Guest Post: Different Ways To Measure A Current
When you say “current” it means running or flowing. Therefore, an electrical current is a flow of charge or an electric charge in motion.
The voltage that is present across a conductor causes the electric charge to flow. Most of the electric charge is carried by the electrons and protons within an atom. That flow of charge carries energy that can be used to do work. The current’s unit measurement is called ampere or amp. You can use a device called ammeter to measure current. There are two primary techniques in measuring current.
- By Magnetic Field
By using a compass, a current was discovered to create a magnetic field. Compass was later refined into the modern galvanometer. Most galvanometers consist of a light coil of wire hanging from a metallic ribbon between the poles of a stable magnet. The current passing through the coil produces a magnetic field which reacts with the magnetic field of the permanent magnet produces a twisting force. Due to this, the coil where the needle is attached rotates to balance the twist of the suspension and will provide a measure of the flow of current in the coil. An analog multimeter will give you an idea of how galvanometer looks like.
- By Voltage
By using a shunt resistor, you can measure current. A shunt resistor is also called a current sense resistor, or simply sense resistor. You can select a shunt resistor value that will give you a suitable voltage range. When you place a resistor in the path of the current, it will produce a voltage. According to Ohm’s Law, the current through a conductor between two points is directly proportional to the voltage across the two points. Therefore, if you already know the resistance, then we measure voltage, you can also calculate current. Most ammeters use dc ammeter shunt resistors which measure direct current and can measure an alternating current as well.
A shunt resistor is designed to cause a voltage drop. A voltage that is too large or an additional resistance can affect the load, causing the circuits to behave differently. Shunt resistance is not a problem since it is so small and would not affect the target circuit. The shunt’s purpose is to create a measurable voltage.
When measuring a large current range, it is advisable to use multiple shunt resistors (each with different resistances) to expand the range, since it would be difficult if you only use a single shunt resistor. It is important to consider the amount of resistance. It will cause an excessive voltage drop when you use a shunt that is too large. On the other hand, a shunt that is too small will not give you an accurate measurement.
Types Of Equipment Used In Measuring Current
Multimeters
Multimeters can measure current and voltage as well since they use internal shunt resistors. It is difficult for multimeters to measure currents that change rapidly or dramatically over time. Hence, they are suitable for measuring constant currents.
Oscilloscopes
An oscilloscope is commonly used in a laboratory to display and analyze the waveform of electronic signals. This instrument draws a graph of the instantaneous signal voltage as a function of time.
Joulescope
Joulescope is the most affordable and easy-to-use precision DC energy analyzer. Joulescope measures voltage and current then calculate power and energy.
You can also take note of these formulas to serve as a reference in calculating the amount of current.
Ampere’s Law
Ampere’s Law relates the integrated magnetic field around a closed loop to the electric current passing through the loop. The equation is: B.dl = μ0I
B: magnetic field
dl: the infinitesimal segment of the integration path
μ0: empty’s permeability
I: enclosed electric current by the path
Ohm’s Law
Ohm’s Law states that the current through a conductor between two points is directly proportional to the voltage across the two points. The equation is: V=IR
V: voltage
I: current
R: resistance
Measuring current is important because if you consume more current then your power supply your project won’t run, and can even cause damage to your power supply. Good thing, there are different ways to measure electrical current.
