Posted to News on 11th Oct 2011, 15:57
Miniature pressure transmitter suits machine pneumatics
Festo is launching the SPTE pressure transmitter, a compact and versatile module for closed-loop control and monitoring of pneumatically-operated automation components. Capable of sensing both pressure and vacuum, the new SPTE pressure transmitter is said to be easy to use. Typical applications include vacuum detection in pick-and-place machines, such as those used in semiconductor chip testing, and surface-mount component placement machines for PCB assembly.
Designed primarily for cost-sensitive, high-volume applications, the SPTE is the smallest pressure transmitter in Festo's product range. It has a grid size of just 10mm, facilitating extremely tight packing densities in crowded control racks, and a very low weight that makes it suitable for mounting on moving machinery. The transmitter's extremely small physical dimensions also mean that it has minimal internal volume, enabling it to react quickly to changes in pressure and provide a fast response.
The SPTE uses a piezo-resistive pressure cell that is capable of measuring vacuum over the range 0 to -1 bar and pressure over the range 0 to 10 bar. The pressure transmitter is available with a choice of 0-10V or 1-5V analogue outputs, enabling users to employ the control scheme of their choice without the need for conversion circuits; the signal can be fed direct to a PLC or other form of control system, thereby helping to minimise installation costs.
Choice of mountings
A benefit of Festo's SPTE pressure transmitter that is claimed to be unique is that it offers users considerable flexibility in mounting, with a choice of three configurations featuring different pneumatic connection schemes.
One configuration, available in 4mm and 6mm sizes, enables the transmitter to be plugged directly into pneumatic socket-type connectors. Another provides push-in fittings for standard pneumatic tubing and is available in 3mm and 4mm sizes. This form of transmitter module can also be used in conjunction with single and eight-way mounting brackets, which use a simple clip-type retainer to facilitate fast assembly and disassembly without the need for tools. The third type of configuration uses a highly cost-effective flange-mounting arrangement, which requires no additional hardware. The module is secured direct to the body of the pneumatic component that it is monitoring - such as a cylinder or valve - and uses an O-ring seal. By dispensing with the need for pneumatic tubes, this approach provides the shortest path between the component and transmitter, thereby minimising evacuation time and resulting in the fastest possible signal generation.
High-throughput pick-and-place machines often use an array of tightly packed vacuum gripper nozzles of various sizes, depending on the parts to be moved. Each nozzle may require a different vacuum level, the presence or absence of which indicates whether or not a part has been successfully picked. Due to limited space, it is often impractical to use sensors with built-in teach functions to determine the performance of each nozzle at its point of use. By using SPTE pressure transmitters to monitor the vacuum levels, the various thresholds can be defined on the control unit.
Accuracy and signal conversion
Festo's SPTE pressure transmitters are supplied complete with a 2.5m cable for electrical connection. Designed for operation with filtered compressed air, the transmitters have a full-scale accuracy of 3 per cent, and accommodate media and ambient operating temperatures over the range 0-50degC.
If required, the SPTE pressure transmitter can be combined with a Festo SVE4 signal converter to produce two digital output signals for applications where an analogue input is not available or cost-effective within the control unit. This arrangement can be used, for example, to monitor upper and lower operating limits.
The Festo SPTE pressure transmitter is a direct result of Festo's on-going research into all-electronic, contactless sensors; in recognition of the advances that the company is making in this area, the product received an honourable mention in the Red Dot Design Awards for 2011. Follow the link for more information about the range of pressure transmitters from Festo.
