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Ref. No. [UMCES] CBL 2016-014
ACT VS16-05
14
Table 2.
Summary of average offset between paired Hach HL4 LDO (sn 0431) DO measures and
Winkler reference DO measures during laboratory trials. No offsets outside of +/- 2 mg/L were
encountered in the dataset. DO measures automatically adjusted for salinity effects by the HL4
sonde software.
nd:
no data recorded by the HL4 sonde.
Trial ID
Instrument – Winkler DO
mean
s.d.
Observed n Possible n
L_T15_S00
0.185
0.200
51
51
L_T15_S10
0.040
0.138
19
39
L_T15_S35
-0.221
0.126
38
38
L_T04_S00
0.304
0.315
39
39
L_T04_S10
-0.137
0.124
36
36
L_T04_S35
nd
nd
nd
37
L_T30_S00
-0.315
0.127
40
40
L_T30_S10
-0.212
0.086
39
39
L_T30_S35
-0.123
0.049
24
40
The precision of the Hach HL4 sensor was also characterized for each of the nine
temperatures and salinity trials (Table 3). Precision trials were conducted at the start of each new
tank test when conditions were most stable. Instruments were equilibrated in test tanks at indicated
temperature and salinities for 45 min then the subsequent 31 one-minute measurements were used
to estimate average tank DO (mg/L) and its variation over that interval. The absolute precision,
estimated as the standard deviation (s.d.) around the mean, ranged from 0.015 – 0.045 mg/L across
trials with an overall average of 0.025 mg/L. Relative precision, estimated as the coefficient of
variation (CV% = (s.d./mean)x100), ranged from 0.125 – 0.804 percent across trials with an
overall average of 0.380%.
Table 3.
Characterization of the precision of the Hach HL4 LDO sensor over a range of temperatures and
salinities test conditions.
Trial ID
Temperature
Salinity
Dissolved Oxygen Reading
mg/L mean
mg/L s.d.
CV%
n
L_T15_S00
15.44
0.00
9.408
0.018
0.188
31
L_T15_S10
15.47
8.82
9.434
0.015
0.161
5
L_T15_S35
15.39
34.20
7.898
0.020
0.256
31
L_T04_S00
5.40
0.00
12.603
0.016
0.125
31
L_T04_S10
5.30
8.98
11.849
0.015
0.127
31
L_T04_S35
5.23
34.77
nd
nd
nd
nd
L_T30_S00
30.22
0.00
4.389
0.035
0.791
31
L_T30_S10
30.51
9.28
6.525
0.039
0.592
31
L_T30_S35
30.61
34.43
5.599
0.045
0.804
31