Connecting the hardware to the computer
Data acquisition hardware comes in many physical formats. A common type is the plug-in card which fits into a free expansion slot in the computer. Its main advantages are its low cost and its speed. Its main drawbacks are the limited potential for system expansion and the fact that the computer has to be located close to the signal source. Microlink systems solve these problems by offering an extensive range of external data acquisition hardware. You can connect this hardware to the computer in several different ways, optimising the system to your requirements.
RS232 | RS485 | GPIB | Ethernet | USB | SummaryRS232 Serial Link
You can connect the Microlink 3000 Series to the computer with an RS232 cable, and the Microlink 826 utility meter monitors. For logging data from instuments from other manufacturers we recommend the Windmill data acquisition software with the COMIML serial driver.
Advantages of RS232
- Up to 50 m between Microlink hardware and computer
- Over 250 channels per Microlink 3000
Disadvantages
- Slow, runs at up to 38 400 baud over short distances; lower speeds as the distance increases owing to capacitance effects
- Maximum logging speed with Streamer software = 700 samples per second, with Windmill software = 35 samples per second
- Only one device can be connected to an RS232 cable
- Computers now rarely have serial ports and a USB-serial (for example) adaptor may be needed.
More details: see our RS232 Notes.
RS485 Serial Link
You can connect the Microlink 3000 Series to the computer with an RS485 cable, and the Microlink 826 utility meter monitors. For logging data from instuments from other manufacturers we recommend the Windmill data acquisition software with the COMIML serial driver.
Advantages
- Up to 1000 m between Microlink hardware and computer
- 32 Devices can be connected to one RS485 cable
More details: see Windmill's RS485 Wiring Notes.
Disadvantages
- Slow, runs at up to 38 400 baud over short distances; lower speeds as the distance increases owing to capacitance effects
- Maximum logging speed with Streamer software = 700 samples per second, with Windmill software = 35 samples per second
- RS485 adaptor card needed in computer
GPIB (General Purpose Interface Bus, also known as IEEE-488)
You can connect the 3000 Series to the computer with GPIB.
Advantages
- Fast, data transfer rate with suitable Windows software = 200 000 bytes per second.
- 14 Devices can be connected to one GPIB
Disadvantages
- Only 2 m between computer and Microlink
- GPIB adaptor card needed in computer
More details: see our GPIB Notes.
Ethernet Link
You can connect the Microlink 3000 Series to the computer with an Ethernet cable, and the Microlink 840 data loggers.
Advantages
- Each cable segment can be up to 185 m
- 29 Devices can be connected to one cable segment
- Several cable segments can be joined
- Fast, maximum logging speed with suitable Windows software = 250 000 samples per second, with Streamer software = 36 000 samples per second, with Windmill software = 120 samples per second
- Up-to-the-second information can be made available to engineers and managers in their own offices, as and when they need it
Disadvantages
- Ethernet adaptor card needed in computer
Universal Serial Bus
You can connect the Microlink 700 Series and 3000 Series to the computer with a USB cable.
Advantages
- 8 Microlinks can be connected to one USB hub
- No need to switch off the computer, or restart Windows, when plugging a Microlink into the USB port
- Maximum logging speed with Windmill software = 80 samples per second
- Other peripherals, like telephones or scanners, can also be connected to a USB hub
Disadvantages
- Only 5 m between computer and Microlink with one cable
- Joining 5 cables with hubs gives 30 m distance
Mix and Match Communications
Any one, or a mixture, of all the communications discussed can be used in a Microlink system. A summary is given below. The speeds quoted are with recommended Windows software, and the distances the maximum that allow reliable results.
| INTERNAL | RS232 | RS485 | GPIB | ETHERNET | USB | |
| Max Distance | 0 m | 50 m | 1000 m | 2 m | 185 m per cable segment | 5 m per cable segment |
| Max Speed samples/sec | 250 000 | 700 | 700 | 1 MHz | 36 000 | 80 |
| Number of Devices | depends on no. of slots | 1 per cable | 31 per cable | 14 per cable | 29 per cable segment | 8 |
| Computer Adaptor | No | No | Yes | Yes | Yes | No |
| Microlink Hardware | 500 Series | 3000 Series 826 units | 3000 Series 826 units | 3000 Series | 3000 Series 840 Series | 700 Series |
You can find more information about communications with the computer in the
Microlink Measurement and Control Systems Catalogue which is available free from Biodata.
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