產品細節(jié)介紹
PCD232A控制處理模塊
RS485通信端口369可以提供直接或遠程通信（通過調制解調器）。使用RS232到RS485轉換器將其連接到PC/PLC或DCS系統(tǒng)。369使用Modicon MODBUS?RTU協(xié)議（功能03、04和16）進行接口帶有PC、PLC和DCS系統(tǒng)。
選擇與369一起使用RS485通信，因為它允許長距離通信高達4000英尺。但是，必須小心操作，確保其正常運行且無故障。列出的建議為了獲得可靠的通信，必須遵循以下要求：a）必須使用并布線雙絞線屏蔽線（最好是24號Belden 9841型或120等效線遠離電力輸送電纜，如電源和CT電纜。b） 同一鏈路上最多可以共存32個設備。但是，如果超過32個設備應采用菊花鏈必須同時使用REPEATER。請注意，中繼器只是另一個RS232到RS485轉換器設備。
這個所有369個單元的屏蔽也應菊花鏈連接在一起，并僅在主控（PC/PLC）處接地。這是因為如果屏蔽層在不同點接地，則接地之間可能存在電位差導致將一個或多個收發(fā)器芯片（用于通信的芯片）置于未知狀態(tài)，即。不接收也不發(fā)送。相應的369通信可能錯誤、間歇或不成功。c） 兩套120? / 必須使用0.5 W電阻器和1 nF/50 V串聯電容器（值與線路的特性阻抗匹配）。一組位于369端，連接在正極和負極端子之間（#46&369上的#47）和通信鏈路另一端的第二個。這是為了防止線路反射和響鈴。如果使用不同值的電阻器，則有線路和通信過載的風險可能是錯誤的、間歇性的或完全不成功的。d） 強烈建議從369通信終端直接連接到接口主設備（PC/PLC/DCS），而不使用短截線和/或接線板。這也是為了最小化線路上的鈴聲和反光。
b） 禁止事項不要對數字輸入施加直流電壓。
有6個開關輸入（備用輸入；差動輸入；速度開關；訪問；緊急重啟；外部復位）
僅設計用于干接觸連接。向輸入端施加直流電壓，可能會導致部件數字輸入電路損壞。RTD的接地不應在兩個地方進行。
在369處接地時，只需要接地一根回路導線，因為所有回路導線都在內部硬接線在一起。沒有錯誤將通過這種方式接地引入RTD讀數。
運行多個RTD回路回接將導致重大錯誤，因為兩個或多個回路并聯已創(chuàng)建。
在重置369之前，不要重置86鎖定開關。如果使用外部86鎖定裝置并連接至369，確保在嘗試重置鎖定開關。如果369仍然跳閘，它將立即重新跳閘鎖定開關。
如果鎖定開關如果保持復位，則鎖定開關線圈的高電流消耗可能會損壞自身和/或369輸出繼電器
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 ? / 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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