Address code review feedback: add bounds validation and fix documentation

Co-authored-by: dorkmo <[email protected]>

Author: Copilot

TankAlarm-112025-Client-BluesOpta/README.md

@@ -110,7 +110,9 @@ Used for sensors like the Dwyer 626-06-CB-P1-E5-S1 (0-5 PSI) mounted near the bo
 - Configuration:
   - `currentLoopType`: "pressure"
   - `sensorMountHeight`: 2.0
-  - `maxValue`: 138.0 (or actual tank height if tank is smaller)
+  - `maxValue`: 118.0 (tank height minus mount height: 120 - 2 = 118 inches)
+
+> **Note:** For pressure sensors, set `maxValue` to the tank's usable height minus the sensor mount height. The implementation adds `sensorMountHeight` to the measured value, so `maxValue` should represent the height of liquid *above* the sensor, not the total tank height.
 
 #### Ultrasonic Sensor (Top-Mounted)
 Used for sensors like the Siemens Sitrans LU240 mounted on top of the tank looking down.

TankAlarm-112025-Client-BluesOpta/TankAlarm-112025-Client-BluesOpta.ino

@@ -789,8 +789,8 @@ static bool loadConfigFromFlash(ClientConfig &cfg) {
     } else {
       cfg.tanks[i].currentLoopType = CURRENT_LOOP_PRESSURE; // Default: pressure sensor
     }
-    // Load sensor mount height (for calibration)
-    cfg.tanks[i].sensorMountHeight = t["sensorMountHeight"].is<float>() ? t["sensorMountHeight"].as<float>() : 0.0f;
+    // Load sensor mount height (for calibration) - validate non-negative
+    cfg.tanks[i].sensorMountHeight = t["sensorMountHeight"].is<float>() ? fmaxf(0.0f, t["sensorMountHeight"].as<float>()) : 0.0f;
   }
 
   return true;
@@ -1332,9 +1332,9 @@ static void applyConfigUpdate(const JsonDocument &doc) {
           gConfig.tanks[i].currentLoopType = CURRENT_LOOP_PRESSURE;
         }
       }
-      // Handle sensor mount height (for calibration)
+      // Handle sensor mount height (for calibration) - validate non-negative
       if (t.containsKey("sensorMountHeight")) {
-        gConfig.tanks[i].sensorMountHeight = t["sensorMountHeight"].as<float>();
+        gConfig.tanks[i].sensorMountHeight = fmaxf(0.0f, t["sensorMountHeight"].as<float>());
       }
     }
   }
@@ -1563,6 +1563,7 @@ static float readTankSensor(uint8_t idx) {
         levelInches = rawLevel + cfg.sensorMountHeight;
         // Clamp to valid range (sensorMountHeight to maxValue + sensorMountHeight)
         if (levelInches < cfg.sensorMountHeight) levelInches = cfg.sensorMountHeight;
+        if (levelInches > cfg.maxValue + cfg.sensorMountHeight) levelInches = cfg.maxValue + cfg.sensorMountHeight;
       }
       return levelInches;
     }

TankAlarm-112025-Server-BluesOpta/TankAlarm-112025-Server-BluesOpta.ino

@@ -1056,7 +1056,7 @@ static const char CONFIG_GENERATOR_HTML[] PROGMEM = R"HTML(
       } else if (type === 2) { // Current Loop (4-20mA)
         heightField.style.display = 'flex';
         heightLabel.textContent = 'Tank Height (in)';
-        heightTooltip.setAttribute('data-tooltip', 'Maximum height of liquid in the tank in inches. For ultrasonic sensors, this is the distance the sensor measures at full tank.');
+        heightTooltip.setAttribute('data-tooltip', 'Maximum height of liquid in the tank in inches. Meaning varies based on sensor subtype.');
         digitalInfoBox.style.display = 'none';
         currentLoopInfoBox.style.display = 'block';
         switchModeField.style.display = 'none';