ICM7216B_04 Datasheet, PDF (12/18 Pages) Intersil Corporation – 8-Digit, Multi-Function, Frequency Counters/Timers

ICM7216B, ICM7216D
In addition, there is a quantization error inherent in any digital
measurement of ±1 count. Clearly this error is reduced by
displaying more digits. In the frequency mode the maximum
accuracy is obtained with high frequency inputs and in period
mode maximum accuracy is obtained with low frequency
inputs (as can be seen in Figure 11). In time interval
measurements there can be an error of 1 count per interval.
As a result there is the same inherent accuracy in all ranges
as shown in Figure 12. In frequency ratio measurement can
be more accurately obtained by averaging over more cycles
of INPUT B as shown in Figure 13.
0
FREQUENCY MEASURE
0.01s
2 0.1s
1s
10s
4
1 CYCLE
10 CYCLES
10² CYCLES
6 ^{103 CYCLES}
PERIOD MEASURE
8
f_OSC = 10MHz
1
10
10³
10⁵
10⁷
FREQUENCY (Hz)
FIGURE 11. MAXIMUM ACCURACY OF FREQUENCY AND
PERIOD MEASUREMENTS DUE TO LIMITATIONS
OF QUANTIZATION ERRORS
0
1
2
3
MAXIMUM TIME INTERVAL
FOR 10³ INTERVALS
4
MAXIMUM TIME
5
INTERVAL FOR
10² INTERVALS
6
MAXIMUM TIME INTERVAL
7
FOR 10 INTERVALS
8
1
10 10² 10³ 10⁴ 10⁵ 10⁶ 10⁷ 10⁸
TIME INTERVAL (µs)
FIGURE 12. MAXIMUM ACCURACY OF TIME INTERVAL
MEASUREMENT DUE TO LIMITATIONS OF
QUANTIZATION ERRORS
0
1
RANGE
2
3
1 CYCLE
10 CYCLES
4
10² CYCLES
10³ CYCLES
5
6
7
8
1
10 10² 10³ 10⁴ 10⁵ 10⁶ 10⁷ 10⁸
f_A / f_B
FIGURE 13. MAXIMUM ACCURACY FOR FREQUENCY RATIO MEASUREMENT DUE TO LIMITATION OF QUANTIZATION ERRORS
12