PRELWE02 -- Water Pressure Sensor (LoRaWAN)
Product Description
Stainless steel pressure sensor with silicone oil measuring cell and silicon sensor for drinking water distribution and hot water heating. Measurement range 1--10 bar, G1/4" connection. T-piece for 3/8" angle valves included. The sensor measures pressure and temperature multiple times per second and triggers alarms at configurable thresholds.
Key Features:
- LoRaWAN Class A/C (EU868), LoRaWAN v1.0.3
- USB-C (5V/1A) or ER26500 lithium battery (approx. 8--10 years with pressure reducer)
- IP65 (main unit) / IP67 (sensor head)
- Bluetooth 5 LE (UART profile)
- Measurement range: 0--1000 kPa (10 bar), accuracy <1%
- Overload: 150% of maximum pressure
Installation
The sensor head has a G1/4" thread (European metric) and thus fits all inspection openings in the water network, e.g., on backflow preventers, main shut-off valves, or pressure reducers.
Mounting at an Inspection Opening
Screw the sensor head directly into an existing 1/4" inspection opening.
Mounting at an Angle Valve
If no inspection opening is available, the sensor head can be mounted at an angle valve:
- Shut off the water at the angle valve
- Loosen the braided hose at the angle valve using the included 3/8" open-end wrench
- Insert the included T-piece between the angle valve and the braided hose
- Reattach the braided hose to the T-piece
- Screw the sensor head into the outlet of the T-piece
- Turn on the water and check all connections for leaks
When reattaching the braided hose, always hold the braided hose to prevent it from twisting. A twisted braided hose can lead to leaks!
Function
The sensor measures water pressure every second and transmits the measurement every 15 minutes via LoRaWAN (incl. operating time, battery usage, and voltage).
Hardware
- USB-C Port: For power supply only. Waterproof connector.
- Waterproof Sensor Head Connection: Threaded connection to the main unit
- 3.5 mm Jack: Connection for external flood sensor
- Battery Compartment (rear): Screw cap with rubber gasket
Alarms
When configured thresholds are exceeded or undercut, an alarm is immediately triggered via LoRaWAN:
| ID | Alarm | Description |
|---|---|---|
| 1 | Flood Sensor | External cable sensor detects water |
| 2 | Frost Risk | Temperature critically low |
| 4 | Underpressure | Pressure falls below lower threshold (parameter 7, default: 2000 mBar) |
| 6 | Overpressure | Pressure exceeds upper threshold (parameter 6, default: 8000 mBar) |
| 12 | Low Battery | Battery needs replacement |
| 13 | Mains Power Lost | USB-C power supply interrupted |
| 14 | Sensor Not Connected | Sensor head disconnected from main unit |
| 15 | Sensor Not in Water | Sensor head connected but no water contact |
The thresholds are automatically calibrated 24 hours after installation and may change through ongoing calibration.
Button Controls
| Action | Function |
|---|---|
| 1x press | Wake up (battery mode) / Send status message (mains mode) |
| 2x press | Acknowledge alarm |
| 3x press | Currently unassigned |
| Hold ~1 sec in battery mode | Wake up |
LED Indicator
| LED | Meaning |
|---|---|
| Yellow breathing | Boot process |
| Red/Green blinking | Factory state or LoRaWAN network search |
| Blue breathing (mains power only) | Connected to internet, standby |
| Red blinking | Active alarm |
| Off | Battery mode (LEDs disabled) |
Configurable Parameters
The thresholds are set via LoRaWAN configuration commands (downlink 0x04):
| No. | Parameter | Default | Description |
|---|---|---|---|
| 1 | System Register | 23550 | Bitmap: sleep mode, buzzer, LED, sampling frequency |
| 3 | LoRaWAN Register | 4093 | Bitmap: Class A/C, ADR, duty cycle, join attempts, TX power |
| 6 | Overpressure Threshold | 8000 mBar | Alarm when exceeded |
| 7 | Underpressure Threshold | 2000 mBar | Alarm when undercut |
| 11 | Frost Warning Threshold | -- | Temperature in 1/10 °C |
| 16 | Temperature Maximum | -- | Temperature in 1/10 °C |
| 19 | Alarm Enable/Disable | 55302 | Bitmap: enable/disable individual alarm types |
| 29 | Reporting Interval | 900 s | Automatic transmission interval (15 min) |
Battery Operation
The device is powered by an ER26500 battery (bobbin cell, size C, lithium-thionyl chloride), which is inserted in the battery compartment on the rear.
- Lifespan: 8--10 years with pressure reducer, approx. 4 years without (at standard measurement interval of 1 second, approx. 10 years)
- The battery can also serve as a backup alongside mains power (USB-C)
- The power source at startup determines the operating mode
In pure battery mode:
- LEDs on the device disabled (status LED remains dark)
- No audible or visual local alarm indication
- Slow command processing
- Cannot receive alarms from external wireless flood sensors
- Sensor data transmitted hourly instead of every 15 minutes
- Only one LoRaWAN JOIN attempt
LoRaWAN Communication
See LoRaWAN Connection for setup, keys, JOIN/Rejoin, and the complete Daisychain Protocol.
Supported Sensor Types
| ID | Sensor | Unit | Example |
|---|---|---|---|
0x01 | Temperature | 1/10 °C | 0x00CD = 20.5 °C |
0x03 | Operating Time | Hours | since last restart |
0x10 | Water Pressure | mBar | 0x0D48 = 3.4 bar |
Alarm Types
| ID | Hex | Alarm |
|---|---|---|
| 1 | 0x01 | Flood sensor triggered |
| 2 | 0x02 | Frost / freezing risk |
| 4 | 0x04 | Water underpressure |
| 6 | 0x06 | Water overpressure |
| 12 | 0x0c | Low battery |
| 13 | 0x0d | Mains power lost |
| 14 | 0x0e | Sensor head disconnected |
| 15 | 0x0f | Sensor head without water |
Scope of Delivery
- Water Pressure Sensor (main unit, without battery)
- Aqua-Scope Sensor Head with 80 cm cable
- 3/8" T-piece for angle valve mounting
- Flood sensor with 130 cm cable and jack plug
- USB-C power cable and power adapter
- 19 mm wrench for T-piece mounting
EU Drinking Water Directive 98/83/EC
The T-piece with drinking water contact complies with European standards. Material: CW509L, listed in the German Federal Environment Agency (UBA) register of approved materials (edition May 14, 2020, section 2.1.3.1).
Technical Specifications
| Parameter | Value |
|---|---|
| SKU | PRELWE02 |
| Power Supply | USB-C 5V/1A (external) |
| Battery | Bobbin Cell C ER26500 (lithium-thionyl chloride) |
| Processor | ESP32-WROOM_32E (Xtensa Dual Core 32-bit, 240 MHz, 520 KB RAM) |
| LoRaWAN | EU868, Class A/C, v1.0.3 |
| Bluetooth | 5 LE (UART profile) |
| Pressure Sensor | 0--10 bar (0--1000 kPa), overload 150% |
| Connection | G1/4" female thread, I2C |
| Accuracy | <1% dynamic |
| Temperature Sensor | Integrated, high-precision |
| Dimensions (main unit) | 91 x 91 x 30 mm |
| Weight (main unit) | 105 g |
| Weight (sensor head) | 140 g |
| Protection Rating | IP65 (main unit) / IP67 (sensor head) |
| Controls | 3-color LED, single button |
| Operating Temperature | -20 to +50 °C |
| Storage/Transport Temperature | -65 to +125 °C |
| Relative Humidity | 0--90% |
| Radio Emissions (LoRa) | 868--869 MHz, 4 dBm (2.5 mW) |