TC-3 Manual
Velocity TC-3
One to Twelve channel thermocouple
(EGT/CHT) indicator
Operating Manual – English 1.02
Introduction
The TC-3 thermocouple display unit is a 12 channel 3 1/8” instrument that contains all the features necessary to monitor
EGT’s and CHT’s. The TC3 can be configured to display up to 12 thermocouples in an easy to read bargraph format.
The TC-3’s high accuracy is due to it’s built in thermocouple linearization curves and cold junction compensation
techniques. Common J, K or E type thermocouple probes are supported.
In addition the TC3 has an individual programmable EGT and CHT alarm with an external output that can switch an
external visual alarm indicator such as a lamp. Maximum temperature for each thermocouple is recorded in permanent
memory and is also indicated by a solid line above that thermocouples bar graph.
The TC3 also features a built in engine leaning facility which allows the pilot to optimize the fuel mixture according to peak
EGT temperatures as well as a cruise mode facility to provide instant identification of changing EGT/CHT trends.
Temperatures can be displayed in degrees Celsius or degrees Fahrenheit from -100ºC to 1200ºC (-148ºF to 2192ºF).
1 Features
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12 Channel thermocouple display unit
Supports J, K and E thermocouple probes
Temperatures can be displayed in degrees Celsius or degrees Fahrenheit from -100ºC to 1200ºC (-148ºF
to 2192ºF)
High accuracy: Built in thermocouple linearization curves and cold junction compensated
Maximum temperature for each thermocouple is recorded in permanent memory and indicated by a solid
line above the thermocouples bar graph
Engine leaning function according to peak EGT temperatures
Engine cruise mode to instantly identify changing EGT/CHT trends
Standard 3 1/8” aircraft enclosure (can be front or rear mounted)
Rotary control plus 2 independent buttons for easy menu navigation and user input
External alarm output as well as a red LED illuminates when the programmable alarm has been activated
Large backlit graphic LCD with adjustable contrast
Wide input supply voltage range of 8 to 30V DC with built in voltage reversal and over voltage protection
for harsh electrical environments
Light weight design
Velocity TC-3 Operating manual
2 TC-3 Layout
Page 2
LED Alarm:
The red LED will illuminate if any of
the temperatures monitored
exceeds the corresponding alarm
set point
Backlit Graphic LCD Display:
Contrast and backlight can be adjusted
in the menu system
Harnesses:
Harnesses connect to
power and thermocouples
Up/F1 Button:
Up button in menu system
Enable/disable engine Leaning
mode during the normal display
mode
Down/F2 Button:
Down button in menu system
Enable/disable cruise mode
during the normal display
mode
Rotary Control (Up/Down) & Enter Button:
Press the rotary control during normal mode to access the menu system.
Rotate anti/clockwise for up/down menu scrolling. During normal mode
rotating the rotary anti/clockwise will display the maximum values recorded.
3 Main Display
EGT Value:
Indicates highest value if
“Highest” is selected or
the highlighted bar value
if “Scan” is selected
EGT group
indicator
EGT alarm level
Maximum temperature
reached indicator
Temperature
display unit
CHT Value:
Indicates highest value if
“Highest” is selected or the
highlighted bar value if “Scan”
is selected
CHT group
indicator
CHT alarm level
Maximum temperature
reached indicator
Velocity TC-3 Operating manual
Page 3
3.1 Permanent maximum values display
This display can be accessed by rotating the rotary control either clockwise or anticlockwise. Pressing the F1 key will
reset the permanent maximum values to the current temperature values. Pressing any other key will return the TC-3 to
the normal display mode.
Note: The permanent maximum values are stored in nonvolatile memory and are recalled on power-up.
3.2 Engine leaning mode
EGT information is also very useful for fuel mixture control. As the fuel mixture is
leaned, so the exhaust gasses get hotter. This rise in temperature is a sign of
increased combustion efficiency as the optimum mixture setting is approached. If the
leaning progresses past a certain point however, the temperature will begin to drop.
This temperature drop is the result of reduced energy output from the diminished fuel
flow. The best operating mixture for aircraft engines is in the vicinity of this peak EGT
reading. The TC-3 has a special Leaning mode, which easily identifies the peak EGT
condition allowing you to adjust your fuel mixture for best performance.
Fuel mixture should be adjusted once you have decided on a suitable cruise power
setting (typically 70%). Press the Up/F1 key at the main display to enable the leaning
mode. The "LEAN MODE" label is displayed at the bottom of the main display to
clearly differentiate it from the normal operating mode.
As the fuel mixture is slowly leaned past the point at which the temperature begins to
drop (by more than 10°C/15°F), the absolute EGT temperatures will change to show
the EGT reading relative to this peak. The sequential order as each cylinder peaks is
also shown.
Leaning mode can be cancelled by pressing the Up/F1 key.
3.3 Engine cruise mode
Once in the cruise, pressing the Down/F2 key will immediately enable Cruise Mode.
The "CRUISE MODE" label is displayed at the bottom of the main display to clearly
differentiate it from the normal operating mode. All EGT and CHT readings are
immediately sampled as reference temperatures for the cruise.
The display then shows EGT and CHT values relative to this reference temperature.
Cruise mode can be cancelled by pressing the Down/F2 key.
Velocity TC-3 Operating manual
Page 4
4 Menu System
The TC-3 will enter the menu system by pressing the rotary control button during the normal display mode. Use the
up/down keys or the rotary control to navigate through the menu system
4.1 Exit Menu
Press the rotary control on this menu item to exit the menu system. All changes made during
navigation of the menu system will be saved in non-volatile memory on exiting the menu system.
If you remove power before exiting the menu the instrument will not save any changes.
4.2 Display Setup
Move the highlight over this menu item and press the rotary button to return to the main menu
Select this menu option to adjust the display contrast
Select this menu option to turn the backlight on and off
Select whether you want the temperature to be displayed in degrees Celsius (ºC) or degrees
Fahrenheit (ºF).
Velocity TC-3 Operating manual
Page 5
4.3 EGT / CHT Setup
Only “EGT SETUP” is shown below, follow the same steps for CHT setup
Move the highlight over this menu option and press the rotary button to return to the “TC Setup”
menu.
Select the number of EGT or CHT channels you want to use. Choices are from 1 to 12. The
temperature display will configure itself to make best possible use of the available display size.
Please note that the minimum number of EGT & CHT channels that can be displayed is 1 and
the maximum number of EGT and CHT channels that can be displayed is 12.
Note: Always install EGT probes starting on Channel 1 followed by the CHT
probes without skipping any channels in between.
This function sets the top end of your temperature bar graph. It has no effect on the actual
temperature range that can be displayed in the digital temperature readout. Select the range to
be just higher than the highest temperature you expect to measure using this channel.
Select this function to “ON” if you want the bar graph display to show the upper half of the
temperature range only. This results in a higher resolution of the temperature range you may be
interested in. For engine temperature measurements we recommend that you set this to “ON”.
Adjust the temperature that you would like to use as an alarm limit. Any temperature above this
limit will activate the alarm. Active alarms will flash the affected channel and also activate the
alarm contact that you can use to switch a lamp on.
Select whether you want to turn the alarm on or off. To avoid false activation of the alarms, the
alarm function is only activated 10 seconds after the instrument has powered up.
Select if you are using a K-type, J-type or E-type thermocouple probe for this channel. All probes
supplied by MGL Avionics are K-Type. J-types are sometimes used with American made CHT
probes. All EGT probes are K-type. E-type probes are seldom used.
A selection between “HIGHEST” or “SCANNING” can be selected. If “HIGHEST “is selected then
the current highest thermocouple temperature is displayed. If “SCANNING” is selected then the
unit will cycle through each thermocouple at the time specified in “SCAN TIME”.
Specify the time that each of the channels must be displayed for. This menu option is only shown
if “SCANNING” is selected for the display mode.
Velocity TC-3 Operating manual
Page 6
5 Loading factory default settings
Pressing and holding the F1 and F2 keys simultaneously during power up will cause
the TC-3 to load preprogrammed factory default settings. The following screen will be
displayed:
6 Operating the alarms
If the alarm is activated, the corresponding item on the display will flash. At the same time the externally available alarm
switch will close. The switch will remain closed until any button is pressed to acknowledge the alarm or until the
condition(s) that activated the alarm no longer exist. The alarm output can be used to switch an external alarm indicator.
The external alarm switch is an open collector transistor switch to ground with a maximum rating of 0.5A DC. It is possible
to wire the alarm contacts of several Stratomaster instruments in parallel should this be desired. To avoid false activation
of the alarms, the alarm function is only active 10 seconds after the instrument has powered up.
7 Cleaning
The unit should not be cleaned with any abrasive substances. The screen is very sensitive to certain cleaning materials
and should only be cleaned using a clean, damp cloth.
Warning: The TC-3 is not waterproof, serious damage could occur if the unit is exposed to water
and/or spray jets.
8 TC-3 Specifications
Operating Temperature Range
Storage Temperature Range
Humidity
Power Supply
Current Consumption
Display
ADC
Dimensions
Enclosure
Weight
Non-volatile memory storage
Thermocouples
Channels
Measurement range
Technology
Measurement accuracy
Inputs
Common mode voltage range
-10ºC to 50ºC (14ºF to 122ºF)
-20ºC to 80ºC (-4ºF to 176ºF)
<85% non-condensing
8 to 30Vdc SMPS (switch mode power supply) with built in 33V over voltage
and reverse voltage protection
Approx. 45mA @ 13.8V (backlight on) 15mA @13.8V (backlight off)
128x64 graphic LCD display. Contrast and backlight is user configurable,
green/yellow backlight
12bit over sampled successive approximation
see Velocity series dimensional drawing
3 1/8” ABS, black in color, front or rear mounting
Approx. 214 grams
100000 write cycles
K-type, J-type or E-type
1 to 12 independent channels
J-Type/K-Type: -100ºC to 1200ºC (-148ºF to 2192ºF)
E-Type: -100ºC to 900ºC (-148ºF to 1652ºF)
Fully cold junction compensated using precision internal temperature
reference, built in thermocouple linearization tables
+/- 5 degrees typical over full temperature range, subject to quality of probe
used. We recommend MGL Avionics EGT and CHT probes
Differential, can use grounded and isolated probes
-2V to +3V
Velocity TC-3 Operating manual
Page 7
9 Installation
The TC-3 provides for up to 12 thermocouple inputs for use with EGT and CHT probes. K, J as well as E-type probes can
be used. K types are used for EGT probes while CHT probes can either be J or K type. E-type probes are seldom used.
Probe types are selected under the “EGT SETUP” or “CHT SETUP” menus of the TC-3
Important: Incorrect selection of probe type will lead to an incorrect temperature display.
The TC-3 will accept both grounded and isolated thermocouple probes. Your only consideration in case of the more
common grounded configurations is that you need to ensure that the thermocouple mounting position (exhaust flange,
etc.) is at the same electrical potential as the negative supply line of the TC-3.
The thermocouple amplifier is a precision device providing full cold junction compensation. In addition the amplifier
measures and corrects for its own errors. This results in very accurate measurements providing you install high quality
probes. Here are some guidelines:
EGT Probes: Select probes that are made from 316 stainless steel and that use glass-fiber insulated conductors. Teflon
insulated conductors as found in many cheap probes introduce errors as the insulation melts moving the measuring point
towards the mounting bolt which transfers a lot of heat to the exhaust material. This results in under reading probes. Stay
away from probes that use simple plastic heat shrink sleeving – it does not last. Choose probes that use a generous
amount of stainless steel spring as strain relief. The bolt itself should be stainless steel as well or it will rust very quickly.
CHT Probes: These are made from washers to fit spark-plug bases. Temperatures are considerably lower so most
thermocouple cables will work without problems. The biggest area of concern should be the connection of the
thermocouple cable to the washer. This often breaks after the spark plug has been changed a few times. Choose a probe
that is suitably reinforced at this point for a long and trouble free life.
EGT and CHT probes supplied by MGL Avionics are of highest quality. We recommend that you consider using our
probes if at all possible.
Warning: Four stroke engines produce much hotter exhaust gases compared to two stroke
engines. Do not use EGT probes made from lower grade stainless steel (for example 310), these
probes will not withstand the high temperatures and can fail as the metal gets very soft at 800
degrees C. Many four strokes (such as the Rotax 912) will produce exhaust gases of up to 850
degrees C.
Important installation note:
EGT and CHT probes use wire made from iron and other basic metals. As a result these probes are not able to withstand
much flexing of the wires due to engine vibrations. Avoid making nice looking coils or similar constructions that will result
in excessive vibration or flexing of the wire. Route the cables from the probe points tightly along suitable engine mounting
points eliminating any chance of unnecessary wire flexing during engine operation.
Note: Connect the ground to the engine block (and engine block to battery
negative). Do not connect the TC-3 ground directly to battery negative. This
must be routed via the engine block.
Note: Always install EGT probes starting on Channel 1 followed by the CHT
probes without skipping any channels in between.
Velocity TC-3 Operating manual
Page 8
9.1 Connection Diagram
The use of an external 1A fuse is recommended. Connect the supply terminals to your aircrafts power supply. The TC-3
can be used on both 12V and 24V without the use of any pre-regulators. Ensure that the supply voltage will not drop
below 8V during operation as this may result in incorrect readings.
Velocity TC-3 Operating manual
Page 9
9.2 Extending leads of thermocouple probes
Thermocouple leads as used with the EGT and CHT probes can be extended either with ordinary copper cable or with
special K-Type extension cable. The choice of either depends on your desired accuracy. If it is possible in your installation
to ensure that both ends of a copper extension cable will be at the same temperature (or very close), then it is quite
possible to use the copper cable. In most open-air installations this will be the case. Should this not be possible or you
require best possible accuracy at all times, you can obtain a special K-type extension cable. This cable is made from the
same metals as your probes cable and uses ordinary plastic sleeving as insulation. In either case, ensure that the cable is
not routed close to sources of electromagnetic interference of any kind. The voltages present in this cable are very small
and are subject to changes applied by external fields. This can lead to false temperature indications. You can check your
installation by using a hand-held transmitter, such as an air band radio. If you transmit a signal, no change in temperature
reading should occur.
9.3 TC-3 Cable connections
Main connector (Bottom DB9 connector)
DB 9 Pin
1
Color
Black
4
NC
6
Red
9
White
Function
Ground. Connect the ground to the
engine block (and engine block to
battery negative). Do not connect the
TC-3 ground directly to battery negative.
This must be routed via the engine
block.
Airtalk communication (Not connected)
Used for firmware upgrading
8-30Vdc power via power switch / circuit
breaker and fuse if required
Alarm Output
Thermocouple (EGT/CHT) input connector (Top DB25 connector)
In case of MGL Avionics K-Type probes + = Yellow probe lead, - = Red probe lead
DB 25 Pin
1
2
3
4
5
6
7
8
9
10
11
12
Function
TC Channel 1 +
TC Channel 2 +
TC Channel 3 +
TC Channel 4 +
TC Channel 5 +
TC Channel 6 +
TC Channel 7 +
TC Channel 8 +
TC Channel 9 +
TC Channel 10 +
TC Channel 11 +
TC Channel 12 +
DB 25 Pin
14
15
16
17
18
19
20
21
22
23
24
25
Function
TC Channel 1 TC Channel 2 TC Channel 3 TC Channel 4 TC Channel 5 TC Channel 6 TC Channel 7 TC Channel 8 TC Channel 9 TC Channel 10 TC Channel 11 TC Channel 12 -
Velocity TC-3 Operating manual
Page 10
10 Warranty
This product carries a warranty for a period of one year from date of purchase against faulty workmanship or defective
materials, provided there is no evidence that the unit has been mishandled or misused. Warranty is limited to the
replacement of faulty components and includes the cost of labor. Shipping costs are for the account of the purchaser.
Note: Product warranty excludes damages caused by unprotected, unsuitable or incorrectly wired
electrical supplies and or sensors, and damage caused by inductive loads.
11 Disclaimer
Operation of this instrument is the sole responsibility of the purchaser of the unit. The user must make themselves familiar
with the operation of this instrument and the effect of any possible failure or malfunction.
This instrument is not certified by the FAA. Fitting of this instrument to certified aircraft is subject to the rules and
conditions pertaining to such in your country. Please check with your local aviation authorities if in doubt. This instrument
is intended for ultralight, microlight, homebuilt and experimental aircraft. Operation of this instrument is the sole
responsibility of the pilot in command (PIC) of the aircraft. This person must be proficient and carry a valid and relevant
pilot’s license. This person has to make themselves familiar with the operation of this instrument and the effect of any
possible failure or malfunction. Under no circumstances does the manufacturer condone usage of this instrument for IFR
flights.
The manufacturer reserves the right to alter any specification without notice.
Other instruments in the Stratomaster Velocity series
ALT-3
ALT-4
ASI-3
ASX-2
AV-2
E-1
FLIGHT-2
FF-3
GF-2
MAP-2
ROTOR-1
RTC-1
RV-3
TC-2
TC-3
TP-2
Encoding aviation altimeter and Vertical speed indicator (VSI)
Encoding aviation altimeter with Serial RS232 & Parallel Gillham code output
Airspeed indicator (ASI) with automatic flight log
Encoding aviation altimeter and Airspeed indicator (ASI)
Artificial horizon and magnetic compass indicator
Universal engine monitor
Primary Flight instrument
Fuel Computer (single or dual fuel tanks)
+-10G tilt compensated dual range G-force meter
Manifold pressure and RPM Indicator
Dual Rotor / Engine tachometer
Aviation real time clock (RTC), outside air temperature (OAT) and Voltage display
Universal engine / Rotor RPM Indicator
4-Channel thermocouple (EGT/CHT) indicator
12-Channel thermocouple (EGT/CHT) indicator
Universal temperature and pressure gauge
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