Citation
(1998), "New smart thermometer signal processing for plcs", Sensor Review, Vol. 18 No. 4. https://doi.org/10.1108/sr.1998.08718dad.011
Publisher
:Emerald Group Publishing Limited
Copyright © 1998, MCB UP Limited
New smart thermometer signal processing for plcs
New smart thermometer signal processing for plcs
The latest optional extra for the multi-channel Landmark graphic thermometer signal processor, from temperature measurement specialists Land Infrared, provides a powerful new mathematical calculation function which can be performed on the inputs of up to four different System 4 radiation thermometers used in a temperature monitoring or control system (see Plate 8).
The new unique add-on LMG Math Function card enables a Landmark graphic processor to simultaneously compute and output two additional values from the following calculations: maximum, minimum, mean, difference, (difference between two thermometer channels), and range (difference between maximum and minimum values from selected channels).
In addition, the expanded span function allows up to four thermometers with different measurement ranges to be linked together to give a single continuous wide temperature span.
Either 0-20mA or 4-20mA outputs can be set to cover the maximum/minimum output ranges selected of the maximum, minimum and mean functions. In difference mode, the mid-span output value (10 or 12mA)is set to indicate zero difference, to produce positive and negative values.
Typical applications for the math function option include: dual redundancy, product uniformity and heating or cooling processes.
In dual redundancy applications, where two thermometers are used to monitor the same target spot, the LMG card can be used to determine and provide an alarm when the readings are outside a user-set difference.
Plate 8 The LMG mathematical calculation
function is the latest add-on for Land Infrared's Landmark graphic signal
processor
In the case of temperature uniformity of a web or product strip, where multiple thermometers are mounted in an array to monitor the full width of the moving target, the LMG card calculates the difference between thermometer readings and trips an alarm if outside a user-set value, in order to ensure an even temperature profile across the product. The mean value can be used for process control purposes.
A large 320 x 240 pixel, back-lit cold cathode LCD panel provides a numeric or bar chart display of temperature, function, calculated value and alarm status for each thermometer channel.
Choice of RS232C or RS458 serial communications and user-adjustable high or low alarm outputs are provided.
For further information contact Tom McDougall, Land Infrared, Dronfield S18 1DJ, UK. Tel: +44 (0)1246 417691; Fax: +44 (0)1246 410585; E-mail: infrared.sales@landinst.com; URL: http://www.landinst.com