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4-2 Cool Only Control
An ETR-3000 is used to control a refrigerator at a temperature below 0 °C. The temperature is lower than the
ambient, therefore a cooling action is required. Select DIRT for OUT1. Since output 1 is used to drive a magnetic
contactor, O1TY should be set to RELY. A small temperature oscillation is tolerable, hence use ON-OFF control to
reduce wear and tear on the mechanical parts and resulting over-all cost. To achieve ON-OFF control, the PB is set
to zero and O1HY is set at 0.1 °C.
Setup Summary:
INPT=PT.DN
UNIT= °C
DP=1-DP
OUT1=DIRT
O1TY=RELY
Refrigerator
RTD
Main
Supply
User Menu:
PB = 0 ( °C )
O1HY=0.1 ( °C )
9
8
10
6
5
O1
O2
ETR-3000
C
Figure 4.2 Cooling Control Example
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