24-01-2013, 03:11 PM
DIGITAL MULTIMETER
[attachment=48320]
Analog to Digital Conversion Techniques
Flash ADC
The input signal is applied to n comparators in parallel. The switching thresholds are set by a resistor chain, such that the voltage difference between individual taps is equal to the desired measurement resolution.
Understanding DMM display specs
Display is specified as digits or as count
Digits: 3 1/2, 4 1/2, etc.
Example: 3 1/2: starting from the least significant digit, 3 “full” digits from 0-9, 1 “half” digit at less than 9. Ex: 1999
Can be confusing: how do you specify 3999?
Count: 6000 5000 4000 3200 etc
4000 count display reads from 0-3999
3200 count display reads from 0-3199
Hands-on: 6000 count display
Select V, measure battery
Understanding DMM specs
Range and resolution
Resolution is the smallest change in measured value to which the instrument will respond
As the range increases, the resolution decreases:
Turn Fluke 179 to Vac and hit Range button (Auto disappears):
Range: Resolution: 600.0 mV .1 mV (=1/10 mV) 6.000 V .001 V (=1 mV) 60.00 V .01 V (=10 mV) 600.0 V 0.1 V (=100 mV) 1000 V 1 V (=1000 mV)
(To exit Manual Range, hold Range button for 2 secs)
For maximum resolution, choose the lowest possible range
[attachment=48320]
Analog to Digital Conversion Techniques
Flash ADC
The input signal is applied to n comparators in parallel. The switching thresholds are set by a resistor chain, such that the voltage difference between individual taps is equal to the desired measurement resolution.
Understanding DMM display specs
Display is specified as digits or as count
Digits: 3 1/2, 4 1/2, etc.
Example: 3 1/2: starting from the least significant digit, 3 “full” digits from 0-9, 1 “half” digit at less than 9. Ex: 1999
Can be confusing: how do you specify 3999?
Count: 6000 5000 4000 3200 etc
4000 count display reads from 0-3999
3200 count display reads from 0-3199
Hands-on: 6000 count display
Select V, measure battery
Understanding DMM specs
Range and resolution
Resolution is the smallest change in measured value to which the instrument will respond
As the range increases, the resolution decreases:
Turn Fluke 179 to Vac and hit Range button (Auto disappears):
Range: Resolution: 600.0 mV .1 mV (=1/10 mV) 6.000 V .001 V (=1 mV) 60.00 V .01 V (=10 mV) 600.0 V 0.1 V (=100 mV) 1000 V 1 V (=1000 mV)
(To exit Manual Range, hold Range button for 2 secs)
For maximum resolution, choose the lowest possible range