Granville-Phillips Series 330, Instruction Manual, Page: 55 / 76

5 Convectron Gauge Module
55
Series 330 Vacuum Gauge Controller
Instruction Manual - 330004 - Rev. 02
5.3.7 Analog Output Full Scale Adjustment
The Analog Output Full Scale Adjustment potentiometer can be adjusted to calibrate the span of the
analog output voltage to the factory setting of 1 volt per decade. This adjustment is common to both
outputs.
5.3.8 Analog Output Offset: Gauges A and B
The Analog Output Offset potentiometers (Figure 5-11) provide adjustable offset voltages to each
analog output. The range of this adjustment allows setting the analog output at vacuum (P = 1 x 10
-4
Torr) anywhere in the range -7 to +1 Vdc by adjusting the Analog Output Offset potentiometers to
yield the desired voltage output when both gauges are at vacuum (pressure less than 1 x 10
-4
Torr).
5.4 Cleaning the Convectron Gauge Tube
The Convectron gauge can be baked to 150º C.
When the fine sensor wire is so contaminated with oil or other films that its emissivity or its
diameter is appreciably altered, a change of calibration will result. Cleaning with trichloroethylene,
perchloroethylene, toluene, or acetone is possible but it must be done very carefully to prevent
damaging to the sensor.
1. Hold the gauge tube with the main body horizontal and the port projecting upward at an angle
of 45º. Slowly fill it with solvent using a standard wash bottle with the spout inserted in the
port to where it touches the screen.
2. Let the solvent stand in the gauge tube for at least ten minutes. Do not shake the gauge tube if
the gauge tube is only partially filled—liquid forces on the sensor can become large enough to
affect the transducer calibration. If the gauge tube is completely filled, shaking is not helpful.
3. To drain the gauge tube, position it horizontally with the port facing downward. Rotate the
gauge tube slowly and tip it end-to-end so all of the solvent drains out. By slightly warming the
gauge tube, a positive pressure will build up internally forcing the solvent out past the screen.
4. Allow gauge tube to dry overnight with the port vertically downward and uncapped. Be
certain no solvent odor remains before reinstalling gauge tube on the system.
The fumes from any of these solvents can be dangerous to your health if inhaled and
they should be used in well ventilated areas exhausted to the outdoors. Acetone and
toluene are highly flammable and should be used away from open flame or electrical
equipment.