© Edwards Limited 2007. All rights reserved. Page 11
Edwards and the Edwards logo are trademarks of Edwards Limited.
Maintenance
D357-25-880 Issue E
5Maintenance
5.1 Zero adjustment
All diaphragm type gauges can exhibit a small drift in zero as a result of frequent cycling, over pressuring or
contamination. This can be corrected by carrying out a zero adjustment.
To zero the ASG, first evacuate the system to a pressure whose value is insignificant when compared to the required
measuring accuracy. Table 1 suggests the pressures that should be achieved for zeroing to give maximum accuracy.
Once the zeroing pressure has been achieved the ASG pressure display should be adjusted to zero. This can be done
using the zero setting potentiometer located on the side of the gauge head under the external O-Ring (see Figure 2).
The second potentiometer is for setting the gauge span and should not be adjusted without appropriate calibration
equipment. If the ASG is used with an Edwards Controller then the zero adjustment can be made at the display rather
than at the gauge head if this is more convenient (refer to the Controller’s instructions for details).
5.2 Cleaning
If the gas being measured contains oil vapour or other condensable products, the diaphragm may periodically become
contaminated which may cause shifts in both zero and span. Any clean solvent that is compatible with stainless steel
316L may be used to dissolve the condensate and flush out the pressure inlet port.
Note: Do not use any ultrasonic procedure in cleaning the gauge since that may damage the unit.
Table 1 - Zeroing pressure
Transducer Full Range (mbar) Zeroing Pressure (mbar)
2000 < 0.02
1000 < 0.01
To Next Page
Loading...