American Magnetics 185 & 186 Liquid Level Instruments (CE-Marked) - Manual (Page 68)

58 Rev. 3
Virtual Instrument Operation
Running multiple GPIB devices
6.2.3 Running multiple GPIB devices
The Model 18X via GPIB.vi in the MODEL18X.LLB library is designed to
have exclusive control of the GPIB bus. AMI recognizes this is generally
not the case for a GPIB bus configuration. Therefore, the Non-exclusive
loop control.vi
example is provided in the COMP18X.LLB library to
demonstrate how the Model 18X via GPIB.vi can be cooperatively executed
on a GPIB bus with multiple devices connected.
In order to use multiple devices from the same host computer and GPIB
bus, the Model 185/186 should be set to a unique primary address. In
addition to modifications required to use other devices present on the bus,
the user should modify the Non-exclusive loop control.vi to both initialize
and then execute the Model 18X via GPIB.vi at a regular interval. The
longer the interval between execution, the less responsive the VI will
appear. This is due to the fact that the VI assumes periodic execution in
order to poll the virtual switches and control fields for user-initiated
changes. The suggested period between execution is 1 second in order to
exhibit a reasonable level of responsiveness from the VI. The requirement
to constantly poll a virtual panel for changes is an unfortunate
requirement for running these types of continuously executing interfaces
using LabVIEW.