The Simarine STR1 is a radar tank level sensor that is attached to the outside of the tank and measures the liquid level noncontact through the tank wall. No drilling, no sensor in the liquid, no moving parts—the sensor sits on top of the tank and uses a high-precision micro-radar to measure the distance to the liquid surface.
How the sensor works
The radar penetrates the tank wall and measures the distance to the liquid’s surface. Based on this, the STR1 calculates the fill level and outputs it simultaneously via three analog signals: 0–190 ohms (European standard), 240–30 ohms (U.S. standard), and 0–5 V. This allows you to connect it to existing fuel gauges, panels, and battery monitors without having to commit to a specific signal standard.
The STR1 is set up via Bluetooth using the Simarine Connect app (iOS and Android). The app automatically detects the tank level, but you can also manually calibrate the calibration curve with up to 100 data points—which is important for irregularly shaped tanks, such as wheel well or underfloor tanks. Firmware updates are also performed via Bluetooth.
How to use it in your camper
- Fresh water tank – check the fill level without a sensor sitting in the drinking water
- Graywater and wastewater tanks—no scaling or slime buildup because nothing comes into contact with the fluid
- Diesel tank for the auxiliary heater and gasoline tanks
- Retrofitting existing tanks where you don’t want to or can’t install an opening
Installation and Connection
The sensor is placed on top of the tank using the adhesive pad—as centered as possible and with a clear, vertical view of the tank bottom. Thoroughly clean the adhesive surface beforehand and let it dry; full adhesive strength is achieved after 24 hours. Once attached, do not move the sensor, as this weakens the bond.
The STR1 works directly on plastic and fiberglass tanks with a wall thickness of up to 10 mm. For metal tanks, you’ll need the S5 flange adapter (sold separately) because metal does not allow the radar signal to pass through.
The wires are assigned as follows:
- Red – 8–35 V DC power supply
- Black – GND
- Green – 0–5 V voltage output
- White – 0–190 ohms
- Yellow – 240–30 ohms
- Blue – COM, galvanically isolated virtual ground
At a Glance
- Non-contact level measurement via micro-radar, attached to the outside of the tank
- Measuring range: Tank height 150–2000 mm
- Resolution approx. 7 mm, accuracy ± 2%, dead zone approx. 10 mm from the radar surface
- Measurement rate: 1 Hz
- Simultaneous outputs: 0–190 ohms, 240–30 ohms, 0–5 V
- Power supply: 8–35 V DC, current consumption approx. 14–20 mA at 12 V
- Dimensions: Ø 62 mm, height approx. 32.5 mm
- Max. tank wall thickness 10 mm, plastic and fiberglass-reinforced plastic (FRP); metal tanks with S5 adapter
- Fluids: Fresh water, gray water, wastewater, diesel, gasoline
- Operating temperature: -20 °C to +70 °C, protection class IP67
- Setup and calibration via Bluetooth using the Simarine Connect app
- 3-year warranty, manufactured in Slovenia
Frequently Asked Questions
Do I need to drill a hole in my tank?
No. The STR1 is attached from the outside and measures through the tank wall. The tank remains leak-proof and unchanged.
Will this work on my metal tank?
Not directly—metal blocks the radar signal. That’s where the S5 flange adapter comes in, which is sold separately.
Can I connect the sensor to my existing fuel gauge?
If your gauge operates at 0–190 ohms, 240–30 ohms, or 0–5 V, yes. All three signals are present simultaneously; you simply select the appropriate wire.
How accurately does it measure an irregularly shaped tank?
The app automatically detects the fuel level. For tanks that aren’t filled evenly, you can additionally calibrate using up to 100 data points so that the display matches the actual volume.
Does the sensor use a lot of power?
No, at 12 V, the current draw is around 14–20 mA. It can remain connected permanently.
