SHT 8815 – active water sensor with resistive output for digital inputs

The active water sensor with resistance output for digital inputs with pull-up or pull-down

The Schabus SHT 8815 is an active water sensor for external control units with the switching principle “unipolar resistance”. It is connected to the digital input of a controller that has an internal pull-up or pull-down resistor and thereby supplies the sensor with voltage.

When the sensor contacts are connected by water or a conductive liquid, the internal resistance of the sensor drops significantly, from several megaohms to a few hundred ohms. The level at the digital input is thereby pulled from HI to LO or from LO to HI. The controller thus detects water without additional relays or adapters.

The SHT 8815 is intended for regularly dry environments with only occasional water occurrences. It is not suitable for direct connection to Schabus water detectors.

Detect water – by resistance change

On contact with water the resistance of the SHT 8815 drops significantly. Your digital input switches reliably.

How the active sensor works

The SHT 8815 changes its internal resistance as soon as liquid connects both contacts.

• Dry: the resistance between the contacts is several megaohms
• Wet: the resistance drops to a few hundred ohms (example value)
• The level at the digital input is pulled from HI to LO or from LO to HI depending on the wiring
• The controller supplies the sensor with voltage via its digital input; an internal pull-up or pull-down resistor is a prerequisite
• The sensor detects conductive liquids, including those with very low conductivity
• When the contacts dry again, the resistance rises back to several megaohms

What is included in the box

The sensor is supplied with the material for mounting.

• SHT 8815 active water sensor
• Mounting material (1 screw, 1 wall plug)
• Operating instructions

How the SHT 8815 is constructed

The SHT 8815 is a compact, fully potted sensor with permanently connected supply cable.

Mounting and connection

Read the operating instructions carefully before mounting and commissioning.

Mounting the sensor

1. Securely screw the sensor with screw and wall plug through the integrated aluminium mounting hole.
2. If the cable is too short it can be extended to a maximum of 20 m, e.g. with LIYY cable (article 300780).

Connecting the sensor

1. Operate the sensor only with safety extra-low voltage (SELV/PELV).
2. Connect the brown core to the digital input (positive, plus) of the controller and the white core to ground (0 V).
3. Evaluate the signal: in the dry state the level remains unchanged; on water contact the level at the digital input is pulled from HI to LO or from LO to HI.

Which liquids does the sensor detect?

The SHT 8815 requires a conductive liquid, i.e. water with free ions.

• Detects conductive liquids such as tap water or salt water
• Also detects very weakly conductive water
• Purest distilled water is not detected
• The low level at the digital input (with 100 kΩ pull-up resistor) depends on the medium and is lower with salt water (2 %) than with tap water and distilled water

Manufacturer’s notes

• Read the operating instructions carefully before mounting and commissioning and keep them
• Do not open the device; it contains no parts that can be serviced by the user
• Packaging material is not a toy and must be kept away from children
• Operate only with operating voltage according to SELV/PELV
• Intended for residential, commercial and industrial areas as well as small businesses connected to the public low-voltage network
• Avoid moisture (splash or rain water), dust and direct sunlight on the device
• Clean only with a dry linen cloth; if heavily soiled, slightly dampened; no solvent-containing cleaning agents
• The manufacturer accepts no liability for damage or losses resulting from the failure to output an alarm signal despite water-level changes
• The CE declaration is available for download on the manufacturer’s website

Warranty, guarantee and disposal

The device is covered by the statutory warranty of at least 2 years in the EU. The manufacturer Elektrotechnik Schabus additionally offers a 5-year guarantee that can be registered online. Repair and spare parts are available directly from the manufacturer.

In the event of a defect please contact the manufacturer and provide your complete address as well as the reason for return. Within Germany you will receive a free returns label by e-mail. Unpaid packages will not be accepted; unjustified returns will be charged subsequently. In the case of statutory warranty the device must be sent in with a description of the fault, proof of purchase as well as address and delivery address.

The device does not belong in household waste. The crossed-out wheeled-bin symbol reminds you to use the take-back systems for waste electrical and electronic equipment (WEEE No. DE91394868).

Why the SHT 8815 is suitable

Areas of application

• Controllers such as Loxone, WAGO, Beckhoff and Siemens LOGO!
• KNX building technology and building management systems (BMS)
• Home Assistant, openHAB and ioBroker (with pull-up)
• PLC and industrial controllers with digital input
• Data centres and technical rooms
• Water treatment and heating systems
• Leakage and water detection on the floor in regularly dry areas
• Home automation and smart home

Once screwed down and connected to the digital input, your system detects water immediately – without detours.

Further active water sensors from Schabus

• SHT 8800 (Art. No. 200362) – active water sensor with switching principle “analogue voltage”
• SHT 8824 (Art. No. 200324) – active water sensor with switching principle “controlled constant-current sink” (4–20 mA)

Frequently asked questions