Testing in rugged applications often includes testing in extreme temperature ranges, which can add constraints to hardware. Cold-start engine testing, for example, uses a test cell that can drop to -40 °C and requires continuous data acquisition such as temperature, pressure, and other various measurements. Placing hardware that is not built to withstand this range into harsh environments can cause components within the hardware to work incorrectly and result in incorrect data or damage to the hardware.
Your hardware can withstand these extreme temperature ranges in two ways. First, you can create an external casing for your hardware. Depending on which side of the extreme temperature range you are using your hardware, you need to implement heating or cooling elements in the enclosure to keep your components at an operating temperature. You might also want to consider using shielding from the environment and evaluating the color of the enclosure to reflect heat. With all of the considerations for designing an enclosure, it can be an expensive and time-consuming process.
Alternatively, you can select hardware built for withstanding extreme temperature conditions. These enclosures are put through extensive thermal tests and validation to ensure the components selected operate within their specifications. This testing also allows the hardware to comply with the international standards for operating within a temperature range.
Shock and Vibration
Another typical consideration when developing a rugged application would be the shock and vibration specifications for your test, and building your setup to withstand it. Applications ranging from monitoring the main gear box of a bucket-wheel excavator power transmission system, to taking analog and digital measurements inside a Formula SAE racecar require consideration of the vibration and shock values induced on the testing hardware. If your hardware is placed within a demanding environment where high vibration or shock values occur and it cannot handle these values, this could damage your hardware components and cause expensive repair or replacement.
When designing a test setup for a rugged environment, there are again a couple of options to compare. You could design an enclosure for vibration to allow the components within the hardware to operate within their given vibration and shock specifications. One approach would be to build within the enclosure a way to isolate the hardware from the vibration occurring within the environment. This could be difficult and require a lot of testing to ensure your hardware is operating properly within the vibration or shock values seen by the environment.
Alternatively, you could select hardware built to withstand these specifications. There are several ways to design hardware to withstand effects of vibration. For example, you can design an internal vibration isolation for the internal components so that they can operate within their specifications. Hardware is available that withstands shock and vibration levels up to 50 g in shock and 5 g in vibration values. After the hardware has been designed, it is recommended that the hardware be mounted to a rigid surface to fully meet all international standards and certify the product to be used in these rugged vibration and shock specifications.
Although temperature range and shock and vibration specifications are crucial to address when developing a rugged application, it is also important to consider the environment in which you are conducting these tests. This is especially true if this environment is a hazardous location with potentially explosive gas or vapor present during abnormal operating conditions. Examples of hazardous locations include chemical factories or refineries. When developing a test setup for an application in these hazardous locations, it is an important part of the process to have the correct certifications for your setup.
The certifications for operating in hazardous locations, depending on where you are regionally, are the UL Hazardous Locations or the European Union Hazardous Locations certifications. Both certify products for use in hazardous locations where explosive atmospheres may be present. The UL certification comes in degrees of classes and divisions. The classes indicate the type of hazardous location, and the divisions indicate the conditions. The classes offered are from Class 1 to Class 3, with the locations ranging from gas or vapor to dust, all the way to dust, fibers, and flyings in a potentially explosive atmosphere, respectively. There are two divisions: Division 1 is for material in normal operating conditions, and Division 2 is for material under abnormal conditions.
Typically, you need to run the entire test setup through all of the certification tests to ensure it is compliant to be used in these harsh locations. Testing all of the hardware can be an expensive and intensive process, but is required for operating in these types of environments.
Another certification common for rugged applications is Lloyd’s Register Type Approval. This certification is an assessment by a third party attesting to a product’s conformity with national and international standards, and verification of the manufacturer’s production quality system. Type Approval applies to products for use in marine and offshore applications, industrial plants and processes, and the information technology sector. In addition to ensuring the product meets appropriate safety standards for a marine environment, Type Approval ensures that the product’s performance is maintained in marine environmental conditions.
To obtain this certification, your hardware must go through an entire process laid out by the third party assessing the hardware. First, the third-party group must review all design of the hardware to ensure it complies with specific specifications and codes. Then, they must witness inspection and testing and have those sent in for further review and validation. If everything is approved, then the hardware is validated and authorized to use the Lloyd’s Register Type Approval mark.
When deciding on hardware for a rugged application, the overall form factor is a big consideration. The test system’s footprint is significant when deciding what hardware to use in demanding environments, such as on an offshore oil rig or in the middle of a desert. If the material the hardware is built out of cannot withstand the harsh environments and needs an enclosure for protection, this could drastically increase the system’s footprint. If the enclosure needed to protect the hardware has too large a footprint, this can limit where you can conduct tests. For more distributed and remote applications, you want to minimize the size of the hardware.
In addition, consider how the hardware cools itself. Hardware can cool in many ways; the main two are passive and active cooling. Hardware that passively cools can be more rugged because there are no moving parts. If your hardware needs moving parts such as fans to cool properly when testing, this could limit where you can conduct tests. With an actively cooled device, there are energy-consuming mechanical components to consider for other rugged considerations, such as the temperature range it can operate in or the shock and vibration specifications it can withstand during operation.
Hardware Built for Ruggedness
There are several ways to design and build your system to withstand the external factors affecting for applications in rugged and demanding environments. A few of the items to investigate include temperature range in the environment, shock and vibration specifications that your hardware needs to withstand, any environmental certifications required, and the type of form factor and features needed for the overall system. When building a system to endure these factors, you can save time and frustration by using hardware that is already built for ruggedness instead of performing tests to make sure the system complies with the environmental certifications, or that it operates properly inside the enclosure built for the hardware.
This article was written by Tommy Glicker, Product Marketing Manager – DAQ & Embedded, for National Instruments, Austin, TX. For more information, Click Here.