Fluke 189 protocol undocumented commands.  See also here for the document part
and for the notes on the names of the other commands, which got me started:

    http://www.cfa.harvard.edu/~thunter/manufacturers.html

More information, maybe, at http://www.consistent.org/fluke-189/

QD 0 response:

    Fixed string of "0\rQD,", five bytes.  All locations will be taken
    AFTER this.

    Location	Bytes	Meaning
    0		4	Time stamp in units of 0.1s
    4		4	Primary display value.
    8		1	# places to shift decimal point in primary value
    9		1	Units.  -1 for milli, 1 for kilo, etc.
    10		4	Secondary reading.
    14		1	# places to shift decimal point in secondary value
    15		1	Units as above.
    16		4	Tertiary reading.
    20		4	Repeat of timestamp
    24		4	Repeat of primary reading
    28		1	Repeat of primary scale
    29		1	Repeat of primary unknown
    30		12	Function unknown.  Presumably knob setting, etc.

    All numerical values are little-endian.

    Values with 0x70 in the high byte indicate that the value is not in use
    or that there is some kind of error.  The low byte indicates what kind.
    0x01 is for unused; other values indicate overflow, missing leads, etc.
    Otherwise they are 2s complement numbers.

    Units indicate the prefix.  -3 is nano, -2 is micro, -1 is milli,
    1 is kilo, 2 is mega, etc.

    The only use I have ever seen for the tertiary reading is the log #
    when in logging mode.

QD 2 response:
    If there ARE NO logs, response of "5\r".  Otherwise, fixed string of
    "0\rQD,", five bytes.  All locations will be taken AFTER this.

    There is then an 18-byte header, which appears only once at the
    beginning.  I know little about it, but presumably it includes
    information about the knob setting, etc.

    Location	Bytes	Meaning
    0		2	?
    2		4	Initial value
    6		1	Decimal point location for initial value
    7		1	Units, as in other places
    8		10	Setting information, as in QD0 starting at byte 30

    The information about the setting is only partially understood.

    Then there are 32 bytes of repeating information:

    Location	Bytes	Meaning
    0		4	Beginning timestamp for entry in units of 0.1s
    4		1	Decimal point location
    5		1	Units.  -1 for milli, 1 for kilo, etc.
    6		4	Lowest value for this time period
    10		4	Maximum value for this time period
    14		4	Actual value, sum of N
    18		4	?, always all 0 in my tests
    22		4	Number of values which were summed
    26		1	Status - 0x05 for normal, 0x85 for last entry, other
			values for range changes or other oddities
    27		1	? - always 0x01 in my tests
    28		4	Ending timestamp for this entry

    Generally, the readings are taken equally distributed over the time
    period, so the value will be an average.  However, in cases of significant
    changes part way through, I have seen the meter use some heuristic to
    split it into separate entries sooner than the specified time period to
    capture this.  In the case of a sharp voltage increase, I saw the first
    part (low value) have status 0x04, the short middle one with the fast
    increase had 0x08, and the final one had 0x05.  The value displayed on the
    meter matched what I got by summing the actual values from the three and
    then dividing that by the sum of the number of readings from the three.

QS response:

    This work thanks to Mr. Christian Holl.  As above, all locations
    taken *after* the standard response, at the beginning of the binary
    data.

    Location	Bytes	Meaning 
    0		2	Logging interval
    2		1	DB Ref type (1=V, 0=mV)
    3		1	Unknown
    4		2	DB Reference setting (default 600, 0x5802)
    6		2	Temperature offset
    8		1	Scale (0=Fahrenheit, 1=Celcius)
    9		1	Unknown (always 00)
    10		2	Backlight off time, deciseconds
    12		4	Time of day
    16		2	Power off time, minutes
    18		1	Frequency setting, 0=50hz 1=60hz
    19		1	Unknown (always 0)
    20		1	Digits setting (0=5 digits, 1=4 digits)
    21		1	Unknown (always 0)
    22		1	Beep setting (0=off, 1=on)
    23		6	Unknown (always 0x00 90 01 c0 00 00)