Technical Innovations
Sonic level control via Thermo Ramsey
 The Grad-Line SonaMat IV from Thermo Ramsey uses sound waves to detect the material level in front of the screed on asphalt pavers. |
Thermo Ramsey's (Booth C-5665) new Grad-Line SonaMat IV Sonic Level Control for asphalt pavers uses sound waves to detect the material level in front of the screed, enabling the machine to achieve a consistent material level. The control knob on the sensor allows for adjustment of the head of material to the desired level. The knob also allows the sensing range to be adjusted from 203 to 914 mm (8 to 36 in), with an LED readout indicating proper range and operation.
Because the sensor is typically mounted on the end gate, proper level is maintained automatically when the screed is extended or retracted. According to the company, the unit can be mounted on almost any paver within minutes and is completely protected from the environment. The sealed ceramic transducer allows for wash down of the machine without the possibility of harming the sensor, which will not get damaged by moisture and can be cleaned with solvent or diesel fuel.
The system features improved electronics that perform better in smoke, haze, and humidity. The control can be programmed for either on/off (NPN or PNP) or proportional valves. Dead band and frequency response are also programmable at the factory, or with an optional software package. Introduced into the market last month, the SonaMat IV, with an operating temperature from -12 to +66°C (10 to 150°F), is a direct replacement for the SonaMat II.
- Linda Trego
CPI's position sensor for hydraulic cylinders
 The installation of CPI's SL200 linear displacement transducer requires the addition of a standard #8 SAE o-ring port and two 6.4-mm (0.25-in) boltholes; the hydraulic cylinder is otherwise unchanged.  |
Control Products Inc. (CPI) (Booth S-16118) was founded in 1946 as a wholly owned subsidiary of the privately held Calculagraph Co., which was established in 1871 as a manufacturer of precision clock assemblies. CPI's first sales were to the U.S. government for military equipment, and applications have expanded into a wide variety of industrial machinery. Manufacturers of heavy equipment currently represent an important market for CPI's electromechanical products, which include waterproof limit switches, pendants, pushbutton switches, and thermal switches.
Five years ago, during talks with key engineering managers of the leading OEMs, CPI recognized that control needs for applications in which constant position feedback was required were by necessity going to become significantly more sophisticated. While all of the elements for advanced control existed, the transducers that were available had a number of drawbacks, making them impractical for the increasing technological demands of heavy-duty equipment. Acknowledging this void, CPI went to work designing a hydraulic sensor that would be robust to shock, vibration, EMI, temperature and pressure extremes, and submersion, while simultaneously being able to fit completely inside the hydraulic cylinder.
CPI has since introduced a linear displacement transducer, the SL200, that mounts into "virtually any type" of hydraulic cylinder. The entire unit is about the size of a large proximity sensor and installs within 90 s. One of the key design requirements was that the sensor use noncontacting sensor technology. A linear variable differential transducer (LVDT) was chosen as its core transduction means because of the LVDT's accurate and robust reputation within the industry. The SL Series sensor acts as a mechanism to couple the relatively long translation of a hydraulic cylinder to the relatively short translation of the LVDT.
 An SL200 configured for stroke lengths to 1219 mm (48 in). |
According to Mac Stuhler, Vice President, CPI, the SL200 is "breakthrough technology for manufacturers incorporating advanced control in their equipment" because it allows functions such as motion profiling, auto leveling, and robotic-type operations such as envelope/teach functions that enable machines to be programmed for improved safety and increased productivity with reduced operator skill requirements.
The standard output is 0 to 5 V dc provided by a vehicle-hardened signal-conditioning board.
- Jean L. Broge
