Shaw dew point meter principle

 The SHAW dew point meter operates on the principle of dynamic equilibrium between water vapor in a gas and a specially designed sensor, a unique sensor that measures trace moisture by exploiting the principles of dynamic equilibrium and automatic calibration (AutoCal). The sensor, constructed from a high-purity aluminium wire coated with a partially hydrated aluminium oxide layer, is designed to saturate with water vapor at its maximum operating range. This saturation forms the basis of AutoCal, allowing for in-situ verification and adjustment without specialized equipment or training. 

Here's a more detailed explanation of the Shaw moisture meter principle:

1. Sensor Construction:

The sensor is made of a high-purity aluminium wire that is chemically oxidized to create a pore-filled insulating layer of partially hydrated aluminium oxide.

These pores act as a reservoir for water vapor, and the amount of water absorbed is directly related to the moisture content of the surrounding gas. 

2. Dynamic Equilibrium:

A dynamic equilibrium is established between the water vapor outside the sensor and the water absorbed within it.

This means the sensor responds to changes in moisture content in the gas sample. 

3. AutoCal (Automatic Calibration):

Each Shaw sensor is precisely manufactured to saturate with water vapor at its design maximum.

When exposed to moisture levels exceeding its maximum range, the sensor reaches equilibrium and ceases to respond further.

This equilibrium point is used for automatic calibration, allowing users to adjust the instrument's calibration to match the sensor's response. 

4. Advantages of Shaw Moisture Meter Principle:

In-situ calibration:

AutoCal allows for calibration in the field, reducing downtime and costs. 

Simple operation:

The AutoCal function and the desiccant dry-down technology make the meter easy to use, according to Shaw Moisture Meters. 

High accuracy:

The precise manufacturing of the sensor and the use of AutoCal ensure accurate measurements of trace moisture. 

Wide range of applications:

Shaw moisture meters are suitable for various industries, including compressed air, process gases, and other industrial applications, according to Shaw Moisture Meters.