Apera Instruments SX716 User manual

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SX716 Portable DO Meter
Instruction Manual
APERA INSTRUMENTS, LLC
www.aperainst.com

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Table of Contents
1Brief Instruction...............................................................................................................- 3 -
2Technical Specifications....................................................................................................- 4 -
3Instructions of the Meter .................................................................................................- 5 -
3.1 LCD Display .......................................................................................................................... - 5 -
3.2 Keypads ............................................................................................................................... - 6 -
3.3 The Storage, Recall and Deletion of Measurement’s Information ........................................... - 6 -
4DO Measurement ............................................................................................................- 7 -
4.1 Preparation before use......................................................................................................... - 7 -
4.2 Meter Calibration................................................................................................................. - 8 -
4.3 Water Sample Test ............................................................................................................... - 8 -
4.4 Special Notes ....................................................................................................................... - 9 -
4.5 Parameter Setting .............................................................................................................. - 10 -
4.6 Replace the Membrane Cap................................................................................................ - 12 -
4.7 Zero Oxygen Calibration ..................................................................................................... - 13 -
4.8 Salinity Calibration............................................................................................................. - 14 -
4.9 Barometric pressure Setting ............................................................................................... - 14 -
5Meter’s Complete Kit..................................................................................................... - 14 -
6Warranty .......................................................................................................................- 15 -
7Appendix....................................................................................................................... - 15 -
7.1 Appendix 1 Meter Parameter Setting Schedule ................................................................... - 16 -
7.2 Appendix 2 Content of Saturated Oxygen in Water at Different Temperature ....................... - 16 -
7.3 Appendix 3 Content of Saturated Oxygen at Different Barometric pressure.......................... - 17 -
7.4 Appendix 4 Content of Oxygen at Different Altitude............................................................ - 18 -

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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. On the basis of improving instrument’s performance
constantly, we reserve the right of changing the content of this manual and accessories
without giving notifications in advanace.
The meter is an outstanding combination of the most advanced electronic technology,
sensor technology and software design. The meter can measure the parameters of DO
and temperature of aqueous solution with high accuracy. It is the most cost-effective
choice of a high-quality portable DO meter. It is suitable for applications in the mining
industry, power plant, environmental monitoring, and etc., especially suitable for in-field
use.
With its built-in microprocessor chip, elegant design, multi-functions, and
user-friendliness, this meter has the following features:
1.1. Built-in microprocessor chip, with the intelligent functions of automatic calibration,
automatic temperature compensation, data storage, function setting, auto power off,
and low voltage display etc. It comes with calibration solutions and a rugged
portable carrying case.
1.2. Adopts digital filter and step slipping technology to intelligently improve meter’s
response speed and accuracy. The smiley face icon will appear when the reading
is stable.
1.3. Equipped with new type of DO electrode with built-in temperature and salinity
sensors, which make DO measuring mode have auto temperature and auto salinity
compensation and manual Barometric pressure compensation. It’s easy to use and
accurate to measure.
1.4. The Polarographic DO electrode has a special electrode calibration cap. The
electrode polarization only takes 3-5 minutes. Electrode adopts a combo-style

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membrane cap, which is very convenient to use. Each DO electrode comes with
three backup membrane caps.
1.5. Meter’s circuit board adopts SMT film-covering technology to improve meter’s
performace reliability.
1.6. Meter’s LCD has clear and bright backlit display.
1.7. IP57 waterproof and dust-proof.
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
Meter: ±0.10 mg/L, connect meter with electrode:
±0.40 mg/L
Response time
≤30s (25˚C, 90% response)
Residual current
≤0.1 mg/L
Temp. compensation range
(0 to 45)˚C (automatic)
Salinity compensation range
(0 to 45) ppt (automatic)
Barometric pressure
compensation 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 groups
Stored content
Serial number, measuring value, measuring unit,
and temperature
Power Supply
Two AA 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 and CMC

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2.3 Working Condition
Environment temperature
5 to 35˚C (0.01 grade)
Environmental humidity
≤85%
IP rating
IP57 Dust-proof and waterproof
3 Instructions of the Meter
3.1 LCD 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—— Measuring value to be stable 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.

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3.2 Keypads
The meter has 5 operation keys in total.
3.2.1. —Power on/off
3.2.2. —Calibration key.
(a) When in the measurement mode, press this key to enter calibration mode.
(b) When in the parameter setting mode, press this key to change the number or the
ON/OFF state.
3.2.3. —Function key
Press the key to enter the parameter setting modes P1, P2, P3…
3.2.4. —Back light and entrance key
(a) When in the measuring mode, short press (less than 1.5s) to turn on/off the back
light display.
(b) When in the calibration mode or the parameter setting mode, press this key to
confirm, and then the meter enters measuring mode;
(c) When in DO mode, long press 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 storing and recalling
(a) Short press (press time less than 1.5s) to save the readings, long press (press
time more than 2s) to recall the saved readings when in the measuring mode.
(b) When in the parameter setting state, press this key to change the number or
ON/OFF state.
3.3 The Storage, Recall and Deletion of Measurement’s Information
3.3.1. Store the measuring information:
In the measuring mode, when the measuring data is stable and smiley face icon
comes up, short-time press key(＜1.5s), LCD will display M+ icon and storage
serial number, and meanwhile store all the measuring data. The meter can store up to
100 groups of measuring data.
3.3.2. Recall measuring information:
(a) In the measuring mode, long press the key, the meter will recall the last
stored information and the storage number. RM icon will appear in the upper right
corner of the LCD. Short press or key again, the meter will recall all

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the measuring data in turn, long press or key to quickly check the
stored data;
(b) In the recalling mode (there are RM and storage serial number in the lower right
corner of the LCD), press key to return to the measuring mode.
3.3.3. Eliminate the stored measuring information:
In the recalling mode, long-press the key for 5 seconds, LCD will appear CLr
for 2 seconds. It means that all the stored data have been eliminated and the meter
returns to measuring mode.
4 DO Measurement
4.1 Preparation before use
4.1.1. Press key to turn on.
4.1.2. Choose units: Long press to choose unit: mg/L, ppm or %; then release.
4.1.3. Check the DO500 DO electrode: see picture (4-1), unplug the bottom lid of
electrode calibration cover, inspect whether the sponge inside is fully soaked. If it
is not, please drop some distilled water, then place the calibration cover upside
down to remove the rest of the distilled water (Attention: Do NOT leave water in
the calibration cover); Inspect the electrolyte within the electrode membrane cap ,
make sure it doesn’t have air bubbles (except the smaller air bubbles). If there are
larger air bubbles, please unplug the membrane cap and add electrolyte and plug
on, then connect the electrode into meter to polarize for 5 minutes.

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4.2 Meter Calibration
Press key, the meter enters calibration mode, CAL will be flashing at the
upper-right corner of LCD. Insert the DO electrode to the calibration cover, and
tighten the cap of calibration cover, place vertically to polarize 3 to 5 minutes.
after the display values is stable and the smiley face icon appears, press key
again to calibrate. LCD will display a flashing 100%, the calibration is finished
after several seconds and return to the measuring mode. If the display value is
unstable, please wait for several minutes and press key until the display
value is completely stable.
4.3 Water Sample Test
4.3.1. To take measurments in flowing water (water sample velocity of flow >5cm/s):
Insert the DO electrode into the water, water surface level should be higher than the
location of the thermistor on the electrode, the angle for the electrode and water
should be 45°to 75°, and slightly shake the electrode, then hold 3 to 5 minutes to
1 —DO500 DO electrode
2 —Calibration cover cap
3 —Calibration cover
4 —Water stored sponge
5 —Calibration cover bottom lip
6 —Temperature electrode
7 —Membrane cap
8 —Cathode (gold slice)
9 —Anode
10 —Salinity electrode

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take the reading after the smiley face icon shows up.
4.3.2. To measure in static water: Insert DO electrode into water, water surface level
should should be higher than the location of the thermistor, the angle for the
electrode and water should be 45° to 75°, quickly move the electrode in water
(speed>5cm/s), hold 3 to 5 minutes to take the reading after smiley face icon shows
up.
4.3.3. To test in the water with slower flowing speed: Use the method from 4.3.1., but the
moving speed of the electrode should be higher.
4.4 Special Notes
4.4.1. The air temperature and water temperature should be close to each other when
calibrating (≤10℃). If the difference is large, please dip the electrode into the
sample water for about 10 minutes, then insert the electrode into the calibrate
cover for 5 to 6 minutes according to 4.2.1 and press the key to finish the
calibration.
4.4.2. After each power-on, the meter must be polarized and calibrated. So do not turn
off the meter while using (when in the DO mode, the auto power off function is
turned off by default).
4.4.3. During DO test, temperature affects a lot on the measuring value. Because the
thermistor of DO electrode is installed on the electrode housing (directly touching
the water), the thermistor and DO sensor have different sensing ablilities on the
waer’s temperature. Generally, it will take 3 to 5 minutes to make the thermistor
temperature and the actual temperature of the electrolyte within the electrode reach
the same level. So the reading time must be > 3 minutes, otherwise there will be
some fairly large errors, especially when the electrode temperature and water
temperature have larger difference (will need to extend the reading time).
4.4.4. DO measurement also can be affected by Barometric pressure (please see chart
Ⅲand Ⅳ). This meter has manual Barometric pressure compensation function.
Once the measuring value is adjusted, the accuracy can be ganruanteed.
4.4.5. DO electrode can not be tested in a static maner in static water, otherwise it will
lead the results to be lower.
4.4.6. When measuring, there can not be any bubbles on the membrane surface of the
DO electrode, which touches with water, otherwise it will affect the measuring

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accuracy.
4.4.7. The electrolyte within the electrode can not have any air bubbles (except for the
smaller ones), otherwise it will affect the response speed and accuracy. If there are
large air bubbles, user should screw out the membrane cap, then add the
electrolyte, and then screw up the cap.
4.4.8. Sensitive membrane surface of the dissolved oxygen electrode should be kept
moist to prevent dry electrolyte at the cathode. At the bottom of the calibration
sleeve there is a storage sponge (see Pic. (4-1)), the user must always remain the
sponge moist. When the sponge is dry, some water should be dropped (let sponge
saturated with water, but you can not have water flow out). Tighten the cap. Let the
dissolved oxygen electrode be stored under humid conditions.
4.4.9. For the salinity electrode installed in DO electrode (see picture (4-1)), its surface is
plated with a layer of metal platinum black to reduce electrode polarization. The
surface of platinum black can not be brushed. It can only be washed by shaking in
water in case of damaging the platinum black coating. Wash the organic component
pollution with warm water containing detergent or alcohol.
4.4.10. 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 and measuring
again.
4.5 Parameter Setting
4.5.1. DO parameter setting schedule (Chart (4-1))
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
℃℉
P5
Back light display time setting
0-1-3-6 min

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P6
Auto power off time setting
0-10-20 min
P7
Restore to producer setting
OFF-On (shut-set)
4.5.2. 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 measuring mode.
4.5.3. Salinity calibration setting (P2)
(a) Under P1 mode, press key to enter P2 mode, show as
picture (4-3).
(b) Immerse the DO electrode into 12.88mS/cm calibration solution,
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 be flashing on the LCD. 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 confirm
and return to the measuring mode.
4.5.4. Barometric pressure setting (P3)
(a) Under mode P2, press key to enter P3 mode, the LCD
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 measuring mode.
4.5.5. Temperature unit ℃/℉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: ℃or ℉.
(c) Press key to enter next parameter setting or press
key to confirm and return to measuring mode.

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4.5.6. 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 back light display function will
be closed if choosing 0 min.
(c) Press key to enter next parameter setting or press key to confirm and
return to measuring mode.
(d) The default setting for P5 is 1 min.
4.5.7. 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 measuring mode.
(d) The default setting for P6 is 0 min (see item4.4.2).
4.5.8. 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 measuring mode after 2 seconds.
4.6 Replace the Membrane Cap
When electrode’s response time becomes longer, error appeared in displaying value,
or when the sensitive membrane of DO electrode is wrinkled, cracked or damaged,
users should replace a membrane cap according to the following steps.
(a) Screw off the membrane cap;
(b) Wash the electrode without membrane cap with distilled water and dry it.
(c) Clean on the cathode surface (gold slice) with a piece of clean tissue;
(d) Inject electrolyte into a new membrane cap slowly and do not let any air bubbles

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appear. After injection, should check the electrolyte to see whether there are air
bubbles in it. If found there are air bubbles, please carefully knock on the
membrane cap to eliminate them.
(e) Put membrane cap on the table and put in the electrode vertically, slowly twist in
clockwisely, and then twist on tightly. Now the redundant electrolyte will be
squeezed out. Please wipe it off with tissue and clear it in distilled water.
(f) Check if there is any air bubbles in electrolyte (except for the smaller air bubbles), If
so, re-assembly is needed.
(g)Do not touch the sensitive membrane when using the electrode and replacing the
membrane cap because the sweat and grease of skin will affect the quality of the
membrane and decrease the rate of oxygen permeability.
4.7 Zero Oxygen Calibration
Generally, zero oxygen calibration is only needed when replacing a new electrode,
replacing membrane cap, or the electrode has not been used for a long time. Usually
there is no need to do zero oxygen calibration. To do zero oxygen calibration, follow
the next steps:
(a) Prepare 100mL of anaerobic water: In a 100 mL beaker, add 5g anhydrous sodium
sulfite (Na2SO3), add 100 mL distilled water, stir to dissolve. The anaerobic water is
effective within 24 hours.
(b) To polarize electrode by connecting it into meter for 15min, and then do calibration
according to the 4.2.1;
(c) Put the electrode into anaerobic water, press key to make the meter enter
calibration mode, when reading is ≤ 0.15mg/L (≤5min), press key again to
calibrate, then the LCD displays a flashing 0.0%, the calibration will be finished
after several seconds and the meter displays 0.00 mg/L, then wash the electrode
with distilled water;
(d) If the reading ≤0.02mg/L within 5 minutes, meaning the response speed of the
meter and residual current are good, and there is no need to do zero oxygen
calibration, press key to return to measuring mode.
(e) If the reading >0.15 mg/L after 5 minutes, meaning the response speed of meter is
slow and there is a lot of residual current, users can change the membrane cap or
remove the membrane cap and take out the polishing paper in the accessories to

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lightly wipe the catholic of gold plane (along the arc of the gold surface), and clean
the surface of cathode with soft tissue), and wash electrode with distilled water and
throw off the water on it.Add some electrolyte into the membrane cap, re-assembly
and screw tightly. Then conduct the full scale and zero oxygen calibration according
to 4.2. and 4.7.
4.8 Salinity Calibration
The meter has automatic salinity compensation, so salinity calibration is needed when
replacing a new electrode or the electrode has not been used in a long time. In
general, there is no need to do salinity calibration. Salinity has already been calibrated
before leaving factory. For the procedure of salinity calibration, please refer to 4.5.3 in
P2.
4.9 Barometric pressure setting
The meter has the function of manual Barometric pressure compensation. It is
suggested to reset the value according to the standard Barometric pressure table
when there is a big change in Barometric pressure in order to ensure the accuracy of
Barometric pressure compensation (Please see the Chart Ⅲand Ⅳ. For the
procedure of Barometric pressure calibration, please see 4.5.4.).
5 Meter ’s Complete Kit
5.1. Model SX716 DO meter *1
5.2. DO500 DO electrode *1
5.3. DO503 membrane cap (DO electrode use) *3
5.4. DO502 DO electrode inner solution (30mL) *1
5.5. Cathode polishing paper *2
5.6. Screw driver *1
5.7. Spare AA batteries *2
5.8. Operation manual *1
5.9. Carrying case *1

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6 Warranty
We warrant this instrument to be free from defects in material and workmanship and agrees to
repair or replace free of charge, at option of APERAINSTRUMENTS, LLC, any malfunctioned or
damaged product attributable to responsibility of APERA INSTRUMENTS, LLC for a period of
two years from the delivery (a six-month limited warranty applies to electrodes and the
electrode’s accesories). This warranty does not apply to defects resulting from actions such as
misuse (violation of the instructions in this manual or operations in the manner not specified in this
manual), improper maintenance, and unauthorized repairs. Warranty period is the time limit to
provide free service for the products purchased by customers, not the service life of the tester or
electrode.

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7 Appendix
7.1 Appendix 1 Meter Parameter Setting Schedule
Mode
Prompt
Mark
Parameter Setting Items
Code
Parameter
Dissolved
Oxygen
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
℃℉
P5
Back light display time setting
0-1-3-6min
P6
Auto power off time setting
0-10-20min
P7
Restore to factory default
setting
OFF-On
7.2 Appendix 2 Content of Saturated Oxygen in Water at Different
Temperature

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Temperature
℃
DO
mg/L
Temperature
℃
DO
mg/L
Temperature
℃
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
7.3 Appendix 3 Content of Saturated Oxygen at Different Barometric pressure
Barometric pressure
Dissovled Oxygen Concentration (mg/L)
mmHg
kPa
15℃
25℃
35℃
750
100.00
9.94
8.14
6.85
751
100.13
9.96
8.15
6.86

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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
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.
7.4 Appendix 4 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

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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: [email protected]
Website: www.aperainst.com