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Data Retrieval Options

Wired Links: Wired links for data retrieval include direct connection to the PC, telephone modems, short haul modems, and multidrop networks. Wired links are usually less expensive and easier to set up. They are also better for real-time data retrieval.

Wireless Links: Wireless links for data retrieval include cell modems, and spread-spectrum radio modems. Wireless links are useful when distances, site traffic, or other obstacles make wired links impractical. Also, to the degree that wireless links eliminate surface runs of cable, they also reduce problems caused by electrical transients.

 

Walk-up: PC is carried to the location of the logger and connected by cable. PC runs a program to retrieve data. This method is least expensive, but it cannot be automated.

walk up
   

Multi-Drop: A multidrop modem is connected to each logger and the PC. Cable runs from modem to modem. PC can address each logger to retrieve its data.

multidrop
   

Telephone: A telephone modem is connected to the logger and to the PC. To retrieve data, the PC calls the modem at the logger.

telephone
   

Spread-Spectrum Radio: A radio modem is connected to each logger and to the PC. To retrieve data, the PC transmits a command through its radio to the radio at each logger. The logger responds by sending the requested data. Radio transmissions require line-of-site and are generally limited to a range of 0.5 to 1 km range. In many countries, no licenses are needed for these radios.

   
Cellular Modem: A cellular modem is connected to the logger. This modem requires its own number and account. A telephone modem is connected to the PC. The PC calls the cell modem to retrieve data from the logger.
   
IP Cellular Modem: A cellular modem is connected to the logger. The modem must have its own data account and a fixed IP address. The PC sends retrieval commands to the logger via the internet, avoiding long-distance charges.

 

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