Apera Instruments SX716 User manual

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SX716 Portable Dissolved Oxygen Meter
User Manual
APERA INSTRUMENTS, LLC
aperainst.com

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Table of Contents
1 Brief Instruction ................................................................................................................ - 3 -
2 Technical Specifications .................................................................................................... - 4 -
3 About the Meter ............................................................................................................... - 5 -
4 Dissolved Oxygen .............................................................................................................. - 7 -
4.1 Preparation before use ........................................................................................................... - 7 -
4.2 DO Calibration (Saturated Oxygen) .......................................................................................... - 9 -
4.3 DO Measurement ................................................................................................................... - 9 -
4.4 Notes about DO Measurement ............................................................................................. - 10 -
4.5 DO Electrode Maintenance ................................................................................................... - 10 -
4.6 Zero Oxygen Calibration ........................................................................................................ - 11 -
4.7 Salinity Calibration ................................................................................................................ - 12 -
4.8 Barometric pressure manual compensation .......................................................................... - 12 -
4.9 Parameter Setting ................................................................................................................. - 13 -
5 What’s in the kit ............................................................................................................. - 16 -
6 Warranty ........................................................................................................................ - 16 -
7 Appendix ........................................................................................................................ - 17 -
7.1 Appendix 1 Content of Saturated Oxygen in Water at Different Temperature ........................ - 17 -
7.2 Appendix 2 Content of Saturated Oxygen at Different Barometric pressure ........................... - 18 -
7.3 Appendix 3 Content of Oxygen at Different Altitude .............................................................. - 19 -
Scan the QR code below to watch the tutorial video on Youtube.

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1 Brief Instruction
Thanks for purchasing Apera Instruments SX716 Portable DO Meter (will be called “the
meter” in short in the following content).
Before using the meter, please read this instruction manual carefully in order to help
you properly use and maintain it.
The meter can measure the parameters of DO and temperature of water solutions with
high accuracy. It is the most cost-effective choice of a high-quality portable DO meter. It
is suitable for applications in aquaculture, mining industry, power plants, environmental
monitoring, etc., especially suitable for in-field use.
The meter has the following features:
1.1. Built-in microprocessor chip with the intelligent functions of auto. DO calibration,
auto. temperature compensation, auto. salinity compensation, manual baromatric
pressure compensation, data storage, function settings, auto. power off, and low
voltage display etc.
1.2. Adopts digital filter technology to intelligently improve meter’s response speed and
accuracy. The smiley face icon will appear when the reading is stable.
1.3. Built with a polaragraphic DO electrode with temperature and salinity sensors,
which enables auto. temperature and auto. salinity compensation.
1.4. The polarographic DO electrode has a special electrode calibration sleeve. The
electrode polarization only takes 5 minutes. Electrode adopts a combo-style
membrane cap, which is very convenient to use. Each DO electrode comes with
three backup membrane caps.
1.6. Meter’s LCD screen has clear and bright backlit display.
1.7. Built-tough. IP57 waterproof and dust-proof.

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2 Technical Specifications
2.1 Dissolved Oxygen
Measuring range
(0 to 19.99) mg/L (ppm); (0 to 200.0) %
Resolution
0.1/0.01 mg/L (ppm) 1/0.1%
Accuracy
±0.30 mg/L (ppm), including electrode error
Response time
≤30s (25˚C, 90% response)
Temp. compensation range
(0 to 45) ˚C (automatic)
Salinity compensation range
(0 to 45) ppt (automatic)
Barometric pressure
cocompensation range
(66 to 200) kPa (manual)
Automatic calibration
Air saturated by water; water saturated by air
Electrode type
Polarographic
2.2 Other Technical Parameters
Data storage
100 sets
Data content
Serial number, measuring value, measuring unit,
and temperature
Power Supply
Two AA alkaline batteries (1.5V x2)
Dimensions and weight
Meter: (65×120×31) mm/180g
Carrying case: (255 x 210x 50) mm/790g
Quality and safety certification
CE, ISO 9001:2015
2.3 Working Condition
Working temperature
5 to 35˚C
Working humidity
≤85%
IP rating
IP57 water-resistant

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3 About the Meter
3.1 Screen Display
① —— Parameter icon
② —— Measuring value
③ —— Serial number and icon as measuring value to be stored and recalled and
indication icon for special states.
M+ — measuring value to be stored; RM — Stored value to be recalled;
④ —— Measurement unit
⑤ —— Temperature measuring value and unit
⑥ —— Measurement stabilization icon
⑦ —— Electrode calibration indication icon
⑧ —— Indication icon of low battery power; appears when the voltage is less than 2.6V,
calling attention to replace the batteries.
3.2 Keypad
The meter has 5 operation keys in total.
Short press: press time <1 seconds; Long press: press time >2 seconds
3.2.1. — Power on/off
3.2.2. — Calibration key.
(a) When in measurement mode, press this key to enter calibration mode.
(b) When in parameter setting mode, press this key to make changes.

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3.2.3. — Function key
Press the key to enter the parameter setting mode P1, P2, P3…
3.2.4. — Backlight and confirmation key
(a) When in measurement mode, short press (less than 1.5s) to turn on/off the back
light display.
(b) When in calibration mode or the parameter setting mode, press this key to confirm,
and then the meter enters measurement mode;
(c) When in measurement mode, hold the key to change units in turn: mg/L→ppm→%,
when the desired unit appears, release the key to select it.
3.2.5. — The combination key of data logging and recalling
(a) Short press to save the readings, long press to recall the saved readings when in
the measurement mode.
(b) When in the parameter setting mode, press this key to change the number or
ON/OFF state.
3.3 Data Log, Recall and Delete
3.3.1. Save the measurement:
In measurement mode, when the reading is stable and smiley face icon stays on screen,
short-time press key to save the measurement data. M+ icon and the data serial
number will show up on the upper right corner. The meter can store up to 100 sets of
data.
3.3.2. Recall saved data:
(a) In measurement mode, long press the key, the meter will recall the last saved
data and the serial number. RM icon will appear in the upper right corner of the
screen. Short press or key again, the meter will recall all the data in
turn, hold or key to quickly review the data.
(b) In data recalling mode (RM and serial number in the lower right corner of the screen),
press key to return to measurement mode.
3.3.3. Delete the saved data:
In data recalling mode, hold key for 5 seconds, CLr will show up for 2 seconds,
meaning that all the saved data have been eliminated. Then the meter will return to
measurement mode.

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4 Dissolved Oxygen
4.1 Preparation before use
4.1.1. Electrode connection

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4.1.2. Connect the DO electrode. Then Press key to power on the meter.
4.1.3. Choose DO unit: Hold to switch among mg/L, ppm and %. When the desired
unit shows up, release the button to confirm the unit selection.
4.1.4. Check the sponge
Check on the DO500 DO electrode: see picture (4-1). Screw off the bottom lid of electrode
calibration sleeve, inspect whether the sponge inside is moist. If it is dried out, add in several
drops of distilled water to the sponge to maintain the satured air inside the calibration sleeve
(Do NOT add too much water so it won’t be dripping).
4.1.1 Electrode polarization
After each power on, the DO electrode must be polarized for 5 minutes before measuring or
calibration. So do not to turn off the meter in the middle of your DO measurement. Otherwise,
you need to polarize the DO electrode again after next power on (The auto. power off
function in DO mode has been turned off by default).
How to polarize the DO electrode –– Just connect the DO electrode to the powered-on
meter without measuring or calibrating.
Electrode polarization is to consume the remaining oxygen inside the inner solution of the
membrane cap so as to ensure fast response and high accuracy. If a new membrane cap is
replaced, or new inner solution is added, the polarization time should be 30 minutes instead
of 5 minutes.
1 — DO500 DO electrode
2 — Calibration sleeve cap
3 — Calibration sleeve
4 — Water stored sponge
5 — Calibration sleeve bottom lid
6 — Temp er ature elec tr o de
7 — Membrane cap
8 — Cathode (gold)
9 — Anode (silver)
10 — Salinity electrode

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4.2 DO Calibration (Saturated Oxygen)
Power on the meter, press key, the meter enters calibration mode, CAL will be flashing
at the upper-right corner. Insert the DO electrode to the calibration sleeve, and tighten the
sleeve cap. Let the electrode sit for 3 to 5 minutes.
When the reading is fully stabilized, press key again to finish the calibration. A flashing
100% will show up, and the calibration will be finished in several seconds and the meter will
return to measurement mode. If the reading is unstable, please wait for several more
minutes. Do NOT press key until the reading is fully stabilized.
4.3 DO Measurement
4.3.1. Measuring DO in flowing water
Power on the meter. Place the DO electrode into the flowing water. The water surface level
should be higher than the location of the temperature electrode. The angle for the electrode
and water surface should be 45° to 75°. Hold the electrode in the flowing water and wait for
a stable reading, then press to record the measurement. If the reading cannot be
stabilized, keep swirling the electrode slowly in water to help you get a stable reading
(typically takes 1-5 minutes).
4.3.2. Measuring DO in static water
Power on the meter. Place the DO electrode into water. The water surface level should be
higher than the location of the temperature electrode. The angle for the electrode and water
should be 45° to 75°. Keep swirling the electrode in water slowly (>5cm/s) for 1 to 5 minutes.
When the reading is fully stabilized, record the measurement (do NOT stop the swirling while
recording the measurement).
Never stop the DO electrode swirling in static water while measuring. Otherwise the
dissvolved oxygen will be consumed by the DO electrode and the reading will keep dropping.

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4.4 Notes about DO Measurement
a) When calibrating, the environment temperature and water temperature should be
close to each other (≤10˚C). If the difference is large, please dip the electrode into
the sample water for about 10 minutes, then calibrate the electrode according to
Section 4.2.
b) Temperature has a large impact on DO measurement. When the electrode
temperature and water temperature have larger difference, the reading time must be
greater than 3 minutes. Otherwise, there could be some large errors.
c) Salinity and barometric pressure also affect DO measurement. The meter has
automatic salinity compensation and manual barometric pressure compensation. For
details, refer to Section 4.7 and 4.8.
d) When the meter is performing abnormally, please set the mode P7 to be “On” to
restore meter to factory default setting, and then do the calibration again before
measuring.
4.5 DO Electrode Maintenance
4.5.1 Always maintain a moist sponge
Screw off the bottom lid of electrode calibration sleeve (see picture 4-1), inspect whether
the sponge inside is moist. If it is dried out, please add in several drops of distilled water to
the sponge to maintain the satured air inside the calibration sleeve (Do NOT add too much
water so it won’t be dripping).
4.5.2 Remove air bubbles
Inspect the inner solution within the electrode membrane cap. Make sure it doesn’t have air
bubbles. If there are air bubbles, please screw off the membrane cap and add in new inner
solution to remove the bubbles. Then screw the cap back on.
4.5.3 Clean the gold cathode
When the gold cathode is contaminated, use the polishing paper (DO504) to lightly wipe the
gold cathode (along the arc of the gold surface); clean the gold surface with a clean tissue

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or kimwipe afterwards; rinse off the electrode with distilled water, then shake off excess
water; Add some new inner solution into the membrane cap; screw on the cap. Then perform
the saturated oxygen calibation according to 4.2 before measuring again.
4.5.4 Replace the membrane cap
When the DO electrode’s response time becomes slower, obvious errors occur in
measurement, or when the sensitive membrane of DO electrode is wrinkled, cracked or
damaged at any extent (the well-functioning membrane surface should look perfectly
smooth), it’s time to replace a new membrane cap (DO503) according to the following steps.
a) Screw off the membrane cap;
b) Rinse off the electrode without membrane cap with distilled water and shake off
excess water.
c) Clean on the cathode surface (gold slice) with a clean tissue or kimwipe;
d) Add new inner solution (DO502) into a new membrane cap (DO503) slowly and do
not let any air bubbles appear. If you found any air bubbles in the cap, carefully flick
on the membrane cap to eliminate them.
e) Place the membrane cap on the table and put in the electrode vertically, slowly twist
in, and then screw on the cap tightly. The excess inner solution will be squeezed out.
Please wipe it off with tissue and rinse off the electrode in distilled water.
f) Check if there are any air bubbles in electrolyte (except for the smaller air bubbles),
If so, re-assembly is needed.
g) Do not touch the sensitive membrane with fingers directly because the sweat and
grease will affect the quality of the membrane.
4.6 Zero Oxygen Calibration
Usually there is no need to do zero oxygen calibration unless you have a high requirement
for accuracy in low oxygen level (<1.0 ppm). To do zero oxygen calibration, follow the steps
below:
Prepare 100mL of zero-oxygen water: In a 100 mL beaker, add in 5.0 g anhydrous sodium
sulfite (Na2SO3); add 100 mL distilled water; mix well to dissolve. Not that the zero-oxygen
water is only effective within 24 hours.

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1) Polarize the meter for 15 minutes, and then perform the saturated oxygen calibration
according to the 4.2.
2) Place the electrode into zero-oxygen water, press key to enter calibration mode.
When the stabilized reading is 0.02 ppm to 0.15 ppm after 5 minutes, press key
again to finish the calibration, then flashing 0.0% will show up, the calibration will be
finished in several seconds and 0.00 ppm will show up. Rinse off the electrode with
distilled water afterwards.
3) If the reading is less than 0.02 ppm after 5 minutes, it means the electrode is in good
condition and there is no need to perform zero oxygen calibration. Just press
key to return to measurement mode.
4) If the reading is greater than 0.15 ppm after 5 minutes, it’s time to replace the
membrane cap according to section 4.5.4 or remove the membrane cap and use the
polishing paper (DO504) to lightly polish the gold cathode according to section 4.5.3.
Then perform the saturated air calibration and zero oxygen calibration before
measuring.
4.7 Salinity Calibration
Dissolved oxygen is also affected by salinity in water. The meter has automatic salinity
compensation, and the salinity electrode is pre-calibrated before leaving the factory. In
general, there is no need to perform salinity calibration. Salinity calibration is only
needed when replacing a new electrode. For the procedure of salinity calibration,
please refer to 4.9.3 in P2.
For the salinity electrode installed in DO electrode (see picture 4-1), its surface is plated
with a layer of platinum black to reduce electrode polarization. When cleaning salinity
electrode, never brush it otherwise the coating will be peeled off. Just rinse it off by
swirling in pure water to remove contaminants. For organic contaminants, rinse off with
warm water containing detergent or alcohol.
4.8 Barometric pressure manual compensation
Dissolved oxygen is also affected by barometric pressure. The meter has the function

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of manual Barometric pressure compensation. We suggest to reset the value according
to the standard barometric pressure table when there is a big change in barometric
pressure to ensure the accuracy of barometric pressure compensation (Please see
Appendix 2 and Appendix 3). For the procedure of Barometric pressure calibration,
refer to 4.9.4.
4.9 Parameter Setting
4.9.1 DO parameter settings (Chart 4-1)
Prompt Mark
Parameter Setting Items
Code
Parameter
P1
Resolution selection
0.01/0.1(mg/L and ppm)
0.1/1(%)
P2
Salinity calibration
P3
Barometric pressure setting
P4
Temperature unit setting
˚F/˚C
P5
Back light display time setting
0-1-3-6 min
P6
Auto power off time setting
0-10-20 min
P7
Restore to producer setting
OFF-On (shut-set)
4.9.2 Resolution selection (P1)
(a) Press key and enter P1 mode, see picture (4-2);
(b) Press key to choose resolution: 0.01→0.1;
(c) Press key to enter the next parameter setting or
press to return to the measurement mode.

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4.9.3 Salinity calibration setting (P2)
(a) In P1 mode, press key to enter P2 mode, see
picture (4-3).
(b) Immerse the DO electrode into 12.88mS/cm calibration
solution (sold separately), solution level should exceed
salinity electrode; let it stand still after stirring; then press
the key when the value is stable and smiley face icon appears. 12.9 will show
up on the screen. The calibration will be finished after several seconds, and the
meter will display a stable salinity value.
(c) Press key to enter the next parameter setting or press key to return to
measurement mode.
4.9.4 Barometric pressure setting (P3)
(a) Under mode P2, press key to enter P3 mode, the
screen displays a barometric pressure measuring value
set earlier (unit is kPa), such as 101.3 kPa, shown as
picture (4-4).
(b) Press or to adjust according to standard
barometric pressure value, and long press them to quickly change the value.
(c) Press key to enter next parameter setting or press key to confirm and
return to measurement mode.
4.9.5 Temperature unit ˚C/˚F setting (P4)
(a) Short press key in mode P3 to enter mode P4, see
picture (4-5).
(b) Press or key to choose temperature unit: ˚C
or ˚F.
(c) Press key to enter next parameter setting or press key to return to
measurement mode.

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4.9.6 Backlight display time setting (P5)
(a) Short press key in mode P4 to enter mode P5, see
picture (4-6).
(b) Press or key to choose the auto-off time of
backlight: 0 min, 1 min, 3 min or 6 min. The backlight
display function will be closed if choosing 0 min.
(c) Press key to enter next parameter setting or press key to return to
measurement mode.
(d) The default setting for P5 is 1 min.
4.9.7 Auto power-off time setting (P6)
(a) Short press key in mode P5 to enter mode P6, see
picture (4-7).
(b) Press or key to choose the time: 0min, 10min
or 20min. The auto power off function will be closed if
choosing 0min.
(c) Press key to enter next parameter setting or press key to confirm and
return to measurement mode.
(d) The default setting for P6 is 0 min (see item4.4.2).
4.9.8 Restore to factory default setting (P7)
(a) Short press key in mode P6 to enter mode P7, see
picture (4-8).
(b) Press or key to choose “On”, meaning that
parameters have been restored to the factory default
setting mode, and the meter returns to measurement mode after 2 seconds.

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5 What’s in the kit
5.1. SX716 DO meter *1
5.2. DO500 DO electrode *1
5.3. DO502 DO electrode inner solution (30mL) *1
5.4. DO503 membrane cap (DO electrode use) *3
5.5. DO504 Cathode polishing paper *2
5.6. Screwdriver *1
5.7. Spare AA batteries *2
5.8. Operation manual *1
5.9. Carrying case *1
6 Limited Warranty
We warrant this instrument to be free from defects in material and workmanship and agree
to repair or replace free of charge, at option of APERA INSTRUMENTS, LLC, any
malfunctioned or damaged product attributable to responsibility of APERA INSTRUMENTS,
LLC for a period of THREE YEARS (SIX MONTHS for the electrode) from the delivery.
This limited warranty does not cover any damages due to:
Transportation, storage, improper use, failure to follow the product instructions or to perform
any preventive maintenance, modifications, combination or use with any products, materials,
processes, systems or other matter not provided or authorized in writing by us, unauthorized
repair, normal wear and tear, or external causes such as accidents, abuse, or other actions
or events beyond our reasonable control.

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7 Appendix
7.1 Appendix 1 Content of Saturated Oxygen in Water at Different
Temperature
Temperature
˚C
DO
mg/L
Temperature
˚C
DO
mg/L
Temperature
˚C
DO
mg/L
0
14.64
16
9.86
32
7.30
1
14.22
17
9.66
33
7.18
2
13.82
18
9.46
34
7.07
3
13.44
19
9.27
35
6.95
4
13.09
20
9.08
36
6.84
5
12.74
21
8.90
37
6.73
6
12.42
22
8.73
38
6.63
7
12.11
23
8.57
39
6.53
8
11.81
24
8.41
40
6.43
9
11.53
25
8.25
41
6.34
10
11.26
26
8.11
42
6.25
11
11.01
27
7.96
43
6.17
12
10.77
28
7.82
44
6.09
13
10.53
29
7.69
45
6.01
14
10.30
30
7.56
15
10.08
31
7.43

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7.2 Appendix 2 Content of Saturated Oxygen at Different Barometric
pressure
Barometric pressure
Dissovled Oxygen Concentration (mg/L)
mmHg
kPa
15˚C
25˚C
35˚C
750
100.00
9.94
8.14
6.85
751
100.13
9.96
8.15
6.86
752
100.26
9.97
8.16
6.87
753
100.40
9.98
8.17
6.88
754
100.53
9.99
8.18
6.89
755
100.66
10.00
8.20
6.90
756
100.80
10.01
8.21
6.91
757
100.93
10.03
8.22
6.92
758
101.06
10.04
8.23
6.93
759
101.20
10.07
8.24
6.94
760
101.33
10.08
8.25
6.95
761
101.46
10.09
8.26
6.96
762
101.60
10.11
8.27
6.97
763
101.73
10.12
8.28
6.98
764
101.86
10.14
8.30
6.99
765
102.00
10.15
8.31
7.00
766
102.13
10.16
8.32
7.01
767
102.26
10.18
8.33
7.02
768
102.40
10.19
8.34
7.02
769
102.53
10.21
8.35
7.03
770
102.66
10.22
8.36
7.04
771
102.80
10.23
8.37
7.05
772
102.93
10.25
8.39
7.06
773
103.06
10.26
8.40
7.07
774
103.19
10.28
8.41
7.08
775
103.33
10.29
8.42
7.09

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Conversion between mmHg and kPa:
mmHg×0.13333=kPa
DOpt = P×DOt ÷ 760
Note:
DOpt — DO concentration under temperature t, Barometric pressure P, mg/L;
P — Barometric pressure, mmHg;
DOt — DO concentration under temperature t, Barometric pressure 760mmHg, mg/L; 760 — Barometric pressure,
mmHg.
7.3 Appendix 3 Content of Oxygen at Different Altitude
Altitude
Barometric pressure
DO
Altitude
Barometric pressure
DO
Foot
meter
kPa
mmHg
mg/l
Foot
meter
kPa
mmHg
mg/l
0
0
101.3
760
8.25
7500
2287
77.1
579
6.28
500
152
99.34
746
8.09
8000
2439
75.63
568
6.16
1000
305
97.6
733
7.95
8500
2591
74.44
559
6.06
1500
457
95.87
720
7.81
9000
2744
72.97
548
5.94
2000
610
94.28
708
7.68
9500
2896
71.64
538
5.83
2500
762
92.54
695
7.54
10000
3049
70.17
527
5.71
3000
915
90.95
683
7.41
10500
3201
68.84
517
5.61
3500
1067
89.35
671
7.28
11000
3354
67.38
506
5.49
4000
1220
87.75
659
7.15
12000
3659
66.58
500
5.42
4500
1372
86.15
647
7.02
13000
3963
65.78
494
5.36
5000
1524
84.56
635
6.89
14000
4268
64.98
488
5.29
5500
1677
83.09
624
6.77
15000
4573
64.18
482
5.23
6000
1829
81.63
613
6.65
16000
4878
63.38
476
5.16
6500
1982
80.03
601
6.52
17000
5183
62.58
470
5.10
7000
2134
78.56
590
6.40
18000
5488
61.79
464
5.03

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APERA INSTRUMENTS, LLC
Address: 6656 Busch Blvd, Columbus Ohio 43229
Tel: [phone]
Email: i[email protected]
Website: aperainst.com