Test Instruments Used by Electronic Technicians - Multimeters and Beyond

All electronic technicians use a variety of instruments to collect information from electronic circuits. Since electricity can not be seen it is up to these instruments to provide the eyes for technicians to see what is going on within an electrical circuit. Sometimes the instruments themselves create the circuit so a component can be tested. Components are things such as capacitors, resistors, inductors, transistors, integrated circuits, and the wiring that connects these components. Digital electronic testing is not covered in this article.

Multimeters commonly used by electronics hobbyist can be purchased from electronic stores and usually measure three things: voltage, current and resistance. An analog multimeter displays readings using a panel meter, a digital multimeter uses a digital display. They each have a place on a technicians bench. More expensive multimeters, like ones made by Fluke, have other measuring capabilities such as frequency and capacitance. Lets break down these functions and add some more instruments that are available for specialized testing.

1.Voltmeter. Voltage measurements come in two flavors, DC and AC, direct current and alternating current. DC is what you would measure a battery with. like your car, flashlight, or cell phone battery. AC is what you would use to measure your household voltage. Keep in mind that alternating current is frequency dependent. Household voltage in the U.S. Is 60 hertz. In a lot of foreign countries it is 50 hertz. There is a more going on here than many may know. AC and DC can travel on the same circuit, at the same time in many electronic circuits. A more expensive voltmeter can separate the two readings, a cheap one only gives an average reading.

2.Current Meter. The amount of current flowing through the circuit is measured by breaking the circuit and inserting the meter in series with it. The meter must be capable of handling the amount of current flowing through it or it may burn out. There are inductive probe type meters that clamp onto a wire and by using inductance it can derive a current measurement, These are used often by electricians, especially for higher current circuits.

3.Ohmmeter. Resistor values can be determined with the ohmmeter function and wires can be tested for continuity to determine if they are open or have "breaks".

4.Frequency Meter. Frequency meters are usually specialized to measure a certain range of frequencies. Most instruments specialize in various ranges to give more precise measurements. One example of measuring frequency is the timing on you vehicle. By using a frequency generator you can input a known frequency into a device such as a musical amplifier and measure the output with the frequency meter. An oscilloscope also does this and gives you even more information.

5.Capacitance Meter . A capacitor is a common electronic component that needs to be charged to a certain voltage level and tested using a capacitance meter. The ability of the capacitor to charge and hold the charge is all part of the measurement process. The capacitance function on most multimeters is limited mainly to lower value capacitors. Wires and coaxial cables operating at higher frequencies called radio frequencies (RF) have capacitance and are measured much differently than standard capacitors.

6.Power supply. Various range power supplies are used to provide known voltage needed for testing or prototyping. These normally provide DC voltage. A variable transformer is typically used to provide AC voltage.

7.Frequency Generator. These are used to produce known waveforms used for testing. RF generators output signals in the radio frequency range. Audio generators give signals in the audible range.

8.Oscilloscope. An Oscilloscope displays waveforms. There are many types of waveforms and it is beyond this article to describe all of them. The most basic is the sine wave. If you measured the AC voltage coming out of a wall outlet in your home you would see a sine wave. From this sine wave you can determine the peak to peak voltage and the time measurement. Since frequency is the inverse of time then you can derive the frequency from the time measurement.

9.Spectrum Analyzer. A spectrum analyzer is similar to an oscilloscope but it measures frequency instead of time and still measures voltage. Readings are taken over a period of time and the results show up as "peaks" or waveforms of various frequencies it has found over that period of time. These instruments are used a lot for testing vibration. A sensor collects data that is fed to the instrument and a peak will occur if there is a vibration present. Professional automobile engineers use these to locate vibrations in engine components. Industry uses these to find pulleys and other rotating devices, that may be going bad. They can also be used with different sensors to find variations in temperature and pressure.

10.TDR. A Time Domain Refractometer is a device that can measure bad places or "discontinuities" in coaxial cables. It can measure what the distance is to the bad spot and measure other factors as well. This is a highly complex device. Optical Time Domain Refractometers ( OTDR) do the same thing for fiber optic cables. They operate in either single mode or multi mode.

This is just a brief overview to give you an ideal of what is out there and being used. Before setting up an electronics shop it is important that you are trained on the use of some of these instruments or you could get hurt, or worse killed, by not knowing what you are doing. It is difficult to give the precise functions of these instruments without elaborating much more on the subject. You can find most of what you need to know by searching the Internet for more detailed information. Electronic knowledge from formal electronics training prepares you to have a sufficient background to gain full use of these instruments.