The Temperature Controlled Silicon Sensor
Temperature Control – a Prerequisite of Good Hygrometry
- The necessity for Temperature Control in hygrometry is determined by the Laws of Physics, which dictate that all hygroscopic materials will lose or gain moisture in relation to their temperature. This is clearly observed, for example, when condensation collects on a cold surface, and is then subsequently removed when the temperature of the same surface is raised above the temperature at which the dew forms.
Stable Operating Temperature = Stable Readings
- This principle applies to any moisture Sensor. Changes in temperature will give rise to a variation in the amount of water the Sensor can hold in a state of equilibrium. This will, in turn, give rise to larger uncertainties associated with any measurement if Temperature Control is not applied. Therefore, if a Sensor is to give a reproducible response to a fixed water concentration, it must operate at a constant temperature. Accordingly, all MCM moisture analysers feature Temperature Control.
Laboratory Performance & Traceability – In the Field
- By applying Temperature Control to a thermally stable Silicon Sensor MCM offers a unique advantage over its competitors who do not use Temperature Control, namely stability and traceability of data. This is particularly relevant when operating at temperatures significantly different from the temperature at the point of calibration.
The Push Purge® Feature
An Effective Means Of Verification
- When sampling a gas for the first time, or if anomalies occur that cause concern, the ability to verify results is invaluable. MCM makes this possible with the Push Purge® feature. When activated the surface of the Sensor is heated rapidly, burning off superficial moisture any hydrocarbon contamination that may be present. As the temperature of the Sensor increases moisture is displaced and the displayed reading drops accordingly. As the Sensor cools, and equilibrium is re-established, the moisture reading will return to its previous value if surface contamination is negligible, confirming the value of the water vapour present in the sample gas. In addition, Push Purge® provides valuable information on the risk of contamination of the Sensor, the gas condition and the electronic functionality of the hygrometer.
Rapid, Repeatable Measurements by Eliminating Hysteresis
- The effects of hysteresis are minimised when using Push Purge® because each measurement is started with the Sensor in a repeatable, dry condition. Equally, the time required for each measurement to stabilise can be vastly reduced by using the Push Purge® Sensor drying function to speed up the equilibrium process. The time it takes for the water vapour equilibrium to be re-established from this dry state will confirm the analyser’s sensitivity to moisture and establish its response time under field conditions.
- Any hygrometer that has the ability to confirm its sensitivity or speed of response to changes in moisture levels, without disturbing the sample condition itself, is a valuable tool for any operator in terms of the confidence it provides in the data that is collected. Push Purge® is, therefore, an invaluable diagnostic tool which aids productivity and Quality Control.