Accutech WI-BR-I-XP User Manual
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Contents
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Rev 1.56 7This section only applies if you have purchased the Analog Output option.If you have purchased the Analog Output option for your Base Radio, thenthe Base Radio is able to output a 4-20mA signal loop via the “Loop” Ter-minal on the Base Radio.To wire the analog output loop, an external loop power supply must besupplied. An example is shown in Figure 3.7.Section 3: InstallationFigure 3.7: Wiring the 4-20mA Loop to theBase Radio3.2.5: Wiring the Analog OutputLoop (WI-BR-XP-AO only)NOTEThe Base Radio Analog Output is only capable of a 4-20mA loop. Do not wire the BaseRadio to a 0-10V or 0-5V loop as this may cause irreparable damage to the Base Radio.3.2.6: Terminating the Base Radio RS-485 is capable of maintaining communications over a maximum dis-tance of 4000 feet. In most (and we recommend all) situations the unit thatcomprises an “end” of an RS-485 network should be terminated by a resis-tor wired across the A and B wires.In the case of a daisy-chained application the end unit should be termi-nated. The end unit is the unit that is located at the end of series of units.In a PC to Base Radio only application, the end unit is the Base Radio.Note: a PC is also an end unit, but the termination for this end unit is donewithin the converter. In a multiple unit daisy-chain application the end unitis shown in Figure 3.8.Termination of an end unit is done by placing a resistor across the A and Bwires of the RS-485 cable. The value of this resistor should match thecharacteristic impedance (Zo) of the RS-485 cable. The characteristic im-pedance (Zo) is published by the manufacturer of the RS-485 cable youare using.If you are using the Belden RS-485 wire recommended under the WiringRS-485 to the Base Radio section the value of the resistor should be a 120ohm ¼ watt resistor.To terminate a Base Radio place one end of the resistor in the open termi-nal block’s B slot and place the other end of the resistor in the open termi-nal block’s A slot. Doing so will place the resistor across the A and Bwires as needed. An example of this is shown below in Figure 3.9.Figure 3.8: Example of End Unit inDaisy-Chain ConfigurationFigure 3.9: Example of Correct Termi-nation Resistor Setup3.2.7: Grounding the Base Radio In order to assure safety requirements on your Base Radio, the Base Radiohousing must be grounded. We have provided a grounding screw locatedon the left side of the Base Radio housing. To ground the Base Radio sim-ply place a wire from the grounding screw to a grounded object. Possiblegrounded objects include:• The building’s metal frame-work• Any electrical conduit• A suitable grounding or lightning rod |
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