GASGUARD IS CONTROLLER Issue: R2, Date: 26/09/2011, CRN: 7502
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2.9.5
Alarm Set-Point Hysteresis
Under normal operating conditions, a measured value from a sensor connected to the Controller, may be sat close to
the value set as an alarm set-point. For example, a slowly rising gas level may have just reached the set-point
threshold. The measured value may briefly cross the set-point threshold and then drop back below it again. If no
alarm delay has been set, then an alarm relay may ‘chatter’ on and off, creating unreliable alarm signals to
connected equipment. To overcome this problem, a hysteresis level may be set for each process alarm on each
channel. The hysteresis value can be set from 0% to 20% of the channel full scale setting.
Figure 1: Effect of Setting Alarm Hysteresis.
Summary of Contents for gasguard
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Page 62: ...GASGUARD IS CONTROLLER Issue R2 Date 26 09 2011 CRN 7502 Page 61 B2 Main Menu Flowchart ...
Page 63: ...GASGUARD IS CONTROLLER Issue R2 Date 26 09 2011 CRN 7502 Page 62 B3 Calibration Flowchart ...
Page 64: ...GASGUARD IS CONTROLLER Issue R2 Date 26 09 2011 CRN 7502 Page 63 B4 Configuration Flowchart ...
Page 74: ...GASGUARD IS CONTROLLER Issue R2 Date 26 09 2011 CRN 7502 Page 73 Appendix C Approvals ...
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