CN104198091B - An intelligent platinum resistance temperature measuring calibrator and calibrating method thereof - Google Patents

Abstract

The invention discloses an intelligent platinum resistance temperature measuring calibrator and its calibrating method. The AC-DC conversion and oscillating circuit converts 220V AC power into 12V DC working power supply, and the RC0.2Hz is mainly composed of a six-invert gate integrated block. The ring oscillator, after being amplified by the power of the composite triode, controls the power-on and power-off of the relay; the platinum resistance temperature calibration circuit mainly consists of a temperature test bridge composed of resistors and potentiometers, the tested platinum resistance Rc and the standard platinum resistance Rt Placed in the heating furnace, Rc and Rt are selectively connected to the temperature test bridge through the normally open and normally closed nodes of the relay, and then the power is amplified by a circuit composed of an integrated operational amplifier, and the output analog signal is passed through the A/D converter sent to the microcontroller. The invention can automatically switch Rc and Rt, use the same channel to amplify the signal and send it to a single-chip microcomputer, and has the characteristics of low production cost and high test precision.

Description

An intelligent platinum resistance temperature measuring calibrator and calibrating method thereof

technical field

The invention relates to an electronic device for calibrating platinum resistors, in particular to an electronic instrument for calibrating parameters such as resistance, voltage and temperature of platinum resistors.

Background technique

Now, there are many ways to measure temperature, such as mercury thermometers that use volume changes, and thermocouples that use material temperature differences. However, these methods either have a narrow range of temperature sensitivity or low test accuracy, and it is difficult to meet the high temperature, precise monitoring and control requirements of power system switches, transformers and other major equipment. According to the analysis and measurement of physical properties, it is known that platinum resistors respond to temperature changes Fast, high precision, and stable performance, it is an ideal device in the measurement control system, so it is selected emphatically.

Platinum resistance is a positive temperature coefficient sensor, and the resistance value rises and falls synchronously with the temperature. Using this feature, the temperature is collected and measured.

Platinum resistance thermometers have been widely used in power systems, but with electromagnetic induction, temperature difference changes, external force impacts, etc., the performance will be affected. Therefore, the inventors will design a higher standard on the basis of temperature measurement. Calibration equipment, regular inspections, in order to make an analysis and judgment of the quality of platinum resistors.

Contents of the invention

The object of the present invention is to provide an intelligent platinum resistance temperature measuring calibrator with high precision and low price.

The purpose of the present invention is achieved in this way: a platinum resistance temperature measurement calibrator, AC-DC conversion and oscillation circuit is composed of: one end of the primary coil of transformer B is connected in series with insurance BX1 and power switch K1, and then connected to the fire wire of 220V AC The other end of the primary coil of transformer B is connected to the neutral line of 220V AC, and the electronic switch K1' controlled by the single-chip microcomputer is connected in parallel with the power switch K1, and the two ends of the secondary coil of transformer B are respectively connected to the diode bridge rectifier circuit D1-4 Two input terminals, the positive output terminal of the diode bridge rectifier circuit D1-4 is connected in series with the input terminal of the integrated voltage regulator IC1 of model 7812, and the positive output terminal of IC1 is connected in series with the relay J1 and then connected to the compound transistor BG1- The collector of 2, the emitter of the composite transistor BG1-2 is connected in series with the resistor R4, and then connected to the negative output terminal of the diode bridge rectifier circuit D1-4, and the 8-pin series resistor R3 of IC2 is connected in series with the resistor R3 of the composite transistor BG1-2. Base, capacitor C3 is connected in series between pin 1 and pin 5 of IC2, pin 1 of IC2 is connected in series with resistor R2, potentiometer W1 is connected to pin 6 of IC2, and the sliding terminal of potentiometer W1 is connected to pin 5 of IC2 Pin 6, pin 14 of IC2 is connected to the positive output of IC1, negative output of IC1 is connected to pin 7 of IC2, pin 7 of IC2 is connected to the negative output of D1-4, capacitor C2 is connected in series to pin 14 of IC2 Between pin 7 and the positive pole of electrolytic capacitor C1 is connected to the positive output terminal of D1-4, and the negative pole of electrolytic capacitor C1 is connected to the negative output terminal of D1-4. The above-mentioned IC2 is a 74LSO4 six-invert gate integrated block;

The platinum resistance temperature calibration circuit is composed of: the power supply E﹢ output by IC1 is connected in series with the tested platinum resistance Rc, the normally open node J1-1 of the relay J1 is connected to one end of the resistance R5, and the other end of the resistance R5 is connected to the power supply E﹢, the power supply E﹢ is connected in series with the standard platinum resistance Rt, the normally closed node J1-2 of the relay J1 is connected to one end of the resistor R5, the power supply E﹢ is connected in series with the potentiometer W2, and then connected to one end of the resistor R6, and the resistor R6 is connected to the other end One end is connected to the power supply E﹣, the sliding end of the potentiometer W2 is connected to one end of the resistor R6, one end of the resistor R5 is connected in series with the resistor R7 and then connected to the inverting input terminal of IC3, one end of the resistor R6 is connected in series with the resistor R8 and then connected to the non-inverting input of IC3 One end of capacitor C4 is connected to one end of resistor R5, the other end of capacitor C4 is connected to power supply E﹣, the positive pole of Zener diode D5 is connected to the non-inverting input end of IC3, the negative pole of Zener diode D5 is connected to pin 4 of IC3, pin 4 of IC3 Connected to the power supply E﹢, IC3’s 7 pins are connected to the power supply E﹢, the resistor R9 is connected in series between the inverting input terminal of IC3 and the signal output terminal, IC3 is an integrated operational amplifier of the model μA741, the resistance of resistor R5 and resistor R6 The value is the same, the resistance value of resistor R7 and resistor R8 is the same, the resistance value of the standard platinum resistor Rt and the potentiometer W2 are the same as the nominal resistance value of the tested platinum resistor Rc, the tested platinum resistor Rc and the standard platinum resistor Rt are both set in a heating furnace;

The central signal processing circuit is composed of: the signal output terminal of the above-mentioned IC3 is connected in series with the A/D converter and then connected to the single-chip microcomputer, and the LCD liquid crystal display, buzzer, storage unit and the above-mentioned electronic switch K1' are respectively connected with the single-chip microcomputer.

The central signal processing circuit also has a host computer connected to the single-chip microcomputer via a USB interface.

The central signal processing circuit also has a keyboard, and the keyboard is connected to the single-chip microcomputer through the receiving processor JCDL8279.

The AC/DC conversion and oscillating circuit also has a power supply indication circuit: the light emitting diode Fg1 and the resistor R1 are connected in series between the positive output terminal and the negative output terminal of the diode bridge rectifier D1-4.

Described heating furnace selects Fluke 9144 metering furnace for use.

The electrolytic capacitor C1 is 2200 μf, and the capacitor C2 is 0.01 μf.

The resistor R7 is 100kΩ, the resistor R8 is 100kΩ, the resistor R9 is 570kΩ, and the model of the Zener diode D5 is 1N4727.

The model of the A/D converter is MAX125, the model of the single-chip microcomputer is 78K0 of NEC, and the storage unit is EEPROM.

The resistance R3 is 100Ω, and the resistance R4 is 10Ω.

Another object of the present invention is to provide a calibrating method for the above-mentioned calibrator.

Another object of the present invention is achieved like this: a kind of verification method of platinum resistance temperature measuring calibrator, carries out according to the following steps:

After the calibrator is initialized, the following parameters need to be inserted: the serial number of the platinum resistance to be tested, the nominal value of the platinum resistance to be tested, and the calibration point of the temperature of the measuring furnace. After the furnace tank is opened, the temperature rises, and the temperature is compared after the sampling process. Judgment, does the detection reach the checkpoint? If it is not satisfied, continue to cycle heating sampling, compare and judge until the requirements are met, and then output a signal to the outside. The signal first starts the buzzer to make a "didi" sound, telling the calibration personnel to turn on the platinum resistance temperature calibration circuit. Detection work; there are two ways to open the temperature calibration circuit:

First, manually press the power switch K1;

Second, the CPU issues a control command to automatically turn on the electronic switch K1'.

After the power switch K1 or the electronic switch K1' is turned on, start the oscillator to generate a 0.2Hz oscillation frequency, that is, a time interval of 5 seconds, and automatically switch and test the standard platinum resistance and the tested platinum resistance respectively, and after the temperature calibration of the above platinum resistance The test circuit carries out voltage division, shaping and amplification, and outputs the voltage analog signal, which is then converted by A/D to become a binary digital signal that can be recognized by the single-chip microcomputer, and is transmitted to the CPU central signal processor, that is, the single-chip microcomputer, through the data bus and address bus;

After the temperature test signal obtained by the standard platinum resistor and the tested platinum resistor is transmitted to the single-chip microcomputer, the single-chip computer performs data analysis and processing, and confirms the three physical quantities of resistance, voltage and temperature, that is, R～V～℃, and performs error calculation, Make judgments about out-of-tolerance and eligibility;

The single-chip microcomputer displays the measured physical quantities of R～V～℃ and the corresponding comparison and judgment results on the LCD liquid crystal display, so that the calibration personnel can observe and record. look at the query;

Then transmit the signal to the host computer through the USB interface, carry out more in-depth and comprehensive classification, statistics, and storage of the calibration situation of platinum resistance thermometers under its jurisdiction, establish a database, and complete the recording and printing of the calibration report, calibration time, and related information at the same time ;Track and monitor the key platinum resistors, and make an evaluation and application selection on performance changes and advantages and disadvantages through historical inquiry and analysis and comparison of new school data.

The beneficial effects of the present invention are: in the research and design of the intelligent platinum resistance calibrator, the inventor also adopted frequency oscillation on the basis of the high-sensitivity bridge comparison test circuit, and realized the calibration of the standard platinum resistance and the tested Automatic switching of platinum resistance temperature measurement, and use the same channel for signal shaping, amplification, and A/D conversion, and send it to the single-chip microcomputer system for data analysis and error calculation, which not only simplifies the circuit, reduces costs, but also reduces errors At the same time, the non-linear characteristics between the resistance value of the platinum resistance and the temperature change are also filtered, thereby further improving the detection accuracy, and connected with the host computer through the USB interface to print the calibration report And establish a database, etc., to form an advanced and perfect calibration instrument.

At the same time, the calibrator is composed of conventional electronic devices, such as a six-invert gate integrated block, an integrated operational amplifier, and a single-chip microcomputer, which has the characteristics of low production cost and is convenient for widespread promotion.

Description of drawings

Figure 1 is a diagram of the AC-DC conversion and oscillation circuit.

Figure 2 is a circuit diagram of platinum resistance temperature measurement.

Figure 3 is a block diagram of the central signal processor hardware structure.

Figure 4 is a flow chart of the platinum resistance calibration program.

detailed description

1. Circuit design

Our intelligent platinum resistance calibrator is based on the bridge test circuit, as a signal acquisition, and then introduces microcomputer technology for analysis and processing, so as to achieve a comprehensive and perfect level. In the case of ensuring high resolution, the error of this calibrator can be lower than the requirement of 0.15°C, so it can be used as an A-level standard to perform calibration and verification of lower-level platinum resistance thermometers.

1.1) Power supply and oscillation

The calibrator is divided into two parts: software and hardware. The hardware includes the power supply and oscillation circuit in the early stage. Please see Figure 1. In the platinum resistance temperature measurement calibrator, the AC-DC conversion and oscillation circuit is composed of one end of the primary coil of transformer B in sequence The fuse BX1 and power switch K1 are connected in series and then connected to the live wire of 220V AC, the other end of the primary coil of transformer B is connected to the neutral wire of 220V AC, and the electronic switch K1′ controlled by the single-chip microcomputer is connected in parallel with the power switch K1, and the secondary coil of transformer B is connected in parallel. The terminals are respectively connected to the two input terminals of the diode bridge rectifier circuit D1-4, and the positive output terminal of the diode bridge rectifier circuit D1-4 is sequentially connected in series with the integrated voltage regulator IC1 and the relay J1 of the model 7812 It is then connected to the collector of the compound transistor BG1-2, the emitter of the compound transistor BG1-2 is connected in series with the resistor R4, and connected to the negative output terminal of the diode bridge rectifier circuit D1-4, and the 8 pins of IC2 are connected in series with the resistor R3 At the base of the composite transistor BG1-2, capacitor C3 is connected in series between pin 1 and pin 5 of IC2, pin 1 of IC2 is connected in series with resistor R2 and potentiometer W1, and then connected to pin 6 of IC2, potentiometer W1 The sliding terminal of IC2 is connected to pin 6 of IC2, pin 14 of IC2 is connected to the positive output terminal of IC1, pin 7 of IC2 is connected to the negative output terminal of D1-4, and capacitor C2 is connected in series between pin 14 and pin 7 of IC2 , the positive pole of the electrolytic capacitor C1 is connected to the positive output terminal of D1-4, and the negative pole of the electrolytic capacitor C1 is connected to the negative output terminal of D1-4. The above-mentioned IC2 is a 74LSO4 six-inverting gate integrated block; the AC-DC conversion and oscillation circuit also has a power supply work indication circuit: The light emitting diode Fg1 and the resistor R1 are connected in series between the positive output terminal and the negative output terminal of the diode bridge rectifier D1-4.

Figure 1 is the AC-DC conversion and oscillation circuit. The 220V AC power supply is stepped down by the switch K1 or the single-chip microcomputer control switch K1′, the insurance (or insurance tube) BX1 and the transformer B1, and the secondary side voltage of the transformer is formed by the diode D1-4. Bridge rectifier circuit rectification, 2200μf electrolytic capacitor C1 filters the power frequency, 0.01μf polyester capacitor C2 filters the high frequency generated in the rectification filter, and the high and low frequency filter makes the DC power supply more pure and reliable, which is conducive to accurate temperature measurement , the light-emitting diode Fg1 and the resistor R1 divide the voltage as a power indicator, and the 7812 integrated voltage regulator IC1 is used for 12V voltage stabilization, and then the RC ring oscillation composed of the 74LSO4 six-inverter integrated block IC2, the capacitor C3, the resistor R2, and the potentiometer W1 The device outputs a frequency of 0.2 Hz (period 5 seconds), which is transmitted to the compound transistor BG1-2 through the resistor R3, and the conduction and termination of BG1-2 make the relay J1 complete the synchronous operation.

1.2) Bridge measurement and comparison

The bridge circuit has a sensitive response function, so using this circuit for temperature measurement is an excellent signal acquisition method, see Figure 2:

Figure 2 is the platinum resistance calibration test circuit. The platinum resistance temperature calibration circuit is composed of: the power supply E﹢ output by IC1 is connected in series with the tested platinum resistance Rc, and the normally open node J1-1 of the relay J1 is connected to the resistance One end of R5, the other end of the resistor R5 is connected to the power supply E﹢, the power supply E﹢ is connected in series with the standard platinum resistance Rt, the normally closed node J1-2 of the relay J1 is connected to one end of the resistor R5, and the power supply E﹢ is connected in series with the potentiometer W2 Then connect to one end of resistor R6, the other end of resistor R6 is connected to power supply E﹣, the sliding terminal of potentiometer W2 is connected to one end of resistor R6, one end of resistor R5 is connected in series with resistor R7 and then connected to the inverting input end of IC3, one end of resistor R6 is connected in series After connecting resistor R8 to the non-inverting input terminal of IC3, one end of capacitor C4 is connected to one end of resistor R5, the other end of capacitor C4 is connected to power supply E-, the positive pole of Zener diode D5 is connected to the same-phase input terminal of IC3, and the negative pole of Zener diode D5 is connected to 4 pins of IC3, IC3's 4 pins are connected to the power supply E﹢, IC3's 7 pins are connected to the power supply E﹢, and the resistor R9 is connected in series between the inverting input terminal and the signal output terminal of IC3. IC3 is the integration of the model μA741 Operational amplifier, resistor R5 and resistor R6 have the same resistance value, resistor R7 and resistor R8 have the same resistance value, the resistance value of standard platinum resistor Rt and potentiometer W2 is the same as the nominal resistance value of the tested platinum resistor Rc, the tested Both the platinum resistance Rc and the standard platinum resistance Rt are placed in the heating furnace; because they are consistent with Figure 1, they are numbered uniformly. Rc or Rt and potentiometer W2 and R5, R6 form a temperature test bridge, the circuit requires R5 = R6, and Rc or Rt, W2 try to choose the same resistance value (the resistance value of Rt, W2 chooses the nominal resistance value of Rc), The potentiometer W2 is for fine adjustment of the resistance value, so that the bridge remains balanced, so that nodes ① and ② have no signal output when it is stable.

The dotted line in Figure 2 represents the configuration of the Fluke 9144 metering furnace (some are called heating furnaces), and the water triple point, zinc, tin, indium melting and freezing point devices defined by relevant temperature scales have been established for the verification and graduation of platinum resistance thermometers. , providing a stable temperature source. In the actual measurement, the two parameters of R0 and R100/R0 are mainly verified. The R0 and R100 of the resistance thermometer to be verified are respectively measured in the metering furnace, and then the ratio of R0 value and R100/R0 meets the specified technical indicators. Determine if the thermometer is acceptable. The tested platinum resistance Rc and the standard platinum resistance Rt are placed in the metering furnace at the same time, feel and measure the same temperature, and reduce the temperature delay error of sequentially inserting Rc and Rt. The upper ends of Rc and Rt are connected to the positive power supply, and the lower ends are respectively connected to the normally open node J1-1 and the normally closed node J1-2 of the relay. With the frequency conversion control of the 0.2 Hz (period 5 seconds) of the IC2 ring oscillator in Figure 1, the standard platinum resistance Rt and the tested platinum resistance Rc are respectively connected to conduct a comparison test.

The specific application process is that when the temperature of the metering furnace rises to the test requirement, the power switch K1 is manually pressed, and the test circuit is put into operation. When K1 is just pressed, the relay J1 has not yet started, and the normally closed node J1-2 is connected to the standard platinum resistor Rt. The resistance value rises with the temperature of the metering furnace, and the voltage of node ① drops, so that U3>U2, and the μA741 integrated operational amplifier IC3 flips over , the measured value is output through pin 6, because of the ring oscillation in IC2, there is a waiting time of 5 seconds, and digital records can be completed during this period. Immediately after the relay J1 starts, the normally closed node J1-2 disconnects, the standard platinum resistor Rt stops testing, the normally open node J1-1 closes, and turns to the tested platinum resistor Rc for temperature testing. Because the same temperature is tested in the same measuring furnace, the Rc can be compared with the data of the previous Rt test, the error value can be calculated, and the judgment of whether it meets the requirements can be made to achieve the purpose of verification.

Platinum resistors have certain nonlinear characteristics in following temperature changes, which brings certain errors to the test. Therefore, as a peripheral circuit, we introduce capacitor C4 for high-frequency filtering processing, thereby improving test accuracy.

The 1N4727 (3V) Zener diode D5 in the circuit in Figure 2 is the reference voltage set, and it is hoped that the positive and negative phases will be compared with the same conditions before IC3 integrates the operational amplifier μA741, so R7=R8 is required, and at the same time, in order to reduce power consumption, generally R7 , The value of R8 is relatively large, and the design of this circuit is 100kΩ. Considering the relationship between the gain calculation formula of the non-inverting input integrated operational amplifier and the quality factor, we determine that the value of R9 is 570kΩ, and bring it into the formula for calculation:

A=1+R9/R7=1+570/100=6.57

That is, a magnification of more than 6 times is obtained. Thus, through the temperature sampling done by the platinum resistor and the comparison and amplification of the integrated block IC3, etc., at pin 6, that is, node ③ becomes a larger voltage signal output.

The test accuracy in the circuit is determined by the standard platinum resistor Rt. The higher the Rt level, the higher the resolution, accuracy, and test accuracy. Therefore, if the platinum resistor Rt level is increased, the level of the calibrator can also be improved.

2. Intelligent system hardware structure

In order to expand and improve the functions, we have introduced single-chip computer technology to intelligently process the test data. The system hardware structure of the calibrator is shown in Figure 3. Considering the power consumption, the accuracy and price of the whole machine, the single-chip controller of the thermometer adopts the 8-bit 78K0 series single-chip microcomputer of NEC, and enables the watchdog function to improve the anti-interference performance of the thermometer. The analog signal output from pin 6 of IC3 in Figure 2, that is, node ③, is introduced into the dotted line box in Figure 3 for further work.

Referring to Fig. 3, the central signal processing circuit is composed of: the signal output terminal of the above-mentioned IC3 is connected in series with the A/D converter and then connected to the single-chip microcomputer, and the LCD liquid crystal display, buzzer, storage unit and the above-mentioned electronic switch K1' are respectively connected with the single-chip microcomputer.

The intelligent hardware structure mainly has the following parts:

2.1) A/D conversion

Because the ③ node in Figure 2 sends an analog signal, but the microcomputer chip responds to a digital signal, so A/D conversion processing is required first. This device specifically uses a MAX125 A/D converter to convert the collected analog signal into a digital signal, and then transmit it to the CPU central signal processor through the data bus and address bus, and carry out the setting signal transmitted from the keyboard setting signal. Combined, in-depth work such as judgment and classification.

2.2) Keyboard Settings

On the right side of Figure 3, the keyboard is connected to the single-chip microcomputer through the IOP (I/O Processor) integrated receiving processor. This processor is the instruction portal of the CPU central signal processor, including the setting of the parameters to be calibrated, the processing of signal instructions, PCI and SCSI bus data transmission, etc., in cooperation with the keyboard, complete the man-machine dialogue, and realize the settings of the detected platinum resistance value, serial number, alarm value, communication protocol, etc. At the same time, historical data can also be checked and inquired through the keyboard. This device specifically uses the JCDL8279 keyboard interface unit (that is, the receiving processor).

2.3) Central Signal Processor

The CPU central signal processor (including single-chip microcomputer) is the intelligent nerve center. After receiving the detected A/D conversion signal and the parameter instruction inserted by the keyboard through the address bus and data bus, it combines software programming to complete data classification. , comparative analysis, error calculation, pass/fail judgment and other processing, and then send command signals such as buzzer, display, storage, switch K1′ control, interface upload, etc., with powerful functions.

2.4) Memory

In order to track and monitor the performance of each platinum resistor, and at the same time facilitate historical data query and comparison, and further make a judgment on whether the new test meets the specified technical indicators, this calibrator uses EEPROM memory to save each calibration data. stand up.

2.5) LCD liquid crystal display

The platinum resistance calibration results are sent to the KS084 (8.4 inches) LCD screen at the same time to display the current test resistance value and temperature data of each section, so as to facilitate the observation and judgment of the testing personnel. Combined with keyboard operation, the historical records of each platinum resistor can also be checked and checked through the LCD liquid crystal screen.

2.6) USB interface

The calibrator is also connected to the host computer through the USB interface. The upper computer reads the data of the lower computer, records the detection time and makes further statistics, analysis, judgment, and processing, and connects the printer to perform a wider range of work such as printing of calibration reports and information transmission.

3. Intelligent system software process

The platinum resistance calibrator uses NEC's 78K0 series single-chip microcomputer, so the compilation and debugging environment is NEC's Project Manager and ID78K0, and the programs are written in C language. The relevant process is shown in Figure 4.

After the calibrator is initialized, parameters such as the serial number of the platinum resistance to be calibrated, the nominal value of the calibrated resistance value, and the temperature calibration point of the metering furnace need to be inserted, and the temperature is compared and judged after the furnace tank is opened, the temperature rises, and the sampling process is performed. , to detect whether the checkpoint has been reached? If it is not satisfied, it will output from the "N" terminal of the query block, continue to cycle heating sampling, comparison, and judgment until it meets the requirements, and then output from the "Y" terminal of the query block.

The signal output from the "Y" terminal first starts the buzzer to make a "didi" sound, telling the calibration personnel that the platinum resistance calibration circuit can be turned on for detection. There are two ways to open the verification circuit:

First, manually press the power switch K1;

Second, the CPU issues a control command to automatically turn on the electronic switch K1'.

Both K1 and K1' are connected in parallel, and any one of them can play the role of switching on oscillation, verification and amplification, which increases the reliability of the detection work.

When K1 and K1' are turned on, the oscillator is started to generate a time interval of 0.2Hz, that is, 5 seconds, and the standard platinum resistor and the platinum resistor to be calibrated are automatically converted and tested respectively, and the output voltage is an analog signal after voltage division, shaping, and amplification. , and then through A/D conversion, it becomes a binary digital signal that can be recognized by the single-chip microcomputer, and is transmitted to the CPU numerical control center through the data bus and address bus.

Here is another feature: the temperature test data of the standard platinum resistance thermometer and the tested platinum resistance thermometer are sent to the computer through the same channel. This is because there is a time interval of 5 seconds, so they can work and transmit separately, so they are not contradictory. interference, but the circuit is simplified and the cost is reduced; and because they go through the same channel, the two completely avoid circuit errors.

After the temperature test signal obtained by the standard platinum resistance thermometer and the tested platinum resistance thermometer is transmitted to the single chip microcomputer, the data analysis and processing will be carried out according to the program. The biggest functional features are the three physical quantities of resistance, voltage and temperature, namely R～V～℃ It will be confirmed, and the error calculation will be carried out, and the judgment conclusion of out-of-tolerance and eligibility will be made.

Further on in the program, the measured physical quantities of R~V~℃ and the judgment results are displayed on the LCD screen, so that the calibration personnel can observe and record. At the same time, the relevant data and conclusions are kept through the ROM memory, so as to facilitate the query.

Finally, we use the USB interface to transmit the signal to the host computer to carry out more in-depth and comprehensive classification, statistics, storage, and establishment of a database for the calibration of platinum resistance thermometers within the scope of our jurisdiction. At the same time, we complete the calibration report, calibration time, and related information. record print. It can also track and monitor key platinum resistors, and make evaluation and application selections on performance changes and pros and cons through analysis and comparison of historical inquiries and new school data.

Claims (10)

1. a kind of platinum resistance temperature measures tester, it is characterized in that, AC-DC conversion and oscillating circuit composition are：At the beginning of transformer B Level coil one end sequentially concatenate insurance BX1 and power switch K1 be followed by it is another in the live wire of 220V alternating currents, transformer B primary coils The zero line of one termination 220V alternating currents, and, transformer B time in parallel with power switch K1 by monolithic processor controlled electronic switch K1 ' Level coil both ends are connected to diode bridge rectifier D1-4 two inputs respectively, diode bridge rectifier D1-4's Positive output end concatenation model 7812 integrated regulator IC1 input, IC1 positive output end concatenation relay J1 be followed by Compound transistor BG1-2 colelctor electrode, compound transistor BG1-2 emitter stage series resistor R4 are followed by diode bridge rectification Circuit D1-4 negative output terminal, IC2 8 pin series resistor R3 are followed by being serially connected in compound transistor BG1-2 base stage, electric capacity C3 Between IC2 1 pin and 5 pin, sequentially series resistor R2, potentiometer W1 are followed by 6 pin in IC2, potentiometer W1 cunning to IC2 1 pin Moved end is connected to IC2 6 pin, and IC2 14 pin are connected to IC1 positive output end, and IC1 negative output terminal is connected to IC2 7 pin, and the 7 of IC2 Pin is connected to D1-4 negative output terminal, and electric capacity C2 is serially connected between IC2 14 pin and 7 pin, and electrochemical capacitor C1 positive poles are being connected to D1-4 just Output end, electrochemical capacitor C1 negative poles are connected to D1-4 negative output terminals, and above-mentioned IC2 is the non-gate ics of 74L,SO4 six；

Platinum resistance temperature checking circuit forms：Tested RTD Rc, relay J1 are sequentially concatenated by the IC1 power supply E ﹢ exported Normally opened node J1-1 is followed by sequentially concatenating standard platinum resistance in resistance R5 one end, another power supply E ﹣, power supply E ﹢ that are terminated at of resistance R5 Rt, relay J1 normally closed node J1-2 are followed by being followed by resistance R6 one end in resistance R5 one end, power supply E ﹢ concatenations potentiometer W2, Another slips for being terminated at power supply E ﹣, potentiometer W2 of resistance R6 are terminated at resistance R6 one end, after the series resistor R7 of resistance R5 one end IC3 inverting input is connected to, resistance R6 one end series resistor R8 is followed by the in-phase input end in IC3, and the ends of electric capacity C4 mono- are connected to Resistance R5 one end, electric capacity C4 is another to be terminated at power supply E ﹣, and voltage-regulator diode D5 positive poles are connected to IC3 in-phase input end, voltage stabilizing two Pole pipe D5 negative poles are connected to IC3 4 pin, and 7 pin that IC3 4 pin are connected to power supply E ﹣, IC3 are connected to power supply E ﹢, resistance R9 and are serially connected in IC3 Inverting input and signal output part between, IC3 is model μ A741 integrated operational amplifier, resistance R5 and resistance R6's Resistance value is identical, and resistance R7 is identical with resistance R8 resistance value, standard platinum resistance Rt and potentiometer W2 resistance value with quilt It is identical to examine RTD Rc normal resistance, tested RTD Rc and standard platinum resistance Rt is placed in heating furnace；

Central signal process circuit forms：Above-mentioned IC3 signal output part concatenation A/D converter is followed by single-chip microcomputer, LCD liquid Crystal display, buzzer, memory cell and above-mentioned electronic switch K1 ' are connected with single-chip microcomputer respectively.

2. a kind of platinum resistance temperature measurement tester according to claim 1, it is characterized in that, the central signal processing electricity Road also has host computer, and host computer is connected through USB interface with the single-chip microcomputer.

3. a kind of platinum resistance temperature measurement tester according to claim 2, it is characterized in that, the central signal processing electricity Road also has keyboard, and the received processor JCDL8279 of keyboard is connected with the single-chip microcomputer.

4. a kind of platinum resistance temperature measurement tester according to claim 1 or 2 or 3, it is characterized in that, the alternating current-direct current turns Change and oscillating circuit also has power work indicating circuit：Light emitting diode Fg1 and resistance R1 are serially connected in diode bridge rectification Between device D1-4 positive output end and negative output terminal.

5. a kind of platinum resistance temperature measurement tester according to claim 4, it is characterized in that, the heating furnace selects good fortune Lu Grams 9144 metering stoves.

6. a kind of platinum resistance temperature measurement tester according to claim 5, it is characterized in that, the electrochemical capacitor C1 is 2200 μ f, electric capacity C2 are 0.01 μ f.

7. a kind of platinum resistance temperature measurement tester according to claim 6, it is characterized in that, the resistance R7 is 100k Ω, resistance R8 are 100k Ω, and resistance R9 is 570k Ω, voltage-regulator diode D5 models 1N4727.

8. a kind of platinum resistance temperature measurement tester according to claim 7, it is characterized in that, the A/D converter model For MAX125, single-chip microcomputer model NEC 78K0, memory cell EEPROM.

9. a kind of platinum resistance temperature measurement tester according to claim 8, it is characterized in that, the resistance R3 is 100 Ω, R4 is 10 Ω.

10. a kind of method of calibration of the tester as described in claim 1-9 any claims, it is characterized in that, according to the following steps Carry out：

, it is necessary to insert following parameter after tester initialization：Tested RTD numbering, tested RTD nominal value and metering furnace temperature Checkpoint is spent, and is opened in stove groove, temperature raises, and after sampling processing, enters trip temperature multilevel iudge, detects whether to reach verification PointIf do not met, heating sampling, multilevel iudge are continued cycling through, until meeting the requirements, the external output signal of, the letter Start buzzer number first and send " drop drop " sound, tell verification personnel, open platinum resistance temperature checking circuit, carry out detection work Make；Opening temperature checking circuit has two ways：

First, it is manually pressed by power switch K1；

Second, CPU send control instruction, turn on automatically electronic switch K1 '；

After power switch K1 or electronic switch K1 ' connections, start oscillator, produce 0.2Hz frequencies of oscillation, i.e. between the 5 second time Every testing respectively standard platinum resistance and tested RTD automatic conversion, and divided through above-mentioned platinum resistance temperature checking circuit Pressure, shaping, amplification, output voltage analog signal, then changed through A/D, turn into the binary digital signal of monolithic function identification, warp Data/address bus and address bus send CPU central signal processors i.e. single-chip microcomputer to；

After the temperature test signal obtained by standard platinum resistance and tested RTD is passed to single-chip microcomputer, data point are carried out by single-chip microcomputer Analysis handle, to resistance, voltage, temperature, i.e. R~V~DEG C three physical quantitys are confirmed, and carry out error calculation, make it is overproof Whether qualified judgement conclusion；

Single-chip microcomputer shows the R~V tested~DEG C physical quantity and corresponding multilevel iudge result on LCD liquid crystal displays Show to come, with profit verification personal observations' record, meanwhile, through eeprom memory, related data and conclusion are remained behind, with profit Retrieve for examination inquiry；

Host computer is transmitted a signal to by USB interface again, the RTD verification situation of administrative area is carried out deeper into comprehensive Classification, statistics, preservation, establish database, at the same complete verify report, checking time, relevant information record print；Counterweight Point RTD is tracked monitoring, the com-parison and analysis through historical query and new school data, is made with regard to performance change and good and bad situation Assess and selected with application.