Oscilloscope

The multimeter has become one of the most indispensable tools of modern electronics today. Capable of functioning as a voltmeter, ohmmeter and ammeter among others, this device has been an essential instrument in troubleshooting and diagnosing probable problems in circuits as small as those found on household appliances to that as large as commercial main feeds. These days, multimeters come in a multitude of forms and varieties each one boasting of different features and advantages. But like most inventions, the conception of the multimeter did not occur all at once but rather, it was a progression of different devices that underwent various improvements to become the tool that has now become very essential.

The very first instrument similar to the multimeter was first utilized during the 1820s and was known as the galvanometer. It was the first moving-pointer electrical detector device. The earliest form of the galvanometer was reported by Johann Schweigger of University of Halle in September 16, 1820. During that time, the device was more popularly known as multipliers due to the multiple coils of wire used to increase the effect of the magnetic field produced by the current being measured. It was only by 1836 when the instrument was widely known as galvanometer, a term derived from the Italian researcher Luigi Galvani.

Unlike modern multimeters, galvanometers relied on the Earth’s magnetic field for the force needed to move the needle of the device. These instruments had to be oriented first before they could be used. Later versions of the instrument began to use opposing magnets and were thus were capable of functioning regardless of their orientation. Later versions were also able to measure both resistance and voltage and enabled the comparison of an unknown quantity to a reference value for voltage and resistance. A major downside to this invention was the fragility and bulkiness of the device.



It was during the 1920s that the first multimeter was invented. It was also during this period that vacuum tube electronic devices as well as radio receivers became more popular. British Post Office Engineer Donald Macadie was credited for the invention of the first known multimeter. During that period, separate instruments had to be brought to the field during routine maintenance of telecommunications circuits. Donald Macadie came up with a solution by inventing an instrument which is capable of measuring electric charge, electric current and resistance in terms of amperes, volts and ohms respectively.

The device invented by Macadie was named avometer after the different units that it was able to read. This was the first multifunction meter. Back then, the meter was a relatively simple device made of a moving coil meter, voltage and precision resistors and most importantly, switches used to set the range of the measurements. Three years after its invention, the first of the avometers were put on sale. The first models ran un-direct current and its mechanisms remained unchanged for quite a while.

Apart from the avometer, pocket watch style meters were also widely used in the 1920s. These were sold at a cheaper price than the avometers. The connection was usually done through the metal case which served the negative connector. This design however resulted in numerous cases of electric shocks. Apart from that, technical specifications of the device were often crude at best.

The typical analogue meters used to take voltage readings back then draws out current and loads the circuit being tested to some extent for its needles to deflect fully. This has often led to faulty readings due to the meter’s effect on the circuit. Readings taken had the tendency to give readings that were lower than the actual values.

Because of this limitation, vacuum tube voltmeters instead of analogue multimeters were often used for voltage measurements requiring high impedance. This instrument had a fixed impedance input through a cathode follower input circuit and in effect, did not load the circuit greatly. Analog transistor and field effect transistor voltmeters were also used for this purpose during that time when digital multimeters were still not introduced.

The development of the digital multimeter happened a few decades after the first analogue versions were sold. The first digital instrument to be sold in the market was a form of digital voltmeter first sold in 1955. This device worked by scaling inputs and digitalizing them before displaying the results in a numeric digital display.

Developments made in the field of display technologies and digital integrated circuit technology paved the way for improvements in digital measurements. It was during the late 1960s that the first versions of the digital avometer appeared. This instrument was later known as the first digital meter.

Since its first development during the 60s, the elements of a typical digital meter have remained the same. Its three basic functional elements are signal conditioning, analog/digital conversion and numeric digital display. A digital meter has an analog-to-digital converter capable of converting a direct current voltage input into a digital form which can then be displayed.

Contemporary multimeters nowadays have undergone so much improvement that several of them contain additional scales such as decibels. In addition to that, modern multimeters have other functions such as the ability to measure capacitance, frequency, and duty cycles. More advanced versions can even measure temperature using a thermocouple probe, measure inductance and is connectible to a computer.

The multimeter is just one of the many examples of how technology is able to shape lives and change the way people do things. From starting out as a simple instrument that is able to measure voltage using the earth’s magnetic field to a digitalized variety packed with a multitude of functions, the multimeter has indeed gone a long way up in the technological ladder. And with lots of other potential enhancements on the way, who knows what this little gadget can do a few years from now? In the end, appreciation of the multimeter and the science and technology behind it would be so much deeper if one knew the history and the stories behind its making.