Threshold Pot

The large pot in the center of the 485T is the threshold pot. In order for RS-422/485 to work properly, you should have a differential input voltage of more than .2 volts across the two lines at the RS- 422/485 receiver. By adjusting this pot you can determine the amplitude of the RS-422/485 signals. Start with the knob turned down to zero volts (full clockwise) with data being sent on your network. The Data LED should be blinking with the data providing that the network is not running at too high of a baud rate. At higher baud rates the LED may be on. Turn the threshold pot up (counterclockwise) until the Data LED stops blinking or turns off. The reading of the pot at that point is the differential input voltage. This reading should be .2 volt or more. If the LED does not stop blinking or turn off with the pot all the way up (full counterclockwise) the reading is above 1 volt. Readings above 1 volt are not available since it would make the lower voltage readings difficult to read. Readings above 1 volt indicate that differential voltage is more than adequate.

Positive Threshold Exceeded LED

The RS-422 Standard states that a network should not have a positive common mode voltage of more than 7 volts. This means that the difference between Signal Ground and either the A or B input should not be more than positive 7 volts. For RS-485 the maximum is 12 volts. The Positive Threshold Exceeded LED will light if these limits are exceeded. This reading is taken with respect to Signal Ground so the GND terminal must be connected properly for the reading to be correct.

NOTE: The RS-422/RS-485 switch is used to control this threshold. It must be in the proper position for these readings to be correct.

Negative Threshold Exceeded LED

Both the RS-422 and the RS-485 Standards state that the network should not have a negative common mode voltage of more than 7 volts. This means that the difference between Signal Ground and either the A or B input should not be more than minus 7 volts. The Negative Threshold Exceeded LED will light if this limit is exceeded. Again this reading is taken with respect to Signal Ground so the GND terminal must be connected properly for the reading to be correct.

Documentation Number 485T1995 Manual

7

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 Threshold Pot, Positive Threshold Exceeded LED, Negative Threshold Exceeded LED
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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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