The correct choice of data acquisition system

Choice of data acquisition method

Data mining technology has made great strides over the past 30 to 40 years. For example, 40 years ago, in general university laboratories, the equipment used to track the temperature rise of a tank of sodium-tungsten-bronze usually included: a thermocouple, a bridge, a look-up table, and a Stacks of paper and pencils, but today's college students are likely to use automated programs directly and analyze the data on a PC personal computer. At present, there are many ways to retrieve data, and which one is the most appropriate choice depends on several factors, including the complexity of the task, the speed and accuracy required, and the desired Filed functions, etc. There are many types of data capture systems, ranging from simple to complex, each with different capabilities and functions.

Paper and pen

Old-fashioned paper and pen recording methods are still useful in some situations, they are cheap, easy to get, fast and easy to start, so you only need to connect a digital multimeter (DMM). Start recording the data by hand. Unfortunately, this method is prone to errors and is slow and requires a lot of manual analysis. In addition, this method is only useful for data from a single channel; although you can use multiple DMMs, the entire system can quickly become cumbersome and difficult to do. Accuracy will depend on the caretaker's care and may require manual adjustment of the input size. For example, if the DMM is not set to handle the temperature sensor, you will need to manually adjust the unit. After fully considering these limitations, this is often an acceptable method if you need to experiment quickly.

2. Strip chart recorder (stript recorder)

The modern version of the precious bar chart recorder allows you to retrieve data from a variety of input sources. This method provides a permanent record of the data on paper, and because the data is graphically presented, it allows you to Immediately see the trend. Once set, most of the loggers are smart enough to operate on their own, without manual intervention or through a computer.

The shortcomings include: lack of application flexibility and low accuracy, often limited to a few percentage points of accuracy, at most only the small changes depicted by the pen can be perceived. When you need to monitor several channels over a long period of time, the logger is suitable, but its value may be limited, for example, it cannot be used to turn another device on or off. Other considerations include the maintenance of the pen and recording paper, the supply of recording paper, and the storage of data, which ultimately lead to excessive use and waste of paper. Still, such recorders are fairly easy to set up and operate, providing permanent record of data for quick and easy analysis.

3. Scanning digital multimeter

Some desktop DMMs have the option of scanning function. There is a slot in the back of the instrument that can be inserted into the scan card. It can be used to switch multiple input signals for multitasking. Generally, multitasking with 8 to 10 channels is quite common. of. The accuracy and functionality inherent in the DMM instrument panel will remain the same, but the flexibility is limited. Because it cannot be expanded beyond the number of channels that can be accommodated in the expansion slot, an external PC is usually used to process the data acquisition and Analysis of the work.

4.PC insert card

The PC Insert Card is a single-board measurement system that uses an expansion slot in the ISA or PCI bus in the PC, and the read rate is typically around 100,000 times per second. The number of common channels is 8 to 16, and the captured data is stored directly on the computer and then analyzed on the computer. Since this plug-in card is basically part of the computer, it is easy to set the test. The price of a PC plug-in card is also quite cheap, in part because it can rely on the host computer to provide power, housing, and user interface.

The disadvantage of a PC plug-in card is that the resolution is usually only 12 bits, so that small changes in the input signal are not noticeable. In addition, the electronic environment in the PC has a lot of noise, high-speed frequency and bus noise will radiate everywhere, often this kind of electronic interference is the accuracy of the PC inserted card is lower than the handheld DMM. These plug-in cards can only measure a fairly limited DC voltage range. To measure other input signals, such as AC voltage, temperature or resistance, you need to connect some kind of signal conditioning accessories. Other considerations include calibration problems and overall system cost, especially if you need to purchase additional signal conditioning accessories or a PC to install the card. After fully considering these factors, PC insertion cards are an attractive method of data collection if your needs match the functionality and limitations of this card.

5. Data logger

The data logger is usually a stand-alone instrument that, once set up, automatically measures, records, and displays data without the intervention of an operator or computer. This data logger can handle a wide variety of input signals, sometimes with up to 120 channels. Its accuracy is comparable to a stand-alone desktop DMM with 22-bit resolution and 0.004% accuracy. Some data loggers also have the ability to adjust measurement results, check measurement results based on user-defined limits, and output control signals.

One of the advantages of using a data logger is that it has built-in signal conditioning capabilities, and most of them can directly measure a variety of different input signals without the need for additional signal conditioning accessories. You can use one of the channels to monitor the thermocouple, another channel to monitor the resistive temperature component (RTD), and still use the third channel to monitor the voltage. In general, the thermocouple reference compensation function is built into the multiplexer module card for accurate temperature measurement.

The built-in intelligence of the data logger helps you set up test routines and specify parameters for each channel. Once you have completed these settings, the data logger can start working independently, just like a logger. Data can be stored directly in its internal memory and can hold approximately 50,000 or more readings. Through the connection to the PC, it is easy to transfer data to your computer for in-depth analysis. Most data loggers are designed to be flexible and simple to set up and operate, and many offer options for remote operation using batteries or other methods.

Depending on the A/D converter technology used, some data loggers read data at a relatively slow rate (especially compared to the speed at which many PCs insert cards), but 250 reads per second. The reading speed of the values ​​is still quite common. Keep in mind that many of the phenomena monitored are inherently physical, such as temperature, pressure, and airflow, which change at a fairly slow rate. In addition, because the data logger has excellent measurement accuracy, multiple reads and averaging operations are not required, but these are often necessary in PC plug-in card solutions.

6. Data capture front end

Data capture front ends are typically modular and are typically connected to a PC or controller and are often used in automated test applications to capture data and control and wrap signals to other components in the test setup. This data capture front end can achieve very high performance, whether it is comparable in speed or accuracy to the best stand-alone instrument. The data capture front end has a variety of implementation methods, including VXI versions, such as the Agilent E1419A multi-function measurement and control VXI module, as well as some special special card cages. Although the price of the front end has been continuously reduced, this system is quite expensive, so unless you need the high performance of this system, the price may make you retreat. In terms of advantages, such a system can provide considerable flexibility and excellent measurement capabilities.

Data logger application

A good low-cost data logger, which has a moderate number of channels (2060 channels) and a relatively low scan rate, is sufficient for many applications that engineers often encounter, some major applications. include:

Product characterization

Analysis of Thermal Effect Characteristics of Electronic Products

Environmental testing, environmental monitoring

Component characteristic measurement

Battery test

Large household appliances (white-goods) test

Building and computer room monitoring

Production process monitoring, evaluation and problem elimination

壹, data logger application:

Automated test machine for evaluating prototype ICs

1. There is a quick mount on the test PC board

2. Fix the PC board on the heater/cooler to test the IC under different temperature conditions

3. Use Visual Basic, GPIB instruments to achieve complete automation

result:

Can reduce the evaluation time to half

Get accurate and consistent results

Easy to write into a file

è´°, data logger application:

Measuring the characteristics of a newly designed power supply

1. Check the output voltage and noise level

2. Simulate the load (using power resistors) and check for temperature rise and conversion efficiency

3. Measure the absolute temperature of the main components

result:

Reduce development time

Increase reliability by limiting internal temperature

Verification of power supply input specifications

Which data capture system is best for you

No data capture system is perfect for all applications, and answering the following questions may help you decide which one best suits your needs:

1. Does the system match your application needs?

What is the measurement resolution, accuracy and noise performance of the system?

How fast is scanning?

What are the supported sensors and measurement functions?

Can you upgrade or expand to meet future needs?

How is portability?

Can it operate as a stand-alone instrument?

2. How much is the cost?

Whether the software is included or needs to be purchased separately

Need to add additional signal conditioning accessories?

How long is the warranty period?

How easy is the calibration and how much is the cost?

3. How easy is it to use?

Is the specification easy to understand?

Is the user interface easy to use?

How difficult is it to reconfigure settings for new applications

Can data be easily transferred to new applications?

Which package applications are supported

in conclusion

There are many ways to capture data, from paper, pen, plus measurement equipment, to high-precision systems consisting of hardware instruments and software analysis tools. When the user purchases a data acquisition device or system, the first step to consider is to determine the nature of the work at hand and the desired output form, and then select the type of equipment and specifications that meet the requirements. All purchased precision equipment and analytical tools are designed to assist users in understanding the phenomena they are monitoring, so tools are just a way to achieve them.

Concerned about surprises

Tags: thermocouple GPIB wrap data transfer system cost

Previous: Introduction to the processing and etching technology of PCB outer circuit Next: PCB backplane design and testing points

Galvanized Roller Shutter Door

Using advanced hot-dip galvanized material , precision roll forming production process, polyurethane foam that free of hydrofluorocarbon inside door, light weight, high strength, appearance nice. The doors have advantages of tamper anti-theft , noise isolation thermal insulation and corrosion resistance;the doors are widely used in shops, garages, houses, supermarkets, warehouses and industrial plants,etc.

Depending on the characteristics of the buildings,we can choose interior, exterior and intermediate three different installation ways, doors stay in the upper part of door after rolling up , this could save garage space, and also could keep the garage clean and beautiful by prevent the mud, rain and snow ,etc going into the garage.

Galvanized Roller Shutter Door,Standard Galvanized Roller Shutter Door,Automatic Galvanized Roller Shutter Door,Steel Roller Shutter Safe Door

Shenzhen Hongfa Automatic Door Co., Ltd. , https://www.hffreezerdoor.com