Product Announcement from Meggitt Sensing Systems - Wilcoxon Research
Meggitt offers a wide selection of cables and cable assemblies for vibration monitoring applications in its Wilcoxon Research industrial product line.
In addition to sensor construction and connector choices, the type of cable and cable material must be carefully chosen to ensure proper operation. The two types of cables most commonly used to connect an accelerometer to acquisition equipment are coaxial and shielded multi-conductor.
- For most sensors, the multi-conductor cable of choice will be a shielded, twisted pair. This type of cable has two conductors - one power/signal and one common - twisted together to provide differential cancellation that reduces electromagnetic interference. Surrounding the twisted pair is a foil or braided shield. Proper termination of the shield will protect the conductors from airborne radio frequency interference. Multiconductor cable is easy to terminate in the field and offers inherent immunity to environmental noise.
- Coaxial cables carry the power and signal on an inner conductor and have a shield or outer conductor which acts as the signal common. Because coaxial cable works well with BNC and Microdot connectors, it is generally used with sensors in a walk-around mode or to connect electronic instrument components together.
Besides the type of cable, coaxial or multi-conductor, the most important decision for cable selection is jacket material. The intended environment will dictate requirements such as temperature, chemicals, radiation, and moisture. Generally Teflon® provides the best temperature and abrasion resistance, although it has a moderate radiation rating. In addition, Teflon® generally cannot be used near certain applications, such as tobacco plants. Polyvinylchloride (PVC) provides fair abrasion and chemical resistance, but PVC manufacturers do not recommend its use above 221ºF (105ºC).
Meggitt's Enviroprene® jacket material is designed to provide excellent performance at a lower price than Teflon®. With the exception of very hot (>250ºF) and abrasive environments, Enviroprene® is generally recommended. For long cable runs, the capacitance and resistance of the cable will begin to act as a low-pass filter and cut-off higher frequency data. More supply current will help overcome the resistance and push this to a higher frequency.