Data Acquisition

These commands set a value internal to the device that the user may only want to setonce, or at least not very often. Parameter commands have a global effect, can be set atany time, take effect immediately and allow the user to set different performance options.A parameter command can often have a wide range of values within the parameter’slimits for a particular device.Where the stand-alone logger/controller is connected as part of a network, allcommands must be preceded by the address of the device for which the command isintended.All data returned to the host PC from stand-alone devices is in simple ASCII text format.The format of the ASCII string is entirely configurable by the user and will be sent in theformat in which the stand-alone device was requested to send it. Data is typicallypresented in two mathematical formats:• Floating point format with ‘n’ (user configurable) significant digits• Exponential format with ‘n’ (user configurable) significant digitsIn addition, the ASCII string can be made more readable by the addition of thefollowing text:• Units applicable to the measurement being taken (e.g. mV, Ohms, Hz etc)• The channel number and type of signal being measured or type of sensorbeing used (e.g. 1 V, 2 LM35)• A channel ID string (e.g. boiler temperature # 1)• The time and date indicating when the reading was taken (e.g. 10:3012/12/99)Where the data is to be imported into a spreadsheet software package, it can beformatted so that it contains no additional text except the time (HR:MIN:SEC format) anddate (DD/MM/YYYY format), is delimited by commas (ASCII 2C), and each line of datais terminated by carriage return (ASCII 0D).If the stand-alone logger/controller is connected as part of a network, the data that isreturned can be configured to include the address of the device from which the data wasreturned.When an error occurs, either in sending a command to the stand-alone device or inperforming some function, the error can be reported by returning error messages to thehost PC.Although not differentiated on all makes of stand-alone device, three types of errors arecommonly recognized:• Command errors• Channel errors• Operational errors