VSAM EPICS Drivers Link Below
ftp://ftp.slac.stanford.edu/groups/controls/soft/epics/
http://www.slac.stanford.edu/grp/cd/soft/epics/site/vsam_index.html


Lab View Software Development Link from SLAC
http://www.slac.stanford.edu/grp/efd/babar-work/files/labview.html

APPLICATIONS:
• 5 digit autoranging 32 channel VME DVM
• Slowly varying analog signals
• Magnet power supply monitoring to check for "contaminating" AC on DC levels
• Radiation and Position Monitor

GENERAL DESCRIPTION:
The VSAM is a single width 6U VMEbus module with two operating modes: normal (23 ms/channel) total refresh rate for the 32 channels is 750 ms and fast (for tweaking) 4ms/channel total refresh rate for 32 channels is 300 ms. Each input line has a single-pole RC filter. The measurement process consists: of range acquisition: digital signal averaging over one 60Hz period to remove normal mode AC components; gain and offset correction, and conversion to single precision IEEE floating point format
The processor requires the ADC to operate in the upper half of its range; if this condition is not met during the signal averaging process, the gain is corrected and the averaging restarted. The processor applies a linear calibration correction to each reading.
The calibration coefficients are determined by a procedure that measures offset values for each PGIA range and an overall system gain. A reference 10.240 volts and analog ground are multiplexed to the PGIA for calibration. The calibration procedure is performed every 10 seconds. AC measurements are made continuously in both normal and fast scan modes; they record the maximum peak-to-peak excursion of the input signal during the 1/60 second signal processing time. The address mode is A24 with the upper 16 bits set by a dip select switch. The VME data format is D32 only. Data is stored in the VME interface memory in big endian mode, the default VMEbus mode. Data can be stored in little endian mode by selecting the little endian bit in the command word.
The signals are connected to the module via a standard DIN 96 pin female type front panel connector. A 10.240 volt reference through a 5.1K 1% resistor with its return also present at this connector. The 10.240 volt reference & returns are used to power external thermocouple "ice point" reference planes.

Ranges:
• +/- 10mV to +/- 10.24 volts full scale in steps of 2X. The ranges are controlled by the internal processor.

DC Accuracy:
• 0.1% of reading +/- 20 micro-volts on all ranges for the normal scan mode.
• 0.2% of reading +/- 40 micro-volts on all ranges for the fast scan mode.
• 0.01% of reading per month.