Multimeters

Digital Multimeters

Davis Instruments offers and extensive range of digital multimeters for all of your measurement and trouble shooting applications. Multimeter features include: capacitance, frequency, temperature, non-contact voltage, low impedance, min/max record, data logging, trending and more! Select a digital multimeter with 3200, 6000, 20000, or 50000 count resolution with basic accuracies to 0.025%.

Selecting a multimeter for the job requires not only looking at basic specifications, but also looking at features, functions, and the overall value represented by a multimeters design. Described below are several important criteria and feature definitions to consider when selecting a digital multimeter.

To choose the multimeter that is best suited to your requirements, you should first consider the following:

1. The applications the multimeter is intended for.
• Environment: industrial, residential, large commercial. (This will determine the category - CATIV, 1000V etc...)
  
• Type of load: non-linear or resistive.
  
• Type of task: verification or diagnosis.
  
  
2. What type of intensity measurement?

• AC & DC or only AC?

3. The measurement scope and method.

• Via a clamp or direct?

4. Additional multimeter measurements needed.

• Frequency, capacity, continuity, diode tests, temperature, etc...


Answering these basic questions above will help determine the multimeter that will best fit your application requirements.

• Resolution -
  Resolution refers to how fine a measurement a multimeter can make. By knowing the resolution of a multimeter, you can determine if it is possible to see a small change in the measured signal.
  
• Digits and counts -
  These are used to describe a multimeters resolution. Digital multimeters are grouped by the number of counts or digits they display.
  
• Accuracy -
  Accuracy is the largest allowable error that will occur under specific operating conditions. In other words, it is an indication of how close the digital multimeters displayed measurement is to the actual value of the signal being measured. Accuracy for a multimeter is usually expressed as a percent of reading.
  
• AC and DC measuring voltage -
  One of the most basic tasks of a digital multimeter is measuring voltage. A typical dc voltage source is a battery, like the one used in your car. AC voltage is usually created by a generator. The wall outlets in your home are common sources of ac voltage. Some devices convert ac to dc.
  
  For example, electronic equipment such as TVs, stereos, VCRs, and computers that you plug into an ac wall outlet use devices called rectifiers to convert the ac voltage to a dc voltage. This dc voltage is what powers the electronic circuits in these devices.
  
• Resistance -
  Resistance is measured in ohms. Resistance values can vary greatly, from a few milliohms for contact resistance to billions of ohms for insulators. Most multimeters measure down to 0.1 ohms and some measure as high as 300 M ohms (300,000,000 ohms).
  
• Continuity -
  A quick go/no-go resistance test that distinguishes between an open and a closed circuit.
  
• Diode test -
  A diode is like an electronic switch. It can be turned on if the voltage is over a certain level, generally about 0.6 V for a silicon diode, and it allows current to flow in one direction.
  
• DC and AC Current -
  Current measurements are different from other digital multimeter measurements. Current measurements taken with the multimeters alone require placing the multimeter in series with the circuit being measured. This means opening the circuit and using the multimeter test leads to complete the circuit. This way all the circuit current flows through the digital multimeters circuitry.
  
  An indirect method of measuring current on a multimeter can be performed using a current probe. The probe clamps are used around the outside of the conductor, thus avoiding opening the circuit and connecting the digital multimeter in series.
  
• True-rms -
  A digital multimeter that can accurately measure both sinusoidal and non-sinusoidal waveforms.