What is a Current Transducer?
Electricity is everywhere and powers everything; it is such a widespread requirement throughout all aspects of our modern world that it is easy to take it for granted. Naturally, we need the ability to monitor such a common variable that is necessary for the infinite amount of processes going on all around us. Enter the current transducer, an instrument that helps us keep track of electricity use, amongst other things. By quantifying the variable of electricity we can create a set of data that helps us observe, control, and automate all sorts of processes in our homes, commercial offices, factories, manufacturing plants; really anywhere that uses electricity could use a current transducer. But what exactly are these instruments and how do they work? Let’s examine: what is a current transducer?
Figure 1: A pair of Enercorp current transducers
What are Current Transducers?
It’s the “transducer” part of current transducer that is key to understanding what this instrument is. A transducer, by definition, converts one form of energy into another. In our case, current is converted into a representative standard analog signal. We’ll discuss the benefits of the analog output a little later in this blog. You may already be familiar with the concept of a transducer from our discussion on ”What is a Pressure Sensor?” For now, know that the current transducers help measure the variable of electricity and translate it into a type of data that can be interpreted by a process control system.
Current transducers come in all sorts of shapes, sizes, colours, and technical specifications. Physically, most will fit in the palm of your hand and they all share the same universal characteristic; an aperture for a process wire. But that’s where the similarities end. Current transducers are rated to measure a specified range of current; some can sense 0…50 Amps and others 0…200 Amps, for example. When installing a current transducer it’s important to consider the job it will be tasked with and the environment where it will be used. Let’s go through some other different characteristics between types of current transducers.
Many current transducers, such as those in Enercorp’s line, have mounting brackets to help fasten the instrument to a surface, keeping installations in a tidy and secure state. This also allows for simple adjustments to existing units or for whole current transducers to be swapped out with ease.
Figure 2: Mounting a current transducer
A split core is a feature of some current transducers that can simplify installation. On these models, the sensing aperture opens and closes on a hinge. This allows a user to clip the current transducer securely around an existing wire. This feature comes at an additional cost but can be an incredible time-saver. Meaning, less exposure to potentially dangerous wiring jobs or downtime while electrical power is cut during an install.
Figure 3: An open SC100-L split core current transducer
Another feature of some current transducers is a switch. This takes a current transducer from being just a data-collecting instrument to a triggering device. The switch allows for the opening or closing of a secondary circuit when the current transducer senses a certain threshold. There is typically an adjustable setpoint so the switching action can be customized to occur when ideal parameters have been reached. We’ll come back and explore this feature in a moment.
Figure 4: The SC250, a current transducer switch with adjustable setpoint
We keep many current transducers in stock ready to ship out to Enercorp customers. Have a look over at our Current section to get a real-world sense of the wide variety of instruments that make up this category. You’ll see the range of choices that have some of the characteristics listed above and get a better idea of just how diverse these sensors can be.
How do Current Transducers work?
Current transducers work via the principle of induction. The wire that is threaded through the current transducer will be the process measured and when an electrical current flows through the wire an electromagnetic field is created around it. The current transducer, encircling the process wire, senses and quantifies this current. That measurement is converted into an analog signal and transmitted as an output to a variety of process controls that can utilize the data in any sort of numerous functions. We’ll talk more about the specifics in another blog “How do Current Transducers Work?” so be sure to read through that to get the whole scoop on the inner workings of current transducers.
Figure 5: A current transducer diagram
Where to Use Current Transducers?
Now that we’ve gone through the basics, who uses these current sensing instruments or where will you find them? The short answer to that: everyone and everywhere. Electricity is so ingrained in every aspect of our modern world that the requirement to measure the medium or trigger specific actions when certain parameters or conditions exist, is equally as universal.
When looking for applications we’ll start close to home, really close. Have you considered how your utility company knows how much power you have used in your house? There is a form of current transducer in your electricity meter.
Figure 6: A building electricity meter
Industry and manufacturing are enormous consumers of electricity and, likewise, they use current transducers throughout the many different processes required to generate, produce, or manufacture their goods. Take just about any electricity-consuming device, like a water pump or fan motor, for example. Another usage for current transducers is to sense if power is being sent to the device and deliver a signal to a central control center or an automated-system. This will indicate that the pump or motor is currently under load.
One of the features of some current transducers, as mentioned earlier, is a switch. With this additional capability, current transducers can be used by an automated system to turn on or off any device that requires electricity. It can then sense the electricity flowing to the unit and respond with a confirming signal that the device is on.
Current transducers can not only sense if a device is using electricity, but it can also monitor the health of the machinery you connect it to. If a refrigeration unit begins to draw more power, it could be time for cleaning or some preventative maintenance. It can even trigger automatic responses; like a sort of safety switch if undesired, or even dangerous, loads are measured. If a water pump begins to run dry there will be a change in the amount of current it draws; a situation that the current transducer could watch out for and send a warning. The possibilities are truly endless for this versatile instrument.
Figure 7: A current transducer on an Enercorp vacuum pump motor test rig
Why use a Current Transducer?
There are other ways to measure the current of electricity. Ammeters, for example, are an alternative to current transducers. You place them in-line and they are a part of the electrical circuit that is being measured rather than being independent like the current transducer. Let’s check out a few reasons why someone may opt for using a current transducer over another instrument.
1. Isolated Signal:
By measuring the current through induction, a current transducer is not directly connected to the current it measures. This keeps electronic noise from distorting the measured signal and causing false readings. Noise is the disturbance of an electrical signal and can occur in many different ways, like electromagnetic interference from nearby electricity-carrying wires or temporary spikes in current or voltage from electrical devices turning on or off. A current transducer will not transmit this sort of outside influence that would give false measurements.
A current transducer can do more than just measure and transmit data, it can help act upon it too. You can program central controls that receive current data to perform actions when it reaches certain parameters. However, current transducers can come with their own on-board switching capability as well. This additional characteristic you can adjust to initiate the switching action when the current measurement reaches the desired level within the range of the current transducer.
3. Analog Signal:
The key to process controls and automation is the standardization of data being used. Some typical analog signals used by current transducers are the 4…20mA and the 0…5VDC standards. By translating process measurements like temperature, pressure, or in our case, current, into a computable form of data we can truly wield the information as a powerful tool instead of a passive string of figures. If this concept sounds new to you be sure to read through our blog on “What does Process Control mean?” to get a better understanding of this sort of action upon information.
Another benefit to the analog signal is that it can be transmitted over a very large distance, potentially further than what the measured current itself could travel. For example, 4…20mA analog signals can go as far as 1km without amplification. Be sure to read through “What is an Analog Signal?” if you’re not caught up on this type of output.
And that is a basic guide to the current transducer. You now know the fundamentals of what this instrument is and what it does. We’ve only briefly touched upon some of the concepts behind this useful tool so be sure to explore through the links within this blog; you’ll find our other discussions that dig a bit more into current transducers. If you still have more questions that have not been addressed then check out our “Question and Answer Guide: Current Transducers” for some more pointed answers to common queries.