Digital Deep Freezer Controller

Libratherm offers Microprocessor based Temperature Controller Model PID-2001 and Model
PID-2002 for the sub zero temperature control of low temperature baths or deep freezers. In a
freezer to attain the low temperature up to -25oC, the refrigeration system using single
compressor and condenser is sufficient, however to obtain the temperature of the order of -80oC,
two compressors in cascade configuration is used. The model featured here is designed to control
the single or two such compressors with the required inter logic.
The controller model PID-2001 accepts two Pt-100 sensors as the input to sense the temperature
in the refrigeration system at two different points. The control output is in the form of DC pulse to
drive solid state relay for controlling the onoff operations of the compressors. The special logic
and programming parameters such as set points and 3 level of hysteresis limits are accessible to
the user for proper control. The temperature of the 1st cooling system (C1) is monitored using the
1st sensor and temperature of the 2nd cooling system (C2) is monitored using the 2nd sensor. The
intelligent interlocking of the outputs prevents the loading of both C1 and C2