The duct 165 of the device 160 includes, for example, two (or other numbers of) electrically conducting electrodes 161A and 161B which are parallel to each other and are sealingly attached between a first duct wall 162A and a second duct wall 162B. The first duct wall 162A and the second duct wall 162B may be parallel to each other and may be made from an electrically isolating material, such as b