B&B Electronics 485T manual RS-422/485 Test

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RS-422/485 TEST

A typical test on an RS-422/485 network might go like this: First start by locating the two wires used for the RS-422/485 network and try to determine which is A and which is B. Also, locate the Signal Ground. This may be the same as the ground on the DC power supply that powers the RS-422/485 device.

Connect the Signal Ground to the GND terminal. Connect the A and B terminals to what you think are the A and B wires. Turn the Threshold Pot to zero (full clockwise), the TERMINATION off, the RS-422 and RS-485 switch to the proper position, and the POWER switch ON. If you are not sure which is A and which is B, test them with a DC voltmeter. With no data being sent, the A line should be negative with respect to the B line. Getting the A and B lines correct is only important for the RS-232 DATA OUT CONNECTOR. It will have no affect on the other tests.

The POSITIVE and NEGATIVE THRESHOLD EXCEEDED LEDs should both be off, both when data is being sent and when the network is idle. If either of these LEDs is on or blinking, you may have a grounding problem. You should first check that the RS- 422/RS-485 switch is in the proper position and that the Signal Ground is connected correctly to the 485T. Refer to B&B Electronics' free RS-422/485 Application Note for information on proper grounding of your network.

NOTE: If the positive or negative thresholds are exceeded, you may damage your RS-422 or RS-485 line receivers. If either of the LEDs is on or blinking you should find out why and fix the problem as soon as possible.

For example, if you have a network with two nodes located in two different buildings about 4000 feet apart. An RS-422 driver in building A can be switching between +5 volts and ground and be powered from building A’s power lines. An RS-422 receiver can be located in building B with a ground potential that is 3 volts DC lower than building A. That receiver will see +8 volts for a high (5+3 volts) and +3 volts for a low (0+3 volts). This is allowed under both standards and should work fine. However, if the difference in ground potential is 10 VDC lower, the high (5+10 volts) will be +15 volts and is NOT allowed. The ground difference voltage can also be an AC voltage which could confuse things even more.

Documentation Number 485T1995 Manual

9

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

PH (815) 433-5100 --

FAX (815) 433-5105

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Contents Internet RS-422/RS-485 Line TesterTable of Contents Introduction Phone 202 457-4900 --- FAX 202 Electronics Industries AssociationFAX 815 4Documentation Number 485T1995 Manual FAX 815 Ground Terminal B TerminalsNegative Threshold Exceeded LED Threshold PotPositive Threshold Exceeded LED RS-232 Data Out Connector RS-422/RS-485 SwitchTermination Switch PowerRS-422/485 Test 10Documentation Number 485T1995 Manual FAX 815 12Documentation Number 485T1995 Manual

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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