Electron-beam volt age-indicator tube EM84

This improved magic-eye tuning indicator comprises a cylindrical tube viewed normal to the axis and illuminates a band width at the curved surface proportional to applied voltage. The normal zinc silicate target-phosphor is replaced by zinc oxide with colour filter and colour change is arranged along the scale. Shadow length changes of 30 mm for 200 V change, un-amplified, and of 20 mm for 20 V change, pre-amplified, are obtained with excitation voltage range of 200-250 V. The scaled indicator shown has an accuracy of 5-15% and freedom from inertia and vibration.