Articles | Volume 6, issue 1
Regular research article
10 May 2017
Regular research article |  | 10 May 2017

Development of a chopper charge amplifier for measuring the cavity pressure inside injection moulding tools and signal optimisation with a Kalman filter

Manuel Schneider, Alexander Jahn, Norbert Greifzu, and Norbert Fränzel

Abstract. This article provides insight into the development of a powerful and low-cost chopper amplifier for piezoelectric pressure sensors and shows its possible applications for injection moulding machines. With a power supply of 3.3 volts and the use of standard components, a circuit is introduced which can be connected to a commercially available microcontroller without any additional effort. This amplifier is specialised for low frequencies and high-pressure environments. With the adjustment of the sample and chopper frequency by means of software, the amplifier can easily be adapted for other applications. This chopper amplifier is a very compact and cost-effective solution with a small number of required components. In this contribution, it will be shown that the amplifier has good results in various laboratory tests as well as in the production process. Furthermore, an approach to fuse data from force and pressure signals by using a Kalman filter will be presented. With this method, the quality of the sensor signals can be significantly improved. This article is an extension of our previous work in Schneider et al. (2016b).

Short summary
This article describes a chopper amplifier which has been specially developed for piezoelectric pressure sensors. It is shown that the amplifier provides good results for pressure measurement in injection moulds. A special feature of this work is the signal optimisation through the use of a Kalman filter.