综合场景例程 3：水箱液位（双泵 + 高低报警 + 报警锁存）

这一页只讲这一个例程。母页 b-05-integrated-scenarios 里留着例程 1，其余例程各自一页、在那一页的目录里点。

场景：水箱补水/排水：液位到高值开泵、低值停泵（回差），超高/超低单独报警，低液位报警要锁存并人工确认。

软元件

软元件	作用
D620	液位（%）
M520	主泵运行（80 开 / 20 停）
M521 / M522	超高（≥90）/ 超低（≤10）
M530	低液位报警锁存
X21	确认按钮
Y0 / Y1	主泵 / 备用泵
Y20 / Y21	高 / 低液位报警

块图（照着拖即可）

对应的 ddc.json（点「生成 JSON」得到的就是它；也可存成 .ddc.json 导入）

{
  "version": 1,
  "name": "水箱液位",
  "scan_ms": 200,
  "lines": [
    {
      "op": "assign",
      "target": {"op":"ref","device":"M","addr":520},
      "expr": {
        "op": "rs",
        "id": "rs_lvl",
        "args": [
          {
            "op": "cmp",
            "cmp": ">=",
            "args": [{"op":"ref","device":"D","addr":620},{"op":"const","value":80}]
          },
          {
            "op": "cmp",
            "cmp": "<=",
            "args": [{"op":"ref","device":"D","addr":620},{"op":"const","value":20}]
          }
        ]
      }
    },
    {
      "op": "assign",
      "target": {"op":"ref","device":"M","addr":521},
      "expr": {
        "op": "cmp",
        "cmp": ">=",
        "args": [{"op":"ref","device":"D","addr":620},{"op":"const","value":90}]
      }
    },
    {
      "op": "assign",
      "target": {"op":"ref","device":"M","addr":522},
      "expr": {
        "op": "cmp",
        "cmp": "<=",
        "args": [{"op":"ref","device":"D","addr":620},{"op":"const","value":10}]
      }
    },
    {
      "op": "assign",
      "target": {"op":"ref","device":"Y","addr":0},
      "expr": {
        "op": "and",
        "args": [
          {"op":"ref","device":"M","addr":520},
          {"op":"not","args":[{"op":"ref","device":"M","addr":522}]}
        ]
      }
    },
    {
      "op": "assign",
      "target": {"op":"ref","device":"Y","addr":1},
      "expr": {"op":"ref","device":"M","addr":521}
    },
    {
      "op": "assign",
      "target": {"op":"ref","device":"Y","addr":20},
      "expr": {"op":"ref","device":"M","addr":521}
    },
    {
      "op": "assign",
      "target": {"op":"ref","device":"M","addr":530},
      "expr": {
        "op": "rs",
        "id": "rs_low",
        "args": [
          {"op":"ref","device":"M","addr":522},
          {
            "op": "and",
            "args": [
              {"op":"ref","device":"X","addr":21},
              {"op":"not","args":[{"op":"ref","device":"M","addr":522}]}
            ]
          }
        ]
      }
    },
    {
      "op": "assign",
      "target": {"op":"ref","device":"Y","addr":21},
      "expr": {"op":"ref","device":"M","addr":530}
    }
  ]
}

要点

• 主泵用启停控制自带回差（80 开 / 20 停），避免液位在临界点抖动时泵反复启停。
• 超低液位要禁开泵：干转几分钟就烧机封，这条比"补水"更重要。
• 报警锁存沿用 B1 例程 4 的结构：启动 = 故障，停止 = 已确认且已恢复。

验证：D620 写 85 → Y0 = 1；写 15 → Y0 = 0、M522 = 1、Y21 = 1；按 X21 且 D620 回到 50 → Y21 = 0。

注意事项

• 液位计断线（0%）→ 一直"超低"，补水场合会缺水。断线要用量程外的判断或通信状态区分。
• 补水 / 排水方向搞反：接程序前先确认泵的作用。
• 超高液位只报警不停泵（补水场合）：会溢流。