diff --git a/app/src/main/java/com/example/medilightv2android/services/AdcCsvLogger.kt b/app/src/main/java/com/example/medilightv2android/services/AdcCsvLogger.kt
new file mode 100644
index 0000000..2ef931d
--- /dev/null
+++ b/app/src/main/java/com/example/medilightv2android/services/AdcCsvLogger.kt
@@ -0,0 +1,84 @@
+package com.example.medilightv2android.services
+
+import android.os.Environment
+import java.io.File
+import java.text.SimpleDateFormat
+import java.util.*
+
+/**
+ * ADC 데이터를 일별 CSV 파일로 저장.
+ *
+ * 파일 위치: Downloads/VesiScan_ADC/YYYY-MM-DD.csv
+ * 행: scan_id × 6채널 (측정 1회 = 6행)
+ * 열: scan_id, timestamp, volume_ml, lr_ratio, channel, sample_0~sample_99
+ */
+object AdcCsvLogger {
+
+    private val dayFmt = SimpleDateFormat("yyyy-MM-dd", Locale.US)
+    private val timeFmt = SimpleDateFormat("HH:mm:ss.SSS", Locale.US)
+    private var scanCounter = 0
+
+    private fun getDir(): File {
+        val dir = File(
+            Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),
+            "VesiScan_ADC"
+        )
+        if (!dir.exists()) dir.mkdirs()
+        return dir
+    }
+
+    private fun getTodayFile(): File {
+        return File(getDir(), "${dayFmt.format(Date())}.csv")
+    }
+
+    /**
+     * 6채널 ADC 데이터를 CSV에 append.
+     *
+     * @param channels 6채널 ADC 버퍼 (List<List<UShort>>)
+     * @param volumeMl BV 추정 결과 (null이면 측정 실패)
+     * @param lrRatio lr_ratio 값
+     */
+    fun log(
+        channels: List<List<UShort>>,
+        volumeMl: Double? = null,
+        lrRatio: Double = 1.0
+    ) {
+        try {
+            val file = getTodayFile()
+            val isNew = !file.exists() || file.length() == 0L
+            scanCounter++
+
+            val timestamp = timeFmt.format(Date())
+            val volStr = volumeMl?.let { "%.1f".format(it) } ?: ""
+            val lrStr = "%.2f".format(lrRatio)
+
+            java.io.FileWriter(file, !isNew).buffered().use { writer ->
+                if (isNew) {
+                    val header = buildString {
+                        append("scan_id,timestamp,volume_ml,lr_ratio,channel")
+                        for (i in 0 until 100) append(",s$i")
+                    }
+                    writer.write(header)
+                    writer.newLine()
+                }
+
+                for ((chIdx, buffer) in channels.withIndex()) {
+                    val row = buildString {
+                        append("$scanCounter,$timestamp,$volStr,$lrStr,CH$chIdx")
+                        for (sample in buffer) {
+                            append(",${sample.toInt()}")
+                        }
+                        // 100개 미만이면 빈 칸으로 채움
+                        for (i in buffer.size until 100) {
+                            append(",")
+                        }
+                    }
+                    writer.write(row)
+                    writer.newLine()
+                }
+            }
+        } catch (_: Exception) {
+            // 로깅 실패는 앱 crash 방지
+        }
+    }
+}
diff --git a/app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PiezoMonitoringView.kt b/app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PiezoMonitoringView.kt
index da8924b..cae2124 100644
--- a/app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PiezoMonitoringView.kt
+++ b/app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PiezoMonitoringView.kt
@@ -154,10 +154,12 @@ fun PiezoMonitoringView(appState: AppState) {
                             bleManager.debugLogger.measurementResult(bvResult.volumeMl, bvResult.lrRatio, totalWallCount,
                                 (0..5).map { allWalls[it]?.let { w -> w.second - w.first } ?: 0 })
                             logService.logMeasurement(bvResult.volumeMl, channelLogs, rawADC)
+                            com.example.medilightv2android.services.AdcCsvLogger.log(rawADC, bvResult.volumeMl, bvResult.lrRatio)
                         }
                     } else if (centerWallCount > 0) {
                         Log.w("PiezoMonitor", "Insufficient center channels: $centerWallCount/4 (need 3+)")
                         bleManager.debugLogger.warn("BV_SKIP center=$centerWallCount/4 total=$totalWallCount/6")
+                        com.example.medilightv2android.services.AdcCsvLogger.log(rawADC, null)
                         android.widget.Toast.makeText(context,
                             "측정 부족 (${centerWallCount}/4채널) — 센서 위치를 조절해주세요",
                             android.widget.Toast.LENGTH_SHORT).show()
@@ -165,6 +167,8 @@ fun PiezoMonitoringView(appState: AppState) {
                 } else {
                     Log.d("PiezoMonitor", "No valid channels — volume unchanged")
                     bleManager.debugLogger.warn("BV_FAIL no valid channels")
+                    val failADC = channels.sortedBy { it.channel }.map { it.buffer }
+                    com.example.medilightv2android.services.AdcCsvLogger.log(failADC, null)
                     android.widget.Toast.makeText(context,
                         "방광이 감지되지 않았습니다. 센서 접촉을 확인해주세요.",
                         android.widget.Toast.LENGTH_SHORT).show()