3. OPERATION
Page 21 © 2002-2007 DH Instruments, a Fluke Company
3.2.2 PRESSURE READY/NOT READY
There is a Ready/Not Ready indication LED on the PPC3 front panel. This indication is
intended to provide the user with a clear and objective criterion for determining when a valid
pressure measurement can be made.
The Ready/Not Ready LED indications are:
<Green, no flash> Pressure Ready, control idle. PPC3 is NOT actively controlling the
pressure. This indicates no control is occurring and the pressure
stability is within the stability limit.
<Green, slow flash> Pressure Ready, control active. PPC3 is actively controlling the
pressure and the criteria for a Ready condition to occur have been met.
<Red > Pressure Not Ready. Either PPC3 is idle and pressure does not meet
the stability test or PPC3 is actively controlling the pressure and Ready
conditions have not yet been met. The control characters in the
middle of the second line of the display flash if control is active.
When pressure control is NOT active: A Ready condition occurs any time NO control
valve is operating and the pressure rate of change is inside the stability limit. The stability
limit is defined in terms of rate of change of pressure in current pressure units per second.
When pressure control is active: The criteria for determining the Ready/Not Ready
condition depend on whether the current control mode is static or dynamic. Pressure
Ready/Not Ready parameters are set by default when AutoRange is used, or a control mode
is selected. The parameters can be customized if desired (see Section 3.4.6).
Dynamic Control Ready/Not Ready
With dynamic pressure control active, a Ready condition occurs whenever:
• The current measured pressure is inside the hold limit.
In dynamic control mode, normal procedure is to assume that when a Ready condition
occurs (pressure inside the control hold limit), the measured pressure equals the target
pressure. For this reason, when the pressure is Ready in dynamic control mode, the
measured pressure display is equal to the target pressure.
Figure 8. Ready/Not Ready in Dynamic Pressure Control Mode
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