Injection Molding: Pressure Transducer Enables Accurate Measurements at Low Pressures and High Temperatures

Nominal Controls Inc. says its TrueMelt pressure transducers avoid the thermal-zero-shift errors that prevent traditional melt pressure transducers from measuring melt pressure in processes like low-pressure molding or extrusion. The company told Plastics Technology that the TrueMelt sensor can measure continuous low pressures at operating temperatures up to 600 C.

Thermal zero shift or drift refers to the false pressure output of a sensor due to temperature increase. Nominal Controls said a typical drift value for a melt pressure sensor can be more than 50 psi/100 F. In applications such as thermoplastic composites that can be manufactured at pressures below 500 psi, zero drift can cause a pressure reading error of 10 percent or more, with potentially significantly impacts on product quality and consistency. TrueMelt transducers reportedly have a rated zero shift error of less than 5 psi/100 F.

An electrical sensor with either 4-20mA, 3.33mV/V or 0-10V DC output, Nominal Controls says its TrueMelt pressure transducers are the only thermally compensated pressure sensors with mV/V signal output. The company says TrueMelt’s are being used to upgrade traditional sensors without thermal compensation technology, as well as other technologies that have a higher cost.