Python interface for a Cryomech CPA1110

The Cryomech CPA1110 compressor supports remote monitoring through serial (RS232/485), as well as ethernet connections, through the Modbus RTU protocol (for serial) or ModbusTCP (for ethernet).

from cpa1110 import CPA1110, Connection

compressor = CPA1110("192.168.1.10", connection_type = Connection.TCP)

# read the coolant in/out temperatures
temp_in = compressor.CoolantInTemperature
temp_out = compressor.CoolantOutTemperature

# start the compressor
compressor.enable_compressor()

# stop the compressor
compressor.disable_compressor()

There are various kinds of registers defined by the Modbus standard, but the CPA1110 only uses two kinds, namely Input and Holding Registers. The registers used are the following [CPAxxxx Digital Panel User Manual]:

• 30,001 - Operating State
• 30,002 - Compressor Running
• 30,003 - Warning State
• 30,004 - Errors
• 30,005 - Alarm State
• 30,007 - Coolant In Temp
• 30,009 - Coolant Out Temp
• 30,011 - Oil Temp
• 30,013 - Helium Temp
• 30,015 - Low Pressure
• 30,017 - Low Pressure Average
• 30,019 - High Pressure
• 30,021 - High Pressure Average
• 30,023 - Delta Pressure Average
• 30,025 - Motor Current
• 30,027 - Hours Of Operation
• 30,029 - Pressure Scale
• 30,030 - Temp Scale
• 30,031 - Panel Serial Number
• 30,032 - Model Major + Minor numbers
• 30,033 - Software Rev
• 40,001 - Enable / Disable the compressor

"Modbus protocol defines a holding register as 16 bits wide; however, there is a widely used defacto standard for reading and writing data wider than 16 bits." [source] "The first two 'Input' registers and the only 'Holding' register are 16 bit integer registers and the rest of the input registers are in 32bit floating point format." [CPAxxxx Digital Panel User Manual]