A new enhanced Howland voltage controlled current source circuit for EIT applications

A current source is one of the most important circuits in Electrical Impedance Tomography (EIT) hardware systems for measuring conductive multiphase flows. One of its important and challenging features is to deliver a relatively large and constant current for a wide range of resistive loads, high signal to noise ratio, and a large bandwidth. This paper presents a new voltage controlled current source for EIT applications. It is based on Howland circuit and uses two similar current sources circuits operating in parallel. Furthermore, the paper suggests a General Inverter Circuit (GIC) to remove the effect of eventual stray capacitances which usually appear across the load. Experimental results using Multisim software indicates that the new suggested circuit presents a more stable impedance output over a range of 100 to 3000 Ω. Furthermore, it was found that the current remains stable for range of 100 to 6000 Ω.