New system of recording using electronic means

AN ELECTRONIC recorder has been developed which will record d-c millivolts and microamperes at energy levels of 4 or 5 microwatts, and, with auxiliary equipment, will record feeble alternating currents and voltages. A pilot element attached to the measuring element of any usual type indicating instrument mechanism is connected in series with a second pilot element at the pen mechanism. A motor element for driving the recording element and carrying the second pilot element coil is driven by an amplifier which receives its indication from the difference in angular position of the 2 pilot elements. The stationary fields of both pilot elements are connected in parallel to the same a-c source.