CN2209335Y

CN2209335Y - Full-automatic digital multitester

Info

Publication number: CN2209335Y
Application number: CN 94229678
Authority: CN
Inventors: 刘建平
Original assignee: SHENFENG ELECTRONIC INSTRUMENT CO Ltd SHENZHON
Current assignee: SHENFENG ELECTRONIC INSTRUMENT CO Ltd SHENZHON
Priority date: 1994-10-08
Filing date: 1994-10-08
Publication date: 1995-10-04
Anticipated expiration: 2004-10-08

Abstract

The utility model discloses a universal meter which comprises a special input attenuating network, an intelligent control switching circuit, an amplifier, a signal concentrating processor, a CPU, an auto processor for interference, a capacitance testing circuit, a transistor testing circuit, an executive component, etc. The input network is attenuated in a plurality of steps, and thus the input voltage is attenuated to 200 mv to be measured; a protective circuit taking a thermal resistor and a voltage-sensitive resistor as sensors ensures that the instrument of the utility model is absolutely safe under all conditions in 1000V-and 750V-; no manual toggle switch is arranged on the panel of the utility model; the CPU control switch of the function and the range of measurement, stopping the accident due to misapplication, increasing the security of the instrument of the utility model, and simplifying the operatio.

Description

Full-automatic digital multitester

The utility model relates to the intelligent multimeter of a kind of automatic switching range and test function.

Existing multimeter with intelligence only has the function of automatic switching range, content measurement changes needs manual switching, and its weak point is that one is to use trouble, and is not easy to one-handed performance in particular cases, the 2nd, electric, the corresponding complexity of wanting of physical construction of table relatively are easy to generate fault.

The purpose of this utility model is intended to design that a kind of function, range automatically switch, effectively holding circuit, fully-automatic intelligent digital multimeter esy to use, safe and reliable under the high pressure in the test rated range and the big current conditions.

The utility model has had new breakthrough on the basis of existing intelligent multimeter; reached above-mentioned purpose of design fully; its circuit comprises fan-in network; switching device shifter; amplifier; processor in the set of signals; the cpu built-up circuit; disturb automatic processor; LCD display; capacitance test circuit; the transistor test circuit; reference voltage; no operation control circuit and circuit for generating negative voltage; the output signal of fan-in network is delivered to switching device shifter; the output signal feed signals of switching device shifter focuses on device; processor in the set of signals; disturb the signal of automatic processor and all circuit of reference voltage all to deliver to microprocessor cpu; the output signal of capacitance test circuit and transistor test circuit links to each other with switching device shifter; it is characterized in that the switching device shifter automatic switching range not only in this table; and voltage can automatically switch; electric current; resistance; electric capacity; transistor; the test function of diode and path; fan-in network is by the high pressure attenuation network; low pressure attenuation network and holding circuit constitute; the output of five output terminals of attenuation network is respectively 10000 times corresponding to the damping capacity of input signal; 1000 times; 100 times, 10 times and 1 times.Except that the measurement of electric capacity, triode, electric current need be inserted measurand the corresponding jack; the measurement of voltage, resistance, diode, break-make need not manually to carry out any switch setting operation and plug test pencil rod; has only power switch on the casing of multimeter; there are not common function, range selector on the panel; its holding circuit can be guaranteed the safety of fan-in network under any test mode, thereby has guaranteed the safety of instrument.

It is active or passive that the utility model utilizes cpu identification measurand, and then control the conversion of test function automatically, its design philosophy novelty, circuit structure is practical, simplify the structure and method of operating, the purpose that reached automatic test, shows has automatically improved automaticity than like product.In a single day this multimeter puts on market, will be subjected to the popular welcome of electronic device, instrument and electrical repair industry surely.

Further specify the utility model below in conjunction with accompanying drawing:

Fig. 1 circuit block diagram

Fig. 2 circuit theory diagrams

Fig. 3 input protection network and holding circuit

The full-automatic digital multimeter front view of Fig. 4

The vertical view of Fig. 5 Fig. 4.

As seen from Figure 1, this multimeter circuit part by processor, cpu built-up circuit (comprising clock circuit, reset circuit) in fan-in network, capacitance test circuit, transistor test circuit, two ranges, function change-over device, amplifier, execution unit, the set of signals, disturb automatic processor, reference voltage, LCD display, direct supply, no operation control circuit and circuit for generating negative voltage to constitute.Capacitance test circuit and transistor test circuit have corresponding testing jack respectively, the output signal of two test circuits and fan-in network is all delivered to range, function change-over device, deliver to after the output signal of this device is exaggerated and deliver to cpu after processor is handled in the set of signals, the output signal of clock circuit, reset circuit, reference voltage is also delivered to cpu, carry out signal analysis, processing by microprocessor, and send steering order, by the execution unit control switch device.

Among Fig. 2; T1; T2; T3; thermistor PTC; voltage dependent resistor (VDR) RVA; resistance R 1～16; R25 constitutes the fan-in network with automatic protection functions; socket HFE; stabilivolt Z1; R42; R43; R47; R49 constitutes the transistor test circuit; amplifier U11; D2～5; socket CZ; U12; analog switch U10 and peripheral circuit constitute capacitance test circuit; analog switch U1 is a voltage; electric current; electric capacity; the function of triode; range switching device; analog switch U4 is a resistance; diode; path; function; range switching device; amplifier U2A; U3; U9 constitutes amplifier circuit; relay J 1; J2; transistor T4; T5; diode D1; D2; resistance R 22; R23; RG is an execution unit, analog switch U5 and amplifier U _2BBe treatment circuit in the set of signals, 555 integrated circuit U6, T3, D3, C3, D4, C4 etc. constitute the negative electricity source generating circuit, 555 integrated circuit U8 and T6, D6, D7, C12, C13, R45 constitute the interference automatic processor, T8, R39, R40, R41, C9, C15 potentiometer RW2 constitute reference power supply, T9, T10, D8, R24, R37, R38, R48, C8, C14 constitute no operation control circuit, U7 is single-chip microcomputer SF.LJP3828, constitutes central microprocessor jointly with T11.

The fan-in network and the holding circuit of this full-automatic digital multimeter are seen Fig. 3.

R4, R5, R6, R7A, R7B are high voltage network, and R10, R11 are secondary network, and relay J K1, JK2 are controlled by cpu, total U _A, U _B, U _C, U _D, U _E, U _FSix output terminals, wherein U _FFor removing the resistance measurement network output, all the other are the evanescent voltage output terminal.When measuring resistance, diode and path, JK1 is normally closed, and JK2 often opens (controlled by cpu), and R9 is by short circuit, and measured signal and resistance test network are connected, and is specifically judged by cpu control and measures.Measuring voltage is divided high pressure, two kinds of situations of low pressure, and low pressure is divided 0～200mV and two kinds of situations of 200mv～2V again.

When tested voltage U I＜200mv,

UI → JK1(is normally closed) → R8 → UE exports tested voltage value (0～200mv) itself;

When 200mv＜UI＜2V,

UI → JK1(is normally closed) → JK2(is normally closed) → (R10/R9=9) → U _D(0～200mv);

The JK2 on off operating mode is controlled by cpu, and R10/R9=9 is 10 times of attenuation networks, and tested voltage U I has been attenuated 10 times to UD;

When 2V＜UI＜20V:

UI → JK1(often opens) → ((R7A+R7B)/(R4+R5+R6)=90) → U _C(0～200mv);

This moment, JK1 controlled break-make by cpu, and tested voltage is to U _CEnd has been attenuated 100 times;

When 20V＜UI＜200V;

UI → JK1(often opens) → ((R7A+R7B+R6)/(R4+R5)=900) → UB (0～200mv);

UI has been attenuated 1000 times to the UB end;

During 200V＜UI＜1000V:

UI → JK1(often opens) → ((R7A+R7B+R6+R5)/(R4)=9000) → UA (0～200mv);

UI has been attenuated 10000 times to UA.

Fig. 4, Fig. 5 have shown this full-automatic multimeter appearance.It is little that it has a volume, the characteristics that knob is few, except that power switch (1) the side, have only the jack (5) of electric capacity socket (2), transistor socket (3), testing current jack (4) and red, black two test pencil rods on the panel of table.Because this multimeter is not provided with the knob that any artificial conversion is stirred, stopped because of user's improper use causes the accident of damaging instrument, thereby Meter Reliability is improved greatly, also made things convenient for the user simultaneously, testing efficiency is improved greatly.

Claims

1; full-automatic digital multimeter; comprise fan-in network; switching device shifter; amplifier; processor in the set of signals; the cpu built-up circuit; disturb automatic processor; LCD display; capacitance test circuit and electric capacity socket; transistor test circuit and transistor socket; reference voltage; no operation control circuit and circuit for generating negative voltage; the output signal of fan-in network is delivered to switching device shifter; the output signal feed signals of switching device shifter focuses on device; processor in the set of signals; disturb the signal of automatic processor and all circuit of reference voltage all to deliver to cpu; the output signal of capacitance test circuit and transistor test circuit is sent switching device shifter; it is characterized in that having the topworks of automatic switchover test function and range; switching device shifter is a function; range switching device; fan-in network is by the high pressure attenuation network; low pressure attenuation network and holding circuit constitute; the UA of attenuation network; UB; UC; UD; the attenuation multiple of UE end corresponds to 10000 times; 1000 times; 100 times; 10 times and 1 times; write among the cpu by identification measured device active passive and controlled the switching of test function and the program of automatic switching range, cpu output signal control executing mechanism is to voltage; electric current; electric capacity; triode; resistance; the test of diode and path is switched.