CN2354139Y

CN2354139Y - Pocket physical-quantity measuring instrument

Info

Publication number: CN2354139Y
Application number: CN 98236318
Authority: CN
Inventors: 王德宪
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-09-03
Filing date: 1998-09-03
Publication date: 1999-12-15
Anticipated expiration: 2008-09-03

Abstract

The utility model relates to a pocket physical-quantity measuring instrument which is composed of a housing, a display screen, a function key and a connecting board. The utility model is characterized in that a circuit board is composed of a sensing signal generating part, a central observing and controlling part, a display part and a power supply part, wherein the sensing signal generating part is formed in the way that an oscillating circuit with frequency modulation, a signal amplifying circuit and a signal shaping circuit are connected in series, wherein the oscillating circuit which is composed of a Venturi bridge type oscillating circuit and is electrically connected to the signal shaping circuit by a coupling capacitor. The measuring instrument can be connected with a resistor, a capacitor and an inductance sensor in a matching mode to detect various physical quantities. The utility model has the advantages of low power consumption, small volume, high measuring accuracy, multi-function, etc., and is particularly suitable for measuring products with high accuracy.

Description

Pocket physical quantity instrument

The utility model belongs to a kind of measuring instrument, particularly a kind of pocket physical quantity instrument.

At present, homemade various physical quantity instruments or instrument product, precision height and function are many generally all adopts traditional type A/D change-over circuit, and general volume and power consumption are bigger, need 220 volts of power supplies arbitrarily not carry and to use.Though the little product of some volumes is also arranged, but still exists power consumption height, precision is low, function is few deficiency.

The purpose of this utility model provides a kind of pocket physical quantity instrument.This measuring instrument, low in energy consumption, precision is high, function is many.

The technical solution of the utility model is: housing, display screen, operating key and wiring board are formed, and described wiring board circuit is made up of transducing signal generation, central observing and controlling, demonstration, power supply four parts.

Above-mentioned transducing signal take place part be by: oscillatory circuit, signal amplification circuit, signal integer circuit compose in series successively, wherein oscillatory circuit is made up of venturi bridge oscillator circuit, comprises transport and placing device (IC8:A), resistance (R21～R25), electric capacity (C24, C25); Signal amplification circuit is made up of transport and placing device (IC8:B), resistance (R27), and electrical signal transfer is given the signal transformation circuit of being made up of rp-drive (IC9:A, IC9:B, IC9:E) through coupling capacitance (C26).Above oscillatory circuit is actually a frequency modulation type oscillatory circuit, and the disposable signal of finishing takes place and the A/D conversion work.

Above-mentioned display part circuit is made up of display driver, liquid crystal display and eight light emitting diodes.Wherein: LCD circuit constitutes 4 half display driver circuits by IC13, IC14, and XSQ is 4 half LCD.

Above-mentioned power unit is made up of charging circuit, battery, electronic switch, stabilized voltage supply monitoring circuit.

Characteristics of the present utility model are: low in energy consumption, volume is little, measuring accuracy is high, function is many.

Further describe the utility model below in conjunction with example.

Fig. 1 is a surface-mounted integrated circuit connecting relation figure of the present utility model.

Fig. 2 is a surface structure sketch of the present utility model.

Fig. 3 sensor signal generating unit parallel circuit figure.

Fig. 4 is the power unit circuit diagram.

Fig. 5 is central control section circuit diagram.

Fig. 6 is the display part circuit diagram.

Among Fig. 2, the shell of pocket physical quantity instrument is circular, the surface of shell is provided with LCDs and eight light emitting diodes, the lower part of LCDs is respectively arranged with operating key, function such as operating key (C, I, Z, E, N, R, P) is represented order, demonstration, zeroing, extreme value respectively, keeps, resetted, switch; Integrated circuit board is placed in the meter case and wiring is connected with display screen, operating key respectively.The integrated circuit board total system is formed its connecting relation by sensor signal generation, central observing and controlling, demonstration and power supply four parts: external sensor signal generation is respectively partly gone up in central observing and controlling, power supply, demonstration four parts.

Fig. 3: 1. oscillatory circuit

This circuit part is made up of IC8:A, R21, R23, R24, R25, C24, C25, and this is a typical venturi bridge oscillator circuit.R21 and R22 constitute the feedback brachium pontis, and R24, C24 and R25, C25 constitute the vibration brachium pontis.Change the value of R24 or C24, oscillation frequency will change thereupon.Therefore, capacitance type sensor can replaced C 24 insert, and resistance-type or inductance type transducer can replace R24 to insert.When measured (simulation) when physical quantity changes, the corresponding resistor/capacitance/inductance values of sensor changes thereupon, causes the variation of oscillation frequency the most at last.Here it is frequency modulation type oscillatory circuit.Because frequency values itself has been a digital quantity,, also finished mould/number conversion task simultaneously so this circuit has not only been finished the generation of transducing signal.Succinct, the efficient characteristics of this circuit are very outstanding.

R22, D5, D6 use do temperature compensation, and its principle is to have utilized the subzero temperature characteristic that diode had.If the sensor (as inductance type) that inserts has positive temperature characteristics, then compensating circuit can be inserted.The size that changes R22 can be regulated the size of compensation rate.2. signal amplification circuit

IC8:B, R27 have constituted the open loop amplifying circuit, are responsible for the sinusoidal signal of oscillatory circuit tentatively is shaped as approximate square wave.C26 is a coupling capacitance.3. signal transformation circuit

IC9:A is the rp-drive of band application schmitt trigger, is used for the square wave of standard that the approximate square wave that prime is sent here is shaped to.IC9:B and IC9:E parallel running have increased the driving load capacity.The square-wave signal of output at the corresponding levels is delivered to 15 pin of single-chip microcomputer IC10, carries out frequency measurement by the counter of single-chip microcomputer.

Fig. 4 power unit 1. charging circuits

The first half of Fig. 4 is a charging circuit.J1 is the external direct current power supply input socket, and BX is a fuse, and D1 is used for power supply and connects anti-protection.IC1, C1, C2 constitute direct current regulation circuit.Q1, Q2, C3, R1～R5 constitute the batch (-type) oscillatory circuit, produce a low-frequency square-wave signal, deliver to the base stage of Q4 by R6.Q4 drives as charging current, and the effect of Q3 and R7 is to make charging current constant.D24 is a charging indicator light, and D2 plays buffer action, prevents that battery current from pouring in down a chimney.2. electronic switching circuit

K7, IC2:A, IC2:B and peripheral cell thereof have constituted electronic switching circuit.IC2:A is connected into monostable circuit, when K7 by by once and after unclamping, equal to have sent into a positive pulse to IC2:A and 3 pin.The preventing jittering circuit that process C5, C6, R9, R10 form is after time-delay a period of time, and 1 pin of IC2:A just sends a positive pulse.IC2:B is connected into bistable circuit, and 11 pin are whenever received a pulse, and the output level of 13 pin just overturns once.This level signal is sent to 7 pin of IC4, controls opening or closing of power supply.

The effect of Q5 is equivalent to K7, and just its switch is by monolithic processor controlled.When needs shut down automatically, send a pulse by 1 pin of single-chip microcomputer IC10, after IC9:C buffering, deliver to the ground level of Q5, make the Q5 conducting once, as K7 by by once.3. mu balanced circuit

IC4 is a slice boost type DC～DC power-switching circuit, and it and L1, C7, C8 have constituted a 5V mu balanced circuit together, and 2.7V～4.5V voltage of being responsible for battery is sent here promotes and be stabilized in 5V.7 pin of IC4 are power supply output control terminals, and 6 pin have output during high level, and low circuit is 6 pin no-outputs at ordinary times.L2, C9 be+filtering circuit of 5V output.IC5, C10, C11 composition+3V mu balanced circuit.IC6, C12, C13 composition-3V voltage conversion circuit, L3 and C14 be-filtering circuit of 3V output.4. voltage monitoring circuit

IC3, D4, R11 have constituted voltage monitoring circuit, and when cell voltage dropped to setting value, 1 pin of IC3 jumped to low level by high level.It is 0# exterior interrupt (INT0) that this low level signal is delivered to single-chip microcomputer IC10 pin, has no progeny in the computing machine response, sends undervoltage warning signal and automatic off signal.

Fig. 5: central observing and controlling part 1. one-chip computer circuit

IC10 is an one-chip computer, also is system-wide command and control center.For compression stroke and simplification circuit, selected the inner singlechip chip that carries the EPROM program storage for use.What this Circuits System adopted is the 87C51 type of 51 series.C28, C29, JZ have formed the system clock oscillatory circuit.The P1 mouth of single-chip microcomputer and P2 mouth are used to show the read-write of output and external data memory.2. keyboard array circuit

The P1 mouth of single-chip microcomputer, 1# exterior interrupt (INT1), R30 and five K switch 1～K5 have formed the keyboard control circuit of system.This part is responsible for importing various control commands to Single Chip Microcomputer (SCM) system, and the implication of each switch is determined by software.3. reset circuit

R28, R29, C27, K6 have constituted the reset circuit of Single Chip Microcomputer (SCM) system.When start, finish the electrification reset of system automatically.When occurring the deadlock situation in the operating process, click the K6 key and go out to make system reset.4. memory circuitry

IC12 is that the EERROM type is deposited chip, has the not characteristic of obliterated data of power down.Therefore, this storer is used for the relevant significant data of storage system needs.This chip operation only needs (P2.5, P2.6, P2.7) three lines just can finish the access task of data in spi bus.5. serial ports communication circuit

IC11 is a RS485 standard serial port change-over circuit, and J5 is the serial ports accessory power outlet.RS485 serial ports communication function has been arranged,, can be linked to be Test Network or form test macro reaching 127 measuring instrument unit and mainframe computer system, thereby finish complicated integration test work according to this communication agreement regulation.

1.4 half liquid crystal display circuits in Fig. 6 display part

IC13, IC14 have constituted 4 half display driver circuits, and XSQ is 4 half LCD.IC14 is used for a minimum driving, and IC13 is used for high 3 half drivings.Need data presented to be sent here by the P0 mouth of single-chip microcomputer IC10, P2.0～P2.3 is the address wire of LCD driver, changes its value and can control corresponding demonstration position.2.LED light emitting diode display circuit

IC15 is the display driver of light emitting diode, and D16～D23 is eight luminotrons that are used to show grouping information.Its video data also is to be sent here by the P0 mouth, and P2.4 is that driver blade is selected the signal controlling end.

Claims

1. pocket physical measurement instrument, form by housing, display screen, operating key and wiring board, it is characterized in that the wiring board circuit is made up of transducing signal generation, central observing and controlling, demonstration, power supply four parts, part takes place transducing signal is to be composed in series successively by frequency modulation type oscillatory circuit, signal amplification circuit, signal transformation circuit, wherein oscillatory circuit is made of venturi bridge oscillator circuit, comprises transport and placing device (IC8:A), resistance (R21～R25), electric capacity (C24, C25); Signal amplification circuit is by transport and placing device (IC8:B), and resistance (R27) is formed, and electrical signal transfer is given the signal transformation circuit of rp-drive (IC9:A, IC9:B, IC9:E) composition through coupling capacitance (C26).

2. according to the described measuring instrument of claim 1, it is characterized in that the display part circuit is made up of display driver, liquid crystal display and eight light emitting diodes, wherein: LCD circuit constitutes 4 half display driver circuits by IC13, IC14, (XSQ) is 4 half LCD.

3. according to the described measuring instrument of claim 1, it is characterized in that power unit is made up of charging circuit, battery, electronic switch, stabilized voltage supply monitoring circuit.