Instruction Manual
MX7M Active Gauge
2.8 Cleaning the MX7M Sensor
Refer to Figure 4 while cleaning the 7M sensor. Before disassembling the sensor, ensure that the unit
is removed from any power source and is removed from the vacuum system. Also ensure that you
have a new copper gasket or a o-ring. See the parts listed below. The cleaning steps are as follows:
1. Remove the sensor from the electronics assembly by loosening the two set screws in the base
of the electronics. A .050” Allen wrench is necessary for this step.
2. Remove the six bolts from the top of the unit. These require a 7/64 Allen wrench.
3. The MX7M ships by default with a copper gasket to allow customers to use the full range of the
MX7M . Any standard CF16 gasket will work with the MX7M . Once the bolts are removed, the
used copper gasket can be pulled free and discarded. Be sure not to scratch the knife-edge
surface.
4. If the gasket has been replaced with an o-ring, handle the o-ring gently and wash with isopropyl
alcohol, methanol, or DI water. Wipe with a lint-free cloth.
5. Visually inspect the o-ring for cracks or tears. If any physical defects are found, the o-ring should
be replaced.
6. Wipe the inside of the tube with scotch-brite or similar. Do not use steel wool due to the magnets
present in the sensor.
7. If wiping the inside of the tube does not remove all build up, bead blast the vacuum wetted
portions of the anode assembly at 30 PSI using 70 to 140 mesh glass beads (labeled with red
and blue in the diagram). Be careful not to damage the knife edge of the sensor.
8. Blast the vacuum wetted portions of the body with glass beads (labeled with blue in the diagram),
concentrating on the pole piece and “O” ring areas, but making sure to clean all surfaces wetted
to vacuum. If the threaded end of the tube needs to be cleaned, it can be bead blasted as well.
9. After cleaning, use compressed dry nitrogen to remove any residual glass beads or dust from
the sensor.
10. Wipe the anode with scotch-brite or similar. Blow with compressed dry nitrogen.
11. Install a new gasket or cleaned o-ring and seat the anode.
12. Before replacing the bolts, observe the keyway locations line up between the anode and the
body.
13. Replace bolts and tighten.
14. Insert sensor into the electronics and tighten the set screws.
15. Reinstall the sensor on the vacuum chamber.
16. Allow several hours for the sensor to degas when your system is pumped down to high vacuum.
17. If properly cleaned and assembled, the sensor is ready for use without re-calibration unless NIST
traceable calibration is required.
Table 3: Replacement Component Part Numbers
Description
Part Number
MX7M replacement anode assembly
1-7900-011
DN16 copper gasket
6-4200-031
DN16 viton o-ring
6-4200-030
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tel: +1 215 947 2500
web: frederickscompany.com
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