Current Sensors (CS) and Current Transformers / Transducers (CTs) are used to monitor the current flowing through an electrical conductor. They generate the raw data needed for metering applications. Though people tend to use the terms ‘current sensor’ and ‘CT’ interchangeably, there are some more than subtle differences between the two terms.
What is the difference between a Current Sensor, Current Switch, Current Transducer, and a Current Transformer?
Let’s start by defining the most general of all the terms: Current Sensor.
A Current Sensor is the generic term for any device that senses current flow. A variety of technologies (Rogowski coil, Hall Effect, transformer, transducer, etc.) fall under the general heading of Current Sensor and each of these technologies produces a specific type of output.
That last bit is key…the type of output you need for your application determines which current sensor technology you should use.
Just as the name suggests, a Current Transducer utilizes a transducer. A transducer takes a signal in and generates a different type of signal for its output. In this case, current is sensed and converted (transduced) into a proportional output (milli-amp or voltage). Output types include: 4 – 20mAdc, 0 – 5Vdc, 0 – 10Vdc, 1Vac, or 0.333Vac. The output range can then be interpreted by software to produce a current reading.
And, just as the name suggest, a Current Transformer utilizes a transformer. A transformer takes in a type of signal and produces a proportional signal of the same type. For example a current transformer produces a proportional current output value. In most heating, ventilation, and air conditioning (HVAC) and electrical metering applications, a current transformer senses the current and produces a 5Amp (current) output.
A Current Switch is a current sensor with an integrated normally open (NO) or normally closed (NC) switch. At a preset current level (trip point) the switch will either open or close. The switch can be used to trigger an alarm or turn on / off a small load.
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