1 - Gas Flow meter    2 - Digitap Board     3 - DBS tap panel

1 - Gas Flow meter 

This ultrasonic gas flow meter measures precisely the velocity of a gas in a pipe of known internal diameter.  The principle of operation consists in measuring the differential transit time of two ultrasonic waves, one going upstream, the other one going downstream. This measurement is a function of the velocity of the gas in the pipe.

The transmission and reception of the ultrasonic waves take place at the tip of two tapered rods facing each other. This original patented design exhibits an excellent signal to noise ratio, even at large flows, thanks to the axial and extended transmission areas. These tapered rods create little disturbance in the flow of gas which enables a precise measurement. This design gives access to more than 4 decades of measuring range.

Fig. 1 : Measuring cell.

The differential transit time is given by the following formula:

Where N designates the number of reflections inside the pipe,
2h, designates the pipe diameter,
vf, refers to the velocity of the gas in movement inside the pipe,
vd and va are the speed of sound respectively in the tapered rods and in the gas.

For a pipe of 14 mm in diameter, the measuring range of the prototype stands from 0 to 8 000 liters/hour with a resolution of 1.8 l/h.

A possible field of application for this instrument concerns the monitoring of human respiration. Because of its fast response time, this device can be used with transient flows such as breathing. Moreover, thanks to its tapered rods, the device provides 2 other parameters, the temperature inside the cell and the speed of sound inside the gas which appears to be very useful in the case of breathing since the presence of exhaled carbon dioxide changes significantly the speed of sound in the inhaled air.  This information when related, in real time, to the exhaled volume of air, yields an indication of the efficiency in the gas washout. In the case of an Asthma crisis, the CO2 washout efficiency is altered and this instrument could measure the severity of the crisis.

Human respiration monitoring: The graphs here below show (a) The averaged (upstream + downstream) transit time during breathing  and (b) the transit time difference in exhaled air before and after physical exercise, thus showing the percentage of exhaled carbon dioxide of an adult at rest, just after squatting 40 times and 5 minutes after exercise.

Exhaled Carbon Dioxyde as a function of exhaled air volume

Other fields of application include industrial process control, laboratory flow control, OEM applications, gas counter, leak detection. 

Specifications of the prototype:



Fluid type

Medium to high density gas (Air, N2, O2, CO2...Xenon)

Flow range

0 - 10 000 liters/hour

Volume counter
(stand alone device)

0 to 5 million liters. Threshold: 0.005 l (18 l/h x 0.5 s)


1.8 l/h


 +/- 0.15% of full scale


1% at 200 l/h ; 0.2% at 3000 l/h ; 0.3% at 6000 l/h

Drift over temperature

+/- 35 liters/hour over ( 5 - 30C)

Zero adjustment

Reset Button

Relative Humidity Range

HR< Dew Point (non destructive if passed)

Temperature Range

+/- 100 C above/below cell temperature
(0-70C) electronics board

Temperature Coefficient

0.17% of measured value / C

Pressure Coefficient

According to used gas

Max Pressure

< 3 bars

Response time

Auto-adjustable: 0.14 s to 0.5 s according to flux stability

Voltage Supply

6 V

Internal diameter

14 mm


LCD, 2 x 20 dot matrix characters
Display of flow l/h, cumulated flow, speed of sound in gas

Calibration Coefficient

Auto compensated in temperature, pressure, humidity

Materials in contact with the fluid

Aluminum or Titane, Polyamide


1/8 MNPT or ISO stainless steel or Viton


Directly to the source

Data transfer

RS232, USB, BlueTooth

Position of the measuring cell


Dimensions of the cell (mm)

170 x 150 x 50

2 - Digitap Board

This board transforms a glass window into an interactive panel. As a touch screen, the panel provides the graphical coordinates and the intensity of a mechanical impact (tap) occurring at its surface. The  principle of operation is based on the differential time of flight of acoustic waves generated by the tap. It is characterized by a fast response time close to 1 ms. Mechanical stresses or adhesives can be applied to the panel without significant distortion. Heavy objects can be laid on tap panels making their use compatible as tables. Tap panels can be programmed to operate as standalone devices with tap zones of various sizes and functionalities. Predefined functionalities include sound "bip", recording and play back of infra red remote commands, digicode keys for building doors, light power switch  and timers.  In service mode (slave) tap panels operate simultaneously as USB or RS232 computer peripherals. The serial port is designed to provide power to  Bluetooth adapters so that wireless control of tap panels is easily done trough a laptop, PDA or mobile phone with Bluetooth compatibility. One single tap triggers successively several events such as sound "bips", power switches, Infra Red remote commands, mouse clicks, voice digitization and transfer, phone calls, etc...

Fields of application include Bluetooth power switch, Point Of Sales (POS) control and information systems, interactive tables, Giant Touch Screens, Multi Modal Remote Control devices, Building doors with built in digicodes, Interphones, etc...

 It has the following characteristics :

1. Excellent signal / noise ratio making the "DBS" tap panels (see below) sensitive to finger taps.
2. Precision: 1 cm/m.
3. Resolution: 1.7 mm.
4. Max tap panel dimensions : 6.8 m x 6.8 m.
5. Max acquisition rate: 140 taps/s (compatible with an ultrasonic stylus).
6. Min response time: 1 ms as a standalone device (no computer).
7. Combined sensors constituting an intelligent microphone emphasizing lateral, central, or omni directional sound sources.
8. Fan management functionality that eliminates spurious noise coming  from fans when recording sound with the glass panel.
9. USB 2.0 (A - mini B cable) and RS232 (SubD-9) connectors.
10. 1 parallel port (8 digital ports controlled simultaneously).
11. Infrared receiver and transmitter with universal remote control capability.
12. Power Switch controlled by Digicode (4 tap zones) or by one Bluetooth command.
13. Serial to Bluetooth wireless connection compatibility.
14. More than 250  tap zones downloadable into the Board Flash memory.
15. Programmable Sound "bips" (0.3 kHz - 80 kHz and 0.01 - 1 second) associated with tap zones.
16. Tap zones can  be piled up (useful to MUTE different Infra Red products in a Point of Sales).
17. Encrypted Data Transmission for wireless secured communication between a host PC and several interactive panels.
18. Many boards to 1 Host PC compability.
19. 1 board to many PC compatibility.
20. Fast and automatic sensitivity adjustment.
21. Small dimensions (167 mm x 101 mm).
22. Single power supply: 12V-0.4A

3 - DBS tap panel

 "DBS" panels are new flat and sensitive tap panels. Their specific design comprises a glass plate with a Double Symmetrically Beveled (DBS) cut. This patented process creates a strong mechanical amplification of the acoustic waves as they reach the edge of the plate (a little bit like a tsunami, but with a beneficial effect). With this method, even thick plates are sensitive to the slightest impacts, even if they are performed with the skin of the finger tip. The panel sensitivity becomes almost independent from the thickness of the panel, so that standard or tempered glass plates, up to 19 mm thick, can be used.

The planar design makes theses interactive panels well suited as interactive tables. They are easily wiped clean.