Board Level Data Acquisition
What It Is, How It’s Used, and How to Buy It
Everyone is after information these days. Management requires it from engineers to substantiate decision-making and future investment; engineers require it to ensure processes are operating as designed. In essence, nothing happens today without the proper data to backup our beliefs. We truly are living in the information age.
As engineers, board level data acquisition provides not only the device-level information you have always required, but it also connects you directly with the operating computer, which can then feed the data even farther into the enterprise as necessary. Because board level data acquisition provides input and output signals between an external machine and the computer that operates it, the relay of various control circuits and the state of operation switches can be supervised with the use of a digital I/O board. Furthermore, ongoing monitoring of controller input/output and digitized data can also be achieved.
To better understand board level data acquisition, it’s important to know the differences between the three board types and their application.
According to Ken Goswamy of Contec Microelectronics USA , the three types of digital data acquisition boards are: opto-isolated I/O, TTL I/O, and relay output.
Relay output boards, such as Contec’s RRY-32 (PCI) board , are used when controlling high-voltage electrical machines in which an operation circuit is AC or exceeds DC 24 V,” says Goswamy. “It uses a mechanical contact relay for the output circuit, and the logic and output circuits on the board are isolated by a mechanical contact relay.”
TTL I/O boards supply high-speed I/O, directly linking the input-output and logic circuits on the board. “These boards, like Contec’s PIO-32/32T (PCI) board , are used when a small TTL level (5 V DC) relay is needed for connection with external machinery,” Goswamy says. Because TTL is easily influenced by electrical noise, these boards are best used when electrical noise is at a minimum and wiring distance is short.
The third type of data acquisition board is the opto-isolated I/O board. Here, the logic and input-output circuits are isolated with an optical photocoupler. Since a photocoupler requires additional power, an external DC power supply is required. Contec’s latest offerings in this area include the PIO-64/64L (PCI) , PI-128L (PCI) , and PO-128L (PCI) boards . These boards are typically used with light machinery where the operation circuits are DC 5-24 V, such as a digital switch or display machine.
Now that you have a clearer understanding about the types of available digital data acquisition boards and what environment is best for each, many other factors must be addressed before moving forward with your purchase.
For starters, you need to consider how many I/O channels you’ll need. Consider the number of relays or switches on equipment to be monitored and functions of these relays and switches like alarm, reset, and handshake. “If relay to control is 10 pieces, then you need a board with more than 10 output channels,” says Goswamy. “If the switch to supervise is 20 pieces, then a board with more than 20 input channels is needed.”
In the case of a digital I/O board, if the type of decimal number or hexadecimal number is used, four bits of output or an input are usually needed for one digit.
“For a rotary encoder, consider the resolution of one rotation,” suggests Goswamy. “If the encoder resolves one rotation every 256 minutes, eight point input is needed. 256 = 2 to the power 8, therefore, eight inputs.”
Once you’ve determined the number of I/O channels needed, you should then look at what I/O circuitry is most suitable.
To control high-voltage machinery, in which the operation circuit is AC or exceeds 24 V DC, a relay output board should be used. When the voltage of the operation circuit in the photocoupler insulation input does not exceed DC 24 V, the best choice is the opto-isolated I/O.
“If the input and output of equipment perform high-speed communication on TTL level, you should consider non-insulated TTL level I/O boards,” Goswamy says. “However, if greater insulation is required, then you should look at insulated TTL level I/O, such as Contec’s PIO-16/16TB (PCI) .”
Other factors to consider include necessary response speed, interrupts, and optional functions. There should also be a good deal of discussion surrounding the selection of support software as it relates to the development environment or control needed.
The case for data acquisition boards
Although you may not see an immediate need to include data acquisition boards in your engineering toolbox, fast moving industry changes are bringing to the forefront a need for the capabilities data acquisition boards offer.
Following are three current, universally applicable realities that make Contec’s new lineup of data acquisition boards an attractive tool:
1. Since ISA BUS slots are fast disappearing from PCs, there is a greater need for PCI BUS boards.
2. Manufacturing and fabrication processes are becoming increasingly complex, thereby requiring more controls and, as a result, more I/O channels.
3. With space in a clean room environment at a premium, system integrators and end-users are intensely focused on making systems more compact. Doubling the I/O channels per board reduces the number of boards needed, cutting the number of slots required by half and reducing the overall size of the system.
The case for Contec
Even after you have narrowed your decision about what type of data acquisition board to purchase, you will still be left with the choice of which vendor to partner with to supply you the board(s) of your choice. Goswamy points out the benefits of doing business with Contec:
“Our Active X software makes it easy for software engineers to do data logging and, for each group of interface boards, our API tools software can be interfaced through various popular programming languages with conveniently and uniformly integrated functions. We also offer Labview drivers for most of our boards to provide a familiar working environment to engineers accustomed to working with National Instruments’ boards.
“In addition, Contec’s three-year warranty on all data acquisition boards is one of the best in the industry. Our boards are highly reliable… they have to be. Considering the expensive and intricate production runs they are used for, just one failure can cost a bundle to the company in terms of scrap material and wasted man hours. When these boards are installed and running properly, they provide a real relief to production engineers.”
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