phone: (215) 947-2500 fax: (215) 947-7464 e-mail: [email protected] web site: www.televac.com
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CHAPTER 8
CHAPTER 6
(cont)
TELEVAC
CHAPTER 7
3.0 Bake-out of the sensor ( 7FR )
3.1 Without removing the sensor from the vacuum system, separate the electronic block from the
sensor as described in
Section 1.0 (Disassembling the 7ER/7FR
)
.
3.2 After separating the electronics from the sensor, but before disassembling of the sensor for
cleaning, use a marker to mark the orientation and positions of the magnets relative to each other
and relative to the stainless steel sensor tube. These are aligned at the factory for optimum
performance of the sensor. When reassembling after cleaning, reassemble I reverse order with
the magnets in their original respective locations and like pole surfaces facing each other (N to N,
S to S).
3.3 Holding the magnets, use a 1/32” Allen wrench to remove three setscrews on the top aluminum
holding ring.
3.4 Slide away the magnet’s washers and aluminum spacers from the tube’s body. Do not remove the
lower aluminum holding ring (one that is closest to the flange).
3.5 Bake out the sensor using heat tape, blanket or other means with temperature controls.
Temperature on the gauge’s surface should not exceed 350°C.
NOTE
: if the bake out temperature
does not exceed 180°C for 2 hours, the sensor could be baked out with the magnets in place.
3.6 After cooling the sensor down to room temperature, re-assemble with the magnets in their original
respective locations and like pole surfaces facing each other (N to N, S to S).
3.7 Put the electronic block onto the sensor and secure it with flat socket screw.
Calibration
All instrumentation is calibrated at the factory. No further calibration at the customer’s facility
should be required, even if the gauge tube is replaced.
For a reliable recalibration at a later date, it is necessary to have a reference standard vacuum
system whose pressure is known to be accurate. For such a calibration, the instrument and sensor tube
should be returned to the factory for re-certification. However, if the vacuum calibration verification must
be done at the customer’s facility, a knowledgeable electronics technician trained in vacuum calibration
should operate equipment of certifiable accuracy.
Troubleshooting
1.0
If display consistently displays “HI”, the pressure may be above the gauge upper limit (1 x 10-2
TORR) units to the gauge or there may be a leak locally. Check the integrity of the vacuum
connection and, if the 7E sensor is used, check the o-ring seal on the sensor tube.
2.0
If the display constantly reads “LO”, the sensor may have become inoperative. Check for correct
reassembly after bake out.
3.0
If the display continues to read “LO” or “HI” after completing step 1.0 or 2.0, the sensor may be
contaminated. Contamination can prevent the sensor from properly discharging (reference
chapter 4, paragraph 4.0 of this manual for information on operation of the sensor). To clean the
sensor, refer to chapter 6, paragraph 2.0 of this manual.
NOTE: If, after doing some or all of the above, the unit is still inoperative, return to the factory for repair.
