Process Chromatography Software for Modbus, Analog Output, OPC and Automated Stream Control
Process chromatography requires more than collecting a chromatogram and calculating a result. In an industrial environment, the chromatography system may need to manage multiple process streams, operate continuously, respond to plant conditions, exchange information with PLC, DCS or SCADA systems, and return results in a form the wider process can use.
Chromperfect provides several specialised modules for these requirements. They are not interchangeable products. Each addresses a different part of the process-integration problem, including automated stream control, Modbus data exchange, conventional analog and digital signals, and OPC-based communication.
Process Chromatography Software for Industrial Integration
Effective process chromatography software must connect the analytical workflow with the operational requirements of the plant.
In a conventional laboratory, a user may load a sample, start an instrument, review the chromatogram and report the result. A process analyser may instead be expected to:
analyse several different sample streams;
perform calibration, validation and blank runs;
switch valves and operate external equipment;
monitor temperature and alarm conditions;
record process information with the chromatographic result;
exchange data with plant control systems;
provide results through digital communications or conventional electrical signals.
Chromperfect supports these requirements through a family of process-focused applications:
Chromperfect Process Control;
the Modbus Repository;
Chromperfect Analog Output;
OPC integration.
The correct choice depends on whether the application requires automation, data exchange, physical process signals or connection to an existing OPC architecture.
Chromperfect Process Control
Chromperfect Process Control, commonly abbreviated to CPPC, is the automation layer used for process-analyser applications.
CPPC operates above the normal Chromperfect acquisition system. It does not replace the Acquisition Server or Acquisition Client. Instead, it coordinates the activities that surround chromatographic acquisition and processing.
A typical installation may have several process sample streams connected to a single gas chromatograph through a multi-position selection valve. CPPC can select the required stream, allow the sample loop to fill, prepare the appropriate analytical conditions and begin the run.
Once the chromatographic run is complete, Chromperfect processes the data in the usual way. CPPC can then proceed with another injection or select the next scheduled stream.
This separation is important. The normal Chromperfect acquisition and processing system remains responsible for collecting and processing the chromatography data, while CPPC manages the wider automated workflow.
Flexible Stream Scheduling
Process applications rarely follow one simple sequence.
CPPC supports several scheduling approaches, including:
continuous analysis;
fixed clock times;
specified time intervals;
priority requests;
operation as a slave to another analyser or stream.
These options allow a process system to combine routine sample streams with calibration standards, validation samples, zero gas and blank injections.
A stream can also use its own Method file and data destination. This allows different analytical, processing and reporting requirements to be associated with different streams.
The analytical cycle itself can contain more than one injection. For example, a configured cycle may include:
Blank → Sample → Sample → Sample → Blank
This makes it possible to prepare the system, perform replicate analyses and check the system after the sample sequence without requiring continuous operator involvement.
Digital Inputs, Outputs and Timed Events
CPPC can interact with external digital input and output hardware.
Digital outputs may be used to operate devices such as:
stream-selection valves;
blocking or shutoff valves;
heaters;
coolers;
external relays.
Digital inputs can provide information to CPPC, including:
maintenance mode;
a request for a priority stream;
an external alarm condition.
Chromperfect Method files can also use timed events to operate relay outputs during a run. This allows a process action to occur at a defined point in the chromatography cycle rather than only before or after the run.
The result is a coordinated system in which the chromatography, external valves and process equipment can operate as part of one controlled workflow.
Recording Process Conditions with the Chromatogram
In process chromatography, the chromatogram is only part of the analytical record.
The plant may also need to know:
which stream was analysed;
whether the run was a sample, blank, calibration or validation;
the current analyser status;
whether an alarm was active;
the temperature associated with the analysis;
the condition of external inputs.
CPPC can record this information in Chromperfect Raw files as User Fields. Documented examples include the run number, scheduling mode, stream type, calibration level, injection description, temperature reading, RTD status, alarm information and analog input values.
This contextual information can then be included in calculations, reports and the audit trail associated with the result. Chromperfect Raw files support User Fields specifically so additional analytical and process information can remain associated with the acquired data.
Temperature Monitoring and Control
Process analyser performance can depend on environmental and sample-conditioning temperatures.
CPPC can read a primary temperature sensor and, where configured, a backup sensor. The measured value can be written into the Raw file so that the temperature associated with the analytical result is preserved.
Configured thresholds can also be used to control heating or cooling outputs and generate alarm conditions.
This means that the analytical record can include not only the final concentration result, but also evidence that the process conditions associated with the measurement were within the expected range.
Why the Modbus Repository Exists
The Chromperfect Modbus Repository provides a structured way to exchange information with a plant PLC or another Modbus system.
A common industrial problem occurs when both systems operate as Modbus masters.
The PLC may be a Modbus master, while a Chromperfect module communicating with field hardware may also be a Modbus master. Two masters cannot communicate directly with each other in the normal Modbus architecture.
The Modbus Repository solves this by acting as an intermediate Modbus slave.
The communication path becomes:
Chromperfect → Modbus Repository ← PLC
Chromperfect can write information into the Repository, and the PLC can read it. The PLC can also write values into configured Repository registers, which Chromperfect applications may then read.
The Repository is therefore bidirectional for data exchange, but it does not independently control the gas chromatograph. It does not start runs, select Method files or issue autonomous control actions. Another configured application, such as CPPC, must interpret a written value and perform the required action.
Combining Modbus Communication with CPPC Control
A useful example is a priority-stream request.
The PLC may write a stream number into a designated holding register in the Modbus Repository. CPPC can monitor that register, recognise the requested stream and activate the corresponding configured priority stream.
In this arrangement:
Modbus carries the value.CPPC performs the action.
This distinction prevents confusion between communication and control. The Repository provides the data-transfer mechanism, while CPPC provides the process automation.
Modbus TCP/IP, Modbus RTU and Register Data
The Modbus Repository can operate using:
Modbus TCP/IP over Ethernet;
Modbus RTU over RS-485.
It can provide up to 2,000 holding registers. Each register can be assigned an address, a descriptive name and a defined data type.
Depending on configuration, the Repository can store:
signed integers;
fixed-point values;
Boolean states;
larger integer values using adjacent registers;
floating-point values using adjacent registers.
This allows the system to publish much more than a single calculated concentration.
Possible values include:
component amounts;
alarm states;
active stream numbers;
instrument status;
run status;
calculated values;
results generated by external processing tools.
The Repository runs as a Windows service and can be configured and monitored using the associated Modbus utilities.
Supporting Modbus Utilities
Chromperfect documentation also describes supporting utilities that can extend the information available through the Repository.
TextToModbus can read data from text or CSV-style files and write mapped values into Modbus registers.
PeepToModbus can receive acquisition-status broadcasts from the Chromperfect Acquisition Service and publish selected status values to the Repository.
The Modbus Calculator can read existing Repository values, perform configured calculations and write the result into another register.
These utilities are supporting tools rather than replacements for CPPC or the Repository itself. Their purpose is to extend the range of information that can be made available to the plant system.
Chromperfect Analog Output
Some process plants still require conventional electrical signals rather than software-based communications.
Chromperfect Analog Output provides a route from a processed chromatographic result to an external analog or digital signal.
The sequence is:
GC run → Raw file → processing → Bound file → Analog Output → process signal
The order matters.
The module does not transmit the live detector signal. It waits until the run has completed and Chromperfect has processed the chromatography data.
The result may already have been:
integrated;
assigned to a named component;
calibrated;
converted into a concentration or other calculated amount.
That completed result can then be scaled to a conventional process signal such as 4–20 mA.
For example:
0–1,200 ppm → 4–20 mA
This provides a familiar interface for PLC, DCS or other plant systems that expect a current-loop input.
Analog and Digital Inputs and Outputs
The Analog Output module can also support digital outputs.
A digital output may switch when a component result moves above or below the high or low limits defined in the Chromperfect Calibration file.
The module can also read analog and digital inputs. External measurements can be written into the Raw file as User Fields before processing.
Examples include:
temperature;
pressure;
flow;
contact-closure states.
This allows external process measurements to become part of the analytical record rather than remaining isolated in another system.
The current Chromperfect price list identifies Analog Output as a separate application option supporting up to eight channels.
OPC Integration
OPC provides another software-based route between Chromperfect and compatible process-control systems.
The documented OPC Client workflow can browse items available from an OPC server, read selected input values and store them in the Chromperfect Raw file.
It can also send calculated component amounts, alarm states and other reportable values back to the OPC server.
This can provide a connection into an existing DCS or SCADA environment where OPC is already part of the plant architecture.
Because OPC compatibility depends on the specific installation, server and system architecture, it should be evaluated for the intended application rather than treated as a universal connection method.
Choosing the Correct Chromperfect Module
The correct process chromatography software module depends on the requirement.
Automating multiple process streams
Use Chromperfect Process Control when the system must select streams, schedule runs, coordinate valves, manage calibration or validation cycles, monitor conditions and automate the analyser workflow.
Exchanging register data with a PLC
Use the Modbus Repository when chromatography results, status values, alarms or other information must be exchanged through Modbus holding registers.
Providing 4–20 mA or digital signals
Use Chromperfect Analog Output when a processed chromatographic result must be converted into a conventional current-loop or digital signal.
Connecting through an OPC environment
Use the OPC Client where the plant already uses a compatible OPC architecture and the application has been technically verified.
Making Chromatography Part of the Wider Process
Chromperfect’s process-focused modules extend chromatography beyond the laboratory workstation.
CPPC controls and coordinates the analyser workflow.
The Modbus Repository stores and exchanges information with plant systems.
Chromperfect Analog Output converts completed chromatographic results into physical analog or digital signals.
OPC provides another software-based communication route into compatible control environments.
Together, these capabilities allow chromatography to become part of a wider process-monitoring and control system while preserving the analytical Methods, calibration, processing, reporting and data records used by the laboratory.
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