Instrumentation System Design –

part 2

Chapter6:

What to choose for Instrumentation System Design?

What to choose?What to choose?

DAQ hardware

Computer bus

Computer system

Sensor

Analysis tools

Include – Computer (HW), Driver and Application Software.

Computer: Once DAQ device was chosen, you can

easily take for granted the process of selecting the right computer for your application.

Provides housing the DAQ device, running the software to control the device, analyzing the measurements, and saving the results

4- Choosing a Computer System (1)

Driver: It handles the communication layer between

hardware devices and application software. While hardware specifications are very important,

poor driver software can greatly impact the development time and performance of your entire system.

Application software: Application software lies at the core of modern DAQ

systems, making it imperative that you select a software tool that fits the needs of your application today and easily scales as your system matures. The last thing you want to do is rewrite all of your code using new application software simply because your old code got too unwieldy to expand.

4- Choosing a Computer System (2)

Think about your Computer Questions:

1) How much processing power do I need?2) Do I need my computer to be portable?3) How much does the computer cost?4) How rugged do I need my computer to

be?5) Do I need my computer to be modular?6) Do I need a real-time operating

system?

4- Choosing a Computer System (3)

1) How much processing power do I need? Three main components affecting data management:

processor (CPU), RAM and HDD. In general, faster is better, but processor speeds

across brands may not be the same. If you need to analyze or save the data you acquired from your application, processing power is a key feature to consider for your computer.

Processor – interprets and executes instructions. RAM – More RAM improves speed and enables

more applications to run at the same time. HDD - More hard drive space gives you the ability

to store more data. Finally, faster processors enable faster operation of

your application GOOD PERFORMANCES

4- Choosing a Computer System (4)

Performance – Let’s look at this…

Computer Structure - Top Level

Computer

Main Memory

InputOutput

SystemsInterconnection

Peripherals

Communicationlines

CPU

Computer

• A machine that had been designed by the people to carry out some numerical and mathematical operations.• The main important part of the computer is the CPU without which nothing can be done.• The other item that comprises the computer are its HW and SW.

Structure - The CPU

ComputerALU

CU

Internal CPUInterconnection

Registers

CPU

I/O

Memory

SystemBus

CPU

• portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. • plays a role somewhat analogous to the brain in the computer.• Two typical components: i- ALU (performs arithmetic and logical operations) ii- CU (extracts instructions from memory and decodes and executes them, calling on the ALU when necessary).

Calculate the processing power of Computer—The computer X has 1.5GHz clock and 10

seconds of CPU time. Design a computer Y that aims for 4 seconds of CPU time and also can have faster clock, but causes 1.2 x clock cycles. How fast must computer Y clock be?

—Hints: Clock rate= clock cycle / CPU time

4- Choosing a Computer System (4)

4- Choosing a Computer System (4)—The computer X has 1.5GHz clock and 10

seconds of CPU time. Design a computer Y that aims for 4 seconds of CPU time and also can have faster clock, but causes 1.2 x clock cycles. How fast must computer Y clock be?

Clock Ratey = Clock Cyclesy /CPU Timey

= (1.2 x Clock Cyclesx)/4s

Clock Cyclesx = CPU Timex x Clock Ratex

= 10s x 1.5GHz = 15 x 109

Clock Ratey = 1.2 x 15 x 109 / 4s

= 4.5GHz

2) Do I need my computer to be portable? Portability is a key feature to consider for your

computer if you are going back and forth between applications or locations frequently.

Example, a portable computer is essential for taking measurements in the field and then returning to the lab to analyze the data.

Portability is also an important feature if you need to monitor applications in different locations.

The key considerations when assessing portability are the product size and weight.

4- Choosing a Computer System (5)

3) How much does the computer cost? Choosing a computer for your application

becomes a trade-off between price and performance; better features cost more and drive up the price.

Example, a computer with a faster processor is more expensive. Additionally, form factor makes a difference in the cost of the computer.

Typically, between a laptop and a desktop with similar features, a laptop is more expensive due to the added portability.

Finally, industrial specifications or optimizations for instrumentation may increase system cost with the added benefit of providing a rugged test platform.

4- Choosing a Computer System (6)

4) How rugged do I need my computer to be?The ruggedness of your computer can be a crucial feature if you are monitoring your application in an extreme environment. Standard off-the-shelf PCs are not designed to withstand the conditions of industrial environments. Example, the operating conditions for computers consist of operating and storage temperature, relative humidity, and maximum operating and storage altitude.

50 °F to 95 °F (operating temperature), -13 °F to 113 °F (storage temperature), 10,000 feet (operating altitude), and 15,000 feet (storage altitude);

Therefore, any computers featuring specifications greater than these are considered rugged.

4- Choosing a Computer System (7)

5) Do I need my computer to be modular? Computer can be crucial if you are considering future applications

or are working on multiple applications. Modularity describes the degree to which a system’s components

may be separated and recombined. If you want to switch modules in your system or modify your applications easily, having a modular system is crucial.

The flexibility you can achieve with a modular computer is unmatched. You can modify and adapt the system to meet your particular needs and expand for the future as well as upgrade individual components without having to buy a whole new system.

With a modular system, you can install a new hard drive if you need more space or use a DAQ device with a faster ADC if you need faster sampling.

Keep in mind that laptops and netbooks provide portability, but they are more integrated, which makes them harder to upgrade.

Modularity can be an important feature if you need to adapt your current application to future

4- Choosing a Computer System (8)

6) Do I need a real-time operating system? OS is an important feature to consider when choosing a

computer for data acquisition. DAQ and control applications occasionally require a more

specialized operating system. A real-time OS gives you the ability to operate

deterministically, meaning applications can execute according to precise timing requirements. A real-time operating system is deterministic because the operating system does not determine which process happens when; rather, the user defines the order and timing of the processes.

This gives you more control over your application and the ability to execute at faster rates than with a nondeterministic operating system.

If you need a computer with a deterministic operating system, then you want to look for computers that meet those requirements.

4- Choosing a Computer System (9)

4- Choosing a Computer System (10)

Driver: 1) Is the driver compatible with my OS?2) How well does the driver integrate with my

application software?3) What documentation comes with the driver?4) Does the driver include any setup or

diagnostic utilities?5) Is the driver scalable other devices?

4- Choosing a Computer System (11)

Application Software1) Is the SW flexible enough to meet my future

needs?2) How long will it take me to learn the software?3) Does the software integrate my chosen driver

and other productivity tools (analysis, visualization, storage)?

4) Is there a community of resources to use when I get stuck?

5) Does this software have proven history of stability and success?

4- Choosing a Computer System (12)

1) Will I need to analyze my data inline, offline or both?

2) Can my analysis tool(s) handle my data (volume, speed)?

3) Does my analysis tool(s) offer the functions I need?

4) Can I expand my application’s analysis options through add-ons?

5) Can I integrate my own or legacy analysis routines?

5- Choosing an Analysis Tools

1) Do I need to visualize my data inline, offline or both?

2) Can my visualization tool(s) handle my data?

3) Does my visualization tool(s) offer the features I need?

4) Can I tailor my visualization to my application’s need?

5) Do I need to visualize measurement data synchronized with data from other sources?

6- Choosing an Visualization Techniques Tools

1) Can my data storage handle my data volume data and streaming speeds?

2) Do I need exchange data with my colleagues?

3) Can my analysis or visualization software use my storage format?

4) Is my storage format flexible enough for my future needs?

5) How do I retrieve my stored data at a future date?

7- Choosing a Data Storage Format

1) Can my reporting tool(s) handle my data?2) Does my reporting tool(s) offer the

visuals that I need?3) Can I use templates to simplify repetitive

reports?4) Can I automate reporting to save some

time?5) Does my reporting tool(s) export reports

in the right format?

8- Choosing the Right Reporting Tools