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26 November 2013

Windmill Software Ltd
Data Acquisition Intelligence


Data Logging from Pilot Plant with Molytek

In 2001, a Hercules pilot plant for the manufacture of water treatment chemicals used an old DOS program to control its data loggers. The plant's Program Manager wanted to upgrade the software but feared he would have to write the program himself, as he could not find a flexible product that would accept custom-made drivers. Then he discovered Windmill software.

"The Windmill software was a great find for me. The free download was used to evaluate application of the software to my datacq hardware. I then purchased a license for three installations."
Jeff Castor, Program Manager, Hercules

This year Mr Castor upgraded the software to Windmill Version 7.

Most of the water treatment chemicals manufactured by the plant are polymers, made by typical batch polymerisation processes (solution, emulsion and dispersion polymerisations). The plant consists of six reaction systems. It employs seven Molytek 2702 loggers, connected via an RS232 link to a PC by means of a code activated switch. The Windmill software suite could easily read and control the Molytek loggers through its serial driver. The suite also included a software Logger application to store and time-stamp many channels of different types of data. Process data logged from the plant by Windmill include: reactor temperature, reactor jacket temperatures (supply and return), reactor jacket flowrate, reactor pressure, overhead temperatures (vapour, distillate, condenser coolant) and various weights, reagent flows and process analytical instrument readings.

Readings taken by Windmill are passed to various data processing tools for analysis and reporting, including Excel, RS/1 and TK!Solver.

The Molytek 2702 was a state of the art logger in the 1980s. It is built of standard mechanical and electronic components and so, can, in theory, be maintained indefinitely. For that reason a lot of 2702s are still around. They make a good, reliable, hardware front end to a low speed data acquisition system.

Windmill is currently on special offer from our on-line catalogue for just £50.


Windmill Settings for the Molytek

If you want to talk to a Molytek through a code switch, in addition to adding the code switch commands ahead of each channel prompt string, you may find it necessary to adjust the "timeout" and "Instrument Idle or Wait Time" values in ConfIML setup. This adjustment will have to be arrived at by trial and error. Other settings are as follows, although you may need to alter them depending on how you are using your Molytek loggers.

Initialisation String: ***
    
An Initialisation message is sent when the instrument driver (COMIML or LabIML) loads, and only then. It should contain any data you need to send just once to the instrument to configure it for use.

Timeout: 5000 ms
    
The timeout is the number of milliseconds that the instrument driver will wait between sending out a prompt string and obtaining a reply. A reading error will be declared if this is exceeded. To avoid spurious timeouts set to between five and ten times the normal response time.

Data persistence time: 5000 ms
    
Once data has been read from an instrument it is stored and returned as a valid reading until the persistence time has expired. Thereafter an attempt to read it directly will cause a new reading to be taken. If you set the persistence time to 0, every channel reading will cause a complete message to be executed. With a longer persistence time the message need only be executed once and all channels can be obtained from the stored data. When reading in the background the persistence time should be longer than the Instrument Idle or Wait Time.

Instrument Idle or Wait Time: 100 ms
    
Some instruments do not like being read from at too high a rate. This setting ensures a minimum time between messages. This is important in Background mode as it is used by the driver to determine the rate at which it reads the instrument.

Read mode: Read Directly (Request/Response on Demand)
    
Messages are only sent when Windmill reads from or writes to a channel. Windmill then waits for a reply from the instrument.

Prompt String: SVAA
    
Depending on the channel being talked to.

Parse String: \I","\I03\E"\C013"
    
Which translates to - Ignore until comma, Ignore next 3 characters (including the comma), Extract data until a carriage return occurs.

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