Experimental Physics and
Industrial Control System

Steven Hunt <[email protected]> · Fri, 24 Feb 2006 09:22:51 +0100

Hi John,

I often do this sort of thing, in a simple way, using just a waveform
and ai record looking at the same hardware.

I my case I use a Hytec 8401 industry pack but I expect your adc has
similar device support.

Firstly I would configure the adc to use an external clock (or a 1 or 2
KHz internal clock if you don't need exactly 1.4 KHz). 

A waveform record (NELM=5000) processing for instance every 5 seconds
will return the last 5000 samples of data from the on-board circular
buffer.

A ai record processing at say 10Hz can in parallel read the same data at
a faster rate (it can also return an average of many samples to reduce
noise and give higher - 18 bit - resolution).

The hardware and device support also allows many more options - for
instance the buffer can be set to fixed length rather that circular, and
acquisition can be started using an external trigger, the waveform
record (SCAN=I/O Intr) will be processed when the buffer is full.

Email me directly if you want me to send you an example db file.

Steve Hunt 

On Thu, 2006-02-23 at 18:40 +0100, John Dobbins wrote:
> Dear All,
> 
> I want to create the following application in EPICS. I have a sixteen 
> channel industry pack ADC that I will be using in a VME crate with an 
> MVME162. EPICS version 3.13.10. I want to read the ADC at ~ 1.4 kHz and 
> record waveforms lasting 5 to 10 seconds. As this is faster then I can 
> imagine record processing taking place I assume I need to create device 
> support that creates a task which runs at 1.4 kHz, maintains data 
> buffers and periodically lets a waveform record (?) know that more data 
> is available (I'd like to be able to see some of the data before the 
> total acquisition is complete.)
> 
> Does anyone have code for something resembling this that I could look
> at?
> 
> Thanks,
> 
> John Dobbins
> Research Support Specialist
> Lab for Elementary Particle Physics
> Cornell University
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System