Capacitive proximity sensors detect almost anything — metal, plastic, glass, wood, water, oil, grain and powder — by measuring a change in capacitance rather than an eddy current. That makes them the answer whenever an inductive sensor cannot see the target.
How capacitive sensing works
The sensing face carries two conductive plates: one is the active electrode, the other a ground reference. An oscillator applies voltage across them, creating an electrostatic field in front of the sensor. When any material with a dielectric constant different from air enters that field, the capacitance changes and the oscillator amplitude shifts. A trigger circuit detects the shift and switches the output.
Because the effect depends on dielectric constant rather than conductivity, materials with high dielectric constants — water, alcohol and most liquids — are detected at longer range than plastics or dry powders.
Sensing through a tank wall
This is the capability customers most often need. Mount the sensor against the outside of a non-metallic tank or pipe and set the sensitivity so it ignores the wall but responds to the product behind it. You get non-invasive level detection with no penetration, no seal and nothing wetted — valuable in food, pharmaceutical and chemical duty.
Wall thickness matters. As a rule of thumb, keep non-metallic wall thickness under about 4 mm for reliable through-wall sensing, and always test with the actual product before committing to a design.
Key features
- Detects metals and non-metals — plastic, glass, wood, liquid, grain and powder.
- Adjustable sensitivity — a trimmer sets the threshold so you can tune out a container wall.
- PNP or NPN output, normally open or normally closed.
- Non-contact and non-invasive — nothing enters the process.
- Short-circuit and reverse-polarity protection built in.
- LED status indicator for setting sensitivity during commissioning.
Technical specifications
| Parameter | Value |
|---|---|
| Wiring | 3-wire DC (supply +, supply −, output) |
| Output type | PNP or NPN, NO or NC |
| Rated switching distance | 8 mm to 15 mm, adjustable |
| Hysteresis | 5–10% of rated sensing distance |
| Repeatability | 5–10% of rated sensing distance |
| Operating voltage | 10–30 V DC |
| Sensitivity adjustment | Multi-turn trimmer potentiometer |
| Protection class | IP68 |
| Housing material | Chrome-plated brass or ABS, depending on size |
| Status indication | LED |
| Standard cable | 2 m, 3-core (custom lengths on request) |
| Available sizes | M12, M18, M30 and rectangular |
Typical applications
- Level detection in tanks, hoppers and silos — through the wall or from the top.
- Detecting plastic bottles, glass jars and cartons on packaging lines.
- Grain, sugar, flour and powder level monitoring.
- Verifying product inside a sealed non-metallic container.
How to order
Tell us the sensing gap, the target material, your supply voltage and the output type your controller needs. If you are replacing an existing sensor, a photograph of the body markings is usually enough for us to identify an equivalent. We will confirm the specification and quote — normally the same day.
Related products
Frequently asked questions
Can a capacitive sensor really detect liquid through a plastic tank wall?
Yes, and it is one of the most common uses. Mount it against the outside of the tank and adjust the trimmer until it ignores the empty wall but triggers when liquid is behind it. Keep the wall under about 4 mm thick, and test with your actual liquid — water responds strongly, oils and solvents less so.
Will dust or condensation on the sensing face cause false triggering?
It can, because moisture and build-up change the capacitance the sensor sees. Reduce the sensitivity, angle the face so material sheds, or fit the sensor where wash-down keeps it clean. In heavy build-up conditions tell us the material and we will advise whether capacitive is the right technology at all.
What is the difference between capacitive and inductive sensors?
Inductive sensors detect metals only, using an electromagnetic field, and are largely immune to dust and moisture. Capacitive sensors detect nearly any material by dielectric change, which is more versatile but more sensitive to contamination and humidity. Use inductive for metal targets and capacitive when the target is not metal.
Need a quote for the 3-Wire Capacitive Proximity Sensor?
Send us your application — target material, sensing distance, supply voltage and housing constraint. We will recommend a part, quote it, and ship from Mumbai.