Multimeter magic Staff Updated: 01/11/2011 @ 10:54am

By Ron Van Zee

Amultimeter, or VOM (volt, ohm, milliampere) meter, is like a Swiss army knife – no farmer should be without one. As essential as a Vise-Grip, a VOM can tell you why your tractor won’t start when its battery is fully charged.

To get started with a VOM, you need to know the basic elements of electricity.

Volts (represented by the letter “E”). This is the force that causes a flow of current in a conductor. Voltage can exist even when there is no current flow in a circuit. But current cannot exist without the push of voltage.

Ohms (represented by “R”). This is a resistance or opposition of electrons flowing through a circuit. Ohms are kind of an electrical back pressure.

Ampere or milliampere (represented by “I”). This is the rate of flow (current) of electrons in a circuit.

Watts (represented by “P”). This is the rate of work being accomplished by electrons moving through a circuit.

To put your VOM to full use, you need to know the following formulas. Write them down and keep them with your VOM for ready reference.

  • I=E/R: Amperes equals volts divided by ohms.
  • E=IR: Volts equals amperes multiplied by ohms.
  • R=E/I: Ohms equals volts divided by amperes.
  • P=EI: Watts equals volts multiplied by amperes.
  • E=P/I: Volts equals watts divided by amperes
  • I=E/P: Amperes equals volts divided by watts.

How The Formulas Come Into Play

A lightbulb provides a good example of how these formulas work. A lightbulb has a tungsten filament with a specific resistance, measured in ohms (R). This bulb is designed to light to a precise brightness, or wattage (P), at a specific voltage (E). A bright lightbulb has more resistance built into the filament than a dim bulb at the same voltage. So more electricity, or amperes (I), are required to light the tungsten bulb using the same power source.

CancelPost Comment

USDA Drops Soybean Stocks, Raises Corn By: 09/30/2015 @ 11:05am The USDA has released the latest Grain Stocks Report, which shows corn stocks are up 41% from…

Brazil Plants Its Most Expensive Soybean… By: 09/29/2015 @ 11:44am As October begins, it is ushering in more currency volatility for Brazilian farmers that are…

3 Big Things Today, Sept. 22 By: 09/22/2015 @ 7:13am Corn, Soybeans Likely to Stay LowerFutures fell overnight and likely will trader lower today after…

This container should display a .swf file. If not, you may need to upgrade your Flash player.
Innovative Features in the New Can-Am Defender