Beside temperature control, industrial kilns often require also pressure control, for example to prevent possible damages of material during firing cycles for ceramics. Differential pressure sensor  model 694 with scale limits +/- 5mm water column is particularly useful for these applications, but a proper installation is necessary to assure optimal operating and accuracy.  An expansion tank is recommended to dampen quick oscillations of pressure (which could damage internal membrane) and to avoid condensate inside connecting pipes.  The attached diagram gives details for correct installation.