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Fourth value, Number of Points Acquired: This number is incremented each time
a point is taken. It is zeroed by the NC command and whenever CBD or LEN is
applied without parameters.
DC[.] n
Dump acquired curve(s) to computer
The operation of this command depends on whether data has been stored into the
Standard or Fast Mode curve buffers.
Standard Mode
In fixed point mode, causes a stored curve to be dumped via the computer interface
in decimal format.
In floating point mode the SEN curve (bit 4 in CBD) must have been stored if one or
more of the following outputs are required in order that the lock-in amplifier can
perform the necessary conversion from %FS to volts or amps:- X, Y, Magnitude,
Noise. Similarly, if the dual reference or harmonic modes are active then the SEN2
curve (bit 21 in CBD) must have been stored in order to perform a similar conversion
from %FS to volts or amps for X2, Y2 and Magnitude2.
One curve at a time is transferred. The value of n is the bit number of the required
curve, which must have been stored by the most recent CBD command. Hence n can
range from 0 to 16, or 0 to 21 if a dual mode is active. If for example CBD 5 had
been sent, equivalent to asserting bits 0 and 2, then the X and Magnitude outputs
would be stored. The permitted values of n would therefore be 0 and 2, so that DC 0
would transfer the X channel output curve and DC 2 the Magnitude curve.
NOTE: When transferring the Frequency curve, which is saved when bit 15 in the
CBD parameter is asserted, the instrument automatically reads the data for each
stored point in both frequency curves (i.e. the lower and upper 16 bits) and sends it
as a single data point.
Fast Mode
Only fixed point mode is supported. One curve at a time is transferred, with the
selected curve being dumped via the computer interface in decimal format.
The value of n defines the curve to be transferred according to the following table:
n
Output and range
0
X Output (±10000 FS)
1
Y Output (±10000 FS)
2
Main signal channel ADC output (digital signal monitor 1
3
ADC1 (±10000 = ±10.0 V)
4
ADC2 (±10000 = ±10.0 V)
Dual modes only:-
5
X
Output (±10000 FS)
2
6
Y
Output (±10000 FS)
2
7
Input to second demodulator (digital signal monitor 2)
The computer program's subroutine which reads the responses to the DC command
needs to run a program loop that continues until all the data has been transferred.
Chapter 6, COMPUTER OPERATION
6-29
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