CN2072211U

CN2072211U - Digital voltage transmitter

Info

Publication number: CN2072211U
Application number: CN 90205227
Authority: CN
Inventors: 王振中; 王宋科
Original assignee: BAOJI INSTRUMENT FACTORY
Current assignee: BAOJI INSTRUMENT FACTORY
Priority date: 1990-04-20
Filing date: 1990-04-20
Publication date: 1991-02-27

Abstract

The utility model discloses a digital pressure transmitter which is composed of a circuit board, a printed board, an amplifying circuit, an A/D conversion circuit, a decoder drive circuit, a simulation deliver and conversion circuit, a polar protection circuit and a regulation circuit. A pressure and electricity conversion element is composed of a foil strain gauge, a pressure measuring membrane, a sensing part main body and a resistor. The utility model has the advantages of stable and reliable working performance, high measuring accuracy, accuracy of reading and wide range of usage temperature. The utility model can be directly interfaced with the computer, printer or digital control system by the digital quantity BCD code output, or be matched with the DDZ-II or DDZ-III system meter of the old system by the standard analog voltage / or current output.

Description

Digital voltage transmitter

The utility model belongs to pressure unit and makes the field.

Prior art in the utility model prior art field is: the simulated pressure transmitter, this device is made up of housing, joint, spring pressure measuring piece, circuit board etc., joint is connected on the housing, and be communicated with the spring pressure measuring piece, the spring pressure measuring piece is connected with circuit, and circuit output end is connected on the connector of housing.Its weak point is: because the limitation on its structural design, the one, output signal is analog quantity output (voltage/or current signal), can't with computing machine, printer or microcomputer digital control system direct interface; The 2nd, there is not numeric display unit, thereby can't be in the operation conditions of using on-the-spot reading or check gauge.

Purpose of design of the present utility model is: avoid weak point of the prior art, design a kind of one be can with computing machine, printer or microcomputer digital control system direct interface, the 2nd, can be enough the Digital Pressure Transducer that shows of numeral.

Design proposal of the present utility model is: 1. the design philosophy of Digital Pressure Transducer is seen accompanying drawing 3.Tested pressure information P directly affacts on pressure-voltage transitions part 16, and that uses that the strain principle detects the millivolt level is worth proportional voltage signal with pressure P.This feeble signal after high precision amplifying circuit 17 is amplified to certain amplitude, the one road contrary go into demonstrate tested pressure P value by decoder driver circuit 19 and light-emitting diode display 13 after A/D change-over circuit 18 is transformed into digital quantity signal, read in for the scene; The binary-coded decimal that the A/D conversion is taken out on another road provides digital quantity output; Simulation (V/I) translation circuit provides analog quantity output.The dc supply of 24V provides required operating voltage through polar protective circuit 22 and mu balanced circuit 23 for system.A, piezo-electric bridgeware 16 adopt permanent elastic stainless steel material C r17Niz. to be designed to the flat diaphragm structure of periphery fixed, are favorable linearity characteristic between the pressure-displacement that obtains, and its center displacement is not enough to 1/3rd of different range diaphragm thickness.For different pressure measurement ranges, only change the thickness of diaphragm and remaining parts all can be general.Circular group metal foil strain gauge sticks on the diaphragm, just detects and the proportional voltage signal of tested pressure P from this Hui Sideng measuring bridge, and the version of this element as shown in Figure 4.B, amplifying circuit 17 are selected precision operations amplifier μ A725 for use, adopt a regulating element 2R in the design ₇, making its both scalable that gains, the circuit of unlikely again reduction common-mode rejection ratio (Fig. 5) is from designing the operational precision that has guaranteed amplifier.On manufacture technology, also reduced the requirement that conventional variable-gain circuit needs three pairs of element precision-matched, in addition,, even can compensate the temperature drift of load cell for the temperature drift that makes amplifier is controlled, the temperature coefficient that reduces whole instrument adopts regulates 2R ₃, utilize the imbalance of input stage quiescent current to reach the mechanism that the compensation temperature is floated, can make temperature coefficient reduce one more than the order of magnitude.C, A/D translation circuit 18 have been selected 3 1/2 A/D transducers of biproduct somatotype single chip CMOS MC14433 for use, this unit has auto-zero, auto polarity conversion, input impedance height, outward element is few and transfer characteristics such as simple, for making circuit have higher anti-power frequency interference capability, clock frequency is designed to 48KHz, and switching rate is about 3 times/second.Because pressure signal has reached top grade after prime is amplified,, so also be of value to digital steady display so the basic range of MC14433 is designed to 2.000V.The dynamic scan display mode is taked in the output of d, MC14433 numeral, and MC14511 and MC1413 consist of decoder driver circuit 19, and seven sections decoding scheme MC14511 of e, BCD-just can make LED charactron (circuit) 13 demonstrate negative sign and three half words.The position selects signal to be driven by MC1413, by the sequential of kilobit, hundred, ten, individual position respectively conducting light.Because MC1413 is the driving circuit of seven road Darlingtons, so the LED charactron can reach enough brightness.F, analog converting circuit 21 are made up of with running device/voltage to current converter voltage, and they can distinguish outputting standard simulating signal 0～5V and 0～10mA/0～20mA/4～20mA.The user just can select to adapt to the signal form of oneself according to the system configuration (the DDZ-II still is the DDZ-III) of oneself.In general, a system only needs the standard signal of own system, in other words, to a certain custom system, he just only needs a kind of form of standard analog signal, so requirement that the producer uses according to the user, with same circuit board,, just can realize different signal output by well-designed printed board cabling and suitable wire jumper, thereby greatly reduce production cost and strengthened dirigibility, this also is a main consideration in this transmitter design.The signal of A/D translation circuit 18 is directly taken from the output of digital signal, so it is the binary-coded decimal signal of positive logic modulation.Control signal EOC(EOC) also offers the user, use in order to other control together with 8 radical word line set signals.The complete machine working current is selected the supply of one group of 24V direct current for use, and it had both met the normalized current of the instrument of DDZ-III system, also took into account other system.Accidentally current polarity is got wrong for preventing to use, design has polar protective circuit 22.Mu balanced circuit 23 be respectively each element circuit provide needed+15V ,+5V and-the 5V power supply, three terminal regulator is assemblied in the watchcase inboard, utilizes the large tracts of land of watchcase to reach the purpose of good heat radiating.In order to guarantee the measuring accuracy of piezo-electric conversion part 16 designs, the driving voltage of Wheatstone bridge must be invariable, this circuit design multistage mu balanced circuit, afterbody has been selected accurate mu balanced circuit chip μ A723 for use, has removed the measuring error that input voltage (24V) fluctuates and causes in a big way fully.2. structural design scheme: the circuit board 2 of Digital Pressure Transducer is positioned at watchcase 1, and piezo-electric bridgeware 16 is positioned at watchcase and is communicated with joint 8 by O-ring seal 6, nut 7, the lead-in wire 1 and 3 in its piezo-electric bridgeware respectively with 1R ₁Link and the 8C in the mu balanced circuit in the circuit board 23 ₂Link connect, lead-in wire 2 with 4 respectively with circuit board in amplifying circuit 17 in the in-phase end of operational amplifier μ A725 and end of oppisite phase be connected and go between 2 and 1R ₂An end connect, 1R ₂The other end and 1R ₁Adjustable end connect; Charactron 13 is fixed on the circuit board by digital display circuit board, its lead-in wire a, b, c, d, e, f, g, h, i and lead-in

wire

13,14,15,16 respectively with circuit board in 4R in the decoder driver circuit 19 ₁～4R ₉An end and 13,14,15,16 the link of MC1413 connect, surface 10 is positioned at the place ahead of piezo-electric bridgeware by supporting member, escutcheon 14 is positioned on the window of surface and charactron, and watch glass is positioned on the watchcase by O-ring seal 9, and the table lid is screwed on the watchcase; Edge connector 15 is positioned on the watchcase, its each link respectively with circuit board in 6R in the analog converting circuit 21 ₈, 6R ₁₀An end, earth terminal, (A/D conversion) circuit in 16,17,18,19,20,21,22,23 and the mu balanced circuit of MC14433 in power lead connect.A, piezoelectricity bridgeware 16 are by foil strain gauge 3, pressure measurement diaphragm 4, detector probe main body 5 and resistance 1R ₁, 1R ₂Constitute, pressure measurement diaphragm 4 is an one with detector probe main body 5, and foil strain gauge 3 sticks on the pressure measurement diaphragm 4,1R ₁Two ends be connected 1R with 1,3 ends of foil strain gauge respectively ₂An end be connected 1R with 2 ends of foil strain gauge ₂The other end and 1R ₁Adjustable end connect.B, circuit board 2 are to be made of printed board, amplifying circuit 17, A/D translation circuit 18, decoder driver circuit 19, analog converting circuit 21, polar protective circuit 22 and mu balanced circuit 23; the earth terminal of mu balanced circuit 23 is connected with earth terminal in amplifying circuit 17, A/D translation circuit 18, decoder driver circuit 19, analog converting circuit 21, the polar protective circuit 22 respectively and meets plinth 15, mu balanced circuit+V ₁,+V ₂,-V and amplifying circuit-the V end is connected, with the A/D translation circuit+V ₁End ,-V end connects, with decoder driver circuit+V ₁End connects, with the analog converting circuit-V ,+V ₂End connects; Amplifying circuit 2R ₆, 2R ₇An end be connected 3 ends of the MC14433 of A/D translation circuit and the 2R in the amplifying circuit with the link of rheotrope K _XAn end connect, MC14433 15,16,17,18,19,20,21,22,23,24 respectively with decoder driver circuit in 4 ends, 1,2,3,4 ends of MC1413,7,1,2,6 end and the 4R of MC14511 of MC14511 ₈, 4R ₉Public connecting

end

16,17,18,19,20,21,22,23 ends that connect back MC14433 connect plinth by line, 9, the 10 edge joint seats of MC14433; The 6R of analog converting circuit ₁, 6R ₂, 6R ₄Link, the 6BG of a termination voltage switch ₁Collector meet the 7C of polar protective circuit ₁Positive pole and 7D ₁Negative pole, 6R ₁₀, 6R ₉An edge joint seat; The 7D of polar protective circuit ₁Positive pole meet 7C ₂An end and plinth; Output terminal and the adjustable resistance 2R of the operational amplifier μ A725 of c, amplifying circuit 17 ₇An end connect, 2R ₇Other end ground connection, 2R ₇Adjustable termination 2R ₁An end, 2R ₁The end of oppisite phase of another termination μ A725.The negative supply generator 20 of d, mu balanced circuit 23 is by 555 integrated circuit, resistance 8R ₅～8R ₇, electric capacity 8C ₃～8C ₆With diode 8D ₁, 8D ₂Constitute 1 termination 8C of 555 integrated circuit ₄～8C ₆An end, 8D ₁Negative pole, 8R ₇An end and ground connection, 8C ₄5 ends of another termination 555 integrated circuit, 8C ₅2 ends, 6 ends and the 8R of another termination 555 integrated circuit ₆An end, 8R ₆7 ends and the 8R of another termination 555 integrated circuit ₅An end, 8R ₅4,8 ends of another termination 555 integrated circuit and 1 end of the three-terminal voltage-stabilizing circuit 7805 in the mu balanced circuit 23,8D ₁Positive pole meet 8R ₇The other end, 8D ₂Negative pole and 8R ₃Negative pole, 8C ₃Positive pole connect 3 ends of 555 integrated circuit, 8C ₆Negative pole meet 8D ₂Positive pole.When the moving point 3 of e, rheotrope pushed at its 1, output current was 0～20mA, when pushing at its 2, output current is 4～20mA.Its complete machine electrical schematic diagram is shown in Fig. 6, pcb map is shown in Fig. 7, Fig. 8.3. the Design of Mechanical Structure of instrument is a machine-electrical integrated, and detector probe spare is directly chewed with adapter and is connected, and PCB design is two, and the digital tube sheet of LED is held out surperficial baffle plate, and display window design chromatic colour escutcheon makes complete machine attractive in appearance, and is digital clear.Watchcase is the alumina based material cast molding, through machine add, the table place is the vermilion baking vanish, is rich in reflecting feel.Corresponding mechanical seal or " O " type seal with elastometic washer way have all been taked in all junctions of watchcase, make that instrument can (low humidity or dust) long-term continuous working in rugged environment comparatively.

For the convenience of debugging and safeguarding, design has regulate and the full scale calibrating installation zero point, and the table lid of need only outwarding winding gets final product adjustment.Complete machine structure as depicted in figs. 1 and 2.The working power line of 24V and the analog and digital signal of output all are connected by 15 line connectors on the watchcase, and this connector has higher life-span and excellent contact performance.After the socket and plug connection screws, use lock screw locked again, further improved the reliability of contact.

The utility model compared with prior art, the flexible member of (1) flat diaphragm structure, measuring accuracy can be up to 0.1%F.S.～0.2%F.S., and measurement range is wide, in 0～60MPa scope, can provide the series of products of 10 kinds of specifications; (2) tested pressure value can directly show (3 1/2) with numeral, has eliminated sight equation, has improved the accuracy of reading; (3) output signal of transmitter both can the digital quantity binary-coded decimal output directly with computing machine, printer or digital control system interface, also can standard analog amount voltage/or the DDZ-II or the DDZ-III system instrument adapted of electric current output and legacy system; (4) serviceability temperature wide ranges (10 ℃～+ 50 ℃), temperature error little (0.015%F.S./℃) (5) have zero point and full journey adjusting gear, are convenient to adjust and calibration; (6) instrument integral body is all-sealed structure, can adapt to than bad working environment (humidity and dust atmosphere); (7) whole instrument does not have mechanical moving component, and the selected CMOS chip of main circuit element has improved the reliability of instrument.

Description of drawings:

Fig. 1 is that the side of Digital Pressure Transducer is cutd open structural representation.

Fig. 2 is the main TV structure synoptic diagram of Digital Pressure Transducer.

Fig. 3 is the electrical schematic diagram of Digital Pressure Transducer.

Fig. 4 is the structural representation of the piezo-electric bridgeware 16 of Digital Pressure Transducer.

Fig. 5 is the sketch of the amplifying circuit 17 of Digital Pressure Transducer.

Fig. 6 is the circuit diagram of Digital Pressure Transducer.

Fig. 7 is the main circuit printed board single face synoptic diagram of Digital Pressure Transducer.

Fig. 8 is the double-clad board synoptic diagram of the display circuit of Digital Pressure Transducer.

The drawing reference numeral explanation:

1-watchcase 2-circuit board

3-foil strain gauge 4-pressure measurement diaphragm

5-detector probe main body 6-O-ring seal

7-nut 8-joint

9-O-ring seal 10-surface

The 11-table covers the 12-watch glass

13-charactron (circuit) 14-escutcheon

15-plinth 16-piezo-electric bridgeware

17-amplifying circuit 18-A/D translation circuit

19-decoder driver circuit 20-negative supply generator

21-analog converting circuit 22-polar protective circuit

The 23-mu balanced circuit

Embodiment:

Fig. 1～Fig. 8 is a kind of embodiment of Digital Pressure Transducer.

Implement: 1. the material of all mechanical component of instrument is home made materials, and its processing can be finished at engine lathe.The Installation and Debugging of instrument just can realize that electronic devices and components market at home all can be purchased with reference to Fig. 1～Fig. 8 and instructions the 5th part under the working condition with production manometer.

2. employed main testing apparatus has:

(1)-30 ℃ constant temperature oven～+ 80

(2) YU0～0.6MPa/YU0～6MPa/YU0～60MPa counterweight checker.

(3) SR-8 dual trace oscilloscope

(4) six bit digital are numerous with table

(5) YJW-30A DC voltage-stabilizing electric current

(6) special digital circuit tester (self-control)

(7) debugging terminal box (self-control)

Claims

1, a kind of prior art of Digital Pressure Transducer is the simulated pressure transmitter, this device is made up of housing, joint, pressure measuring piece, circuit board etc., joint is connected on the housing, and be communicated with pressure measuring piece, pressure measuring piece is connected with circuit, and circuit output end is connected on the connector of housing, of the present utility model being characterised in that: circuit board 2 is positioned at watchcase 1, piezo-electric bridgeware 16 is positioned at watchcase and is communicated with joint 8 by O-ring seal 6, nut 7, the lead-in wire 1 and 3 in its piezo-electric bridgeware respectively with 1R ₁Link and the 8C in the mu balanced circuit in the circuit board 23 ₂Link connect, lead-in wire 2 with 4 respectively with circuit board in amplifying circuit 17 in the in-phase end of operational amplifier μ A725 and end of oppisite phase be connected and go between 2 and 1R ₂An end connect 1R ₂The other end and 1R ₁Adjustable end connect; Charactron 13 shows circuit board by number and is fixed on the circuit board, its lead-in wire a, b, c, d, e, f, g, h, i and lead-in wire 13,14,15,16 respectively with circuit board in 4R in the decoder driver circuit 19 ₁～4R, an end and 13,14,15,16 the link of MC1413 connect, surface 10 is positioned at the place ahead of piezo-electric bridgeware by supporting member, escutcheon 14 is positioned on the window of surface and charactron, watch glass is positioned on the watchcase by O-ring seal 9, and the table lid is screwed on the watchcase; Edge connector 15 is positioned on the watchcase, its each link respectively with circuit board in 6R in the analog converting circuit 21 ₈, 6R ₁₀An end, earth terminal, A/D translation circuit in power lead in 16,17,18,19,20,21,22,23 and the mu balanced circuit of MC14433 connect.

2, Digital Pressure Transducer according to claim 1 is characterized in that: piezo-electric bridgeware 16 is by foil strain gauge 3, pressure measurement diaphragm 4, detector probe main body 5 and resistance 1R ₁, 1R ₂Constitute, pressure measurement diaphragm 4 is an one with detector probe main body 5, and foil strain gauge 3 glues and is posted on the pressure measurement diaphragm 4 1R ₁Two ends be connected 1R with 1,3 ends of foil strain gauge respectively ₂An end be connected 1R with 2 ends of foil strain gauge ₂The other end be connected with the adjustable end of 1R.

3, Digital Pressure Transducer according to claim 1; it is characterized in that: circuit board 2 is to be made of printed board, amplifying circuit 17, A/D translation circuit 18, decoder driver circuit 19, analog converting circuit 21, polar protective circuit 22 and mu balanced circuit 23; the earth terminal of mu balanced circuit 23 is connected with earth terminal in amplifying circuit 17, A/D translation circuit 18, decoder driver circuit 19, analog converting circuit 21, the polar protective circuit 22 respectively and meets plinth 15, mu balanced circuit+V ₁,+V ₂,-V and amplifying circuit-the V end is connected, and the A/D translation circuit+V ₁End ,-V end connects, with decoder driver circuit+V ₁End connects, with the analog converting circuit-V ,+V ₂End connects; Amplifying circuit 2R ₆, 2R ₇An end be connected 3 ends of the MC14433 of A/D translation circuit and the 2R in the amplifying circuit with the link of rheotrope K _XAn end connect, MC14433 15,16,17,18,19,20,21,22,23,24 respectively with decoder driver circuit in 4 ends, 1,2,3,4 ends of MC1413,7,1,2,6 and the 4R of MC14511 of MC14511 ₈, 4R ₉Public connecting end connect 16,17,18,19,20,21,22,23 ends of back MC14433 by Connecting line joint seat, 9, the 14 edge joint seats of MC14433; The 6R of analog converting circuit ₁, 6R ₂, 6R ₄Link, the 6BG of a termination voltage switch ₁Collector meet the 7C of polar protective circuit ₁Positive pole and 7D ₁Negative pole, 6R ₁₀, 6R ₉An edge joint seat; The 7D of polar protective circuit ₁Positive pole meet 7C ₂An end and plinth;

4, Digital Pressure Transducer according to claim 1 is characterized in that: output terminal and the adjustable resistance 2R of the operational amplifier μ A725 of amplifying circuit 17 ₇An end connect, 2R ₇Other end ground connection, 2R ₇Adjustable termination 2R ₁An end, 2R ₁The end of oppisite phase of another termination μ A725.

5, Digital Pressure Transducer according to claim 3 is characterized in that: the negative supply generator 20 of mu balanced circuit 23 is by 555 integrated circuit, resistance 8R ₅～8R ₇, electric capacity 8C ₃～8C ₆With diode 8D ₁, 8D ₂Constitute 1 termination 8C of 555 integrated circuit ₄～8C ₆An end, 8D ₁Negative pole, 8R ₇An end and ground connection, 8C ₄5 ends of another termination 555 integrated circuit, 8C ₅2 ends, 6 ends and the 8R of another termination 555 integrated circuit ₆An end, 8R ₆7 ends and the 8R of another termination 555 integrated circuit ₅An end, 8R ₅4,8 ends of another termination 555 integrated circuit and 1 end of the three-terminal voltage-stabilizing circuit 7805 in the mu balanced circuit 23,8D ₁Positive pole meet 8R ₇The other end, 8D ₂Negative pole and 8R ₃Negative pole, 8C ₃Positive pole connect 3 ends of 555 integrated circuit, 8C ₆Negative pole meet 8D ₂Positive pole.

6, Digital Pressure Transducer according to claim 2 is characterized in that: when the moving point 3 of rheotrope K pushed at its 1, output current was 0-20mA, and when pushing at its 2, output current is 4-20mA.