This four slot filter-wheel was originally designed for the US military to work in a 10^-7 Torr vacuum environment. Today, a standard non-vacuum version and the original vacuum version are available. The vacuum version is manufactured in a Class 10,000 clean room, fully baked out, and meets Class A cleanliness standards. Please note that the optional external control electronics is not designed to operate in a vacuum. It must operate in ambient pressure environment.

Control Electronics
The motorized filter-wheel is operated through a non-vacuum grade model MD-100 stepper motor controller (available at extra cost). The MD-100 controller must therefore be placed outside the vacuum chamber and connected to the RS-232 serial port of a Windows based computer to receive control commands.

Software Control
The motorized filter-wheel comes with Active-X software controls to move the filter positions. It also has available TCP/IP support such that the filter-wheel can be controlled over a computer network rather than on the local host computer. This software is included with the filter-wheel but not the MD-100 stepper motor controller which must be purchased separately.

Bi-Directional Rotation
When used with Sciencetech MD-100 Stepper Motor Controller and Sciencetech Sci-FilterWheel Active-X software, the filter-wheel can change slot positions bi-directionally. For example, if the filter-wheel is on Slot Position 3, the Sci-Filterwheel software would instruct the filter-wheel to move forward to Slot Position 4 or move backwards to Slot Position 2. It would not say, move from Slot Position 3 to Slot Position 2 by going forward around the entire slot positions. However, there is still one small software flaw that needs to get fixed. Since Sci-Filterwheel software is used universally for all Sciencetech filter-wheels from the 4 slot model to the 8 slot model, it cannot apply this intelligent logic at the cross over point from the last slot to the first slot. For example, in a 4 slot filter-wheel, it would still go back 3 positions from Slot Position 4 to Slot Position 1 rather than going forward one position.

Home Position
A mechanical cherry switch is used to identify the home position, which is the same as the first slot position. Please note that there is only one home position rather than a home position for each filter slot. The location of the other filter slots is calculated within the Sci-FilterWheel or Sci-Spec/Sci-LDA software once the home position is identified.

Direct Drive Shaft Coupling System
The filter-wheel is coupled directly to the drive shaft without any gear work or belt drive. This reduces backlash and assures the rotation precision is as precise as the micro-stepping capability of the stepper motor which is 2000 counts per 360 degree revolution. Since the stepper motor is always energized even in a stopped position, there is no noticeable backlash or positional drift once stationary in a slot position.

Light Tight Housing and Flat Surface Mounting
The aluminum housing is light tight and with the stepper motor mounted on one side of the filter-wheel, the opposite side remains completely flat without obstruction for mounting purposes.

Cleanliness Standards
The filter-wheel meets Class A cleanliness standard (less than 1mg of non-volatile residue per square foot) with all parts ultrasonic cleaned or wiped down with IPA reagent and assembled in a Class 10,000 clean room.

Space Flightware Qualification
Although this filter-wheel has not been space flightware qualified, it can be qualified through Sciencetech's space partner MD-Robotics, the makers of the CanadaArm on the Space Shuttle and International Space Station. Please inquire about this qualification procedure. So far, this filter-wheel has only been used in a ground based vacuum chamber to simulate space environment.

Technical Specifications
Filter-Wheel Weight: ~500g (without filters)