CN110032063B - PID experiment platform based on differential pressure transmitter and application thereof - Google Patents
PID experiment platform based on differential pressure transmitter and application thereof Download PDFInfo
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Abstract
The invention discloses a PID experiment platform based on a differential pressure transmitter and application thereof, comprising the differential pressure transmitter and a PID regulator capable of manually adjusting parameters; the differential pressure signal input end of the differential pressure transmitter is connected with a differential pressure gas circuit; the electrical signal output end of the differential pressure transmitter inputs a differential pressure electrical signal PID regulator to a first signal input end of the PID regulator through an intelligent display instrument, and a current signal in the PID regulation process is output to a paperless recorder through an ammeter; the paperless recorder can generate a PID output characteristic curve changing along with time according to a current signal in the PID adjusting process. The PID experimental platform based on the differential pressure transmitter is used for inspecting the connection operation of a circuit and a gas circuit; the device is used for demonstrating zero setting, range adjustment and zero point migration of the differential pressure transmitter; the PID regulator is used for demonstrating the influence of parameter adjustment of the PID regulator on a PID output characteristic curve; the open loop step test is used for the PID regulator. The invention has the advantages of both real object operation sense and direct appearance sense.
Description
Technical Field
The invention relates to a teaching experiment platform, in particular to a PID experiment platform based on a differential pressure transmitter.
Background
The PID experiment platform of the existing differential pressure transmitter is built by adopting a pure electric or pure pneumatic instrument, the output indication is only the action of an observation pointer, the change of the output characteristic cannot be directly observed, a corresponding output characteristic curve is obtained, the influence brought by the change of the adjustment of different parameters is not convenient for students to understand and analyze, and the later maintenance and management cost is higher. Or a computer simulation mode is adopted for carrying out relevant experiments, only computer operation is adopted, physical operation perception cannot be given to students, and simulation operation is unstable in output characteristic and high in randomness.
At present, no experiment teaching platform is built in a gas and electricity combined mode in each college and universities. The problems related to the electrical and electrical connection mode, parameter matching and the like of the device are to be solved. If the problem of matching of related electrical parameters can be successfully solved, the output characteristics are recorded by adopting the paperless recorder, which is helpful for visually knowing the influence of the changed related parameters of the PID regulator on the output characteristics, so that the knowledge of the use, operation, adjustment and the like of the PID regulator can be mastered.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the PID experiment platform based on the differential pressure transmitter, which solves the technical problem that the prior art cannot give consideration to the physical operation feeling and the direct observation of the output characteristic curve, can improve the physical operation feeling in the teaching experiment process, can output the characteristic curve, and enables students to understand and analyze the influence caused by the adjustment change of different parameters.
In order to solve the technical problem, the invention adopts the following technical scheme: a PID experiment platform based on a differential pressure transmitter comprises the differential pressure transmitter and a PID regulator capable of manually adjusting parameters; a differential pressure signal input end of the differential pressure transmitter is connected with a differential pressure gas circuit; an electrical signal output end of the differential pressure transmitter inputs a differential pressure electrical signal to a first signal input end of the PID regulator through an intelligent display instrument; the signal output end of the PID regulator outputs a current signal in the PID regulation process to the paperless recorder through the ammeter; the paperless recorder can generate a PID output characteristic curve changing along with time according to a current signal in the PID adjusting process;
the differential pressure gas circuit comprises an air compressor for providing a gas source, and the air compressor is respectively output to the first gas source branch and the second gas source branch through a pressure reducing valve; the first air source branch and the second air source branch are respectively connected with the positive input end and the negative input end of the differential pressure transmitter; the first gas source branch comprises a first valuator and a first gas valve which are connected in series, and the second gas source branch comprises a second valuator and a second gas valve which are connected in series; the first gas source branch is connected with the second origin branch through a third gas valve, and a fourth gas valve serving as a pressure release valve is further connected to the second gas source branch; the pressure gauge also comprises a first pressure gauge, a second pressure gauge and a third pressure gauge which are respectively used for detecting the pressure of an outlet of the pressure reducing valve, the pressure of an outlet of the first valuator and the pressure of an outlet of the second valuator.
Furthermore, one end of the first air valve is connected with the output end of the first setter, and the other end of the first air valve is connected with the positive input end of the differential pressure transmitter; one end of the second air valve is connected with the output end of the second valuator, and the other end of the second air valve is connected with the negative input end of the differential pressure transmitter; two ends of the third air valve are respectively connected with the positive input end and the negative input end of the differential pressure transmitter; one end of the fourth air valve is connected between the second valuator and the second air valve, so that the other end of the fourth air valve can discharge control in the differential pressure air circuit.
Furthermore, a current generator is connected to the second signal input terminal of the PID regulator.
Furthermore, the PID regulator adopts a KZ8 series artificial intelligence industrial regulator/temperature controller, so that a current signal input to the PID regulator by the current generator can be converted into a temperature signal for display.
Furthermore, the differential pressure transmitter adopts a 3051 differential pressure transmitter and adopts an intelligent display instrument capable of adjusting the range coefficient.
Furthermore, the intelligent display adopts a 2008 series DDZ-II type intelligent digital display controller.
Further, the output air pressure of the air compressor is 0-1.0 Mpa; the measuring range of the differential pressure transmitter is 0-0.7Mpa, and the output signal range is 4-20 mA; the output signal range of the PID regulator is 4-20 mA.
The application of the PID experimental platform based on the differential pressure transmitter disclosed by the invention 1 is used for inspecting the connection operation of a circuit and a gas circuit; the device is used for demonstrating zero setting, range adjustment and zero point migration of the differential pressure transmitter; the PID regulator is used for demonstrating the influence of parameter adjustment of the PID regulator on a PID output characteristic curve; open loop step test for PID regulators.
Compared with the prior art, the invention has the following beneficial effects:
1. the air source conditions required by the differential pressure transmitter for zero adjustment, range adjustment, zero point migration and the like can be realized through the differential pressure air circuit. And the gas source signal adjustment of the differential pressure transmitter depends on manual operation, and the PID regulator can manually adjust parameters, so that the practical operation feeling is ensured.
2. The output signal of the differential pressure transmitter is used as the input signal of the PID regulator, so that the comprehensive investigation of the operation flows of the differential pressure transmitter and the PID regulator is realized. The output signal of the current generator is more convenient and faster than the output signal of the differential pressure transmitter, the current generator can be used as the input signal of the PID regulator, the PID operation can be independently investigated, and the operation is more convenient and faster.
3. The paperless recorder is used for recording the PID output characteristic curve in real time, so that the influence of the changed relevant parameters of the PID regulator on the output characteristic can be visually known, and the knowledge of the use, operation, adjustment and the like of the PID regulator can be mastered.
4. The PID regulator adopts KZ8 series artificial intelligence industrial regulator/temperature controller, and can demonstrate PID output characteristic curves aiming at different systems, namely a temperature control system and a pressure control system. And because the output signals of the thermocouple and the thermal resistor are not convenient to control, the PID regulator is difficult to obtain an ideal input model, so that the current generator is adopted to replace the thermocouple and the thermal resistor, and meanwhile, the PID regulator can convert the current signal output by the current generator into a temperature signal for displaying, thereby being capable of visually demonstrating the actually measured temperature (namely the analog measurement value converted from the current signal of the current generator) and the set temperature.
5. Because 3051 differential pressure transmitter can not adjust the range directly, adopt the intellectual display instrument that can adjust the range coefficient, thus can change the range coefficient and adjust the differential pressure signal beyond the range of differential pressure transmitter to its range and reveal through the intellectual display instrument.
6. The output signal range of the PID regulator is the same as the signal output range of the current generator and is equal to the signal output range of the differential pressure transmitter, so that the differential pressure transmitter, the PID regulator and the current generator can be electrically matched smoothly.
Drawings
FIG. 1 is a schematic diagram of a PID experimental platform based on a differential pressure transmitter in the present embodiment;
FIG. 2 is a schematic diagram of a 3051 differential pressure transmitter;
FIG. 3 is a load characteristic of a 3051 differential pressure transmitter;
FIG. 4 is a PID output characteristic curve 1;
FIG. 5 is PID output characteristic curve 2;
FIG. 6 is a PID output characteristic curve 3;
FIG. 7 is a PID output characteristic curve 4;
FIG. 8 is a PID output characteristic curve 5;
fig. 9 is a PID output characteristic curve 6.
Detailed Description
The present invention will be described in further detail with reference to the drawings and preferred embodiments.
Referring to fig. 1, a PID experiment platform based on a differential pressure transmitter comprises a differential pressure transmitter and a PID regulator capable of manually adjusting parameters; a differential pressure signal input end of the differential pressure transmitter is connected with a differential pressure gas circuit; an electrical signal output end of the differential pressure transmitter inputs a differential pressure electrical signal to a first signal input end of the PID regulator through an intelligent display instrument; the second signal input end of the PID regulator is also connected with a current generator; the signal output end of the PID regulator outputs a current signal in the PID regulation process to the paperless recorder through the ammeter; the paperless recorder can generate a PID output characteristic curve changing along with time according to a current signal in the PID adjusting process;
the differential pressure gas circuit comprises an air compressor for providing a gas source, and the air compressor respectively outputs the gas source to the first gas source branch circuit and the second gas source branch circuit through a reducing valve; the first air source branch and the second air source branch are respectively connected with the positive input end and the negative input end of the differential pressure transmitter; the first gas source branch comprises a first valuator (namely, a valuator 1 in the figure 1) and a first gas valve V1 which are connected in series, and the second gas source branch comprises a second valuator (namely, a valuator 2 in the figure 1) and a second gas valve V3 which are connected in series; the first gas source branch is connected with the second origin branch through a third gas valve V2, and a fourth gas valve V4 serving as a pressure relief valve is further connected to the second gas source branch; the pressure gauge also comprises a first pressure gauge (a pressure gauge 1 in the figure 1), a second pressure gauge (a pressure gauge 2 in the figure 1) and a third pressure gauge (a pressure gauge 3 in the figure 1) which are respectively used for detecting the pressure of an outlet of the pressure reducing valve, the pressure of an outlet of the first constant value device and the pressure of an outlet of the second constant value device.
In order to ensure that the differential pressure transmitter, the PID regulator and the current generator can be electrically matched smoothly, in the specific embodiment, the output air pressure of the air compressor is greater than the measurement range of the differential pressure transmitter; the output signal range of the PID regulator is the same as the signal output range of the current generator and is equal to the signal output range of the differential pressure transmitter.
In order to meet the requirements of electrical matching, in particular: the PID regulator adopts KZ8 series artificial intelligent industrial regulator/temperature controller, so that the current signal input to the PID regulator by the current generator can be converted into a temperature signal for display. The differential pressure transmitter adopts a 3051 differential pressure transmitter, and adopts an intelligent display instrument capable of adjusting range coefficients, wherein the intelligent display instrument adopts a 2008 series DDZ-II type intelligent digital display controller.
1. Study 3051 electric characteristics and optimal composition scheme of differential pressure transmitter and PID regulator
(1) 3051 Electrical characteristics of differential pressure transmitter
The DP3051 type differential pressure transmitter is selected, key raw materials, components and parts of the transmitter are imported, and the whole transmitter is strictly assembled and tested. The differential pressure transmitter is mainly characterized in that: the precision is high; the stability is good; a two-wire system (in particular, a four-wire system); a solid element, a plug-in printed circuit board; small size, light weight, firm and shock-resistant; the zero point and the measuring range are continuously adjustable. The requirements of experimental equipment are met.
The working principle of the DP3051 differential pressure transmitter is shown in fig. 2. The capacitance value of the sensor is changed by the pressure or differential pressure introduced from the outside, the capacitance value is converted into a frequency signal through digital signal conversion and then is sent to the microprocessor, the microprocessor outputs a current control signal after operation and sends the current control signal to the current control circuit to be converted into 4-20mA analog current for output, and meanwhile, the microprocessor is responsible for interaction and other operations.
The parameters of the differential pressure transmitter are as follows:
using the object: liquids, gases and vapours
Measurement range: 0-0.7MPa
Outputting a signal: 4-20mADC (special for four-wire 220VAC power supply, 0-10mA DC output)
A power supply: 12-45VDC, typically 24VDC
Load characteristics: referring to fig. 3, the load capacity at a certain power voltage is shown in fig. 3, and the relationship between the load impedance RL and the power voltage Vs is: r1 is less than or equal to 50 (Vs-12)
Range and zero: the exterior is continuously adjustable.
Positive and negative migration: after the zero point is subjected to positive or negative migration, the absolute values of the measuring range and the upper limit value and the lower limit value of the measuring range cannot exceed 100 percent of the upper limit value of the measuring range.
Temperature range: temperature range of the amplifier: -29 to +93 ℃; measurement element filled with silicone oil: -40 to +104 ℃.
Precision: plus or minus 0.25 percent
Load impact: if the power supply is stable, the load has no effect.
Power supply effects: less than 0.005%/V of output range
Damping: step response: when silicone oil is filled, the time is continuously adjustable between 0.2s and 1.67 s.
Isolating the diaphragm: 316 stainless steel
An exhaust drain valve: 316 stainless steel.
Filling liquid: silicone oil or inert oil.
Bolt: 316L stainless steel
Electronic shell material: low copper aluminum alloy
The pressure guiding connecting rod: the flange NPT1/4, the center distance is 54mm, the joint NPT1/2 or M20x1.5 steel thread spherical conical surface is sealed, and the center distance is 50.8mm when the joint is provided.
(2) Electrical characteristics of PID regulator
A large number of types of PID regulators are consulted, and most of the PID regulators adopt a self-tuning mode to adjust parameters such as PB, ti, td and the like, and cannot be manually adjusted, so that the experimental requirements cannot be met. Therefore, a 'KZ 8' series artificial intelligent industrial regulator/temperature controller is selected to replace a PID regulator, the controller can have current input and current output, parameters such as PB, ti and Td are adjustable, and the experimental requirements are met. The main electrical parameters of the controller are as follows:
inputting a division number: K. e, S, J, N, pt 100, cu50, current input
And (3) outputting: 4-20mA
And (3) measuring precision: grade 0.5
Resolution ratio: 1 deg.C/0.1 deg.C
Power supply: AC220
Power consumption of the power supply: less than or equal to 3W
Ambient temperature: 0-55 deg.C
Relative humidity: less than or equal to 85 percent
(3) Electrical matching of differential pressure transmitter and PID regulator
Because the adjustment of the measuring range of the DP3051 differential pressure transmitter can not be directly adjusted, an intelligent digital display controller is needed to be selected to adjust the measuring range, provide a power supply for the differential pressure transmitter, take out signals and the like. Therefore, a 2008 series intelligent digital display controller DDZ-II type instrument is selected and matched. The electrical parameters of the instrument are as follows:
inputting a signal: analog quantity is 4-20mA, and input impedance is less than or equal to 250 omega
Measurement range: -1999 to 9999
And (3) measuring precision: 0.2% of FS or 0.5%
Resolution ratio: 1. 0.1, 0.01, 0.001
Temperature compensation: 0 to 50
The display mode is as follows: -1999 to 9999 measurement values show; -1999-9999 settings display
And (3) analog quantity output: DC4-20mA (load capacity is less than or equal to 500 omega)
Supply voltage: AC220V
Power consumption: less than or equal to 5W
The intelligent display instrument can realize the functions of setting an alarm position, adjusting a measuring range and the like.
Therefore, the connection scheme is that the output of the differential pressure transmitter is sent to the intelligent display instrument, and the output of the intelligent display instrument is sent to the PID regulator.
(4) Study of the PID regulator step characteristic test scheme and the best display mode of the output curve
The PID regulator step characteristic test can adopt a pointer instrument or a digital instrument. For more intuition, an R6100 color paperless recorder is selected, and the recorder can display output parameters in a curve form and customize related recording software. The parameters of the recorder were as follows:
inputting a specification: maximum support of 4-path universal analog input
Voltage input: 0-5V, 1-5V, 0-20mV, 0-100mV
Current input: 0-10Ma, 4-20mA, 0-20mA
Resistance input: 0-400 omega
And (4) an output function: the power distribution output supports 1-path centralized power distribution of +24VDC to the transmitter
A recording function: 1 second to 240 seconds, and is selectable in 11 grades. 1/2/4/8/12/24/36/60/120/180/240 seconds, and the length of the recording time is related to the capacity of the memory, the number of input points and the recording interval.
Data unloading: and the output data of the U disk is supported, and the data is copied to a computer for analysis.
A power supply: 220VAC
Error precision: 2 seconds/day
2. Installation of objects
In order to make whole device look compact, convenient operation, specifically made experimental instrument mounting bracket, differential pressure transmitter installs on the platform desktop, and gas circuit connection differential pressure transmitter adopts three-way valves to connect the copper pipe, and the gas circuit adopts 8mm copper pipe. In order to make the table top look simple, the valuator is placed under the table top, the knob is placed on the valuator, and the copper pipe for the air path is placed under the table top. The pressure gauge for display is placed above the platform, so that the observation is convenient. The 2 pneumatic constant value devices are selected as the input pressure adjustment and the valve switch of the differential pressure transmitter, the arrangement can conveniently adjust the pressure of the high pressure side and the low pressure side of the differential pressure transmitter, and the operations of zero setting, range adjustment, zero point migration and the like of the differential pressure transmitter are effectively carried out. The connecting copper pipes are connected by adopting elbows as much as possible, the copper pipes are not bent, and the discharge valves are placed below the platform. For the convenience of operation, the differential pressure transmitter is sunk and installed on the horizontal panel, so that the differential pressure transmitter is more stable.
The compressed air is provided by a movable air compressor, the output air pressure of the movable air compressor is 0-1.0Mpa, and the measurement range of the differential pressure transmitter of the experimental platform is 0-0.7Mpa, so that the requirement can be met.
After the 220V power supply is introduced, the power supply firstly passes through an air switch to play a role in safety and then is distributed to each electric device. The output of the powered device is typically not directly connected to the next device, but rather passes through the low voltage terminal and then into the next device as needed. This facilitates maintenance.
Signals from the thermocouple temperature sensor and the thermal resistance temperature sensor are inconvenient to operate, so that a current generator is selected to replace 4-20mA signals output by the thermocouple or the thermal resistance. This facilitates operation and enables selection of signal inputs as desired.
3. Operation of PID experiment platform based on 3051 differential pressure transmitter
1. Operation of differential pressure transmitter
(1) Zero setting of differential pressure transmitter
(1) And checking the circuit and the gas circuit, and turning on the power supply under the conditions of no disconnection and short circuit.
(2) Turning off a valuator (off), turning off V1, opening V2, V3 and V4, inputting delta P =0 into the differential pressure transmitter, observing whether the output of the intelligent display instrument is 4mA, opening a right end cover of the differential pressure transmitter if the output of the intelligent display instrument is not 4mA, and simultaneously pressing two buttons on a cover plate to automatically zero the differential pressure transmitter.
(2) Range adjustment for differential pressure transmitter
(1) After zero setting, the air compressor is started, the pressure reducing valve is adjusted, and the pressure reducing valve outputs 0.7Mpa.
(2) The setting device 1 is adjusted to make the pressure gauge 1 output 0.7Mpa.
(3) Slowly opening the V1, hearing the sound of air leakage of the V4, gradually closing the V2 to form a differential pressure delta P =0.7Mpa, observing whether the intelligent display instrument is 20mA, and if not, adjusting the range coefficient of the intelligent display instrument to display the range coefficient to be 20mA.
(4) The method for adjusting the range coefficient comprises the following steps:
pressing the 'SET' key, moving up and down to find 'PASS', pressing the 'ENT' key, inputting '555', and pressing the 'SET' key for 1 second, the instrument enters the second-level parameter setting. Finding E1 is the measuring range coefficient, which can be adjusted in the range of 0-1.999 according to the actual situation.
(3) Zero point migration for differential pressure transmitter
(1) The setter 1 is adjusted so that the output of the setter 1 is zero, and V1, V2, V3, and V4 are opened.
(2) And closing the V2, the V3 and the V4, and adjusting the valuator 2 to enable the valuator 2 to output the upper limit value of the measuring range.
(3) And slowly opening the V3 to enable the input pressure at the minus end of the differential pressure transmitter to be the upper range limit, checking the output value of the differential pressure transmitter, if the input pressure is not 4mA, opening a right end cover of the differential pressure transmitter, and simultaneously pressing two buttons on a cover plate to automatically zero the differential pressure transmitter. Shown as 4mA.
(4) The setter 2 is adjusted so that the output is zero, and V1, V2, V3, V4 are opened. And observing whether the intelligent display instrument is 20mA, and if the measuring range coefficient of the intelligent display instrument is not adjusted, displaying the intelligent display instrument as 20mA.
(5) And adjusting to obtain the negative migration range value of the differential pressure transmitter.
Operation of the PID regulator
(1) Checking gas circuit, circuit connection
(2) Setting of parameters PB (proportional band), ti (integration time), td (differentiation time)
In the normal display state, after pressing the 'SET' key for 3 seconds, the parameter setting state is displayed in the PV display of the PID regulator, the corresponding actual measurement value is displayed in the SV display of the PID regulator, and the following parameter symbols are displayed by sequentially pressing the 'SET' key:
TABLE 1 PID regulator parametertable
*1: the instrument is PID control AT P # 0, values of 'I and D' need to be reasonably set AT the time, the 'AT' self-tuning function can be started AT the time of initial use to enable the control to reach an optimal state, and the instrument is ON/OFF control AT P =0, so that the value of good control can be set AT the time.
*2: this is the PID internal reference value, which is generally not set by human, and the AT will automatically set this value after self-tuning.
*3: the relay contact is output for 20 seconds, and the voltage pulse output/thyristor drive flip-flop output/thyristor drive control pipe is output for 2 seconds.
*4: setting data Lock (LCK) functionality
The set data lock function is used to prevent certain infrequently set parameters from being manipulated. In the three-level lock-off state, the parameter can be locked off by each level of state, and the parameter cannot be set or changed but can be monitored after being locked.
When LCK =0000, all parameters may be modified
When LCK =0001, all data except SV, AL1, AL2 are not modifiable
When LCK =0011, all data except SV is not modifiable
When LCK =0111, all data is not modifiable
(3) Tuning of PID regulator parameters
A. Adjusting PID parameters by an attenuation curve method:
cutting off the effects of I and D
Placing the proportional band at a larger value, gradually reducing the proportional band, and recording the PBs and the oscillation period Ts when the proportional band meets the attenuation ratio of 4;
table 2 sets PB, ti and Td.
TABLE 2 empirical formula of attenuation curve method
| Law of control | PB(％) | Ti(min) | Td(min) |
| P | PBs | ||
| PI | 1.2PBs | 0.5Ts | |
| PID | 0.8PBs | 0.3Ts | 0.1Ts |
B. Critical proportional band method setting PID parameter
Cutting off the effects of I and D;
setting the proportional band at a larger value, and gradually reducing PB until constant amplitude oscillation is achieved; note down PBk and period of oscillation Tk
Table 3 sets PB, ti and Td.
TABLE 3 empirical formula of critical ratio band method
| Law of control | PB(％) | Ti(min) | Td(min) |
| P | 2PBk | ||
| PI | 2.2PBk | 0.85Tk | |
| PID | 1.7PBk | 0.5Tk | 0.125Ts |
Through actual operation, the experiment teaching platform can effectively perform zero adjustment, range adjustment, zero point migration and other operations on the differential pressure transmitter, achieves the expected effect, can be used for developing the teaching experiment of 'using operation and adjustment of the electric differential pressure transmitter' and meets the requirement of evaluation examination of a maritime affairs bureau. The differential pressure transmitter adjustment process is shown in table 4.
TABLE 4 differential pressure transmitter tuning procedure
Different output curves are obtained by adjusting PB, ti and Td of the PID regulator, the corresponding output curves are analyzed, and an idea of adjusting corresponding parameters and a step characteristic testing method are provided. Students can complete related experiments according to the operation instruction of the experiment platform, and submit experiment reports according to the regulations, thereby meeting the requirements of the aptitude of related posts. The corresponding test procedure for the PID controller is shown in table 5.
TABLE 5PID control regulating procedure
Through testing, the experiment platform can effectively conduct zero adjustment, range adjustment and zero point migration of the differential pressure transmitter, adjustment of PB, ti and Td of the PID regulator, and observation of the influence of the adjustment of the parameters on control output, so that relevant parameters are adjusted to be in an ideal state, step characteristic testing of the PID regulator can be conducted, and corresponding PB, ti and Td actual values can be measured smoothly. The development and application of the differential pressure transmitter and the PID regulator are facilitated.
Set PB and T welliAnd TdAfter the parameters, the parameters are verified by a step characteristic test. The method comprises the following steps:
a. the current measurement value is 50 ℃, the set temperature value is 50 ℃, the input range is 0-100 ℃, the output is stabilized at 12mA, and the output range is 4-20mA electric signal.
b. Assuming PB is set to 50%, the current generator is changed and the analogue measurement is reduced to 40 ℃ and the output will reach 17-18mA, at which point the output starts to decrease, entering the differential action phase, recording time T1, when decreasing to 15.2mA, at which time it is proportional output, recording time T2, then the output will gradually increase, at which time it is integral output, when increasing to 18.4mA, recording time T3, and finally the output will reach saturation, i.e. 20mA.
T2-T1 is the differential time Td, and T3-T1 is the integration time Ti.
Through the design and the manufacture of the experiment teaching platform, the experiment platform basically achieves the expected effect, can effectively meet the requirement of evaluation examination of the maritime administration, and can also effectively develop corresponding experiment teaching. The project group basically grasps the development and research thinking of the related experimental equipment through the manufacture of the experimental equipment, accumulates part of the research and development experience of the experimental equipment and lays a foundation for further developing the related experimental equipment.
If the conditions are mature, the experimental equipment can expand the online monitoring function, develop the online output of the paperless recorder and have the control function.
Claims (3)
1. The utility model provides a PID experiment platform based on differential pressure transmitter which characterized in that: the device comprises a differential pressure transmitter and a PID regulator capable of manually adjusting parameters; a differential pressure signal input end of the differential pressure transmitter is connected with a differential pressure gas circuit; an electrical signal output end of the differential pressure transmitter inputs a differential pressure electrical signal to a first signal input end of the PID regulator through an intelligent display capable of adjusting the range coefficient; the signal output end of the PID regulator outputs a current signal in the PID regulation process to the paperless recorder through the ammeter; the paperless recorder can generate a PID output characteristic curve changing along with time according to a current signal in the PID adjusting process;
the differential pressure gas circuit comprises an air compressor for providing a gas source, and the air compressor respectively outputs the gas source to the first gas source branch circuit and the second gas source branch circuit through a reducing valve; the first air source branch and the second air source branch are respectively connected with the positive input end and the negative input end of the differential pressure transmitter; the first gas source branch comprises a first valuator and a first gas valve which are connected in series, and the second gas source branch comprises a second valuator and a second gas valve which are connected in series; the first gas source branch is connected with the second origin branch through a third gas valve, and a fourth gas valve serving as a pressure release valve is further connected to the second gas source branch; the pressure sensor also comprises a first pressure gauge, a second pressure gauge and a third pressure gauge which are respectively used for detecting the pressure of an outlet of the pressure reducing valve, the pressure of an outlet of the first valuator and the pressure of an outlet of the second valuator; one end of the first air valve is connected with the output end of the first setter, and the other end of the first air valve is connected with the positive input end of the differential pressure transmitter; one end of the second air valve is connected with the output end of the second valuator, and the other end of the second air valve is connected with the negative input end of the differential pressure transmitter; two ends of the third air valve are respectively connected with the positive input end and the negative input end of the differential pressure transmitter; one end of a fourth air valve is connected between the second valuator and the second air valve, so that the other end of the fourth air valve can discharge air in the differential pressure air path;
the differential pressure transmitter is used for converting pressure or differential pressure into a current signal to be output, the air pressure output by the air compressor is larger than the measurement range of the differential pressure transmitter, and the signal output range of the differential pressure transmitter is the same as the output range of the PID regulator; the second signal input end of the PID regulator is also connected with a current generator; the output signal range of the PID regulator is the same as the signal output range of the current generator and is equal to the signal output range of the differential pressure transmitter;
the PID regulator adopts KZ8 series artificial intelligent industrial regulator/temperature controller, so that the current signal input to the PID regulator by the current generator can be converted into a temperature signal for display; the differential pressure transmitter adopts a 3051 differential pressure transmitter; the output air pressure of the air compressor is 0 to 1.0Mpa; the measuring range of a differential pressure transmitter is 0 to 0.7Mpa, and the output signal range is 4 to 20mA; the output signal range of the PID regulator is 4-20mA.
2. The differential pressure transmitter-based PID experimental platform of claim 1, wherein: the intelligent display instrument adopts a 2008 series DDZ-II type intelligent digital display controller.
3. The use of a differential pressure transmitter-based PID experimental platform according to claim 1, wherein: the device is used for inspecting the connection operation of the circuit and the air path; the device is used for demonstrating zero setting, range adjustment and zero point migration of the differential pressure transmitter; the PID regulator is used for demonstrating the influence of the parameter adjustment of the PID regulator on the PID output characteristic curve; the open loop step test is used for the PID regulator.
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