10Documentation Number 485T1995 Manual

See B&B Electronics' free RS-422/485 Application Note for information on proper wiring and grounding of an RS-422/485 network.

If the POSITIVE and NEGATIVE THRESHOLD LEDs are both off, you can then test for proper signal amplitude. With the THRESHOLD pot turned to zero (full clockwise), the DATA LED should blink or stay on when data is sent. When data is being sent on the network, turn the THRESHOLD pot counterclockwise until the LED goes out.

If, for instance, the LED goes out when the pot is pointing at .5, then you have a differential input voltage of plus or minus .5 volts. Both RS-422 and RS-485 require at least plus or minus .2 volts to work properly. If your network node is below this level, you may need a line booster, a repeater, or you may need to change your wiring layout. Refer to B&B Electronics' free RS-422/485 Application Note for information on network wiring. If the LED does not go out with the THRESHOLD pot turned up to 1.0 (full counterclockwise), then your differential input voltage is more than 1 volt. Most RS- 422/485 drivers start out with a differential of about 2 volts but the resistance, inductance, and capacitance in the line can reduce it considerably.

NOTE: The differential voltage you are trying to measure is the RECEIVED voltage. You should only make the threshold measurement when the node you are testing is RECEIVING data, not when it is transmitting. If you have a multiple node system with each node at a different location, you may have to have each node transmit separately while you take a reading. You may get a different differential voltage reading from each node.

For example, if you have an RS-485 network with five nodes each located 1000 feet apart for a total of 4000 feet. Node 1 is at one end, node 2 next, etc., and node 5 is at the far end. If you connect the 485T Tester to node 1 and watch while data is sent from node 2, there will only be 1000 feet of wire and the signal should be fairly strong.

However, when node 5 sends data, there will be 4000 feet of wire and the signal will be weaker. If you have the different nodes sending randomly it will be impossible to take a reading. You have to have only one node sending to take a proper reading. You may be able to turn the power off unwanted nodes to stop them from transmitting. However, this may change the loading on the line, so be careful using this method.

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485T specifications

B&B Electronics has been a prominent player in the field of industrial connectivity solutions, and one of their notable products is the 485T. The 485T is a robust serial communication device designed specifically for converting RS-232 signals to RS-485. This device is particularly valuable in environments that necessitate reliable signal transmission over extended distances, which is where traditional RS-232 connections typically fall short.

One of the standout features of the B&B Electronics 485T is its ability to support communication over long distances of up to 4,000 feet. This makes it an ideal solution for applications in industrial settings, where distances between devices often exceed the limitations of standard serial connections. With data rates of up to 115.2 kbps, the 485T ensures that information can be transmitted swiftly and efficiently, making it suitable for various real-time monitoring and control applications.

The 485T incorporates advanced technologies that enhance its performance and reliability. For instance, it features built-in surge protection, which safeguards the device and connected equipment from voltage spikes and transient events. This is crucial in industrial environments where electrical noise and surges can be commonplace. Additionally, the device is designed to support multiple nodes on the RS-485 network, accommodating up to 32 devices simultaneously. This versatility allows for expanded networking capabilities, making it easier to integrate multiple devices and sensors into a cohesive communication system.

In terms of configuration, the B&B Electronics 485T is user-friendly, featuring jumper settings that allow for quick adjustments to accommodate different application requirements. Users can easily switch between half-duplex and full-duplex modes, providing greater flexibility based on the needs of their specific communication networks.

The 485T's compact design makes it easy to integrate into existing systems without taking up excessive space, and its durable construction ensures reliability in demanding environments. Furthermore, with a temperature range designed to withstand industrial conditions, the device can function effectively in both warm and cold settings.

In conclusion, the B&B Electronics 485T is a powerful solution for anyone in need of reliable and long-distance RS-232 to RS-485 conversion. With its high data rates, long-distance capabilities, and enhanced durability, the 485T serves as an excellent choice for industrial communication applications, ensuring that devices remain connected and operational even in the most challenging environments.