USING SHUNTS IN CONJUNCTION WITH DIGITAL PANEL METERS

In the medical world a shunt is a means of diverting, e.g., blood from its typical path to another route. Shunts work in a similar manner in the realm of electronics, allowing current to bypass one point in a circuit and travel to another point.

An example of this would be Christmas lights. Because they are set in series, when one bulb fails the entire circuit goes out. Modern lights prevent this with shunts: each bulb has its own shunt in order to pass the current along, so to speak, when a filament fails.

Circuits are commonly tested for current, resistance, and voltage. Some devices — e.g. ammeters, voltmeters, and ohmmeters — individually measure these parameters. Other devices, like digital multimeters, can test several parameters at once. Digital panel meters are used to measure, display, and record a circuit’s current, resistance, and voltage; but because they are continually subjected to the parameters which they measure, they are prone to damage. However, using panel meters in conjunction with shunts mitigates the risk of damage.

When you combine shunts and panel meters you end up with shunt-resistive circuits which enable you to circumvent predetermined levels of current surrounding a piece of electronic testing equipment. Using a shunt and panel meter together (i.e., a shunt resistor) reduces the excess flow of current through your instruments and helps keep them better protected.

Moreover, combining a shunt and digital panel meter can extend the range of the shunt, which is known as a meter shunt. When you divide current between parallel shunt resistors you increase the range of an ammeter by adding another parallel resistor. Let’s say your meter can only read between zero and one milliamperes but your test requires full-scale detection of one hundred milliamperes. In this situation you can use a shunt to take on the difference between the detection capabilities of your meter and the desired level of full-scale detection. With regard to our example, your shunt would have to be able to handle the remaining current (i.e., ninety-nine milliamperes).

Shunts have myriad uses in electronics testing, but their chief utility comes from their ability to protect delicate equipment and boost the capabilities of panel meters, making shunts exceedingly useful for those who do serious electronic testing.