What are the different types of Stainless Steel used in Pressure Transducer design

Whilst examining the suitability of materials used in the construction of a pressure transducer you will notice that different grades of stainless steel are used for the parts exposed to the pressure media.  The choice of which stainless steel to use in a design is dependent on the required material strength, toughness, ease of manufacture, and corrosion resistance.

Stainless steel is a family of corrosion resistant iron alloys which have a Chromium (Cr) content of at least 10.5%. When exposed to Oxygen (O) either in the atmosphere or process media a self passivation process forms a surface layer which is corrosion resistant. The passive surface layer will naturally maintain itself over the life of the material.

There are 5 main groups of stainless steel which are Ferritic, Martensitic, Austenitic, Duplex and Precipitation-Hardenable Martensitic.

Why some Pressure Sensing Devices require the selection of an Elastomer Seal

When selecting pressure sensor options, occasionally you will come across a choice of seal materials to choose depending on the sensor design.

An all welded construction provides a high integrity and homogeneous material design.  The main disadvantages of this kind of sensor design is the lack of flexibility to customise for different applications, induced measurement errors from mechanical stresses caused by the welding process and higher manufacturing costs.

Specifying a General Purpose Pressure Sensor

If you need a sensor to measure gas or liquid pressure in a factory or laboratory environment there are a few parameters that should be considered in order to determine whether a general purpose device is going to be suitable.

The pressure of a fluid or gas is transmitted in all directions equally and over large distances, it is possible to install a pressure sensor some distance away from the process being measured via some suitable pipework.

Does Precision mean the same as Accuracy for Pressure Measurement Devices?

These two terms are indistinguishable to many people, even the Oxford Dictionary gives "Very Accurate" as one of the definitions for "Precision".  However, as pointed out in their use of "Precise" the two words have slightly different meanings which is particularly relevant to pressure measurement. 

In the context of a pressure measurement device, precision refers to how well it provides repeatable and linear results with increasing or decreasing pressure over many cycles. It is therefore an indication of the quality of measurement technology utilised and is a major factor effecting the cost of an instrument.

Calibration Hand Pump performance depends on test volume

Most air hand pumps that are designed to be used as pressure calibrators include a coarse pressure generator and a fine pressure adjuster. The effectiveness of both is dependent on the test volume connected to the pump.

The coarse or main pressure generator is typically a piston and cylinder arrangement which is actuated either by a set of calipers, a plunger, or a lever. The coarse change in pressure is applied by compressing the air to a high level inside a small cylinder which is then released to the lower pressure test volume increasing the pressure upon each cycle of the pump.