manual air data boom v3

Icasim Smart Air Data Boom V3

Icasim Flight Test Equipment (IFTE)

Valentin BuergelSimtec Buergel AG2007-12-03/V2.0

ICASIM SMART AIR DATA BOOM V3Icasim Flight Test Equipment (IFTE)

Icasim Smart Air Data Boom V3

Sampling Rate

Air data (impact pressure, static pressure, angle of attack, angle of side-slip and total air temperat-ure) is sampled at 300 Hz and filtered with a sinc3-filter with -3 dB at 79 Hz. Every 20 ms an analog-to-digital conversion takes place. The five channels are successively processed, so that every 100 ms each channel data is available. Every 500 ms the internal temperature of the probe is trans-mitted.

Data Output Rate

The default output rate of the airdata probe is 10 Hz. On request Simtec is able to decrease the out-put rate down to 1 Hz or increased output rate up to about 30 Hz. Note that an increased output rate will also increase baud rate.

Serial Data Protocol

The ordering of the data is such that the least significant bit (LSB) is the first bit received, moreover the most significant bit (MSB) is the last bit in the sequence.

At power-up, the airdata probe sends factory data via the serial interface. This information can be displayed on a dummy terminal.

icasim airdata V3.01

The serial data transfer protocol has the following format:

Channel ID Sensor Type Msg. Format Range Output RateChannel 1 Impact Pressure 1cccc 0 .. 65535 10 HzChannel 2 Difference Pressure AoA 2cccc 0 .. 65535 10 HzChannel 3 Difference Pressure AoS 3cccc 0 .. 65535 10 HzChannel 4 Static Pressure 4cccc 0 .. 65535 10 HzChannel 5 Total Air Temperature 5cccc 0 .. 65535 10 HzChannel 6 Internal Temperature of Probe 6cc 0 .. 255 2 Hz

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Any c in the message format represents an ASCII character A...P . The characters itself represent the hexadecimal numbers 0x0...0xF :

ASCII HexChar NumberA 0x0B 0x1C 0x2D 0x3E 0x4F 0x5G 0x6H 0x7I 0x8J 0x9K 0xAL 0xBM 0xCN 0xDO 0xEP 0xF

Transmission time between successive channel transmissions is filled with the binary symmetric AS-CII characters U if power voltage is normal and with the ASCII character f if battery voltage falls be-low the critical value for save operation. If the battery voltage falls below the critical value the meas-urement data is subject to errors.

The following Java function converts a message to the corresponding unsigned integer value:

public static long bytesToUnsignedInt(byte b1, byte b2, byte b3, byte b4) { // convert ASCII character A..P to hex value b1 -= 0x41; b2 -= 0x41; b3 -= 0x41; b4 -= 0x41; // shift and add return (b1<<12) + (b2<<8) + (b3<<4) + b4; }



Conversion of an Integer Value to a Physical Value

Unsigned integer values i of channel 1 to 5 are converted to a physical value v by the following for-mula:

v=abxcx2dx3

a ,b ,c ,d: Values are provided for each sensor channel

The integer value i of channel 6 is converted to a temperature T by the following formula:

TCelsius=i−80

2

Example Message

The following is a reasonable message (Version 3.0) from the airdata probe if battery voltage is nor-mal:

1HPMA UU 2HPGC UUU 3NPNL UU 4KNLG U 5HDCM UUU 6BP

Channel 1 : HPMA decodes to hexadecimal 0x7FC0 which equals to decimal 32704.

Channel 6 : PB decodes to hexadecimal 0x1F which equals to decimal 31. The in-ternal temperature is computed from the above equation to -24.5°C.

The following is the same message as above but from an airdata probe where battery voltage has fallen below the critical value. Even so the probe may send some data the result is questionable be-cause of the low battery voltage.

1HPMA fff 2HPGC ffff 3NPNL ff 4KNLG f 5HDCM ffff 6BP

External Interface Characteristics

The electrical signals used are those for the RS-232 communication port. Only the transmit line is re-quired. The serial port is asynchronous and should be set up with 1 start bit, 8 data bits, no parity bit, and one stop bit. A default baud rate of 9'600 is used. A RS232 to TTL (CMOS) level converter is available on request. It may be connected at the end of the RS232 cable. The air data probe features a standard M8 receptacle (male contacts) at the back side of the aluminum housing. The wireless data modem is connected directly to this receptacle.



Pin assignment:

1 (brown) : power supply +6 to +12 VDC, power consumption is approx. 60 mA.

2 (white) : reserved (+24VDC for internal heater if available)

3 (blue) : GROUND (data and power)

4 (black) : TXD (RS232 level) data output of air data probe

Male Contacts 4-Pole:

Female Contacts 4-Pole:

All connectors with screw locking

IP 68 Standard

Color code of leads according to Europe standard (EN 50044)

Standard Sensor Receptacles are available from Simtec Buergel Ltd. or:

Richard Hirschmann GmbH & Co., Steckverbindungstechnik Industrie, Stuttgarter Strasse 45-51, D – 72654 Neckartenzlingen, http://www.hirschmann.de

Lumberg Automation Components GmbH & Co. KG, Im Gewerbepark 2, 58579 Schalksmühle, Ger-many, http://www.lumberg.com


http://www.hirschmann.de/

http://www.lumberg.com/


Installation

Simtec provides a special tutorial on how to best install the Icasim Smart Air Data Boom.

Note that the temperature sensor must point downwards to get angle of attack and angle of sideslip values with the correct algebraic sign. If the temperature sensor points downwards it is less affected by the sun.

The lastest probe design has an internal temperature sensor. The small notch at the front of the 25mm tube has to point upwards. The flat portion on the 12mm tube may be used to precisely adjust the probe.


manual air data boom v3

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