Introduction

Many articles have been written, and presentations have been presented, for ammonia leak detectors and the various sensor technologies. All too often, these articles and/or presentations introduce some misleading information that can confuse most people that work in the industrial refrigeration industry. So, let’s do this in very simple terms!

First and foremost, there is no such thing as a perfect sensor! Now, the detector itself may be perfect due to the features that it may provide, but the one weak link is the actual sensor cell itself. Why? Because depending on the various sensor cell technologies, they each have their strengths and, of course, their weaknesses. Let’s explore these different technologies!

Sensor Technology

Basically, there are three sensor technologies used in the industrial refrigeration environment: solid-state, electro-chemical, and infrared. Since the two most common sensor technologies that are utilized today are solid-state and electro-chemical, we will focus our attention on them.

Let’s start with a little bit of history! Electro-chemical sensors were developed and being used starting in the 1950’s. Some of the strengths of this type sensor are that they are designed to be a little bit more specific to the target gas that they are sensing with a reduction (not elimination) in picking up other gases. Their weaknesses include, but are not limited to, short sensor life (12-24 months) due to exposure to ammonia vapors and/or heat and humidity, high cost of sensor replacement, and high cost of calibration (recommended every 6-months).

Of course, since sensor technology is constantly evolving, people wanted a sensor that was much more robust and would not deplete especially during an actual ammonia leak! So, in the 1970’s, some of the first solid-state sensors were designed and being used. Their strong capabilities are no sensor depletion due to ammonia vapors and/or heat and humidity, long sensor life (up to 10 years), low cost of sensor replacement, and low cost of calibration (recommended once per year). Some of the weak capabilities, depending on the solid-state technology, would be that they may sense other limited gases such as smoke (though some people would argue that this may be a strong capability), paint fumes, or ethanol vapors. Of course, most of these issues can be resolved by putting the detectors into service or bypass mode.

Summary

Hopefully, with the simple discussion above, this helps to dispel any misleading statements and/or presentations that you may have heard and/or seen. Having a good basic understanding of the two basic different sensor technologies, explained in layman’s terms, can only help when making a major decision on which sensor technology to use in your facility. For further information, please either review the
'Sensor Selection Guide' at the right or contact Cool Air Incorporated.


PDF : Sensor Selection Guide