When you're introduced to a new level sensor or pressure transducer for the first time, you might pick it up to feel its weight. Not because weight is a key determining factor in sensor selection, but because you want to get a rudimentary idea of the quality of the sensor’s construction.
This is akin to kicking tires while shopping for a car or truck. While good automobiles tend to have sufficient air in their tires, correlation is not causation.
Likewise, a heavy sensor is not necessarily a well-built sensor. So to get a better idea of what contributes to a quality sensor, let’s explore 7 characteristics many robust sensors have in common.
A good sensor must be built out of the right materials for the application. That material may be 316L stainless steel, or it might be a good polycarbonate blend.
This is a careful consideration for us during the design phase. If the sensor is to be used in a wide variety of applications, it may require a few options. We also want to avoid using materials that, while sturdy, are unnecessary for the application. If we used 316L stainless steel for everything, some sensors would cost more than they should.
When two pieces come together, it’s a natural weak point. If not done properly, you may experience a leak or complete structural failure.
So the joining of two parts of a housing is critical. Heavy-duty sensors are typically built of metal and welded, or use carefully selected bolts with properly rated thread and shear characteristics.
As a matter of principle, we often use both threads and welds. In other words, behind each weld, there are likely threads with an o-ring seal. In the case of a poly housing, we use glue instead of a weld. It may sound like overkill, but if a weld has a small leak in it, we want the o-ring to catch it.
Testing the sensor for an IP rating should be standard practice for most manufacturers. However, it’s certainly not always listed in the specifications. IP ratings tell you how protected the electronics are from moisture and dust ingress.
NEMA ratings typically apply to an enclosure – such as a control box – and rate how protected the electronics are from things like moisture, dust, ice, oil, or human access. Some sensors rely on the box to keep them protected, and that’s okay if it works for your application.
Always pay attention to IP and/or NEMA ratings. We test nearly all of our sensors for IP ratings and list them on both our website and datasheets.
It’s easy to split hairs when chemical compatibility comes into play. There are several liquids and gasses out there that will corrode just about anything. However, many materials will hold up for a while. So we often speak to instrumentation techs and engineers who accept that the material isn’t quite compatible because they can’t find a better solution for the money.
At this point, material thickness comes into play. We try to stay cognizant of these situations and offer a thicker material where it makes sense. For example, we have pressure sensors with different thicknesses of diaphragms. If there is a question of chemical compatibility, we’ll recommend proceeding with a thicker diaphragm – if at all.
As a general rule, however, we attempt to offer the right material for the expected applications to marginalize the situations where we have to worry about corrosion.
If the sensor is to hold up to shock, vibration, or rough handling in general, secured internal wires and electronics are important. This is a detail that you won’t typically find in a datasheet (including in ours), but it directly impacts how well the sensor will endure in a tumultuous environment.
To secure our electronics for vibration we ensure high quality soldering practices and we secure anything that could shake itself loose. This can be done with additional soldering, epoxy, or clips.
If the sensor’s circuit board and electronics aren’t built to handle tough environments, then neither is the sensor.
Potting is a gel that we pour over our electronics inside the sensor housing. The gel hardens and provides an additional layer of protection for the electronics. It keeps moisture and dust away from the circuit board and protects all the components from vibration.
While not all sensors can have potting inside of them, those destined for heavy-duty applications likely do – depending on a few key considerations. If we can pot the sensor, we will to improve its reliability in the field.
To be fair, there is a disadvantage to potting a level or pressure sensors. It means we likely can’t service the sensor later on in its life. And if we can, it increases the cost. However, the benefits typically outweigh the costs.
Finally, and this has been hinted at several times already, the sensor has to be appropriate for the application. Robust means something totally different to someone measuring hydrochloric acid than to someone monitoring a flowback tank.
As we design a sensor, we carefully consider where the sensor will be installed, what chemicals it will encounter, what temperatures and pressures it will experience, among a host of other details. It’s your responsibility to be considerate of your application needs as well.
In the end, this may be the most important means of getting a sensor that will last for years – mating it with the right application.
If you have questions about which level sensor or pressure transducer is right for your application, just ask us. We’ll be honest with you. It’s in our best interest and yours to get you a sensor that will last as long as possible.
top photo credit: William Warby via flickr cc
