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Utilizing Diaphragm Seals To Isolate Pressure Loggers

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This case study discusses the use of a diaphragm seal to separate and protect a Track-It™ Pressure/Temperature Data Logger from the medium (liquid or gas) being measured.


What are diaphragm seals?

Wika Diaphragm - Colonial Instruments

The purpose of a diaphragm seal is to isolate a pressure measuring device
(in this case, a Track-It Pressure/Temp. or Vacuum/Temp. Data Logger)
from the media being processed in challenging environments where the
process media should not come into contact with the pressurized parts
of the logger, in order to protect and extend its life.

A diaphragm protected pressure gauge uses the deflection of a thin,
flexible diaphragm element, to displace diaphragm seal transfer fluid into the pressure gauge. The components are assembled and vacuum filled with a transfer fluid such as silicone, and then calibrated together, in order to retain accurate pressure readings. The diaphragm isolates internal components from the media, making the logger suitable for use with corrosive and/or contaminated liquids or gases.

How to choose the right diaphragm seal configuration?

Not every pressure measurement application requires a diaphragm seal, but when conditions warrant, it’s important to understand the environment.

What is the application?
• High-temperature media
• Suspended solids
• Viscous or crystallized media
• Corrosive media

With the application identified, there are other considerations:

  • Connection: threaded, in-line, flanged, or sanitary
  • Wetted material: such as 316L stainless steel, plastics, titanium, etc.
  • Additional transfer fluids: depending upon the application, transfer fluids such as silicone or FDA mineral oil, glycerine, etc. may be required
  • Maximum Allowable Working Pressure (MAWP): as diaphragm seals are designed to withstand MAWP
  • Add-ons: such as pressure snubbers, cooling elements, etc.

How to choose the right data logger for your pressure measuring application?

Again, not every pressure measurement application requires a diaphragm seal, but when conditions warrant, it’s important to understand the environment.

Monarch Instrument data loggers have 1.5x/150% “over-range” pressure capacity. However, you should choose a pressure data logger that is closest to your application’s pressure range and max pressure to ensure optimal accuracy of the pressure sensor (versus relying on the over range capacity).

The Pressure sensor is located in the nozzle port of the Logger. The Temperature sensor is located inside the logger housing, therefore measurement is more ambient temperature versus media temperature.


We are thankful for the collaboration with COLONIAL INSTRUMENTS, INC. for this use case.

Colonial Instruments is a stocking wholesale distributor of pressure and temperature instruments. Colonial Instruments offers full service diaphragm seal filling and repair services and partners with Monarch Instrument as our subject matter experts for diaphragm seal applications.

Phone: 603-881-4040