diff --git a/app/src/main/java/com/example/medilightv2android/ble/BleManager.kt b/app/src/main/java/com/example/medilightv2android/ble/BleManager.kt
index 665d11c..aea0331 100644
--- a/app/src/main/java/com/example/medilightv2android/ble/BleManager.kt
+++ b/app/src/main/java/com/example/medilightv2android/ble/BleManager.kt
@@ -789,6 +789,7 @@ class BleManager private constructor(private val context: Context) {
                     if (status == BluetoothGatt.GATT_SUCCESS) {
                         if (txCharacteristic != null && rxCharacteristic != null) {
                             isServiceReady.value = true
+                            com.example.medilightv2android.services.AdcCsvLogger.newSession()
                             startBatteryPolling()
                             startWatchdog()
                             sendDeviceInfoQuery()
diff --git a/app/src/main/java/com/example/medilightv2android/services/AdcCsvLogger.kt b/app/src/main/java/com/example/medilightv2android/services/AdcCsvLogger.kt
index e48c72b..7ea5702 100644
--- a/app/src/main/java/com/example/medilightv2android/services/AdcCsvLogger.kt
+++ b/app/src/main/java/com/example/medilightv2android/services/AdcCsvLogger.kt
@@ -6,19 +6,19 @@ import java.text.SimpleDateFormat
 import java.util.*
 
 /**
- * ADC 데이터를 일별 CSV 파일로 저장.
+ * ADC 데이터를 세션별 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
+ * 파일 위치: Downloads/VesiScan_ADC/YYYY-MM-DD_HHmmss.csv
+ * newSession() 호출 시 새 파일로 전환 (BLE 연결 시 자동, 수동 호출 가능)
  */
 object AdcCsvLogger {
 
-    private val dayFmt = SimpleDateFormat("yyyy-MM-dd", Locale.US)
+    private val sessionFmt = SimpleDateFormat("yyyy-MM-dd_HHmmss", Locale.US)
     private val timeFmt = SimpleDateFormat("HH:mm:ss.SSS", Locale.US)
     var lastScanId: Int = 0
         private set
     private var scanCounter = 0
+    private var sessionFile: File? = null
 
     private fun getDir(): File {
         val dir = File(
@@ -29,24 +29,24 @@ object AdcCsvLogger {
         return dir
     }
 
-    private fun getTodayFile(): File {
-        return File(getDir(), "${dayFmt.format(Date())}.csv")
+    fun newSession() {
+        scanCounter = 0
+        lastScanId = 0
+        sessionFile = File(getDir(), "${sessionFmt.format(Date())}.csv")
+    }
+
+    private fun getFile(): File {
+        if (sessionFile == null) newSession()
+        return sessionFile!!
     }
 
-    /**
-     * 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 file = getFile()
             val isNew = !file.exists() || file.length() == 0L
             scanCounter++
             lastScanId = scanCounter
@@ -58,7 +58,7 @@ object AdcCsvLogger {
             val thrStr = if (analyzer.useAdaptiveThreshold && analyzer.lastOtsuThreshold > 0)
                 "%.0f".format(analyzer.lastOtsuThreshold) else "%.0f".format(com.example.medilightv2android.managers.GreenZoneConstants.lowEchoAmp)
             val dpsStr = "%.3f".format(com.example.medilightv2android.managers.PiezoHW.distancePerSample)
-            val sgStr = if (com.example.medilightv2android.managers.PiezoEchoAnalyzer.shared.useSgFilter) "ON" else "OFF"
+            val sgStr = if (analyzer.useSgFilter) "ON" else "OFF"
 
             java.io.FileWriter(file, !isNew).buffered().use { writer ->
                 if (isNew) {
@@ -76,7 +76,6 @@ object AdcCsvLogger {
                         for (sample in buffer) {
                             append(",${sample.toInt()}")
                         }
-                        // 100개 미만이면 빈 칸으로 채움
                         for (i in buffer.size until 100) {
                             append(",")
                         }
@@ -85,8 +84,6 @@ object AdcCsvLogger {
                     writer.newLine()
                 }
             }
-        } catch (_: Exception) {
-            // 로깅 실패는 앱 crash 방지
-        }
+        } catch (_: Exception) {}
     }
 }
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 5ed5efb..cf45846 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
@@ -117,7 +117,9 @@ fun PiezoMonitoringView(appState: AppState) {
         Log.d("PiezoMonitor", "Sending measurement command...")
 
         bleManager.piezoCollector.onMultiChannelComplete = { channels ->
-            handler.post {
+            // 분석을 백그라운드에서 수행 후 UI 업데이트만 메인으로
+            Thread {
+                val analysisStart = System.currentTimeMillis()
                 lastMultiChannelResult.clear()
                 lastMultiChannelResult.addAll(channels)
 
@@ -235,9 +237,9 @@ fun PiezoMonitoringView(appState: AppState) {
                         bleManager.debugLogger.warn("BV_SKIP scan=${com.example.medilightv2android.services.AdcCsvLogger.lastScanId} center=$centerWallCount/4 total=$totalWallCount/6")
                         com.example.medilightv2android.services.AdcCsvLogger.log(rawADC, null)
                         if (!isAutoMeasuring) {
-                            android.widget.Toast.makeText(context,
+                            handler.post { android.widget.Toast.makeText(context,
                                 "측정 부족 (${centerWallCount}/4채널) — 센서 위치를 조절해주세요",
-                                android.widget.Toast.LENGTH_SHORT).show()
+                                android.widget.Toast.LENGTH_SHORT).show() }
                         }
                     }
                 } else {
@@ -246,44 +248,51 @@ fun PiezoMonitoringView(appState: AppState) {
                     val failADC = channels.sortedBy { it.channel }.map { it.buffer }
                     com.example.medilightv2android.services.AdcCsvLogger.log(failADC, null)
                     if (!isAutoMeasuring) {
-                        android.widget.Toast.makeText(context,
+                        handler.post { android.widget.Toast.makeText(context,
                             "방광이 감지되지 않았습니다. 센서 접촉을 확인해주세요.",
-                            android.widget.Toast.LENGTH_SHORT).show()
+                            android.widget.Toast.LENGTH_SHORT).show() }
                     }
                 }
 
-                // 볼륨 업데이트: Auto면 윈도우 trimmed mean (valid≥4만), Spot이면 즉시
-                if (rawVolumeMl != null && rawVolumeMl > 0) {
-                    if (isAutoMeasuring) {
-                        if (totalWallCount >= 4) {
-                            autoVolumeWindow.add(rawVolumeMl)
-                            Log.d("PiezoMonitor", "AUTO window[${autoVolumeWindow.size}/$autoWindowSize] +${"%.1f".format(rawVolumeMl)}ml (valid=$totalWallCount)")
+                val finalRawVol = rawVolumeMl
+                val finalTotalWalls = totalWallCount
+                val analysisMs = System.currentTimeMillis() - analysisStart
+                Log.d("PiezoMonitor", "Analysis took ${analysisMs}ms")
+
+                // UI 업데이트는 메인 스레드에서
+                handler.post {
+                    if (finalRawVol != null && finalRawVol > 0) {
+                        if (isAutoMeasuring) {
+                            if (finalTotalWalls >= 4) {
+                                autoVolumeWindow.add(finalRawVol)
+                                Log.d("PiezoMonitor", "AUTO window[${autoVolumeWindow.size}/$autoWindowSize] +${"%.1f".format(finalRawVol)}ml (valid=$finalTotalWalls)")
+                            } else {
+                                Log.d("PiezoMonitor", "AUTO skip ${"%.1f".format(finalRawVol)}ml (valid=$finalTotalWalls < 4)")
+                            }
+                            if (autoVolumeWindow.size >= autoWindowSize) {
+                                val displayVol = trimmedMean(autoVolumeWindow.toList())
+                                lastVolumeMl = displayVol
+                                maxVolumeMl = maxOf(maxVolumeMl, displayVol)
+                                Log.d("PiezoMonitor", "AUTO trimmedMean=${"%.1f".format(displayVol)}ml from ${autoVolumeWindow.map { "%.0f".format(it) }}")
+                                autoVolumeWindow.clear()
+                            }
                         } else {
-                            Log.d("PiezoMonitor", "AUTO skip ${"%.1f".format(rawVolumeMl)}ml (valid=$totalWallCount < 4)")
+                            lastVolumeMl = finalRawVol
+                            maxVolumeMl = maxOf(maxVolumeMl, finalRawVol)
                         }
-                        if (autoVolumeWindow.size >= autoWindowSize) {
-                            val displayVol = trimmedMean(autoVolumeWindow.toList())
-                            lastVolumeMl = displayVol
-                            maxVolumeMl = maxOf(maxVolumeMl, displayVol)
-                            Log.d("PiezoMonitor", "AUTO trimmedMean=${"%.1f".format(displayVol)}ml from ${autoVolumeWindow.map { "%.0f".format(it) }}")
-                            autoVolumeWindow.clear()
-                        }
-                    } else {
-                        lastVolumeMl = rawVolumeMl
-                        maxVolumeMl = maxOf(maxVolumeMl, rawVolumeMl)
                     }
-                }
 
-                if (lastVolumeMl > 0) {
-                    val maxVol = appState.piezoSettings.maxVolume.toDouble()
-                    val pct = if (maxVol > 0) (lastVolumeMl / maxVol).coerceAtMost(1.0) else 0.0
-                    val level = (pct * BladderLevel.MAX_LEVEL).toInt().coerceIn(1, BladderLevel.MAX_LEVEL)
-                    appState.bladderLevel = appState.bladderLevel.copy(currentLevel = level)
+                    if (lastVolumeMl > 0) {
+                        val maxVol = appState.piezoSettings.maxVolume.toDouble()
+                        val pct = if (maxVol > 0) (lastVolumeMl / maxVol).coerceAtMost(1.0) else 0.0
+                        val level = (pct * BladderLevel.MAX_LEVEL).toInt().coerceIn(1, BladderLevel.MAX_LEVEL)
+                        appState.bladderLevel = appState.bladderLevel.copy(currentLevel = level)
+                    }
+                    isMeasuring = false
+                    measureRetryCount = 0
+                    try { measureDoneSignal.complete(Unit) } catch (_: Exception) {}
                 }
-                isMeasuring = false
-                measureRetryCount = 0
-                try { measureDoneSignal.complete(Unit) } catch (_: Exception) {}
-            }
+            }.start()
         }
         bleManager.piezoCollector.onLog = { msg -> Log.d("PiezoCollector", msg) }
 
diff --git a/app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PlacementGuideView.kt b/app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PlacementGuideView.kt
index db905e9..613ed8f 100644
--- a/app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PlacementGuideView.kt
+++ b/app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PlacementGuideView.kt
@@ -368,10 +368,12 @@ fun PlacementGuideView(appState: AppState) {
                         verticalArrangement = Arrangement.spacedBy(6.dp)
                     ) {
                         Text("Echo Waveforms", fontSize = 13.sp, fontWeight = FontWeight.Bold, color = MlPrimary)
-                        for (chData in lastChannelData.filter { it.buffer.isNotEmpty() }) {
-                            val detected = if (chData.channel < channelDetected.size) channelDetected[chData.channel] else false
-                            val chAnalysis = analyzer.analyzeChannel(chData.buffer, chData.channel)
-                            val showWalls = chAnalysis.result
+                        for (ch in 0 until 6) {
+                            val chData = lastChannelData.find { it.channel == ch }
+                            val detected = if (ch < channelDetected.size) channelDetected[ch] else false
+                            val showWalls = if (chData != null && chData.buffer.isNotEmpty()) {
+                                analyzer.analyzeChannel(chData.buffer, ch).result
+                            } else null
                             Column(verticalArrangement = Arrangement.spacedBy(2.dp)) {
                                 Row(verticalAlignment = Alignment.CenterVertically) {
                                     Box(
@@ -379,7 +381,7 @@ fun PlacementGuideView(appState: AppState) {
                                             .background(if (detected) Color(0xFF4CAF50) else Color.Red.copy(alpha = 0.4f))
                                     )
                                     Spacer(modifier = Modifier.width(4.dp))
-                                    Text("CH${chData.channel}", fontSize = 11.sp, fontWeight = FontWeight.Bold)
+                                    Text("CH$ch", fontSize = 11.sp, fontWeight = FontWeight.Bold)
                                     if (showWalls != null) {
                                         Spacer(modifier = Modifier.width(6.dp))
                                         Text(
@@ -388,16 +390,23 @@ fun PlacementGuideView(appState: AppState) {
                                         )
                                     }
                                 }
-                                PlacementWaveformChart(
-                                    buffer = chData.buffer,
-                                    peakIndex = chData.peakIndex.toInt(),
-                                    analyzer = analyzer,
-                                    antIndex = showWalls?.ant,
-                                    postIndex = showWalls?.post,
-                                    modifier = Modifier.fillMaxWidth().height(80.dp)
-                                )
+                                if (chData != null && chData.buffer.isNotEmpty()) {
+                                    PlacementWaveformChart(
+                                        buffer = chData.buffer,
+                                        peakIndex = chData.peakIndex.toInt(),
+                                        analyzer = analyzer,
+                                        antIndex = showWalls?.ant,
+                                        postIndex = showWalls?.post,
+                                        modifier = Modifier.fillMaxWidth().height(80.dp)
+                                    )
+                                } else {
+                                    Box(modifier = Modifier.fillMaxWidth().height(80.dp).background(Color.Gray.copy(alpha = 0.05f), RoundedCornerShape(4.dp)),
+                                        contentAlignment = Alignment.Center) {
+                                        Text("No data", fontSize = 10.sp, color = MlSecondaryText.copy(alpha = 0.5f))
+                                    }
+                                }
                             }
-                            if (chData.channel < lastChannelData.last().channel) {
+                            if (ch < 5) {
                                 HorizontalDivider(color = Color.Gray.copy(alpha = 0.2f))
                             }
                         }