TABLE OF CONTENTS Scott Stever
Voltage, and current, both ac and dc, and resistance are quantities commonly measured by electronic instruments. In the simplest case, each measurement type is performed by an individual instrument a voltmeter measures voltage, an ammeter measures current, and an ohmmeter measures resistance. These instruments have many elements in common. The more classical, electromechanical meters are the easiest-to-use instrument for performing these measurements. A multimeter combines these instruments, and sometimes others, together into a single, general-purpose multifunction instrument.
There are two primary types of meters general purpose and specialty. General-purpose meters measure several types of electrical parameters such as voltage, resistance, and current. A digital multimeter (DMM) is an example of a general-purpose meter (Fig. 25.2.1). Specialty meters are generally optimized to measure a single parameter very well, emphasizing either measurement accuracy, bandwidth, or sensitivity. Listed in Table 25.2.1 are various types of meters and their measuring capabilities.
| Type of meter | Multifunction | Measuring range | Frequency range | Speed, max readings/second | Best accuracy | Digits |
|---|---|---|---|---|---|---|
| General Purpose | ||||||
| Handheld DMM | Y | 10 ?V ?1000 V; | 20 Hz ?20 kHz | 2 | 0.1% | 31/2 ?41/2 |
| 1 nA ?10 A; | ||||||
| 10 m ? ?50 M ? | ||||||
| Bench DMM | Y | 10 ?V ?1000 V; | 20 Hz ?100 kHz | 10 | 0.01% | 31/2 ?41/2 |
| 1 nA ?10... |
