The Air Gap Sensor DPA series is a pneumatic, high precision sensor capable of "checking the adhesion" between the workpiece and the jig.
If air is available, you can check not only "presence/absence" but also "adhesion (gap)" at the same time with a repeatability of ±0.5μm. Prevents processing defects and equipment downtime due to improper seating.

It has been introduced in highly automated processing such as precision workpiece clamping, semiconductor manufacturing processes, and transfer lines. It is also compatible with the "IO-Link" communication standard and supports information visualization.


Function of Air Gap Sensors

  • High-precision seating confirmation of workpiece and jig
  • Prevention of machining defects and equipment downtime due to seating defects
  • Automatic positioning of rotating grinding wheel on NC grinder
  • Workpiece inside diameter measurement

Why METROL Air Gap Sensor Wins Customers

Reason 1:


High accuracy of ±0.5µm ensures detection of gaps of 20µm or less

We the following inquiries have been brought to our attention.

“With the current gap sensor, I can see if something is there or not, but I can't detect if it has a gap or not.”

Since the air gap sensor can detect “gaps” of a few microns caused by chips, it is used as a seating confirmation sensor in machining lines that require high machining precision, such as brake parts for automobiles and HDDs.

Reason 2:


Anyone can easily set thresholds.
Simple operation

The "threshold value" that serves as the criteria for the sensor can be set at the push of a button.
There is no need to read complicated manuals or train operators for learning how to use the sensor.

Reason 3:


Versatility for use in a wide variety of applications

Air gap sensors are not only used for "checking adhesion.
There are various applications that utilize the high accuracy of the sensor, such as
"Automated positioning of the rotating grinding wheel of NC grinders*" and
"Efficient measurement of the inside diameter of workpieces". In response to a NEDO (New Energy and Industrial Technology Development) grant in FY2020, we are collaborating with Okamoto Machine Tool Works, Ltd. in a joint-research.

Reason 4:


Coolant resistance IP67 protection rating

The air microsensor has an IP67 protection rating and can be installed inside machine tools where coolant splashes.
Air piping to the air nozzle can be shortened, which speeds up response time and improves productivity.

Reason 5


Compatible with the worldwide communication standard "IO-Link"

Models that support the IO-Link communication standard can send and receive data from inside the sensor to PLCs and networks.
Predictive maintenance and remote control of sensors via Ethernet are now possible and are effective in identifying the cause and preventing downtime even in unforeseen circumstances.

*Supported model: LK-DPA series

Product Line

Product name Detection range Threshold purchase Download



1 - 100um 1-point setting type VONA



80 - 350μm 1-point setting type VONA



1 - 100um 2-point setting type

3 classifications(-NG/OK/+NG)



80 - 350μm 2-point setting type

3 classifications(-NG/OK/+NG)



80 - 350μm 3-point setting type



1 - 100um 1-point setting type ×3



1 - 100um 8-point setting type

Comparing Our Sensors to Other Brands

Air Gap Sensor
Other Brand's
Air Sensor / Gap sensor
Repeatability ±0.5μm - × ±20μm -
Workpiece “Precision seating confirmation” can be realized.

Minimal signal point variation and effective detection of workpiece floating due to cutting entrance.

Accurate seating confirmation can be conducted within the allowable tolerance, preventing machining defects.
Only workpirce “Existence detection” possible

Large signal variation means only workpiece existence detection is possible.

It is impossible to detect workpiece floating due to cutting chips and to accurately confirm workpiece and jig seating.
Detection range 1 - 350μm × 40 - 250μm
Protective structure IP67
(Can be used under harsh environment where coolant splatter)
× IP66
(Not suited in harsh environment)
Response speed About 0.8 seconds (Tube length: 1.5m)

Air piping can be shortened by installing sensor inside machine tools.
About 5 seconds (Tube length: 12m)

Longer air piping is necessary because sensor shoud be installed outside machine tools
Numeral display × No display (only ON/OFF signal)* With display