PREWIE02 -- Water Pressure Sensor (WLAN)
Product Description
The PREWIE02 is a high-precision water pressure sensor with a stainless steel measuring cell and silicone oil filling for the measuring range of 1--10 bar. The sensor head with a G1/4" thread is screwed directly into the water supply network -- either at a test port or via the included T-piece at the angle valve.
The device measures pressure and temperature multiple times per second and triggers alarms immediately when configurable thresholds are exceeded. Via WLAN, the measurement data is transmitted to the Aqua-Scope app, an MQTT server, or a custom web service.
Key Features:
- Stainless steel sensor head with silicon sensor in silicone oil
- Measuring range: 0--10 bar, accuracy <1%
- G1/4" connection, T-piece for 3/8" angle valves included
- Wired flood sensor (3.5 mm jack socket)
- WLAN + App + MQTT + JSON Webhook + Bluetooth 5 LE
- Power supply: USB-C (5V/1A) or ER26500 battery
- IP65 (main unit) / IP67 (sensor head)
Installation
The sensor head has a G1/4" thread (European metric) and therefore fits all test ports in the water supply network, e.g., on backflow preventers, main shut-off valves, or pressure reducers.
Installation at a Test Port
Screw the sensor head directly into an existing 1/4" test port.
Installation at an Angle Valve
If no test port is available, the sensor head can be installed 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 the water back on and check all connections for leaks
When reattaching the braided hose, always brace the braided hose to prevent it from twisting. A twisted braided hose can lead to leaks!
Connection and Communication
The WLAN setup is performed via the device's configuration page (SSID "Scope"). A detailed step-by-step guide can be found at WLAN Connection.
For Advanced Users
In addition to the Aqua-Scope app, further communication options are available and can be activated via Configuration -> Communication Options in the app:
- MQTT -- Integration into MQTT-based systems
- Home Assistant -- Automatic discovery in the dashboard
- JSON Webhook -- Custom web service with HTTP POST
- Modbus IP -- Industrial protocol (TCP Port 502)
- Local Web Server -- Direct access via browser on the LAN
The local web server and Modbus IP are only available in mains-powered mode, not in battery mode.
Function
The sensor measures water pressure every second and transmits the measurement every 15 minutes to the app (including uptime, battery consumption, and battery voltage).
Hardware
- USB-C Port: For power supply only (KTEC power adapter recommended). Waterproof connector.
- Waterproof Sensor Head Connector: Threaded connection to the main unit
- 3.5 mm Jack Socket: Waterproof connection for an external flood sensor
- Battery Compartment (rear): Screw cap with rubber seal for water protection
Alarms
When configured thresholds are exceeded or undershot, an alarm is triggered immediately:
| Alarm | Description |
|---|---|
| Flood Sensor | External cable sensor detects water |
| Overpressure | Pressure exceeds upper threshold (Parameter 6, default: 8000 mBar) |
| Underpressure | Pressure falls below lower threshold (Parameter 7, default: 1 mBar) |
| Temperature | Temperature limit exceeded (Parameter 16) or undershot (Parameter 11) |
| Sensor Not Connected | Sensor head disconnected from main unit |
| Sensor Not in Water | Sensor head connected but no water detected |
Alarms are delivered via the app with push notifications and optional email/voice forwarding. They are automatically cleared when the condition normalizes.
Button Operation
| Action | Function |
|---|---|
| Press once briefly | Wake up / send status report |
| Press twice briefly | Acknowledge alarm |
| Press three times briefly | Currently not assigned |
| Hold for 5 sec. (on first start) | Factory reset |
LED Indicators
| LED | Meaning |
|---|---|
| Yellow/multicolor blinking | Boot process |
| Red/green blinking | Factory state -- ready to connect |
| Blue or green slowly breathing | Connected to network and external power supply |
| Red blinking | Active alarm |
| Off | Not connected or battery mode |
Configurable Parameters
| No. | Parameter | Default | Description |
|---|---|---|---|
| 6 | Overpressure threshold | 8000 mBar | Alarm when exceeded |
| 7 | Underpressure threshold | 1 mBar | Alarm when undershot |
| 18 | Temperature sensor offset | 0 | Calibration in 1/10 °C |
| 29 | Transmission interval | 900 s | Data transmission interval (15 min.) |
Sensor Values
| Index | Modbus Register | Measurement | Unit |
|---|---|---|---|
| 0 | 100/101 | Uptime | Hours |
| 1 | 102/103 | Temperature | 1/10 °C |
| 2 | 104/105 | Battery voltage | mV |
| 3 | 106/107 | Battery consumption | mAs |
| 4 | 108/109 | Water pressure | mBar |
| 5 | 110/111 | Valve status | 1=open, 0=closed |
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 back.
- Battery life: 8--10 years with pressure reducer, approx. 4 years without
- 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 are disabled (status LED remains dark)
- No acoustic or visual local alarm indication
- Slow command processing (up to 1 hour instead of ~10 seconds in mains mode)
- Cannot receive alarms from external wireless flood sensors
- Sensor data is transmitted hourly instead of every 15 minutes
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 installation
- Flood sensor with 130 cm cable and jack plug
- USB-C power cable and power adapter
- 19 mm wrench for T-piece installation
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 | PREWIE02 |
| 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) |
| WLAN | IEEE 802.11 b/g/n (2.4 GHz) -- Aqua-Scope Cloud, MQTT, JSON |
| Bluetooth | 5 LE (UART profile) |
| Pressure sensor | 0--10 bar (0--1000 kPa), overload 150% |
| Connection | G1/4" internal thread, I2C |
| Accuracy | <1% dynamic |
| Temperature sensor | Integrated in sensor head |
| 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 (WLAN) | 2.4 GHz broadband (EN 300 328) |