Guarantee High Assignment

 

An opcode with a GH prefix stands for guarantee high.  During a recipe, a guarantee high will allow the recipe timer to run only while the PV is at or below the upper limit.  The upper limit is the value of the set point plus the wait limit. 

 

If the PV moves above the upper limit, the recipe will pause and a new timer will begin.  This timer is called the Default Hold Time and can be found and adjusted in the Menu under Furnace Setup.  This timer will keep track of the amount of time the PV has been above the upper limit.  If the PV fails to move below the upper limit within the Default Hold Time, the programmer alarm will be activated.  Once the PV moves below the upper limit, the recipe timer will resume.   

 

For example, if the PV is temperature with a 1500° set point and the wait limit is 15°, the recipe timer will continue to run as long as the PV is at or below 1515°.  If the PV moves above 1515°, the recipe timer will pause and the Default Hold Time countdown will begin.  The recipe timer will resume once the PV moves back to 1515° or below.