Stanford Research Systems SR865A, Operation Manual

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138 Programming Chapter 4
SR865A DSP Lock-in Amplifier
1 2 Capture triggered, either by
TTL or remote command
2 4 Capture wrapped
If capture is waiting for a hardware trigger to start capture, then all 3 bits remain 0 until
the trigger is received. Once capture is started, bits 0 and 1 both become 1 (giving a
return value of 3).
Bit 0 remains 1 while capture is recording data. After receiving the
CAPTURESTOP
command, bit 0 may remain 1 until the current 2kbyte block of data is filled.
If the capture buffer wraps around, then bit 2 becomes 1; this occurs at the end of a
OneShot capture, or when a Continuous capture begins overwriting old data.
Bits 1 and 2, once set, will remain set until cleared by resetting the capture system with a
CAPTURECFG , CAPTURELEN or CAPTURESTART command.
Example
CAPTURESTAT? Returns the capture buffer state
CAPTUREBYTES?
The CAPTUREBYTES? query returns the number of bytes of data that have been
captured thus far. This query is “live” and may be used to monitor the progress of the
capture. For Continuous captures that are overwriting old data, the number of captured
bytes decreases by 2048 bytes before increasing again.
After capture has stopped, this query returns the actual number of bytes of non-zero data.
For example, an 8kB buffer is being filled with data being captured every trigger. After
capturing 1250 samples of X (5000 bytes of capture), capture is stopped.
CAPTUREBYTES? will report 5000 bytes of data, while CAPTUREPROG? will report
6 kB of data as it counts in 2kB increments. CAPTUREVAL? 1249 will return the last
sample captured before capture was stopped, and CAPTUREVAL? 1250 will return zero.
Example
CAPTUREBTYES? Returns the amount of data captured, in bytes
CAPTUREPROG?
The CAPTUREPROG? query returns the number of kilobytes of data that were written
during the most recent capture acquisition. Capture must be stopped before performing
this query.
If the acquisition wrapped during operating in Continuous mode, CAPTUREPROG? will
simply return the value of CAPTURELEN .
Example
CAPTUREPROG? Returns the amount of data captured, in kilobytes
CAPTUREVAL? [ n ]
The CAPTUREVAL? query returns data from the capture buffer in plain text (ASCII)
format. Data is returned as comma-separated values of one, two, or four floating point