Level monitoring probes Type WST 10

Level monitoring probes 

Type WST 10 DC 9 / 32 Volt 

Type WST 40 DC 18 / 32 Volt 

Weber Sensor Technologies 

Martin Weber 

Zollamtstrasse 28 • 4020 Linz - Austria 

Tel.: ++43 (0) 732 / 78 37 02 • Fax: ++43 (0) 732 78 37 02-50 

office@sensor-technologies.com 

www.sensor-technologies.com

Index 

General description 3 

Installation instruction for all Weber sensors 5 

Functionality of level probes minimum 6 

Functionality of level probes maximum 7 

Probe type WST 10 with connector bayonet 16 S 8 

for a voltage range of 18 to 32 V 

Probe type WST 40 with connector bayonet 16 S 10 

for a voltage range of 18 - 32 V 

In addition to our standardised sensors we are in a position to develop sensors according to 

your specifications. 

- 2 -

General description 

Weber level monitoring probes 

Our sensors monitor the level of oil-like and aqueous liquids. They are applied in commercial 

vehicles, power units, engines and ships. On engines they are employed to check the oil 

level, the coolant level and the fuel tank. On ships they are used to supervise engine states 

and supply and waste water tank and the bilge. The sensors are suitable for automatic liquid 

filling and refilling units, e.g. engine oil supply and the fuel service tank. 

In all situations where temperature sensors or manometric switches are currently used as 

level monitoring components, our probe has the advantage that it displays a critical operating 

state much sooner. Temperature sensors often respond with considerable delay because the 

medium which is checked no longer exists. As a result, the increase in temperature is not 

handed on to the generator. A manometric switch shows the lack of oil only in case of an 

entire lack of oil and thus too late to protect the engine. The level sensor gives a warning 

signal when there are insufficient quantities of the medium present. 

Weber level monitoring sensors differ from float-type switches in their compact design and 

immunity to vibrations. As they do not consist of any mechanically moved parts, their 

successful operation cannot be affected by dirt particles or other influences. On the probe no 

current is sent into the medium via an electrode. Thus an insulation of the sensor and 

electrolysis in the system is not possible. 

Operating principle 

The monitoring probe works on the capacitive principle. A change in capacitance is detected 

when an insulated electrode surrounded by air is immersed in a fluid medium. This change in 

capacitance is detected by sensor electrode which sets an oscillator in motion (frequency 

approx. 600 kHz). This signal is processed by a digital evaluation electronics unit. 

Switching output 

The level sensors have a short-circuit-resistant switching output, 

• Minus-switching: The output transistor switches the minus potential to the load. 

• Plus-switching: The output transistor switches the plus potential to the load. 

For switching currents of more than 1A, a relay must be interconnected. For this a freewheeling 

diode must be switched parallel to the relay as excess voltage protection at 

inductive load (see technical specifications). 

Medium variants 

The level sensors are configured for two different types of media: 

• For electrically conducting liquid media with a relative dielectric constant in the range of 

εr: 35...85 (water, coolant, water glucose mix) 

• And for non- electrically conducting liquid media with a relative dielectric constant in the 

rang of εr: 1,8...6 (engine oil, fuels, hydraulic oil) 

- 3 -

Automatic function control 

The sensors are fitted as standard with approx. 2 second function control. If the supply 

voltage is applied (e.g. ignition is initiated), the signal appears for approx. 2 seconds and 

thus signals that the sensor is ready. If the signal does not appear then the sensor needs to 

be checked. This self-monitoring allows the level monitoring sensor to be checked for 

functional readiness as well as cable breakage from a central point. The control of 

conventional level switches is extremely difficult especially in large- scale branching systems 

such as those found on ships. Other function control times can be supplied on request. 

Reporting delay 

In order to avoid faulty readings caused by fluctuating liquid surfaces and thus the brief 

deviations above or below the level that this produces, the output signal comes fitted with a 

reporting delay period of about 7 seconds. Other reporting delay on request. 

- 4 -

Installation instruction 

All WEBER monitoring sensors may be installed in any attitude. 

Please observe the following instructions when installing the probe: 

1. To prevent false indication, install the probe in a smooth area where it is not affected by 

splashing media as may be the case when it is installed in a gear unit or directly in the 

motor oil slump. 

2. To prevent false indication, install the sensor at least 15 min from the wall away. 

Only for water- sensors: 

3. False indication may also occur if the sensor is mounted from above in a plastic 

container, with the medium carrying no potential. In all other mounting attitudes the 

housing will be in contact with the medium so as to ensure potential is available. 

4. Connection Diagram 

- 5 -

Functionality: level probes minimum 

Minimum 

Output works 

Output does 

not work 

Minimum probes: 

Probe in 

medium Probe in medium 

Probe out of medium 

Switching 

delay 

If a minimum probe is removed from the medium, its outlet becomes active after the report 

delay. Its outlet becomes low-impedance after the report delay and a signal is available at 

the outlet. 

If a minimum probe is immersed in the medium, its outlet immediately becomes passive. Its 

outlet becomes high-impedance after immersion and a signal is no longer available at the 

outlet. 

- 6 -

Functionality: level probes maximum 

Output works 

Output does 

not work 

Probe in 

medium 

Maximum probes: 

Switching 

delay 

Probe out of medium 

If a maximum probe is immersed in the medium, its outlet becomes active after the report 

delay. The outlet becomes low-impedance after the report delay and a signal is available at 

the outlet. 

If a maximum probe is removed from the medium, its outlet immediately becomes passive. 

The outlet becomes high-impedance after the removal and there is no longer a signal 

available at the outlet. 

- 7 - 

Probe in medium

Technical data for type WST 10 at TU = 20 °C 

Operating voltage: 

Power consumption: 

Load carrying capacity of exit S: 

Switching point vertically mounted: 

Switching point horizontally mounted: 

Medium temperature: 

Ambient temperature: 

Storage temperature: 

Response delay: 

Integral control function: 

Reverse polarity protection: 

Function: 

Caution: 

DC 9 to 32 V 

5 to 10 mA (without load) 

up to 1 A (resistive and inductive load, short-circuit proof, overload 

protected in the whole operating voltage and temperature range); 

10 to 25mm from feeler nib 

2.5 mm ± 1 mm 

-40 °C to +105 °C 



see product table on following pages 


in-built between plus and minus terminal 


Minus switching probes: Do not connect minus potential to the signal terminal or plus 

potential to the minus terminal, as otherwise the probes may be destroyed. 

CE marking according to EC-directive 89/336/EWG (EMC directive) 

- 8 -

Type WST 10 with bayonet 16 S 

Environmental protection IP 67 DIN 40050 

Probe suitable for aqueous media Probe suitable for oil or fuel 

Type WST 10 with bayonet 16 S Signal output 

minus potential 

Thread Monitoring Integral control Monitoring Aqueous liquids 

Oil and fuel 

display function delay 

Ref. No. 

Ref. No. 

M 14 x 1,5 MIN 2 sec. 7 sec. 1010575 1020595 

M 14 x 1,5 MIN 0 sec. 0 sec. 1010528 ---- 




M 14 x 1,5 MIN 2 sec. 0 sec. ---- 1020562 


M 18 x 1,5 MIN 0 sec. 7 sec. ---- 1020031 

1/4“NPTF MIN 2 sec. 7 sec. 1010577 1020597 

1/4“NPTF MIN 1 sec. 17 sec. 1010401 ---- 




1/4“NPTF MIN 0 sec. 0 sec. ---- 1020529 

Accessories for probes with bayonet 16 S 

Ref. No. Description 

1000672 Straight connector for bayonet 16 S, for corrugated tubing NW 10 

1000673 90° connector for bayonet 16 S, for corrugated tubing NW 10 

1000772 Straight connector for bayonet 16 S with 5.6 mm cable sealing 

1000773 90° connector for bayonet 16 S with 5,6 mm cable sealing 

1000641 Braze-in adapter 1/4"NPTF 

1000644 Braze-in adapter M14x 1,5 


- 9 -

Technical data for type WST 40 at TU = 20 °C 

Operating voltage: 

Power consumption: 

Switching capacity: 

Switching point vertically mounted: 

Switching point horizontally mounted: 

Medium temperature: 

Ambient temperature: 

Storage temperature: 

Response delay: 

Integral control function: 

Function: 

Housing: 

Caution: 

DC 18 to 32 V 

10-15 mA (without load) 

max. 2 W (resistive Last, not overload protected) 

10 to 25mm from feeler nib 

2.5 mm ± 1 mm 

-30 °C to +110 °C 


-40 °C to +115 °C 





Minus switching probes: Do not connect minus potential to the signal terminal or plus 

potential to the minus terminal, as otherwise the probes may be destroyed. 

- 10 -

Type WST 40 with bayonet 16 S 

Environmental protection IP 67 DIN 40050 

Probe suitable for 

aqueous media 

Type WST 40 with bayonet 16 S Signal output 


Thread Monitoring Integral control Response Aqueous liquids 

Oil and fuel 

display function delay 

Ref. No. 

Ref. No. 

M 14 x 1,5 MIN 2 sec. 7 sec. 421575-24V 421595-24V 

M 14 x 1,5 MAX 0 sec. 7 sec. 421579-24V 421599-24V 

1/4“NPTF MIN 2 sec. 7 sec. 421577-24V 421597-24V 

1/4“NPTF MAX 0 sec. 7 sec. 420993-24V ----- 

Accessories for bayonet 16 S 

Ref. No. Description 

1000672 Straight connector for bayonet 16 S, for corrugated tubing NW 10 

1000673 90° connector for bayonet 16 S, for corrugated tubing NW 10 

1000772 Straight connector for bayonet 16 S with 5.6 mm cable sealing 

1000773 90° connector for bayonet 16S with 5.6 mm cable sealing 

1000641 Braze-in adapter 1/4"NPTF 



- 11 - 

Probe suitable for 

oil or fuel

Level monitoring probes Type WST 10

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