What Is an Optical Multimeter?
Optical multimeters are measuring instruments that use light.
They incorporate functions for measuring various optical characteristics. It is sometimes called an optical loss tester, optical loss tester, or optical loss test set.
The name “optical loss tester” is derived from the fact that it has an optical power meter to measure the intensity of light and a loss tester/return loss tester to measure how much of an optical fiber signal is lost. Some are also equipped with a laser as a light source and can be used as a stable light source.
Uses of Optical Multimeters
Optical multimeters are measuring instruments that use light in electrical circuits and are mainly used to measure current and voltage. Suitable for high-frequency current and high-voltage measurements, they are not only widely used in many industrial fields, but are also used in medical and other fields because of their high-speed and highly reliable measurements.
1. Testing Electronic Circuits
Optical multimeters can be used to measure voltages, currents, resistances, capacitance, etc. inside circuits to check the operating conditions of circuits. Optical multimeters are also suitable for checking the operation of high-speed circuits because of their high-speed measurement capability.
2. Temperature Measurement
Optical multimeters are also used for thermal imaging and non-contact temperature measurement, which detects infrared radiation emitted from surfaces to image temperature distribution. Examples include evaluating the thermal insulation performance of buildings and detecting overheating of electrical equipment.
Depending on the surface temperature of the object being measured, infrared or near-infrared radiation is emitted. By detecting this emitted light with an optical multimeter, the temperature of the object can be measured without direct contact.
3. Medical Treatment
It is used for the diagnosis and treatment of skin and eye diseases. In particular, ophthalmologists may use optical multimeters to diagnose and treat diseases such as glaucoma.
Another situation is the development of technology for functional brain imaging, which uses near-infrared light to non-invasively image brain activity. This is expected to find applications in the fields of neuroscience and clinical medicine.
Principle of Optical Multimeters
Optical multimeters are measuring instruments that utilize light in electrical circuits. The principles of signals and light sources are as follows.
1. Signal Principle
Optical multimeters transmit and receive light using optical fibers. The optical fiber is made of very thin glass fiber, which transmits light from the transmitter to the receiver.
The optical sensor at the receiving end receives the light and converts it into a signal, which is read as an electrical parameter of the circuit. In addition to enabling measurement with extremely high accuracy, this system is less susceptible to electrical noise in electrical circuits, enabling highly reliable measurements.
2. Principle of Light Source
Light-emitting diodes or laser diodes are the main light sources used for optical multimeters. These light sources are suitable for optical multimeters because of their low power consumption and very high brightness.
The transmitted light enters the circuit to be measured and is reflected, refracted, or scattered inside the circuit. These lights are again returned to the receiving section via an optical fiber, converted into optical signals by an optical sensor such as a photodiode, and displayed as measured values.
Thus, the use of optical fiber enables non-contact, highly-accurate measurements. Optical fiber is also suitable for high-speed measurements because it has less signal delay than electrical signals.
Characteristics of Optical Multimeters
Since measurement is non-contact, it is characterized by high safety and reliability and does not cause damage to the object being measured. On the other hand, since it measures the surface temperature of the measurement object, it cannot measure internal temperatures or the deterioration state of components.
Depending on the environment in which it is used, the accuracy of the measurement may be affected. Therefore, it is essential to understand the measurement target and conditions beforehand and to take measurements carefully.