A simple diaphragm type transducer for small differences in gas pressures is described together with a suitable electronic arrangement for using it as a control element. The sensitivity of the arrangement is limited by ambient temperature effects on the diaphragm. A zero stability of about 0.1 &mgr; Hg has been achieved and this could probably be improved on by sufficiently good thermostating. An important feature of the diaphragm is that it may be subjected to large unbalanced pressures without damage, although such pressures will produce zero shifts equivalent to a few microns of mercury.