Signal conditioning has been around since the dawn of instrumentation and the requirement of taking measurements in the process plant. Many measurement issues have been dealt with over the years with standardisation for the sake of improved consistency, reliability and compatibility. Performance issues like sensitivity, accuracy, linearity and resolution are all established in today's signal conditioning instrumentation.
So what is new about new generation signal conditioning? Well less is more!
The less is more requirement
Omniflex offers a wide range of signal conditioning capability in a small range of products. This is the direct result of the attention paid to lowering the cost of ownership of signal conditioning.
At a quick glance, most signal conditioning modules look the same. But the following factors need to be considered in choosing a product range:
* Installation costs.
* Spares stock holding.
* Re-calibration costs.
* Reliability.
* Plant safety.
Each of these factors has been taken into account in the design of the OMNITERM 'B' series range. A solution from the following product groupings can be selected to meet performance and budget requirements:
Loop isolators
This is a typical challenge that relates to all plants no matter how old or new. The elimination of ground loops in analog 4-20 mA signal loops is the key to reliable and accurate measurements. Loop powered isolators simplify the wiring since they are simply inserted directly into the current loop. There are OMNITERM products that can solve these system problems, whether there is a need to isolate a transmitter from its power source, to boost an overloaded loop, or to split the loop into two for the addition of data acquisition or monitoring.
Loop splitters
A common condition on the modern plant is the requirement for more process information for improved control. This often means that signal conditioning systems need to be shared by supervisory and control applications. Adding more devices in a current loop often leads to problems with isolation and loading of the loop. The loop splitter converts one current loop into two fully independently isolated loops. Each output loop is independent of the other for example shorting one loop has no effect on the other.
Signal transmitters
Some of the latest conversion technology combined with full software configurability makes these OMNITERM products one of the most accurate and versatile in their class. Universal inputs ensure a decrease in installation costs, spares holding and re-calibration costs. A single transmitter is capable of accommodating the following options:
Inputs:
* Thermocouples.
* Resistance (RTDs).
* Millivolts.
* DC voltage.
* DC current.
Outputs:
* DC voltage (bipolar)
* DC current (bipolar).
* Pulses out (linear integration).
Other transmitter units for:
* AC voltage.
* AC current.
* Frequency.
Limit alarms/trip amplifiers
A range of alarm modules are available from simple limit alarms with manually adjustable set-points to software configurable units capable of rate-of-change alarming direct from the sensor input. The sophistication of the scada and control systems are migrating to field signal condition devices.
Computation
It is a well accepted fact that most computation is done on a scada, PLC or DCS on the plant. However, when there are a few analog signals that require manipulation or computation, the ideal solution is to process those signals directly in the plant. These modules are designed to solve those tricky special functions required in certain processes, where the sensors require to be conditioned according to a more complex mathematical formula. Available functions include deviation, addition, subtraction, multiplication, linearisation, rate-of-change, peak, valley, ratio and track-and-hold.
Safety systems - IEC61508
IEC61508 is a standard being adopted for many industries and the requirements are such that the individual components of a system need to be analysed for compliance within the context of the safety system and its safety life cycle. The OMNITERM 'B' series are compliant with a SIL 1 Rating making them easy to apply in safety critical applications and saving time in the Haz Ops study phase of a project.
For more information contact Ian Loudon, Omniflex, +27 (0) 31 207 7466, [email protected], or visit www.omniflex.com
| Tel: | +27 31 207 7466 |
| Email: | [email protected] |
| www: | www.omniflex.com |
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