Sometimes, engineers must make measurements of stress, strain, load, torque, temperature and other physical characteristics on rotating equipment. I’ve seen slip-ring assemblies that provide power to rotating measurement equipment and pick off measurement signals. But, these types of commutators can take a lot of space and and require permanent installation. They have high prices, too.
As an alternate, companies provide wireless transfer of power and signals to and from rotating devices. A recent introduction caught my attention: The Series 8179 Universal Single Channel Telemetry Systems from PCB Load & Torque. A small wireless module attaches to a rotating component and broadcasts information from one channel to a stationary receiver. The rotating transmitter can use a small battery also attached to the rotating device, or the transmitter can pick up power from an inductive loop on the receiver. The small transmitter does not affect the operation of the rotating device and doesn’t take much space, so it will fit into small spaces in mechatronic equipment. The transmitter’s antenna wraps around a shaft, for example, so it will broadcast to the nearby receiver in any shaft position.
The receiver unit provides inductive power to the rotating electronics that in turn supplies a regulated 5V-DC excitation signal to the strain gages. The small rotating-electronics package takes the stain-gage signal, converts it to a frequency and uses it to modulate an RF signal. The receiver demodulates the RF signal and converts the strain-gauge information back to a frequency and then to a voltage between -10 and +10 volts to represent the strain gauge’s full-scale range.
PCB Load & Torque sells three receivers and three transmitters and buyers can specify either a strain-gauge or a thermocouple version of the transmitters. The smallest transmitter weigh 7 grams and measures 31 x 17 x 7 mm. Find a data sheet for the PCB Series 8179 Single Channel Telemetry Systems at: www.pcb.com/Linked_Documents/Force-Torque/LT_Series8179_Lowres.pdf. The company also sells two instruments that the receivers can connect to: the table-top 8179-CUT0 and the rack-mount 8179-CUR0. (That’s a zero at the end of the product number.)
If you work with drive trains, robotic systems, motors, and similar equipment, this type of measurement device can be a life saver. –Jon Titus
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