Campbell TX312 Specifikace stáhnout pdf (Strana 72)

Appendix F. High Resolution 18-Bit Binary Format

F-2

Where 17 represents bit 17 - the most significant bit and is used to

determine the sign.

Converting the 18 bit data point to an integer can be done manually. Don’t

forget the 18 bits are numbered 0 through 17. Bit 17 is the sign bit, when bit 17

is set, the number is negative. If bit 17 is set, subtract 1 from the number then

take the complement of the number. If bit 17 is not set, simply convert the

number to its decimal equivalent.

Example positive data point conversion:

Byte Label byte 3 byte 2 byte 1

Actual data point 01000101 11110010 11010010

Drop first 2 bits of

each byte 000101 110010 010010

Combine the 3

bytes into one word 000101 110010 010010

Convert from Binary to Decimal 23698

Example of a negative data point conversion:

Byte Label byte 3 byte 2 byte 1

Actual data point 01111010 11001101 11101101

Drop first 2 bits of

each byte 111010 001101 101101

Notice bit 17 is set,

Combine the 3

bytes into one word 111010 001101 101101

Subtract 1 from the number 111010 001101 101100

Take the complement of

each bit 000101 110010 010011

Convert the binary value

into a decimal value, don’t

forget the negative sign -23699

1 2 ... 67 68 69 70 71 72 73 74 75 76 77 ... 95 96

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Campbell TX312 Specifikace Strana 72