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Why You Should Consider Using Isolated Measurement Systems

The Benefits of System Isolation

By keeping data acquisition signals separate, electrical isolation adds a layer of protection to your measurement equipment, both for the system’s components and to its collected data. But what exactly is electrical isolation, and what amount of isolation does your data acquisition system need? In this latest White Paper from CAS DataLoggers, we discuss why you should consider using isolated data acquisition systems and data loggers in your process-critical applications.

What is Electrical Isolation?

Electrical isolation is a protective design feature of many data loggers and data acquisition systems. Isolation is implemented to separate measurement signals from each other in order to keep them from interacting and causing electrical issues.

A specific type of isolation, galvanic isolation, separates different sections in the system to cut off the flow of current among them. This protects the system’s electrical components while still allowing for communication and data exchange per usual between electric circuits. For example, you can use Hall effect sensors which incorporate magnetism to transfer data across galvanically-isolated system components. By allowing no DC paths, galvanic isolation keeps unintended current from flowing between the system segments.

Your existing data acquisition equipment may already have isolation; if you’re unsure, check the device’s specification sheet. If your system is multiplexed (combining several signals into one), it already features a level of isolation between channels. Devices with greater communication capability often have (or require) galvanic isolation owing to their greater need to safeguard data. Note that solid-state systems lack galvanic isolation.

Why Isolate Your Systems?

Isolation is often required in real-time data acquisition applications such as:

  • Automotive manufacturing
  • Machine monitoring (turbines, motors, etc.)
  • Food processing operations
  • Materials Engineering (alloys, etc.)
  • Many other heavy industrial uses

One excellent reason to use isolated data acquisition systems is to protect yourself or your personnel from electrical accidents. In particular, galvanically-isolated systems protect operators from being exposed to unsafe currents and high voltage. Otherwise, current flowing between the system’s units can cause serious harm.

Likewise, electrical isolation also ensures that your system’s circuits are safe from damage from excessive current and voltage levels.

Another good reason to use isolated measurement systems is to ensure that your measurements are free (as much as possible) from signal noise. In electronic equipment, signal noise is a very common wiring issue which corrupts your devices’ program signals, leading to data distortion or drops. Signal noise is caused by unintended current carried by a ground feedback loop, which is in turn formed when two or more connected electrical systems are accessing more than one path to the ground. Resistance changes these currents into voltage fluctuations, causing the problem.

As mentioned in our earlier White Paper, ‘Seven Ways Signal Noise Can Impact Your Electrical Equipment,’ applications with high signal noise and electromagnetic interference can greatly benefit from system isolation. Many manufacturers of data acquisition systems offer several different models of their basic product, featuring different levels of isolation such as channel-to-channel, galvanic, etc.)

While it’s true that all measurements have a certain amount of inaccuracy, if you’re working in a high-accuracy application then you’ll need to reduce this inaccuracy as much as possible. An isolated design helps to prevent signal noise by likewise preventing ground loop feedback.

Galvanic isolation offers an additional benefit in the form of common-mode voltage rejection, which reduces signal noise by ignoring those signals (voltages) which are common to both inputs. This is especially useful if you’re trying to record accurate measurements in areas with high levels of electromagnetic interference.

What Risks are Posed by Non-Isolated Systems?

While isolated measurement systems are fractionally more costly than non-isolated products, you may find that the cost of repairing or replacing your system is much higher!

For the average user of a data acquisition system, the most likely risk is that the analog/digital signals will be corrupted or that the system will be damaged as a result of unintended ground current flow. For example, your system’s circuits can fry in an instant if this threat is not mitigated beforehand by isolation. For all practical purposes, non-isolated systems also restrict your choice of input signal types.

However, Ground loops pose one of the greatest threats, both to measurement signals and to users themselves:

  • Data Loss: Networked data systems lacking isolation are at great risk of losing data through signal degradation. Isolation safeguards data from signal degradation while also helping to protect your initial investment in your data acquisition system.
  • Physical harm: Users of non-isolated systems face a real risk of harm caused by high current or voltage.

Isolation prevents these ground loops from forming, thereby protecting the system and measurement signals. If you need to take additional precaution, galvanic isolation prevents ground loops by preventing the current paths which cause current to flow between units in the first place (i.e. by breaking the loop).

If you’re working in a process application, you’ll want isolation as an extra precaution against measurement and control system failures, which can cause a costly process delay or shutdown.

If you’re a systems integrator or contracted purchaser, you should consider isolating your data acquisition systems to avoid complaints or even lawsuits from customers whose systems were damaged from ground loops and other electrical issues. By supplying systems with built-in isolation, you can also gain a reputation for quality products in the heavy industrial market.

Summary:

No matter what application you’re considering sourcing a data acquisition system or data logger for, we highly recommend you first consider whether or not you’ll need a system with built-in isolation. If so, the marginally higher cost is well worth it considering the potential for lost data, damaged components, and/or physical risk to the operator. If you’re not sure whether or not your application requires isolation, be sure to address this with a trusted solutions provider.

For more info on Data Acquisition Systems, or to find the ideal solution for your application-specific needs, contact a CAS Data Logger Applications Specialist at (800) 956-4437.