CPA1110

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).

Installation

This project now uses uv for dependency management, but the package can also be installed with pip.

Install the package with:

uv add cpa1110

or:

pip install cpa1110

For local development:

uv sync

Example

Using a context manager:

from cpa1110 import CPA1110, Connection

with CPA1110("192.168.1.10", connection_type=Connection.TCP) as compressor:
	# read the coolant in/out temperatures
	temp_in = compressor.coolant_in_temperature
	temp_out = compressor.coolant_out_temperature

	# start the compressor
	compressor.enable_compressor()

	# stop the compressor
	compressor.disable_compressor()

Without a context manager:

from cpa1110 import CPA1110, Connection

compressor = CPA1110("192.168.1.10", connection_type=Connection.TCP)
try:
	temp_in = compressor.coolant_in_temperature
	temp_out = compressor.coolant_out_temperature
	compressor.enable_compressor()
	compressor.disable_compressor()
finally:
	compressor.close()

Modbus protocol

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]