Midcontinent CH93 Series Technical Document

ManualNumber

9018205
RevisionF
April1,2021

Manual Number 9018205 Revision F, April 1, 2021 1
FOREWORD
This manual provides information intended for use by persons who, in accordance with current
regulatory requirements, are qualified to install this equipment. If further information is required,
please contact:
Mid-Continent Instruments and Avionics
Attn: Customer Service Dept.
9400 E. 34th Street N.
Wichita, KS 67226 USA
PH [phone]
FX [phone]
www.mcico.com
We welcome your comments concerning this manual. Although every effort has been made to
keep it free of errors, some may occur. When reporting a specific problem, please describe it
briefly and include the manual part number, the paragraph/figure/table reference and the page
number. Send your comments to:
Mid-Continent Instruments and Avionics
Attn: Technical Publications
9400 E. 34th Street N.
Wichita, KS 67226 USA
PH [phone]
FX [phone]
[email protected]
All products produced by Mid-Continent Instrument Co., Inc., including those identified as
Mid-Continent Instruments and Avionics or True Blue Power, are designed and manufactured
in Wichita, KS, USA.
© Copyright 2018
Mid-Continent Instrument Co., Inc.
Download the current
version of this installation
manual using your
smartphone or tablet.

Manual Number 9018205 Revision F, April 1, 2021 2
TABLE OF CONTENTS
SECTION 1GENERAL DESCRIPTION ........................................................................................ 4
1.1INTRODUCTION ...................................................................................................................... 4
1.2PHYSICAL ATTRIBUTES ........................................................................................................ 4
1.3MODEL AND PART NUMBER IDENTIFICATION .................................................................... 6
1.4TECHNICAL SPECIFICATIONS .............................................................................................. 6
SECTION 2PRE-INSTALLATION CONSIDERATIONS ............................................................... 8
2.1COOLING ................................................................................................................................. 8
2.2EQUIPMENT LOCATION ......................................................................................................... 8
2.3ROUTING OF CABLES ............................................................................................................ 8
2.4LIMITATIONS ........................................................................................................................... 8
2.5MODIFICATION ....................................................................................................................... 9
SECTION 3INSTALLATION ....................................................................................................... 10
3.1GENERAL .............................................................................................................................. 10
3.2PRE-INSTALLATION INSPECTION ...................................................................................... 10
3.3PARTS ................................................................................................................................... 10
3.4CABLE HARNESS ................................................................................................................. 11
3.5INSTALLATION ...................................................................................................................... 13
SECTION 4OPERATION ............................................................................................................ 14
4.1UNIT ARCHITECTURE .......................................................................................................... 14
4.2CLOCK AND USB PROTECTIVE FEATURES ....................................................................... 14
4.3USB OPERATION .................................................................................................................. 15
4.4DIMMING FUNCTIONS .......................................................................................................... 15
4.5OPERATIONAL MODES ........................................................................................................ 17
4.6TEMPERATURE PROBE INSTALLATION ............................................................................ 28
SECTION 5CONFORMANCE ..................................................................................................... 30
5.1INSTRUCTIONS FOR CONTINUED AIRWORTHINESS ....................................................... 30
5.2ENVIRONMENTAL QUALIFICATION STATEMENT ............................................................. 31

Manual Number 9018205 Revision F, April 1, 2021 3
REVISION HISTORY
Rev Date Detail Approved
A 07/15/2014 Initial release. BAW
B 09/15/2014 Revised EQF, added DO-311A Compliance Qualification
Form and provided additional limitation details (sec 2.5) WVC
C 03/12/2015 Added Environmental Qualification Statement to Section 6. TV
D 03/21/2016 Added Qualifications to Section 1.3. WVC
E 10/30/2018
Updates for MOD 1 function enhancements. Revised
elapsed timer to include countdown timer function. Timer
reset function operates only when timer is stopped.
WVC
F 04/01/2021
Updated style and brand to meet Marketing and
Engineering guidelines. Added -0, -3, -4 and -5 units and
temperature probe information.
Removed reference to -1 version.
DLR

Manual Number 9018205 Revision F, April 1, 2021 4
SECTION 1 GENERAL DESCRIPTION
1.1 INTRODUCTION
The CH93 series, part numbers 6420093-( ), is a multi-function digital clock / chronometer /
voltmeter / temperature unit with multiple options for USB Charging Ports. The unit fits into a
standard, rear-mounted, 2-¼” avionics panel cutout. Power is drawn from the aircraft main bus to
light a white, six digit, seven segment LED clock. The clock can display several different modes:
local time, universal time, flight timers, elapsed and countdown timers and optionally, bus voltage
and up to two temperature inputs. The CH93 display is daylight readable with two methods of
brightness control. It can be controlled automatically using the internal photocell or manually with
an external dimming bus voltage. The CH93 clock has an internal battery to maintain clock time
and flight timer memory when the aircraft is not in use.
The USB Charging Ports are designed as DCPs (Dedicated Charging Ports) to industry-standard
protocol per the USB Battery Charging 1.2 Compliance Plan. Some models also comply with the
higher power requirements of USB Power Delivery 2.0 and 3.0. Early-generation or smaller
consumer electronics typically accept one (1.0) amp during charging. However, newer electronics,
such as tablets and larger devices can accept, and in some cases, require up to 3 amps to charge
and operate. Unlike most dual USB chargers which provide one (1.0) amp on one port and 2.1
amps on the second port, the CH93 provides 3 amps per port. The Type A High Power (HP) USB
ports provide a 5 volt output at 3 amps and the Type C Max Power USB-PD port provides 3 amps
at 5, 9, 15, or 20 volts depending on the type and needs of the device. This provides enough
power to charge any USB device, including the higher demand products. Refer to Section 1.4 for
specific details on charging port configurations for each model. With features like short circuit
protection, over-current protection, low voltage shut-down and temperature monitoring, it handles
abnormal conditions safely.
1.2 PHYSICAL ATTRIBUTES
The CH93 is a single, integrated component contained in a metal enclosure, fitting into a standard
2 ¼” avionics instrument panel cutout. Two types of units are available within the series. Type 1
units have a 4-pin input connector on the rear of the unit for power, external dimming control and
flight timer operation. Type 2 units have a 9-pin D-shell connector that add connections for
temperature probe inputs and a countdown timer external alarm signal. The series includes
versions with and without USB charging ports, located on the front of the unit below the display,
and three control buttons for user interface: Mode, + (plus), and – (minus). The modes are
annunciated with backlit indicators for UTC, Flight, Timer, Volts, and OAT.
Refer to Figures 1.1 and 1.2 for unit dimensions.

Manual Number 9018205 Revision F, April 1, 2021 5
4X 6-32 UNC
1.86
2.39
1.86
2.39
Ø2.25 MAX
0.12
1.15
Photocell
dim adjust
Aircraft
dim adjust
Pin 1
6 digit display
window
Push button
operation (3x)
Dual USB
Charging Ports
Figure 1.1
CH93 Type 1 Drawing (-2 Unit)
1.86
2.39
1.86
2.39
4X 6-32 UNC 6420093-0 6420093-3
6420093-5
1.22
Ø2.25 MAX
Replaceable
Coin Cell (BR2032) Cover
Pin 1
6420093-4
Figure 1.2
CH93 Type 2 Drawing (-0, -3, -4 and -5 Units)

Manual Number 9018205 Revision F, April 1, 2021 6
1.3 MODEL AND PART NUMBER IDENTIFICATION
Chronos Models and Type
Part Number:
6420093-0
6420093-2
6420093-3
6420093-4
6420093-5
Model:
CH93
CH93HP
CH93HP
CH93HP
CH93MAX
Type:
Type 2
Type 1
Type 2
Type 2
Type 2
USB Charging Ports:
None
Dual Type A
Single Type A
Dual Type A
Type A / Type C
Table 1.1
Feature Summary
Feature UTC
Time
Local
Time
Flight
Timers
Elapsed
Timers
Alert
Output
Volts OAT Replaceable
Battery
Type 1 Y Y Y Y N N N N
Type 2 Y Y Y Y Y Y Y Y
Table 1.2
1.4 TECHNICAL SPECIFICATIONS
Electrical Attributes
Input Voltage:
-0,-2,-3,-4:
-5:
10 – 32 VDC
22 – 32 VDC
Input Power:
-0
-2
-3
-4
-5
5 watts max; 0.3 amps @ 14 VDC / 0.15 amps @ 28 VDC
36 watts max; 2.6 amps @ 14 VDC / 1.3 amps @ 28 VDC
21 watts max; 1.5 amps @ 14 VDC / 0.75 amps @ 28 VDC
36 watts max; 2.6 amps @ 14 VDC / 1.3 amps @ 28 VDC
84 watts max; 3.0 amps @ 28 VDC
USB Output Voltage: Type A: 5 VDC ± 0.25 VDC per port
Type C: 5, 9, 15, or 20 VDC ±0.25 VDC per port
(auto-adjustable)
USB Output Power: 3.0 amps max per USB port
(15 watts Type A; 60 watts Type C)
Efficiency: ≈ 90% nominal
Clock Accuracy: ±15 seconds per month
Compatible Temp Probes:
RTD:
Current Sense:
500 Ω Resistor
AD590 Temperature Transducer
Alarm output (Type 2 only): Open drain ground limited to 100mA, max 32 VDC
Table 1.3

Manual Number 9018205 Revision F, April 1, 2021 7
Physical Attributes
Weight: 5.0 ounces (142 g)
Dimensions
(not including connector)
Type 1
Type 2
2.39 inches wide x 2.39 inches high x 1.15 inches deep
(61 mm wide x 61 mm high x 29 mm deep)
2.39 inches wide x 2.39 inches high x 1.22 inches deep
(61 mm wide x 61 mm high x 31 mm deep)
Charging Ports Type
-0:
-2,-3,-4:
-5:
Not Applicable
Type A USB
Type A USB; Type C USB
Clock Digits: 0.360” H x 0.138” W
Connector Kit
Type 1
Type 2
MCIA P/N 9018178
MCIA P/N 9018178-1
Mounting: Rear Panel Mount
Table 1.4
Internal Battery Attributes
Type: Primary (non-rechargeable) coin cell;
poly-carbonmonofluroride lithium
Model:
Type 1
Type 2
BR2330 (factory replaceable only)
BR2032 (field replaceable)
Output Voltage: 3 VDC
Capacity / Energy:
Type 1
Type 2
0.255 Ah / 0.765Wh
0.190 Ah / 0.570Wh
Certification: UL 1642 (see section 2.4)
Table 1.5
Qualifications
Certification FAA TSO-C71
EASA ETSO-C71
Environmental Qualification RTCA/DO-160G (See Section 5.2)
Table 1.6

Manual Number 9018205 Revision F, April 1, 2021 8
SECTION 2 PRE-INSTALLATION CONSIDERATIONS
2.1 COOLING
The CH93 will become warm when in use; however no external cooling is required. This is normal
and within operational parameters. No special mounting considerations are required, although
mounting to a metal surface can help dissipate any heat generated and extend the life of the
product.
2.2 EQUIPMENT LOCATION
The CH93 Digital Clock / USB Charging Port is designed for a circular rear panel mount
configuration, allowing for installation in a cockpit or cabin. Clearance should be provided for the
input mating connector which may require an additional inch of clearance beyond the rear of the
unit.
2.3 ROUTING OF CABLES
Avoid sharp bends in cabling and routing near aircraft control cables. Avoid close proximity and
contact with aircraft structures, avionics equipment or other obstructions that could chafe wires
during flight and cause undesirable effects.
2.4 LIMITATIONS
Environmental qualifications were verified per RTCA DO-160, Revision G in lieu of those identified
within the minimum performance standards (MPS) of the TSO.
The conditions and tests for TSO approval of this article are minimum performance standards.
Those installing this article, on or in a specific type or class of aircraft, must determine that the
aircraft installation conditions are within the TSO standards, specification of the article and
deviations as listed above. TSO articles must have separate approval for installation in an aircraft.
The article may be installed only according to 14 CFR part 43 or the applicable airworthiness
requirements.
Note: Per 8300.16 job aid applicable to airplanes certified under Title 14 of the Code of Federal
Regulations part 25 (Section H. Alterations or Repairs, Element H.7). (Approval is required for)
Changes to designs involving lithium batteries or battery systems except for the following cases:
1. Very small batteries or battery systems (e.g., button/coin cells) not required for safe
operation of the airplane that have less than 2 watt-hours of energy and meet UL
1642,UL 2054 or International Electrotechnical Commission(IEC) 62133.
The battery in the CH93 is non-rechargeable and considered “very small”. It is less than two Watt-
hours and is certified to UL 1642. No STC or coordination with the ACO is required.

Manual Number 9018205 Revision F, April 1, 2021 9
2.5 MODIFICATION
This product has a nameplate that identifies the manufacturer, part number, description,
certification(s) and technical specifications of the unit. It also includes the “MOD” or modification
number representing notable changes in the hardware design of the unit.
Modification (MOD) 0 is the initial release of the product and is identified on the nameplate by the
lack of marking on the MOD numbers 1 through 9 (i.e. 1-9 are visible). All subsequent
modifications are identified on the nameplate by the marking/blacking out of that particular MOD
number (i.e. for MOD 1, the number 1 is not visible and 2-9 are visible - see Figure 2.1 for
examples). MODs do not have to be sequentially inclusive and may be applied independent of
each other.
For additional details regarding specific changes associated with each MOD status refer to the
product published Service Bulletins at www.mcico.com.
Figure 2.1
Nameplate and MOD Status Example
M
O
M
O
MOD 1
& MOD 2

Manual Number 9018205 Revision F, April 1, 2021 10
SECTION 3 INSTALLATION
3.1 GENERAL
This section contains interconnect diagrams, mounting dimensions and other information
pertaining to the installation of the CH93 Digital Clock / Dual USB Charging Port. After installation
of cabling and before installation of the equipment, ensure that power and ground are applied to
the proper pins specified in Section 3.4.2, Pin Assignment Information.
3.2 PRE-INSTALLATION INSPECTION
When unpacking this equipment, make a visual inspection for evidence of any damage that may
have occurred during shipment.
3.3 PARTS
Included Parts
A. Digital Clock (with USB Charging Port(s)) MCIA P/N 6420093-( )
B. Installation and Operation manual MCIA P/N 9018205
C. Installation Kit (for Type 1) MCIA P/N 9018178
 Mating Connector, 4-Pin
 Pins (6) (4 required, 2 spares)
 Screws (5), #6-32 x 3/8” Flat Head (4 required, 1 spare)
D. Installation Kit (for Type 2) MCIA P/N 9018178-1
 Mating D-Sub Connector, 9-Pin
 Screws (5), #6-32 x 3/8” Flat Head (4 required, 1 spare)
Available Parts
A. 500 Ω Outside Air Temperature Probe MCIA P/N B-10-1
B. 500 Ω Cockpit/Cabin Temperature Probe MCIA P/N B-11-1
C. Current Sense Cockpit/Cabin Temperature Probe MCIA P/N B-11-2
Installer Supplied Parts
A. Cable Harness Wire, See Section 3.4.1 for specifications
B. Circuit Breaker Recommendations:
 -0,-2,-3,-4 units: 3 amps (1.5 amp may be sufficient for 28V aircraft - as
needed per system requirements)
 -5 units: 5 amps for 28V aircraft
C. Davtron C307PS or 655 current sense probes (if applicable).

Manual Number 9018205 Revision F, April 1, 2021 11
3.4 CABLE HARNESS
Construct the cable harness following the instructions outlined below and per Tables 3.1, 3.2 (Type
1 units) and 3.3 (Type 2 units). Refer to Section 2: Pre-Installation Considerations for routing
precautions.
Wire Gauge Selection
Use of PTFE, ETFE, TFE, Teflon or Tefzel insulated wire is recommended for aircraft use.
The wire harness should utilize 20-24 AWG stranded wire. Refer to Table 3.1 below for
suggested minimum wire size.
Wire Gauge Wire Length
20 AWG stranded wire >35 ft.
22 AWG stranded wire >14 ft.
24 AWG stranded wire <14 ft.
Table 3.1
Wire Gauge and Length
Note: For Type 1 units (-2) pins should be crimped using Molex Hand Crimp Tool 63819-
0000 (preferred), 63811-2800 (obsolete) or 11-01-0200 (obsolete). See the Molex Hand
Crimp Tool User Manual for crimp procedures. For Type 2 units (-0,-3,-4,-5) pins should be
crimped using Positronic Hand Crimp Tool 9507-0-0-0 (preferred), Daniels AFM8 (optional)
or Mil P/N M22520/2-01 (optional).
Pin Assignment Information
See Table 3.2 for pinout definition and Figure 3.1 for pin locations on Type 1 units. Refer to
Table 3.3 for pinout definition and Figure 3.2 for pin locations on Type 2 units.
Pin
Number
Signal
1 Aircraft Power
2 Ground
3 Aircraft Lighting Bus
4 Flight Timer Input
Table 3.2 Figure 3.1
Power Input Connector Pinout (Type 1) CH93 Rear View (Type 1)

Manual Number 9018205 Revision F, April 1, 2021 12
Pin
Number
Signal
1 Ground
2 Power Input (DC)
3 Flight Timer Input
4 RTD Temp A
5 Alarm Out
6 Current Temp Return
7 Current Temp Power
8 Aircraft Lighting Bus (DC)
9 RTD Temp B
Table 3.3 Figure 3.2
Power Input Connector Pinout (Type 2) CH93 Rear View (Type 2)
Harness Verification
Failure to install aircraft power and ground wires in the proper mating connector locations
could damage the unit.
Once the cable harness is prepared, prior to connecting the CH93, activate the aircraft power
bus and use a multimeter to verify that aircraft power and ground are supplied with
appropriate voltage on the proper pins within the mating harness.
The CH93 must not be installed with input terminals reversed as this could damage the unit.
Verify the correct polarity of any harness or equipment prior to connecting to the CH93.
W
ARNING
Replaceable
Coin Cell (BR2032) Cover
Pin 1

Manual Number 9018205 Revision F, April 1, 2021 13
3.5 INSTALLATION
The CH93 is rear mounted using a standard 2 ¼” panel cutout. Prepare the panel cutout as shown
in Figure 3.2 below. For Type 1 units, the display dimming should be adjusted according to Section
4.4 prior to installing the unit. Mount the CH93 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 on
Type 1 units. Type 2 units can accommodate a screw length up to 1” in length.
Using screws longer than the recommended maximum length may damage the CH93 unit!
Figure 3.2
Rear Panel Mount Installation
W
ARNING

Manual Number 9018205 Revision F, April 1, 2021 14
SECTION 4 OPERATION
4.1 UNIT ARCHITECTURE
The CH93 is comprised of two functional building blocks, a USB charger and digital clock. The DC
input voltage is regulated over its specified range using a DC-DC converter to power the USB
charger and all clock functions. A charging port controller manages power output for the USB
charging ports. An internal battery maintains clock functions (local time, universal time, flight timer)
when input power is removed for up to ten years. Type 1 units require factory serviced to be
replaced and Type 2 units have a field-replaceable battery. Refer to Section 5.1 for details.
The user interface is comprised of the display, three control buttons, and the mode annunciation.
The display has six, seven-segment, white LED digits that are 0.360” tall and 0.138” wide. The
three user interface buttons (MODE, – and +) are used to switch between modes of operation, set
clock time, and manage timer functions for the CH93. Backlit annunciations on the front bezel
indicate the current mode of operation with each mode visible only when active. When aircraft
power is removed, the display clock and all annunciations will be turned off.
4.2 CLOCK AND USB PROTECTIVE FEATURES
The following features are included in the design of the CH93 and protect both the unit and any
devices being charged from damage in the event of the fault conditions listed below.
Short Circuit Protection
The CH93 is capable of surviving a short circuit event without permanent damage. The unit
enters an over-current condition so that the average current is significantly reduced and the
device is protected. Removal of the short allows the unit to return to normal operation.
Over-Current Protection
The CH93 monitors current draw individually on each USB port. During an over-current
condition the voltage is reduced. If the voltage falls below 3.8 VDC the output is turned off for
a period of 12 seconds. The output is then checked for continued over-current conditions
every 16 milliseconds. This condition is referred to as a hiccup mode. The device stays in this
mode until the over-current condition is removed, then returns to normal operation.
Low Input Voltage Shutdown
If the input voltage applied to the CH93 drops below the specified minimum, the unit will shut
down until the applied voltage returns to a level within the operating range.
Over-Temperature
If the temperature of the CH93 exceeds designed thresholds due to a fault or excessive load,
the unit communicates with the USB portable device to reduce the charge current output to a
1.0 amp limit. This allows the charger to continue charging while the unit returns to a
temperature within designed limits. When temperature returns to an acceptable level the unit
automatically returns to normal operation.

Manual Number 9018205 Revision F, April 1, 2021 15
4.3 USB OPERATION
For units with USB Charging Ports, there are single and dual Type A versions available as well as
the CH93MAX dual Type A/Type C version.
The Type A USB Charging Ports convert the specified DC input voltage range to a 5 VDC output.
Type C USB-PD (Power Delivery) Charging Ports convert the specified DC input voltage range
specified to either 5, 9, 15, or 20 VDC. Both types employ intelligent control and use voltage
signals to negotiate the maximum power (voltage and current) that each individual Personal
Electronic Device (PED) allows. This provides for the fastest charging speeds possible for all
devices including phones, tablets, and laptops. The output voltage and power is applied to the
USB-A ports in per the USB Battery Charging 1.2 Compliance Plan and the USB-C/PD ports in
accordance with USB 3.1 and the USB Power Delivery standards, versions 2.0 and 3.0.
To ensure enhanced cybersecurity protocols, no data is transferred from the unit to the attached
device or from the device to the unit or aircraft systems. Only power and power negotiation signals
are exchanged between the CH93 and the device(s) being charged.
4.4 DIMMING FUNCTIONS
The brightness control on the CH93 can use fully automatic control or a combination of external
and automatic control. For fully automatic control, the internal photocell is used to adjust the
brightness from minimum to maximum brightness by sensing and responding to the current
ambient light conditions. For external control using a dimming bus adjustment, the brightness can
be manually controlled by supplying a lighting input voltage. The lighting input voltage will be
compared to the power input and will control the lighting when it is between 20-100% of the power
input. A voltage equal to the aircraft bus voltage (100%) corresponds to maximum brightness. If
the lighting voltage is less than 20% of the power input voltage (or off), dimming will be
automatically controlled by the ambient light sensed by the photocell built into the unit.
Display Dimming Adjustment (Type 1 units)
To adjust the brightness range of the clock on Type 1 units for optimal daytime and night-time
viewing, as well as balance amongst other panel instruments, use the two trimming
potentiometers (trim pot) adjustments on the rear of the unit as shown in Figure 3.1. 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 completely dark conditions
and turn the “Photocell Dim Adjust” screw to raise or lower the brightness.
NOTE: For Type 1 units, the adjustment screw has a single 360° range of rotation.
Exceeding its limits past the stops will damage the unit. Adjust lightly.
CAUTION

Manual Number 9018205 Revision F, April 1, 2021 16
Display Dimming Adjustment (Type 2 units)
For Type 2 units, the brightness range of the clock can be adjusted before or after installation
using the control buttons on the front of the unit. With the unit in either LOCAL or UTC mode,
simply pressing the – or + buttons will adjust the brightness setting. The CH93 will
automatically detect and adjust the brightness control method that is currently active. If the
automatic photocell is active, ADJ1 is displayed. It is recommended to set the photocell
adjustment level in a dark or night-time cockpit environment. If the unit is receiving a dimming
input voltage, ADJ2 is displayed. If used, both should be set to the appropriate preference.
Once set, the photocell and lighting bus adjustments will be saved in the clock configuration.
If the brightness of the clock needs to be increased or decreased during flight, this can be
performed in either LOCAL or UTC mode using the same procedure previously described.
Refer to Figure 4.3 for detailed instructions on adjusting dimming for Type 2 units (for both
photocell and lighting bus display dimming modes).
Figure 4.1 Figure 4.2
Photocell Dimming Adjustment Bus Voltage Dimming Adjustment
(-5 unit shown) (-5 unit shown)
Figure 4.3
Dimming Adjustment (Type 2 units only)

Manual Number 9018205 Revision F, April 1, 2021 17
4.5 OPERATIONAL MODES
The CH93 has six modes of operation representing up to nine separate functions. Each mode,
when applicable, is indicated by a backlit annunciation on the display. See table 4.1 for details.
Mode Annunciation Functions
Local Time
Universal Time
Flight Timer
Timer
Voltage*
Temperature*^
(none)
UTC
FLIGHT
TIMER
VOLTS
OAT
Display and set local time
Display and set UTC time
Resettable and non-resettable flight timers
Elapsed (count up) and count-down timers
Displays bus voltage
Displays OAT and/or cockpit/cabin temperature
* Only available on Type 2 units
^ Requires temperature probe sensors
Table 4.1
Modes and Functions
Pressing the MODE button scrolls through the six different operational modes in a counter-
clockwise direction on the display. Figure 4.4 depicts the overall flow of the unit modes of
operation. Details for each mode are provided in the subsequent sections.
Figure 4.4
Modes of Operation

Manual Number 9018205 Revision F, April 1, 2021 18
Local Time Mode
When power is applied to the CH93, the system defaults to Local Time mode (in this mode,
there is no mode indication/annunciation; refer to Figure 4.5). Pressing and holding the
MODE button will enter the configuration menu. The local time can be configured to display
preferences for 12- or 24-hour format and to either display or hide seconds (displaying or
hiding seconds setting applies to both local and UTC time). Setting hours in local time is
independent of UTC time. For setting the minutes, Type 1 units apply the setting to both local
and UTC time concurrently and are linked. For Type 2 units, the minutes in local time are
independent of the UTC time minutes. For both unit types, the seconds are synchronized
and linked between the two time modes. Refer to Figure 4.6 for detailed instructions.
Figure 4.5
Local Time Clock Mode (-5 unit shown)
Figure 4.6
Setting Local Time

Manual Number 9018205 Revision F, April 1, 2021 19
Universal Time Mode
When in Local Time mode, pressing the Mode button once changes the unit to Universal
Time mode and the UTC annunciation will be backlit (refer to Figure 4.7). Pressing and
holding the MODE button will enter the configuration menu. UTC time is always displayed in
24-hour format and seconds can be configured to be displayed or hidden (displaying or
hiding seconds setting applies to both local and UTC time). Setting hours in UTC time is
independent of local time. For setting the minutes, Type 1 units apply the setting to both local
and UTC time concurrently and are linked. For Type 2 units, the minutes can be set for UTC
time in 15-minute increments, independently of local time, to allow for time zones with offsets
that are less than 1-hour increments. For both unit types, the seconds are synchronized and
linked between the two time modes. Refer to Figure 4.8 for detailed instructions.
Figure 4.7
Universal Time Clock Mode (-5 unit shown)
Figure 4.8
Setting Universal Time