Mid-Continent Instruments and Avionics
Revision D, March 21, 2016
Manual Number 9018205
11
3.5 INSTALLATION
The MD93 is rear mounted using a standard 2 ¼” panel cutout. Prepare the panel cutout as shown in
Figure 3 below. Prior to installing the unit, the display dimming should be adjusted according to section
3.5.1, Dimming Functions. Mount the MD93 with #6-32 flat head screws (provided with installation kit).
NOTE:
The maximum screw length used to mount the unit is 9/32” (0.280”) + panel thickness.
*** WARNING ***
Using screws longer than the recommended maximum length may damage the MD93 unit!
Figure 3
Rear Panel Mount Installation
3.5.1 Dimming
Functions
The MD93 will accept a power input from the aircraft bus between 10 to 32 volts on pin 1. The unit
brightness can be manually controlled by supplying a lighting input voltage on pin 3. The lighting input
voltage will be compared to the power input and will control the lighting when it is between 10-100% of
the power input. A voltage equal to the aircraft bus voltage (100%) corresponds to maximum brightness.
If the lighting voltage is less than 10% of the power input voltage, dimming will be automatically controlled
by the ambient light sensed by the photocell built into the unit.
To adjust the brightness range of the clock for optimal daytime and night-time viewing, as well as balance
amongst other panel instruments, use the two adjustments on the rear of the unit as shown in Figure 2.
Set the input voltage/lighting bus to maximum and turn the “Aircraft dim adjust” screw to raise or lower the
brightness. Next, turn the input voltage/lighting bus off in dark conditions and turn the “Photocell dim
adjust” screw to raise or lower the brightness.
NOTE:
the adjustment screw has a single 360° range of rotation. Exceeding its limits past the stops will
damage the unit.
The brightness of the unit can be automatically controlled based on ambient light conditions using
the internal photocell at all times simply by not installing the lighting input voltage on pin 3. To
adjust the desired brightness range, follow the “Photocell dim adjust” method in the previous
paragraph in dark conditions.
