Sensor Not Appearing in the App
Likely Cause
The gateway cannot detect the sensor — most commonly caused by reversed RS485 A/B wiring or missing 12V power to the sensor.
How to Fix
- 1Verify RS485 A and B wires are not swapped at the gateway terminal block — reversed polarity is the most common cause.
- 2Confirm the sensor has 12V DC power by measuring voltage at the sensor power terminals with a multimeter.
- 3Check that the sensor RS485 Modbus address is unique on the bus (factory default is typically 1).
- 4Run a manual RS485 scan from the app: Gateway → RS485 Scan, and wait up to 60 seconds for results.
- 5Inspect the cable for damage, cuts, or water ingress at the connector or junction box.
Guided Help Center
Open the HPzenAi app.
Sensor Reading Zero Despite Water in Tank
Likely Cause
The sensor pressure port is blocked by sediment, the sensor is not fully submerged, or the RS485 connection is intermittent causing stale zero readings.
How to Fix
- 1Confirm the sensor body is fully submerged — a partially or non-submerged pressure sensor reads zero.
- 2Lift the sensor slightly and check if the pressure port at the sensor tip is clogged with sediment or debris.
- 3Rinse the sensor tip gently under clean water to clear any blockage.
- 4Check RS485 terminal connections at the gateway — a loose wire causes intermittent data that may display as zero.
- 5Verify the sensor Modbus address has not been reset to 0 — address 0 is reserved and will not respond to gateway polling.
Sensor Reading at Maximum (Full Scale)
Likely Cause
The sensor range is too small for the actual water depth, the sensor is resting on sediment, or the vent tube is blocked causing incorrect atmospheric compensation.
How to Fix
- 1Confirm the sensor range (2M/4M/6M/8M/10M) is greater than the maximum water depth in the tank — a reading pegged at maximum indicates the water depth exceeds the sensor range.
- 2Check if the sensor is resting on the tank floor or buried in sediment — lift the sensor to 50–100 mm above the floor.
- 3Inspect the vent tube at the cable exit — blockage causes the sensor to over-read due to incorrect atmospheric pressure compensation.
- 4Ensure the vent end of the cable is in open air, dry, and not submerged.
- 5If the tank is genuinely at maximum depth and the reading is correct, select a higher-range sensor model.
Erratic or Fluctuating Readings
Likely Cause
Water turbulence around the sensor, loose cable connections, or electrical interference on the RS485 bus causes reading instability.
How to Fix
- 1Position the sensor away from pump inlets and areas of high water turbulence — mount it in a calm area of the tank.
- 2Check all RS485 terminal connections and tighten any loose screws.
- 3Ensure the RS485 cable is not routed alongside 230V AC mains cables or motor wiring — separate signal cables by at least 200 mm.
- 4Use shielded twisted-pair cable for the RS485 run and connect the shield to earth at the gateway end only.
- 5If the cable run is long, install a 120 Ω termination resistor between RS485 A and B at the furthest sensor.
Sensor Shows Negative Reading
Likely Cause
The sensor is reading below its zero reference — this occurs when the sensor range is mismatched, the vent tube is kinked, or the sensor was calibrated at a different elevation.
How to Fix
- 1Confirm the vent tube is unkinked and unblocked — a partially blocked vent can cause the zero reference to drift negative.
- 2Check that the sensor has not been installed inverted or at an elevation higher than the minimum water level.
- 3Re-zero the sensor from the app when the tank is at its lowest expected level: Device → Settings → Calibration → Set Zero Point.
- 4If the reading is consistently slightly negative (less than −0.1 m), recalibrate the sensor offset via the app calibration tool.
Sensor Offline After Power Interruption
Likely Cause
The sensor does not reconnect to the gateway because the RS485 address or power supply was not restored correctly after the power outage.
How to Fix
- 1Verify the 12V DC supply to the sensor has been restored and is within 11.5–13.5 V.
- 2Wait up to 5 minutes after power is restored — the gateway re-polls all RS485 devices automatically.
- 3If the sensor remains offline after 5 minutes, run a manual RS485 scan from the app.
- 4The gateway buffers readings during connectivity outages and uploads them to the cloud once reconnected — check historical data in the app for any gap periods.
- 5Inspect the RS485 cable for damage that may have occurred during the power event (e.g. from a power surge or nearby lightning strike).
Water Ingress into the Sensor Connector or Junction Box
Likely Cause
Condensation or direct water entry into the cable connector or junction box corrodes the RS485 terminals and disrupts communication.
How to Fix
- 1Inspect the cable gland where the sensor cable exits the tank — retighten or replace if sealing is compromised.
- 2Check the junction box (if used for cable extension) for water inside — dry out and re-seal with weatherproof enclosure sealant.
- 3Form a proper drip loop in the cable before it enters the junction box or gateway enclosure to divert water away from the connection.
- 4Apply self-amalgamating tape over any exposed connector or splice area that may be exposed to moisture.
- 5If terminal corrosion is severe, replace the corroded terminal block and re-terminate the cable ends.
Address Conflict — Multiple Sensors Not Detected
Likely Cause
Two or more sensors on the same RS485 bus have the same Modbus address, causing data collisions that prevent all affected sensors from being detected.
How to Fix
- 1Disconnect all sensors except one from the RS485 bus and scan — verify the single sensor is detected.
- 2Note the address of the detected sensor, then disconnect it and reconnect the next sensor, scanning individually.
- 3Set a unique Modbus address (1–32) on each sensor individually before connecting them to the shared bus.
- 4Refer to the sensor address configuration section in the quick-start guide — address changes are made via a configuration tool or app command.
- 5Once all sensors have unique addresses, reconnect them to the bus and run a full RS485 scan from the gateway.
Guided Help Center
Open the HPzenAi app.
Sensor Reading Not Matching Known Tank Level
Likely Cause
The sensor needs calibration, the tank height parameter in the app is incorrect, or the sensor range model does not match the tank depth.
How to Fix
- 1Open the device tile in the app and go to Settings — confirm the tank height is correctly configured (the maximum water depth the tank can hold).
- 2When the tank is at a known level (e.g. empty or full), use the app calibration tool to set the reference point: Device → Settings → Calibration.
- 3Confirm the sensor model range (LS-PRE-2M/4M/6M/8M/10M) is appropriate for the tank — the sensor accuracy is rated to ± 0.5% of full scale.
- 4Check that the sensor is at the very bottom of the tank — any gap between the sensor and the tank floor reduces the measured water column.
- 5Inspect for sediment buildup above the sensor body that may reduce the effective water column being sensed.