产品细节介绍
PCD232A控制处理模块
RS485通信端口369可以提供直接或远程通信（通过调制解调器）。使用RS232到RS485转换器将其连接到PC/PLC或DCS系统。369使用Modicon MODBUS®RTU协议（功能03、04和16）进行接口带有PC、PLC和DCS系统。
选择与369一起使用RS485通信，因为它允许长距离通信高达4000英尺。但是，必须小心操作，确保其正常运行且无故障。列出的建议为了获得可靠的通信，必须遵循以下要求：a）必须使用并布线双绞线屏蔽线（最好是24号Belden 9841型或120等效线远离电力输送电缆，如电源和CT电缆。b） 同一链路上最多可以共存32个设备。但是，如果超过32个设备应采用菊花链必须同时使用REPEATER。请注意，中继器只是另一个RS232到RS485转换器设备。
这个所有369个单元的屏蔽也应菊花链连接在一起，并仅在主控（PC/PLC）处接地。这是因为如果屏蔽层在不同点接地，则接地之间可能存在电位差导致将一个或多个收发器芯片（用于通信的芯片）置于未知状态，即。不接收也不发送。相应的369通信可能错误、间歇或不成功。c） 两套120Ω / 必须使用0.5 W电阻器和1 nF/50 V串联电容器（值与线路的特性阻抗匹配）。一组位于369端，连接在正极和负极端子之间（#46&369上的#47）和通信链路另一端的第二个。这是为了防止线路反射和响铃。如果使用不同值的电阻器，则有线路和通信过载的风险可能是错误的、间歇性的或完全不成功的。d） 强烈建议从369通信终端直接连接到接口主设备（PC/PLC/DCS），而不使用短截线和/或接线板。这也是为了最小化线路上的铃声和反光。
b） 禁止事项不要对数字输入施加直流电压。
有6个开关输入（备用输入；差动输入；速度开关；访问；紧急重启；外部复位）
仅设计用于干接触连接。向输入端施加直流电压，可能会导致部件数字输入电路损坏。RTD的接地不应在两个地方进行。
在369处接地时，只需要接地一根回路导线，因为所有回路导线都在内部硬接线在一起。没有错误将通过这种方式接地引入RTD读数。
运行多个RTD回路回接将导致重大错误，因为两个或多个回路并联已创建。
在重置369之前，不要重置86锁定开关。如果使用外部86锁定装置并连接至369，确保在尝试重置锁定开关。如果369仍然跳闸，它将立即重新跳闸锁定开关。
如果锁定开关如果保持复位，则锁定开关线圈的高电流消耗可能会损坏自身和/或369输出继电器
RS485 Communications Port
The 369 can provide direct or remote communications (via a modem). An RS232 to RS485 converter is used to tie it to a PC/PLC or DCS system. The 369 uses the Modicon MODBUS® RTU protocol (functions 03, 04, & 16) to interface with PCs, PLCs, and DCS systems. RS485 communications was chosen to be used with the 369 because it allows communications over long distances of up to 4000 ft. However, care must be taken for it to operate properly and trouble free. The recommendations listed below must be followed to obtain reliable communications:a) A twisted, shielded pair (preferably a 24 gauge Belden 9841 type or 120 equivalent) must be used and routed away from power carrying cables, such as power supply and CT cables. b) No more than 32 devices can co-exist on the same link. If however, more than 32 devices should be daisy chained together, a REPEATER must be used. Note that a repeater is just another RS232 to RS485 converter device.
The shields of all 369 units
should also be daisy chained together and grounded at the MASTER (PC/PLC) only. This is due to the fact that if shields are grounded at different points, a potential difference between grounds might exist resulting in placing one or more of the transceiver chips (chip used for communications) in an unknown state, i.e. not receiving nor sending. The corresponding 369 communications might be erroneous, intermittent or unsuccessful. c) Two sets of 120 Ω / 0.5 W resistor and 1 nF / 50 V capacitor in series must be used (value matches the characteristic impedance of the line). One set at the 369 end, connected between the positive and negative terminals (#46 & #47 on 369) and the second at the other end of the communications link. This is to prevent reflections and ringing on the line. If a different value resistor is used, it runs the risk of over loading the line and communications might be erroneous, intermittent or totally unsuccessful. d) It is highly recommended that connection from the 369 communication terminals be made directly to the interfacing Master Device (PC/PLC/DCS), without the use of stub lengths and/or terminal blocks. This is also to minimize ringing and reflections on the line. b) DON'Ts Don’t apply direct voltage to the Digital Inputs. There are 6 switch inputs (Spare Input; Differential Input; Speed Switch; Access; Emergency Restart; External Reset) that are designed for dry contact connections only. Applying direct voltage to the inputs, it may result in component damage to the digital input circuitry. Grounding of the RTDs should not be done in two places. When grounding at the 369, only one Return lead need be grounded as all are hard-wired together internally. No error will be introduced into the RTD reading by grounding in this manner. Running more than one RTD Return lead back will cause significant errors as two or more parallel paths for return have been created. Don’t reset an 86 Lockout switch before resetting the 369. If an external 86 lockout device is used and connected to the 369, ensure that the 369 is reset prior to attempting to reset the lockout switch. If the 369 is still tripped, it will immediately re-trip the lockout switch. Also if the lockout switch is held reset, the high current draw of the lockout switch coil may cause damage to itself and/or the 369 output relay
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