Use of Digital Instruments
- The type of digital instrument needed depends on the measurements to be made:
Digital Instruments Table
- Note that the top-pan balance doesn't necessarily measure the mass of an object directly, but its weight
- The mass can then be calculated using the equation W = mg where W is the weight and g is the acceleration due to gravity (9.81 m s-2)
Digital Multimeter
A digital multimeter
- A digital multimeter is capable of measuring voltage, current and resistance
- Therefore, it can be used as a voltmeter, ammeter or ohmmeter
- These are often used because it is very hard to measure very small currents and voltages on standard digital ammeters and voltmeters (especially of the order of mA or μA)
- The advantage of a multimeter is that it can measure a greater range of readings from μA to kA (same for volts and Ω)
- This is done by turning a dial in the middle to the appropriate ammeter, voltmeter or ohmmeter setting
- However, if the dial is set at a small current setting, but a very large current is measured instead, this will blow the fuse in the multimeter and it will have to be replaced
- Therefore, it is important the correct range of currents or voltages is estimated before setting the dial
- Most of the time, the multimeter will be set to measure a DC voltage
- It is important to remember to turn off the multimeter after use so the battery doesn't run out
How to use a multimeter to measure the resistance of a resistor
