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INTERMEDIATE RELAYS
EXAMPLE 4

TM-5-3895-374-24-1 Paving Machine Bituminous Material: Crawler Mounted Diesel Engine Driven Manual
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TM 5-3895-374-24-1 GP470FA APPENDIX C: ON TIME CALCULATIONS AND EFFECTS OF TUNING PARAMETERS The following examples illustrate the calculations preformed by the controller to determine output relay operation.  Various deviations, proportional bands and cycle times are used to show their effect on the control action. EXAMPLE 1: Dryer Draft (PV) = -0.30" wc Setpoint (SP) = -0.20" wc Transmitter Range (RG) =  1.00" wc (0.00" to -1.00" wc) Proportional Band (PB) = 50% Cycle Time (CT) - 5 seconds Since the measured draft is greater than the setpoint the deviation is a positive value and the controller will respond by energizing Relay 1 in order to Close the exhaust damper.  The on time of relay 1 is calculated as follows: DEV    = (SP - PV) = -0.20") - (-0.30") = 0.10" DEV Output = PB x RG 0.10 0.50 x 1.0 = 0.20 Displayed as OUT 70.0 (50 + 20) On Time = : CT x Output : = : 5 x 0.20 : = 1.0 seconds Relay 1 will be on for 1.0 seconds and off for 4.0 seconds. (page 3-49)







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