Current Sensor
Contact Manutech Europe for Current Sensor products of small or large quantities by a trusted supplier online. We provide Magnelab products consisting of Current sensors, Voltage Transformers, Power meters and more.
What is a Current Sensor?
CT’s work by detecting electric currents in circuits then generating a proportional signal. This signals can be measured, displayed or stored for analysis. A CT can measure AC and DC current and there are two main types.
Open-loop Sensors give electrical isolation between the circuit being measured. The primary current is measured without electrical contact with the primary circuit which is what gives galvanic isolation. Open loop current transformers, due to their low power needs and small footprint features, are usually preferred in circuits powered by battery. Open-loop current transformers are also typically cheaper than closed loop CT’s.
- Magnetoresistive Sensor – When a current flows through the plate the property of certain materials changes the value of its resistance. Resistance is increased and decreased at the shorter distance as currents flow for a longer distance.
- Hall Effect – These devices feature signal conditioning circuitry and have a core Hall Effect device. It produces a potential difference when the Hall device is exposed to magnetic field from the core it which can be measured and amplified. Current sensors work as a current conductor passes through a magnetically permeable core and this concentrates the conductors magnetic field.
- Inductive Sensor – This type uses coils which current-carrying wires pass and this makes power current flow in the coil that is proportional to the current. Current flow then can be measured or transformed.
Types of Current Sensors
Step-up CT – This sensor increases voltage as it reduces current and has a greater number of windings on the side it outputs energy. For an example the cathode ray tube screen requires thousands of volts, and runs off 110V wall sockets.
Step-down Sensor – This sensor is used for reversing the winding ratio and this shows because battery-operated devices can also be plugged into wall sockets. Therefore the radio can run on 12V batteries and also run on 11V adapters with a step-down current sensor.
Isolation Sensor – Isolation current sensors can serve a number of purposes such as being able to break a circuit into a primary and a secondary. This stops direct-current noise through and prevents capacitance build up of the primary and secondary which causes a high-frequency noise. They cease incidental connections from primary and secondary by isolating the secondary circuit from the primary’s current preventing shock and grounding from high voltage discharge.
Variable Auto-Sensor – A variable auto-current sensor changes voltage to the secondary (energy-output) circuit whilst the primary and secondary’s number of windings vary using a dial. The proximity of the primary and secondary windings are used with low voltages because this prevents arcing like the Current Sensor.
Signal Matching – These types of sensors are used to convey frequencies to and from different circuits because communication electrical like signal matching current sensors use low power levels making power loss a concern. In order to achieve maximum impedance matching the signal current sensor is selected or tuned based on the impedance of other components within the circuits.
Current Sensors can alter the voltage in alternating circuits by connecting two at the magnetic core and then the energy-input circuit to the energy-output circuit of the voltage change the ratio of windings around the core. A CT can fall into two broad categories which are signal matching and power supply.
Open Loop vs Closed Loop
Open Loop CT – These current sensors feature a Hall sensor mounted inside the air gap of a magnetic core and the conductors give a magnetic field which is comparable to the current. The Hall sensor current sensor measures the magnetic field and it is concentrated by the core. As it is low, the signal from the Hall generator is amplified which becomes the current CT output. Usually a open-loop current sensor has circuitry that provides the compensation of temperature and calibrated high-level voltage output. This current sensor is usually cheaper and can be prone to saturation and drift in temperature. Although if one were to inject a positive coefficient within the control current to reduce the drift in sensitivity over temperature the drift can be reduced.
Closed loop CT – This sensor provides electrical isolation, measure both AC and DC currents, offer reliability for their fast response, low temperature drift and high linearity. The output of the close loop is quite immune to electrical noise because the current sensor feeds back a contrasting current into the secondary coil – due to this the Closed- Loop CT is often called a ‘Zero-Flux’ sensor. The current sensors secondary coil is wound on the magnetic core in order to zero the flux created in the magnetic core by the primary current. Closed-loop current sensors are a good choice when high accuracy is priority.
High Frequency Sensor
Due to the primary winding of the series with the current carrying conductor supplying a load the current sensor is renowned as a “series sensor”. Although the secondary winding can be wound on a laminated core of magnetic material with low-loss and feature more coil turns. To ensure that the density of the magnetic flux made is low using smaller cross-sectional area wiring, the core features a greater cross-sectional area. This is reliant upon how much the current must be stepped down as it tried to output a constant current that is independent of the connected load of the current sensor.
Opposing to the voltage transformer the primary current of a current sensor is managed by an external load which is not dependent of the secondary current load. The rating of the secondary current is often at a standard 1 Ampere or 5 Amperes for greater ratings. Acute and small instruments are applicable with CT’s being insulated apart from high-voltage power lines as Current sensor instruments are able to reduce or “step-down” current levels from thousands of amperes to a standard output of a ratio to 5 Amps or 1 Amp.
The Current sensor is built differently to a voltage and power sensor as its primary winding allows only one or few turns. This primary winding can be:
- A coil of heavy duty wire wrapped around the core
- A conductor or bus bar placed through a central hole or
- A single flat turn, or just as shown.
Secondary Winding
Often the current sensor secondary winding connects to a, closed at all time, burden and the current flows via both the primary and secondary windings. The amperes turns of each winding are opposite and equal. The secondary turns of a current sensor is constantly 1% and 2% less than the primary winding turns and the difference is used in a magnetising core. the burden of a current transformer is defined by the load connected along the secondary sensors value which shows by the output in volt-amperes (VA). the value of the rated burden is defined by the burden on the nameplate of the Current sensor due to the voltage and current on the secondary when the sensor is supplying the instrument.
It is known that the secondary of a current sensor connects along ammeter, has a small resistance and 1.0 is the secondary windings voltage drop. To remove the ammeter will make the secondary winding open-circuited leading the current sensor to act as a step up current sensor. This is due to the huge increase in magnetising flux of the secondary cores as the leakage reactance influences the secondary induced voltage. An opposing current in the secondary winding would prevent this from happening.
Product Information
The team at Manutech Europe have years of experience with our products and are happy to give advice on current sensor enquiries.
Accurate products
The current sensors we stock are made for accuracy and effectiveness in current reading. You can trust our products to offer value and quality in any current sensor task.
Fast Readings
Current sensors from Manutech do not waste time, sensing current in fast time scales giving you your reading when its needed.