American Magnetics 135 & 136 Liquid Helium Level Instruments (CE-Marked) - Manual (Page 54)

42 Rev. 3
Virtual Instrument Operation
RS-232 Virtual Instrument
and the baud rate to which the Model 135/136 is set (see page 22 for
instructions on setting the baud rate). The user may then start the VI.
Please refer to your LabVIEW documentation for instructions on how to
start and control the execution of VI’s.
5.1.2 Interacting with the running VI
While the VI is running the user may manipulate the virtual toggle and
rotary switches in the same manner as required for the front panel
operation of the actual instrument. See the Operation section of this
manual for instructions on operating the front panel controls, however,
please note that there are some minor differences discussed below.
The RAISE/LOWER toggle switch functions slightly different in the VI. If
the RAISE/LOWER toggle switch is moved from the center position to the
RAISE or LOWER position, then the display changes to show the
appropriate parameter. After approximately 4 seconds in the RAISE or
LOWER position, the display will begin incrementing or decrementing by
tenths. After approximately 12 additional seconds, the display will begin
incrementing/decrementing by ones. Move the RAISE/LOWER toggle
switch back to the center position to stop the incrementing or
decrementing function.
As previously discussed, only the sampling mode toggle switch or fill toggle
switch should be manipulated via the front panel of the actual instrument
while the VI is running. The VI representation of the sampling mode toggle
switch forces the actual instrument to perform an immediate
measurement when placed in the UPDATE position. When placing the VI
switch in the UPDATE position, it must be left in the UPDATE position for
at least a couple of seconds in order to be recognized. Simply place the
switch back in the SAMPLE position to return to the operational mode
specified via the actual instrument’s sampling mode toggle switch.
The virtual instrument’s FILL LED indicator is only accurate if the fill
toggle switch is in the AUTO position. There is no remote monitoring or
control of the manual override states of the fill toggle switch available
through the communication command set.
As a more convenient option for controlling the settings, the user may
scroll to the area above the VI and enter the values for the Sensor Length,
Hi Setpoint, Lo Setpoint, and Interval directly in the control fields (please
observe the specified units). Any changes in the fields are recognized and
sent to the actual instrument in the form of the appropriate command
string. Any settings changed by the VI virtual panel toggle switches or
control fields are saved in permanent memory in the actual instrument.
The VI may be gracefully stopped by using the STOP toggle switch in the
lower left corner of the VI. After stopping the VI, this switch must be
placed back in the up position in order to restart the VI.