Ametek 7280 Instruction Manual page 161

The reason why bit 4 and, for dual reference modes, bit 21, which store both the
sensitivity and the IMODE setting, are needed, is to allow the instrument to transfer
the acquired curves to the computer in floating point mode. Without this information,
the unit would not be able to determine the correct calibration to apply.
Note that the CBD command directly determines the allowable parameters for the
DC, DCB and DCT commands. It also interacts with the LEN command and affects
the values reported by the M command.
Since the reference frequency requires 32-bit wide data points, it occupies two curve
positions. For ease of use, if bit 15 is selected for storage then bit 16 will be
automatically selected as well, and vice-versa.
NOTE: At least one of the curves selected for storage in the curve buffer must be
chosen from those marked with an asterisk(*) in the above table.
LEN [n] Curve length control
The value of n sets the curve buffer length in effect for data acquisition. The
maximum permitted value depends on the number of curves requested using the CBD
command, and a parameter error results if the value given is too large. For this
reason, if the number of points is to be increased and the number of curves to be
stored is to be reduced using the CBD command, then the CBD command should be
issued first.
NC New curve
Initializes the curve storage memory and status variables. All record of previously
taken curves is removed.
STR [n] Storage interval control
Sets the time interval between successive points being acquired under the TD or TDC
commands. n specifies the time interval in milliseconds with a resolution of 1 ms.
The longest interval that can be specified is 1000000 s corresponding to one point in
about 12 days.
TD Take data
Initiates data acquisition. Acquisition starts at the current position in the curve buffer
and continues at the rate set by the STR command until the buffer is full. If an
oscillator frequency and/or amplitude sweep has been defined and linked to the curve
buffer using the SWEEP command with a parameter of 9, 10 or 100, then this sweep
will be started as well.
TDT n Take data triggered
Sets the instrument so that data acquisition will be initiated on receipt of a trigger at
the TRIG connector on the rear panel. If an oscillator frequency and/or amplitude
sweep has been defined and linked to the curve buffer using the SWEEP command
with a parameter of 9, 10 or 100, then this sweep will be started as well.
Two triggered modes are possible, as set by the value of n:
n function
0 One complete curve or set of curves, each one consisting of the number of points
specified by the LEN command parameter, is acquired for each trigger
1 One data point or set of data points is acquired for each trigger. Hence in order to
Chapter 6, COMPUTER OPERATION
6-27