Mechanical Movement Indicators Remote Indicating Fuel and Oil Pressure Gauges 10-29 Figure 10-51.  Remote pressure sensing indicators change linear motion to rotary motion in the sensing mechanism part of the synchro  transmitter.  D C B A D C A B Indicator pointer Diaphragm Vent Rotor Rotor Stator Stator Pressure connector AC power Open to atmosphere To engine oil pump Oil pressure indicator (instrument panel) Oil pressure transmitter (engine) Often on twin-engine aircraft, synchro mechanisms for each  engine can be used to drive separate pointers on the same  indicator. By placing the coils one behind the other, the  pointer shaft from the rear indicator motor can be sent through  the hollow shaft of the forward indicator motor. Thus, each  There are many instruments on an aircraft that indicate the  mechanical motion of a component, or even the aircraft itself.  Some utilize the synchro remote-sensing and indicating  systems described above. Other means for capturing and  displaying mechanical movement information are also used.  This section discusses some unique mechanical motion  indicators and groups instruments by function. All give  valuable feedback to the pilot on the condition of the aircraft  in flight.  By locating the transmitter of a synchro system remotely,  fluid pressure can be directed into it without a long tubing run.  Inside the transmitter, the motion of a pressure bellows can be  geared to the transmitter rotor in such a way as to make the  rotor turn.  [Figure 10-51]  As in all synchros, the transmitter  rotor turns proportional to the pressure sensed, which varies  the voltages set up in the resistor windings of the synchro  stator. These voltages are transmitted to the indicator coils  that develop the magnetic field that positions the pointer. Fuel and oil pressure indications can be conveniently obtained  through the use of synchro systems. As stated previously,  running fuel and oil lines into the cabin to direct reading  gauges is not desirable. Increased risk of fire in the cabin and  the additional weight of the lines are two primary deterrents.  Aircraft with digital instrumentation make use of pressure-  sensitive solid-state sensors that output digital signals  for collection and processing by dedicated engine and  airframe computers. Others may retain their analog sensors  but may forward this information through an analog to  digital converter unit from which the appropriate computer  can obtain digital information to process and illuminate  the digital display. Many more instruments utilize the  synchro remote-indicating systems described in this  section or similar synchros. Sometimes simple, more  suitable, or less expensive technologies are also employed. pointer responds with the magnet’s alignment in its own  motor’s magnetic field while sharing the same gauge housing.  Labeling the pointer’s engine 1 or 2 removes any doubt about  which indicator pointer is being observed. A similar principle  is employed in an indicator that has side-by-side indications  for different parameters, such as oil pressure and fuel pressure  in the same indicator housing. Each parameter has its own  synchro motor for positioning its pointer. rotor magnetic field flux is allowed to flow. The important  characteristic of all synchro systems is maintained by both  the autosyn and magnasyn systems. That is, the position of  the transmitter rotor is mirrored by the rotor in the indicator.  These systems are used in many of the same applications  as the DC systems and more. Since they are usually part of  instrumentation for high performance aircraft, adaptations of  autosyn and magnasyn synchro systems are frequently used  in directional indicators and in autopilot systems. 