model is a buffering and isolation function-equipped current signal collection circuit for an electric fire monitor. The current signal collection circuit comprises a current transformer, an amplitude limiting circuit, a sampling resistor, a voltage follower, and an operational amplifier. Specifically, the current transformer is used for collection a phase current. The amplitude limiting circuit is connected in parallel with secondary two ends of the current transformer. The sampling resistor is connected in parallel with the secondary two ends of the current transformer. The input terminal of the voltage follower is connected with the output of the sampling resistor. And the positive input terminal of the operational amplifier is connected with the output of the voltage follower; and the negative input terminal of the operational amplifier is connected with a 2.048-V voltage source. According to the utility model, after the processing on the collected signal, the signal loss is reduced and the collected data are accurate.

Description

The current signal Acquisition Circuit that is used for electrical fire monitor band buffering isolation features

Technical field

The utility model relates to a kind of band buffering for electrical fire monitor and the current signal Acquisition Circuit of isolation features.

Background technology

The signals collecting of existing electrical fire monitor is generally: collection signal is inputted, and then amplifies by amplifier to input to A/D convertor circuit; When if this method is used for the current signal collection, because the current signal collection is completed with the two-stage mutual inductor, so the impedance of sample circuit is increased, thereby make loss of signal too much, the distortion meeting is very large after amplifier is amplified again, makes the rear numerical value of AD conversion and true value depart from excessive.

The utility model content

For the problems referred to above, the utility model purpose is to provide a kind of band buffering for electrical fire monitor and the current signal Acquisition Circuit of isolation features.

For addressing the above problem, the utility model adopts following technical scheme:

A kind of current signal Acquisition Circuit for electrical fire monitor band buffering isolation features is characterized in that comprising:

Current transformer is used for gathering phase current;

Amplitude limiter circuit, its secondary two ends with described current transformer are in parallel;

Sample resistance, its secondary two ends with described current transformer are in parallel;

Voltage follower, its input end is connected with the output of described sample resistance;

Operational amplifier, the positive input terminal of this operational amplifier connects the output of described voltage follower, and the negative input end of this operational amplifier connects the voltage source of 2.048V.

The utility model has the advantages that: after above-mentioned processing to collection signal, the loss of signal is reduced, the data of collection are more accurate.

Description of drawings

Fig. 1 is voltage source circuit figure;

Fig. 2 is the circuit theory diagrams of the utility model in electrical fire monitor;

Fig. 3 is the utility model composition frame chart.

Embodiment

The utility model relates to the current signal Acquisition Circuit of band buffering and isolation features.

As shown in Figure 3, it comprises: current transformer is used for gathering phase current; Amplitude limiter circuit, its secondary two ends with described current transformer are in parallel; Sample resistance, its secondary two ends with described current transformer are in parallel; Voltage follower, its input end is connected with the output of described sample resistance; Operational amplifier, the positive input terminal of this operational amplifier connects the output of described voltage follower, and the negative input end of this operational amplifier connects the voltage source of 2.048V.The voltage source of described 2.048V is comprised of the voltage follower circuit that reference source REF3020 and amplifier LM258 form, and forms the voltage source of the low output impedance of a 2.048V.The output terminal of operational amplifier connects single-chip microcomputer.

Be described further below in conjunction with accompanying drawing.

As shown in Figure 1, circuit adopts reference source REF3020 and amplifier LM258 to form the voltage source that voltage follower circuit produces the low output impedance of a 2.048V.

Figure 2 shows that the signal acquisition circuit of phase current, in figure, the input end of the signal acquisition circuit of A phase current is the input end of the primary current mutual inductor of A phase line, T1 is the secondary current mutual inductor, 2D1 and 2D2 form amplitude limiter circuit, prevent the excessive amplifier that burns out of input signal, 2R1, 2R2 (preventing the excessive resistance that burns out of electric current) in parallel forms sample resistance, if the inductive coil of T1 produces induced voltage u, the inductive coil internal resistance is r, sample resistance two ends electric potential difference is 75u/ (r+75), sampled signal passes through 2R3, the voltage follower that 2U1A forms is input to by 2R5, 2R6, 2R7, the operational amplification circuit that 2U1B forms, signal after amplification is input to AD converter through 2R8.

In amplification advance row buffering and isolation, described buffer compartment is from referring at the current signal back making alive follow circuit that gathers, the output impedance of collection signal to be reduced to the current signal that gathers for the utility model.

Because the input impedance of amplifier is very large, if directly use the signal of sampling, after having passed through two-stage mutual inductor and sample circuit based on sampled signal so, signal weakens, so can make loss of signal excessive and cause distorted signals when the high impedance amplifier is amplified again; After using voltage follower, utilize the effect that its output impedance is low and have isolation and buffering, make the loss of signal lower, distortion is less.

Above-mentioned embodiment of the present utility model is carried out detailed explanation, for those skilled in the art, can implement technical solutions of the utility model according to above-mentioned narration.

Claims

1. one kind is used for the current signal Acquisition Circuit that the electrical fire monitor band cushions isolation features, it is characterized in that comprising:

Current transformer is used for gathering phase current;

2. the current signal Acquisition Circuit for electrical fire monitor band buffering isolation features as claimed in claim 1 is characterized in that:

The voltage source of described 2.048V is comprised of the voltage follower circuit that reference source REF3020 and amplifier LM258 form, and forms the voltage source of the low output impedance of a 2.048V.