Current and Voltage sensors

Here’s an article by our dear member Martin M. focusing on current and voltage sensors in terms of features, applications, and benefits. Enjoy and leave your impressions.

Introduction

Majority of faults, incidents, and accidents associated with electrical equipment and systems are as a result of undervoltage and overvoltage. It is important to know the exact amount of current and voltage is a particular system and application as it enables the engineer or technician to make and implement safety-critical decisions.

In addition, knowing the amount of current or voltage in a system allows one to gauge the performance of the various subcomponents in a system.

Current Sensors

There are two primary types of current sensors, direct and indirect sensors. The direct sensor applies Ohms Law and Halls Effect. It has an integrated coil. By placing the coil around a current-carrying conductor, there in an induced voltage, which is proportional to the current in the system. By using various amplifiers such as shunt and operational amplifiers, as well as a user-friendly interface, it is then easy to detect and measure the current in the system.

Do note that the shunt is designed to withstand short-circuit currents without any distortion to the resistance value. This allows an external, non-invasive way to measure the current. Direct sensors are used for low currents (<100A). For higher currents (100-1000A), the indirect method is used. It works on Ampere’s and Faraday’s Laws by measuring the magnetic field that surrounds a current carrying conductor.

Current Sensors and Voltage Sensors 1

Traditionally, current sensors were used for circuit protection and control. However, the values are presently used to monitor and enhance performance of different electronics and electrical equipment.

The various applications include the following:

  • Linear and switch-mode power supplies monitoring
  • Motor control
  • Overload protection
  • Over current protection
  • Ground fault detection, amongst others

Voltage Sensors

The primary function of voltage sensors is to detect and measure AC and/or DC voltage levels. When the presence of voltage is detected, the sensors provide an output in the form of analogue voltage signals, current levels, frequency and modulated frequency outputs or audible sounds.

A typical sensor features a needle or pointer, while the digital versions feature an alphanumeric interface. The sensors in use include handheld voltage sensors, DIN rail mounted sensors, and PCB mounted voltage sensors.

Current Sensors and Voltage Sensors 2

The voltage sensor is able to measure the presence of a voltage without making metal contact i.e. on insulated wires. A voltage sensor consists of a resistive voltage divider. The integrated resistors, embedded in a casted resin (for voltages between 1-72kV), have a low value inductance. The arrangement, mostly in a zigzag arrangement, together with the resin permittivity, results to a capacitance. This capacitance is more than any capacitance straying to the ground.

Electric principles dictate that the smaller the capacitor, the larger the voltage. Thus, when you hold the voltage sensor in your hands, and place the tip near a live conductor, you create high impedance on the tip, thus forming a capacively-coupled series circuit. The circuit is complete through you, the ground, and back to the circuit. Thus, the voltage detector sensor tip is a small capacitor that is capacively-coupled to a live voltage.

There are various applications associated with voltage sensors. The common areas of use include power demand control areas, power failure detection, safety switching, revenue metering, load control especially in motors, power quality monitoring especially near VAR compensators and energy management control systems.

Others include:

  • Power measurement: this is usually done on industrial equipment to measure efficiency
  • DC voltage measurement
  • Power quality measurement
  • Earth fault measurement
  • Switchgear optimization

TOP 5 Best Sellers Voltage Tester on amazon

Bestseller No. 1
Non-Contact Voltage Tester with Adjustable Sensitivity, LCD Display, LED Flashlight, Buzzer Alarm,...
190 Reviews
Non-Contact Voltage Tester with Adjustable Sensitivity, LCD Display, LED Flashlight, Buzzer Alarm,...
  • Non-Contact & Safe Voltage Tester - Testing can be achieved without physical contact for its NCV Inductive Probe; Insulation operation ensures the safety of testing; In testing AC voltage, it can...
  • Adjustable Sensitivity & Dual Range Testing - Adjustable sensitivity makes its measurement more sensitive and flexible;The Voltage Tester Pen has the dual testing range, you can adjust the sensitivity...
  • High Definition LCD Screen & Low Battery Indicator - When testing the voltage, the brightness bar on the screen will tell you the voltage intensity; The screen will light up in red or green to...
  • Buzzer Alarm & LED Flashlight - A white LED flashlight with high brightness and low power consumption helps in illuminating the workspace in dark; The lighting lamp and the probe are combined...
  • Auto Power Off & Portable Pencil Hook - After about 3 minutes without any operation or signal detection, the voltage detector will be automatically shut down to extend the battery life and save...
Bestseller No. 2
Klein Tools NCVT-2 Non Contact Voltage Tester, Dual Range Pen Voltage Detector for Standard and Low...
1,358 Reviews
Klein Tools NCVT-2 Non Contact Voltage Tester, Dual Range Pen Voltage Detector for Standard and Low...
  • Automatically detects and indicates low voltage (12-48V AC) and standard voltage (48-1000V AC) allowing broad application
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Bestseller No. 3
Klein Tools NCVT-1 Voltage Tester, Non-Contact Voltage Detector for AC Voltage, Low Battery...
302 Reviews
Klein Tools NCVT-1 Voltage Tester, Non-Contact Voltage Detector for AC Voltage, Low Battery...
  • Non-contact detection of voltage in cables, cords, circuit breakers, lighting fixtures, switches, outlets, and wires
  • High intensity, bright green LED indicates the tester is operational and aids in illuminating the workspace
  • When voltage is detected, a high intensity, bright red LED illuminates and a warning tone sounds
  • Discreet digitally controlled ON/OFF power button
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Sale 2019Bestseller No. 4
Fluke 1AC-A1-II VoltAlert Non-Contact Voltage Tester
1,551 Reviews
Fluke 1AC-A1-II VoltAlert Non-Contact Voltage Tester
  • Voltbeat technology and continuous self-test - so you always know it is working
  • Upon detection, tip glows and beeper sounds
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  • Range 90-volt to 1000-volt
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Bestseller No. 5
Neoteck Non-Contact Voltage Tester 12-1000V AC Voltage Detector Pen Circuit Tester Tool with Led...
139 Reviews
Neoteck Non-Contact Voltage Tester 12-1000V AC Voltage Detector Pen Circuit Tester Tool with Led...
  • 【Non-Contact Voltage Tester with Wide Testing Range】 This Non-Contact Voltage Tester Voltage within 12-1000V AC, All Electric Appliances in Your Family can be Tested by it
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  • 【Multifunction, Easy to Use】 It Also Acts as an Emergency Flashlight which can Illuminate the Working Area, You can Use the Non Contact Voltage Detector in Circuit Breakers, Lighting Fixtures,...
  • 【CE CAT III600V RoHS Certificate】 A Professional Tester, It is Perfectly Suitable also for DIY'ers, Hobbyists and Home Owners, It Helps You Make the First and the Most Important Safety Check

Thanks for reading,

Martin M.

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