Du Pont SORVALL RC-5 Service Manual page 118

Refrigeration
SystemSon/all®
CentrifugesRTDRELAYSELECTIONCOMPARATOR
REQUESTHOLD
TIMING(ENFORCED)15
SEC
ON120
SEC
OFFRUN
TIMING40
SEC
OFF(ENFORCED)NO
ON
LIMIT7/79RCS/44Figure
5-4.
Temperature
Control
Circuit,
Block
DiagramThe
selection between the red and blue set points is made
by
the RUN-HOLD relay
K205and
relays
K2
and K3.
Relay
K205
and
K2
are energized
when the centrifuge
is in
theRUN
mode,
and
refrigeration is
controlled
by
the blue
pointer.
K205 is
unenergized
andK3
is energized when the centrifuge is In
the HOLD
mode,
and refrigeration is
controlledby
the red
pointer.The
refrigeration signal is applied to
the differential amplifier and compared against
areference
voltage.
When
the refrigeration signal is higher
than the
reference voltage,
K55-6