CN104460496A - Numerical control constant current source circuit based on PLC - Google Patents

Abstract

The invention discloses a numerical control constant current source circuit based on a PLC. The numerical control constant current source circuit comprises the PLC, a keyboard, a DAC, a low-pass filter, an operation amplifier, a current output circuit and an ADC conversion circuit. The output end of the PLC is connected with the input end of the DAC, the output end of the DAC is connected with the input end of the low-pass filter, the output end of the low-pass filter is connected with the input end of the current output circuit and the input end of the ADC conversion circuit, the output end of the ADC conversion circuit is connected with the input end of the PLC, and the keyboard is connected with the input end of the PLC. The numerical control constant current source circuit has the advantages that the accuracy and the efficiency of the circuit are improved, errors and power losses caused by power amplification can be reduced, and a flexible and adjustable microampere-level current can be output.

Description

Based on PLC digital-control constant-flow source circuit

Technical field

The present invention relates to a kind of constant-current source circuit, be specifically related to based on PLC digital-control constant-flow source circuit.

Background technology

Constant current source is that a kind of extraneous electric network source produces fluctuation or electric network impedance characteristic changes, and still can keep constant current source by output current.Microampere order constant current source is compared with general constant-current source circuit, and microampere order constant current source output current is little, is widely used in intelligent instrument and advanced detection technique.But microampere order constant current source is vulnerable to the impact of ripple and noise in circuit.At present, the magnitude of voltage that microampere order constant current source mainly exports as requested, single-chip microcomputer calculates corresponding magnitude of voltage, by DA conversion links output voltage, the process of circuit after filtering, with links such as operational amplifier, transistor, current sampling circuit and Voltage to current transducer, export constant electric current in loop, pull-up resistor place.But have the leakage current of several microamperes or few tens of microamps, affect the precision of circuit, power attenuation is large, far exceedes the error range that microampere order circuit allows, and can not meet the demand exporting small area analysis.So, develop and a kind ofly can reduce error because power amplification causes and power attenuation, export high-precision current, improve circuit efficiency, there is important practical significance.

Summary of the invention

The technical problem to be solved in the present invention be to provide a kind of have improve the precision of circuit and efficiency, the error because power amplification causes and power attenuation can be reduced, export microampere order constant current adjustable flexibly based on PLC digital-control constant-flow source circuit.

Based on PLC digital-control constant-flow source circuit, comprise PLC, keyboard, DAC converter, low-pass filter, operational amplifier, current output circuit, ADC change-over circuit, the output terminal of described PLC connects the input end of DAC converter, the output terminal of DAC converter connects the input end of low-pass filter, the output terminal of low-pass filter connects the input end of current output circuit and ADC change-over circuit respectively, the output terminal of ADC change-over circuit connects the input end of PLC, and described keyboard connects the input end of PLC.

Further, described PLC output terminal is also connected with display circuit, convenient display electric current current set value and electric current moment output valve.

Further, current detecting amplifying circuit is also connected with between described operational amplifier and ADC change-over circuit.

Preferably, described operational amplifier is FET type amplifier.

Beneficial effect of the present invention is: the present invention arranges output current value by keyboard, data are sent into liquid crystal display display current set value by PLC, data are sent into DAC converter simultaneously, after low-pass filter, operational amplifier process, export the adjustable microampere order constant current source of numerical control; This signal is converted to digital signal by ADC, and these data are read in internal data memory by PLC, by the feedback element of digital quantity form, makes electric current more stable, then sends into LED display, sees predetermined value and output valve by display.

Accompanying drawing explanation

Fig. 1 is the structured flowchart that the present invention is based on PLC digital-control constant-flow source circuit.

Embodiment

Accompanying drawing discloses concrete structure of the present invention without limitation, and below in conjunction with accompanying drawing, the invention will be further described.

As shown in Figure 1, based on PLC digital-control constant-flow source circuit, comprise PLC, keyboard, DAC converter, low-pass filter, operational amplifier, current output circuit, ADC change-over circuit, the output terminal of described PLC connects the input end of DAC converter, the output terminal of DAC converter connects the input end of low-pass filter, the output terminal of low-pass filter connects the input end of current output circuit and ADC change-over circuit respectively, the output terminal of ADC change-over circuit connects the input end of PLC, and described keyboard connects the input end of PLC.Described PLC output terminal is also connected with display circuit.Current detecting amplifying circuit is also connected with between described operational amplifier and ADC change-over circuit.Described operational amplifier is FET type amplifier.

Claims (4)

1. based on PLC digital-control constant-flow source circuit, comprise PLC, keyboard, DAC converter, low-pass filter, operational amplifier, current output circuit, ADC change-over circuit, it is characterized in that: the output terminal of described PLC connects the input end of DAC converter, the output terminal of DAC converter connects the input end of low-pass filter, the output terminal of low-pass filter connects the input end of current output circuit and ADC change-over circuit respectively, the output terminal of ADC change-over circuit connects the input end of PLC, and described keyboard connects the input end of PLC.

2. according to claim 1 based on PLC digital-control constant-flow source circuit, it is characterized in that: described PLC output terminal is also connected with display circuit.

3. according to claim 1 based on PLC digital-control constant-flow source circuit, it is characterized in that: between described operational amplifier and ADC change-over circuit, be also connected with current detecting amplifying circuit.

4. according to claim 1 based on PLC digital-control constant-flow source circuit, it is characterized in that: described operational amplifier is FET type amplifier.