Approximating the error, Type 3 errors – YSI 55 User Manual
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11
Type 3 Errors
A. Altitude:
Operator Error:
A 1000 foot error in altitude (when calibrating) is equal to an error of
approximately 3.6% at the 10 mg/L level.
Instrument Error: The maximum DO error caused by calibrating to altitude in increments
of 100 feet: ±0.18% (< 0.015 mg/L at 25°C)
B. Humidity:
Errors occur if calibration is performed at less than 100% humidity. The worst possible case
would be calibration at 0% humidity. The error varies with the calibration temperature as
follows:
Temperature
Calibration Error at 0% humidity
0
o
C
0.09
mg/L
10
o
C
0.14
mg/L
20
o
C
0.21
mg/L
30
o
C
0.33
mg/L
40
o
C
0.50
mg/L
Approximating The Error
It is unlikely that the actual error in any measurement will be the maximum possible error. A better
error approximation is obtained using a root mean squared (r.m.s.) calculation:
r.m.s. error = ±[1a
2
+ 1b
2
+ 2a
2
+ 2b
2
+ 3a
2
+ 3b
2
]
½
mg/L
NOTE: This sample calculation is for a near extreme set of conditions.