JSN-SR04T Waterproof Ultrasonic Sensor
Waterproof ultrasonic sensor for tank level measurement and outdoor robotics.
A sealed, probe-style ultrasonic sensor built for liquid-level sensing and outdoor robotics where the open-faced HC-SR04 won't survive. Unlike the exposed dual-transducer face of an HC-SR04, the JSN-SR04T's transducer is embedded in a waterproof probe connected to the driver board by a cable, letting it be mounted through a tank lid or exposed to rain and moisture while the electronics stay protected — making it the standard choice for DIY water tank level monitors and outdoor obstacle-avoidance robots.
Specifications
| Sensor type | Waterproof probe-style ultrasonic ranging sensor with separate driver board |
| Operating voltage | 5V DC (some variants accept 3.3-5.5V) |
| Operating current | ~8 mA typical, ~30 mA during ranging pulse |
| Measuring range | 20cm to 600cm (varies slightly by revision, some rated to 450cm) |
| Blind zone | ~20-25cm minimum detection distance — objects closer than this are not reliably detected |
| Probe design | Waterproof transducer housed in a sealed metal/plastic probe on a cable, separate from the driver PCB |
| Interface | Trigger/Echo pulse mode (HC-SR04-compatible timing) on most revisions; some variants also support UART mode |
| Beam angle | Narrower than the HC-SR04, which helps reduce false echoes in a tank but also means careful aiming |
Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | VCC | Power, 5V DC (check your specific revision for 3.3V tolerance) |
| 2 | Trig | Trigger input — send a short pulse to start a ranging cycle |
| 3 | Echo | Echo output — pulse width proportional to round-trip time |
| 4 | GND | Ground |
Code and wiring are largely identical to a standard HC-SR04 in pulse mode, but the 20-25cm minimum blind zone is significantly larger, so mount the probe with enough clearance from the closest expected surface (e.g. the bottom of an empty tank). Because the transducer sits inside a probe, some condensation or splashing near the tip is fine, but the driver PCB itself should still be kept dry and away from direct water exposure.
Variants
Choose the JSN-SR04T whenever the sensor will be exposed to moisture, humidity, or needs to be mounted through a sealed tank wall. For dry, indoor obstacle-avoidance projects, the plain HC-SR04 is cheaper and has a smaller minimum blind zone.
| Variant | Temp range | Hum range | Accuracy | Protocol | Price |
|---|---|---|---|---|---|
| JSN-SR04T (probe + driver board) | ~$3-6 | ||||
| JSN-SR04T-2.0 | ~$4-7 | ||||
| HC-SR04 (non-waterproof) | ~$1-2 |