The information may be useful tor your research

Differential Pressure Flowmeters

The calculation of fluid flow rate by reading the pressure loss across a pipe restriction is perhaps the most commonly used flow measurement technique in industrial applications (Figure 2-1). The pressure drops generated by a wide variety of geometrical restrictions have been well characterized over the years, and, as compared in Table 2, these primary or "head" flow elements come in a wide variety of configurations, each with specific application strengths and weaknesses. Variations on the theme of differential pressure (d/p) flow measurement

Ref:www.omega.com/literature/transactions/volume4/T9904-07-DIFF.html

Hello Andrew,

can you provide a sketch of your problem?

What is the expected order of magnitude for your pressure differences?

There is a wide variety of differential pressure sensors. When, however, both sides of the sensor are connected to a liquid the sensor might become quit expensive.

For a testrig I once used an LPM9000 series sensor from General Electric. This sensor type can be ordered for a wide variety of pressure ranges.

Best regards

Bastian

Validyne provides differential pressure sensor such as DP15 and DP103 for your problem. You can easily check their website for details. In my experience, DP15 is better for maintenance, but DP103 provides a wider pressure range. 

for low differential pressures (low airspeed) I can suggest you   SDP1000 - the link below.. I could provide you schematic with 12 bit ADC and microcontroller interface (PIC or Arrduino) along with C++ routine..

resolution may be as low as tenths of pascal..

http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/DiffPressure/Sensirion_Differential_Pressure_SDP1000_SDP2000_Datasheet_V5.pdf

Druck Ltd company in England offers such sensors.

Regards

Dear Andrew. Bastian that this right, the ways to measure this parameter are as varied and numerous that it is impossible to give a consistent answer without more information.

Re: numbers - to estimate the differential pressure range to be measured you may use well known equation for dynamic pressure

q = rho*V^2/2 (rho is fluid density, V is free flow velocity)

having in mind characteristic (expected) maximum flaw velocity and density (air or water) you can have the range of pressure magnitudes your instrument should measure.. it is simple..

Hello, Andrew J. Neverman !

I think that in the case of using a pressure sensor chip with the separation of two media, i.e. it should not be a microphone with through holes, you can use a Honeywell NSC 250, 400, 600 LD sensor - this is the most sensitive pressure sensor I've seen on sale. It is capable of measuring flow fluctuations