{
  "id": "emitters:pad-mount-transformer",
  "collection": "emitters",
  "slug": "pad-mount-transformer",
  "name": "Pad-mounted or pole-mounted distribution transformer",
  "summary": "A local transformer produces a strong but rapidly decaying magnetic field: often tens of milligauss at a metre, at or near background by five metres.",
  "status": "verified",
  "lastVerified": "2026-08-12",
  "data": {
    "aliases": [
      "distribution transformer",
      "green box transformer"
    ],
    "category": "elf-magnetic",
    "environment": [
      "outdoor",
      "home"
    ],
    "bands": [
      {
        "label": "Power frequency and harmonics",
        "minHz": 50,
        "maxHz": 2000
      }
    ],
    "dutyCycle": "Continuous, proportional to the load of the served customers.",
    "distanceProfile": [
      {
        "meters": 1,
        "value": {
          "quantity": "magnetic-flux-density",
          "unit": "mG",
          "value": 5,
          "max": 50,
          "basis": "measured",
          "note": "Typical range at 1 m from the enclosure under normal load.",
          "sourceIds": [
            "niehs-emf"
          ]
        }
      },
      {
        "meters": 3,
        "value": {
          "quantity": "magnetic-flux-density",
          "unit": "mG",
          "value": 1,
          "max": 10,
          "basis": "measured",
          "note": "Typical range at 3 m.",
          "sourceIds": [
            "niehs-emf"
          ]
        }
      },
      {
        "meters": 5,
        "value": {
          "quantity": "magnetic-flux-density",
          "unit": "mG",
          "value": 0.2,
          "max": 3,
          "basis": "measured",
          "note": "Usually background by 5 m.",
          "sourceIds": [
            "niehs-emf"
          ]
        }
      }
    ],
    "mitigations": [
      {
        "action": "Keep habitable rooms and outdoor seating more than 5 m from the unit where site layout allows.",
        "effect": "Transformer fields decay faster than transmission-line fields because the source is compact."
      },
      {
        "action": "If readings do not fall with distance, look for the secondary service conductors rather than the transformer.",
        "effect": "Unbalanced service conductors, not the transformer core, are the usual cause of persistent elevated readings."
      }
    ],
    "measureWith": [
      "elf-gaussmeter"
    ],
    "related": [
      "emitters:transmission-line"
    ]
  },
  "sources": [
    {
      "id": "niehs-emf",
      "title": "Electric and Magnetic Fields",
      "publisher": "National Institute of Environmental Health Sciences",
      "url": "https://www.niehs.nih.gov/health/topics/agents/emf",
      "kind": "government",
      "retrieved": "2026-08-12"
    }
  ],
  "links": {
    "self": "https://emfbase.com/api/emitters/pad-mount-transformer",
    "html": "https://emfbase.com/emitters/pad-mount-transformer",
    "markdown": "https://emfbase.com/emitters/pad-mount-transformer.md",
    "collection": "https://emfbase.com/api/emitters"
  }
}