The new invention is to establish the Frequency acquisition and Processing using In
Built Time Processing Unit of a Microcontroller.
BACKGROUND OF THE INVENTION
During the time of flight, Civil or Military aircraft Engine components faces many
environmental conditions so acquisition and processing of critical Engine parameters
like frequency is very essential for aircraft snags identification or for crash
investigation or training purposes. Frequency acquisition and processing plays
important role for any flight of the aircraft. After completion of flight, all critical
parameters are analyzed in Ground Equipment, if any random deviation is found
during acquisition of frequency (Engine RPM) this will show whether the Engine of
that particular aircraft suffers Snag.
SUMMARY OF PRESENT INVENTION
In accordance with one aspect of present invention for Frequency acquisition and
Processing using In Built Time Processing Unit of Microcontroller with Built in Test
facility .
In accordance with second aspect of present invention, the frequency signals are fed
through high reliable MIL grade resistor network differentially to the frequency
module to avoid noise and to maintain min threshold voltage at low and high
frequency. Circuit is invented for frequency voltage range from 2V to 26V rms.
Annexure-II
In accordance with another aspect of present invention this frequency signal is fed to
high-speed Si-gate CMOS device voltage comparator (Schmitt Trigger), which
squares the sinusoidal signal and converts into TTL logic levels.
In accordance yet another aspect of present invention after converting frequency
signals into TTL logic levels it is fed to TPU (Time Processing Unit) channel of
microcontroller for period measurement of frequency signal.
In accordance yet another aspect of present invention is to processes frequency
signal and base on time period, the frequency is being calculated with high
accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1: It shows the Frequency Acquisition Block.
Figure 2: It shows the Frequency processing after acquisition.
Figure 3: It shows the Interconnection with Ground Equipment.
DETAILED DESCRIPTION
Referring to Figure 1, 2 & 3, the present invention is a Frequency acquisition and
processing, using In Built Time Processing Unit of Microcontroller, consists of printed
circuit board (PCB) assembly mounted with resistive network, Op-amp, Schmitt
Trigger and Processor (Microcontroller) and associated electronic circuitry for
frequency acquisition and Processing. The connection between the frequency
acquisition circuit and processing circuitry associated equipment is achieved through
the interface board and socket which could be easily plugged into a connector on the
associated Ground equipment. Following activities are performed during Frequency
acquisition and Processing:
1. Initially Application procedure performs the BIT test of frequency
conditioning circuit by giving known set of frequency.
Annexure-II
2. Further, known frequency is read and compared to read back value
and on this basis it declares the BIT (Built in Test) Pass/Fail.
3. If BIT test is fail, associated circuit used for indication provides
necessary indication to the user.
4. The frequency signals are fed through resistor network differentially to
the frequency module.
5. Resistor network works as signal limiter and it limits amplitude of input
frequency to +/- 15 volts DC.
6. This frequency signal is fed to high-speed Si-gate CMOS device
voltage comparator (Schmitt Trigger), which square the sinusoidal
signal and converts into TTL logic levels. This signal then fed to TPU
(Time Processing Unit) channel of microcontroller for period
measurement of frequency signal.
7. Time Processing Unit of microcontroller further acquires and processes
frequency signal and base on time period, the frequency is being
calculated.
8. When frequency acquisition is completed then microcontroller sends
processed frequency signals to protected flash memory for data
retention and it can be read back for analysis purpose using ground
Equipment.

WE CLIAMS:-Accordingly, the description of the present invention is to be considered as illustrative only and is for the purpose of teaching those skilled in the art of the best mode of carrying out the invention. The details may be varied substantially without departing from the spirit of the invention, and exclusive use of all modifications which are within the scope of the appended claims is reserved. We Claim

1. This procedure has been developed to Frequency acquisition and Processing using In Built Time Processing Unit (TPU) of Microcontroller.

2. Is for use on Civil/Military aircraft for airborne application. However, the invention is not limited to airborne application and can be used where Frequency acquisition & Processing is required.

3. The frequency signals are fed through resistor network differentially to the frequency module. Resistor network works as signal limiter and it limits amplitude of input frequency to +/- 15 volts DC.Gain of the signal can also be adjusted according to requirement.

4. Frequencies are multiplexed by analog multiplexer and fed to an Instrumentation Amplifier where it is converted to single ended signal.

5. This single-ended Frequency signal is fed to high-speed Si-gate CMOS device voltage comparator (Schmitt Trigger), which squares the sinusoidal signal and converts into microcontroller/processor compatible TTL logic levels.

6. Schmitt Trigger is capable of transforming slowly changing input signals into sharply defined, jitter-free output signals.

7. This procedure has been developed to support sampling rate of 2 samples /second for two channels of frequency acquisition & Processing in present configuration. However, it can be configured for up to 4 channels of Frequency acquisition & Processing. Circuit uses standard power supply of +/- 15 volts and + 5 V DC.

8. This procedure has been developed to detect any random behavior of frequency source by online acquisition of frequency (Engine frequency) and replaying back on the ground by using ground equipment.

9. Qualified for extreme operating temperature range of -40 ºC to 85 ºC. ,TagSPECI:As per Annexure-II