CONTROLS AND CONNECTIONS ON THE 485T

A and B Terminals

The two signal lines used in an RS-422 or RS-485 network should be labeled A and B. These lines should be connected to the A and B terminals of the 485T Tester. If your lines are not marked (or are marked using another method) you can use a DC voltmeter to determine which is which. With no data being sent, the A line will be negative with respect to the B line. On an RS-485 network, if all of the drivers are off, the voltmeter will read zero volts. Under these conditions, it is not possible to use a voltmeter to determine which line is A and which is B. Having them connected backwards will only be a problem when using the RS-232 Data Out Connector.

Some networks will use four wires instead of two. In these networks, one pair will be used to send data out from a master device. The other pair will send data back from one or a multitude of other devices. These networks can be tested using the 485T by treating them as two separate networks. You would first run your tests on one pair of signal lines and then run them again on the other pair.

NOTE: Make sure that you are connected to the correct two lines when using the tester. It is possible for the tester to look like it is working properly when one line is connected and the other is floating or connected to a wire in another pair.

Ground Terminal

The GND terminal on the 485T Tester should be connected to Signal Ground for the device under test. The Signal Ground is usually the same as the power supply ground for your unit. Some systems will also have a Frame Ground that is usually connected to the “Green Wire Ground” of your power supply AC plug. Frame Ground can also be connected to the wire shield if your pair of wires is shielded. You want Signal Ground not Frame Ground. In some systems, Frame Ground will be connected to Signal Ground, usually through a 100 ohm one-half watt resistor. You still want to be connected to Signal Ground to make proper measurements, since they may be at different voltages. There is a 100 ohm one-half watt resistor connected internally between the GND terminal and the internal Signal Ground (power supply ground) of the 485T. This is the optional grounding method from both the RS-422 and the RS- 485 Standard.

6Documentation Number 485T1995 Manual

B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350

PH (815) 433-5100 -- FAX (815) 433-5105

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B&B Electronics 485T manual B Terminals, Ground Terminal
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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.
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