Foreword

In the oil and chemical production process, the tubes of liquid and gas flow measurement and control of the production process is to achieve an important component of automation. Vortex Flowmeter a wide range, it is undeniable moving parts, reliable operation and maintenance of simple, small pressure loss, has certain advantages, such as precision measurement. [1] particularly in a wide range of its measurement and medium density, viscosity and other properties of unrelated and therefore was generally welcomed. This paper presents an MCS 51 SCM application of intelligent design vortex flowmeter, the vortex flowmeter inherent in the nonlinear amendment and have the show, printing, the type of test parameters and data processing functions, thereby widening the vortex Flowmeter scope of application.

Principle

Vortex Flowmeter is based on the principle of Carmen vortex made of oscillation of a fluid flow meter. That is, in the flow of fluid in place a streamlined non-symmetrical shape of the object (vortex flow sensor in the body as a whirlpool), in its downstream side will have two regular whirlpool that is Carmen vortex, swirl Frequency proportional to the flow speed: [2]
FS t ud 1
In FVortex frequency
dWhirlpool in width
uFlow rate
S t Strouhal number
St whirlpool in the value and width of the d and Reynolds number Re. When the Reynolds number Re <2 10 4 circumstances, St for the variables: When Re in 2 10 4 ~ 7 10 6 within the scope, St values basically remain unchanged, this range is the basic measurement of the flow meter .
(1) show that when d and St for the value, whirlpool and the frequency F fluid is proportional to the average velocity u, made use of this characteristic of the vortex flow meter. As vortex sensor is not measured by the average velocity, and is about the vortex flow occurred on both sides of the body. [3] The turbulent state, different Reynolds number, the velocity distribution is different. That is different under different flow velocity distribution, then that the vortex flow sensors to detect the main reflected in the whirlpool of pipelines on both sides of the speed and the relationship between the average velocity is not the only identified. This shows that the vortex flow sensor is non-linear error detection mechanism by the decision. In actual use, the first sensor instrument drawn factor and the frequency of the tests f (F)
K= f (F)=KGF 2
Type in G (F) is the same calibre of the Taiwan instrument the same curve shape (just a different displacement). K factor is the average instrument. In this paper, an MCS 51 SCM smart vortex flowmeter, through the test curve shape of G (F) prior to curing the EPROM flowmeter, and allows users to combine the specific conditions at the scene through the keyboard input K values, Vortex sensors to achieve the non-linear correction.

Hardware design

Figure 1 is a block diagram of the hardware.

Figure 1 block diagram of hardware

According to the design requirements, SCM applications [4] Including: (1) accept the transmitter and sent directly proportional to the pulse flow, and its timing, counting the circuit; (2) monitor, keyboard, printer interface circuit (3) external memory expansion circuit; major Circuit introduced as follows:

1 keyboard / monitor and printer interface [5]

To enable interface hardware as little as possible, design, only a 8155 I / O interface chip to complete intelligent instrument keyboard input, LED printer output and the output interface tasks. I will be used for 8155 show that the PC-on-demand and keyboard-scan output, PB I used to display fields and the output of the decimal point, the 8031 external interrupt INTO for keyboard input response, PA I used an external printer output. As shown in Figure 2.

Figure 2 keyboard / monitor and printer interface circuit

1Display Interface Design

Design of six LED display as the instrument display. PB 8155 the population defined as output, low four PB0 ~ PB3 output data show that the code BCD, and the 74 LS249 BCD decoder decoding the evacuation of the code-LED, PB4 as measuring the results of the decimal point in the drive after LED to the decimal point of LED; PB5 as a polarity control of a separate control of light-emitting diodes to display the measurement results of plus or minus. 8155's PC I defined as output, PC0 ~ PC5 respectively control the six-LED strobe, and dynamic scan display.

2Keyboard interface design

In Figure 2 shows the keyboard interface, the six key components from the keyboard. 8031 using external interrupt INTO status as a keyboard output. In six keys, one of two key defined as "plus-one key" and "cut a key." Another four were key print button, programming button, reset button and option keys. Press the button programming, programming into the state, the average user input instrument factor. Options button used to determine the flow show that expression (such as traffic volume, mass flow, etc.), keyboard out of the scanning signals from the PC output of LED-mouth communication of the election: the keyboard to input signal from the keyboard be closed . Did not press the button, the key condition for the opening, INTO HIGH bit, not to be interrupted trigger; if they press the button, the key condition for the closure, INTO into the high-low, interrupted by the falling edge trigger signal, to CPU interrupt request issued. CPU interrupt response after I read the PC output state, judgement PC0 ~ PC5 output of low-level to complete the keys to scan and identify key.

3Printer Interface Design

16 GP using a common smart micro-printer, comes with 8039 MCU. It can be sent in 8031 to the string of data, graphics data or print out three ways; instrument with the interface design shown in Figure 2, the eight two-way three-state data lines D0 ~ D7 directly with the 8155 PA0 ~ PA7 attached to the chip-select signal CS 8155 and the chip-select signal common SCM system decoder output port address Y7, WR and RD directly with the 8031 WR, RD attached to its hardware design is very simple.

2 External memory expansion

1The expansion program memory EPROM

Since 8031, no EPROM, 8031 MCU is a need to expand outside EPROM2764 (8K bytes). P0 I sent in the low eight address, address ALE signal from the falling edge of control latches to latch, the high-five from P2.0 ~ P2.4 to offer a latch 74 LS373 latch, control ALE connected directly with the client. Reading the program memory, communications election PSEN control the output to allow EPROM2764-OE.

2The expansion of data storage

MCS SCM within a 51 for 128 bytes RAM, its capacity can not meet design requirements, the local expansion of 8 K bytes RAM6264 a static. The machine, the expansion of RAM and EPROM circuit as shown in Figure 3:

Figure 3 external memory expansion

As can be seen from Figure EPROM2764 and RAM6264 the address of the same, but their control signals are different. 2764 is the election of communications, PSEN, and the 6264 read or write is by RD WR models or control, so no data conflicts.

Software Design [6]

The software used module structure, its four main parts are as follows.

1 Main program

The main program-based equipment monitoring procedures. The procedures in the operation, we must first initialize the system, the work-unit, home and counter-sign the initial value, self-inspection indicator, a suspension to start the counter and so on. Instruments and a miniature keyboard compatible LED indicator light, so that the various equipment functions clear and orderly.
Keyboard routines including: scanning the keyboard routines. Its function is to find whether there is a button press, the importation of key procedures; key scanning process; table driver; show routines, such as GM. Key scanning routines are based on the functions of the keys to his position of the scan. Table key driver of judgement which is the function keys. GM's function is to show that subprogram will be displayed in the buffer zone into the code of the code into the display, showing the fonts. Almost all procedures should be used in this process, called the Universal show routines, and to display pieces of distinction.

2 Interrupted service program

The measurement equipment, conversion and other proceedings were interrupted by way connected with the main program, SCM, the two gates used as a timer counter. Because of the frequency of traffic measurement is very important, so timer TO be used to survey and is scheduled to Senior interruption. Measurement of measuring frequency interrupt service routines flow chart shown in Figure 4.

3 Block procedures

Equipment ordered through the keyboard input, users have ready access to the necessary results, which need to function block. Functional blocks include: display, print, block cleared, and other functions. Shows that the role of function blocks is based on the needs of users onto the corresponding import parameters, and then after the code conversion, sent to the show in the buffer zone. Print procedures, including print quality and volume of traffic flow, the instantaneous flow and the cumulative flows.

4 The use of computing routines include procedures for calculation of the flow

Floating-point system is used in computing routines, these operations can be directly subroutine calls.