8
Analog Output
The VAS - 4 has an analog output, which will allow the vacuum to be
remotely monitored. The connection for this is located in the upper left
section of the printed circuit board (see Fig. 1). Two spade lugs are
provided for the connection. They are labeled GND for ground and OUT for
the output. The output is capable of sourcing 0 to 3 VDC or 0 to 3 ma. If a 4
to 20 ma loop is required, a signal conditioner can be used to convert the
output. These are available from many sources.
Maintenance and Calibration
Once the VAS - 4 has been in operation for approximately one week, the
unit should be checked for the correct zero reading. This is the reading
when no vacuum is present. Ideally, the zero reading would be 00.0.
However, due to the ambient temperature, some variation is normal. If the
zero reading is over 00.7 then an adjustment is needed. The zero
adjustment pots are located in the upper right hand comer of the board. One
of the pots, if looked at from, the middle of the board, is rotated all the way
to the right and the other pot is rotated to approximately the 12:00 position.
The pot that is close to the 12:00 position is the pot to adjust. Slowly turn
this pot to get the zero reading as close to 00.0 as you can. This will end
the zero calibration. If the reading still does not read 00.0 then slowly adjust
the other pot until a reading of 00.0 is set.
NOTE: AT LEAST ONE OF THE POTS MUST ALWAYS BE ROTATED ALL
THE WAY TO THE RIGHT.
Once a month the system should be functionally tested. This testing should
include all relays, LED indicators, delay timer and vacuum level accuracy. To
perform this test adjust your vacuum level up and down to cause the high and
low alarms to engage. The delay timer and reset can also be tested in the
same manner. At this time, inspect the board for any corrosion or loose wires.
If corrosion is present check all fittings for a snug fit.
DO NOT ATTEMPT TO CLEAN ANY CORROSION FROM THE BOARD.
HIGH VOLTAGE EXISTS ON THE BOARD.
Corrosion can only be removed by a trained technician. The outside of the
enclosure can be cleaned with warm water and a damp cloth.
