Apera Instruments TN420 User manual

TN420 Portable Turbidity Meter
Instruction Manual
APERA INSTRUMENTS, LLC
aperainst.com

Table of Contents
1Introduction...............................................................................................................- 1 -
2Technical Specifications............................................................................................- 2 -
3Instrumentation Illustration........................................................................................- 3 -
3.1 Overview ............................................................................................................- 3 -
3.2 Configuration ......................................................................................................- 4 -
3.3 Display Mode......................................................................................................- 4 -
3.4 Keypad ...............................................................................................................- 5 -
3.5 Power Supply .....................................................................................................- 6 -
4Meter Calibration ......................................................................................................- 6 -
4.1 Preparation for Calibration..................................................................................- 6 -
4.2 Calibration Procedure (Take 0 NTU and 20 NTU as an example) ......................- 8 -
4.3 Notes for Calibration...........................................................................................- 9 -
5Turbidity Measurement ...........................................................................................- 10 -
5.1 Sample Cuvette Handling.................................................................................- 10 -
5.2 Measurement Preparation ................................................................................- 10 -
5.3 Measurement Mode..........................................................................................- 10 -
5.4 Notes for Measurement .................................................................................... - 11 -
6 Lamp Replacement.................................................................................................... - 11 -
6.1 Light Source Check ..........................................................................................- 12 -
6.2 Lamp Replacement ..........................................................................................- 12 -
7 Warranty.....................................................................................................................- 13 -
8 Replacement Parts ....................................................................................................- 13 -
V1.1
*Please fully charge the battery before first-time use.

- 1 -
1INTRODUCTION
Thank you for purchasing Apera Instruments TN420 Turbidity Meter (hereafter referred to as the
instrument). The instrument uses tungsten filament lamp (400 – 600nm) as the light source and 90°
scattering method, which is compliant with U.S EPA 180.1 method for the determination of of turbidity in
drinking, ground, surface, and saline waters, domestic and industrial wastes. It is suitable for on-site and
laboratory use.
The instrument provides accurate results with simple measurement and calibration, giving you unparalled
confidence in turbidity test results and easy of use. The main functions and features include:
⚫Intelligent functions such as automatic calibration, operation navigation, parameter setup, automatic
power off, low voltage indication, and a replaceable tungsten filament lamp.
⚫Large TFT color screen with blue background for measurement mode, green background for
calibration mode.
⚫Operation guidance and reminders in the process of calibration, measurement and parameter setting.
⚫Average measurement mode automatically takes multiple consecutive readings, and calculate the
average from 10 times of measurement, which is ideal for sample solutions with rapid settling and
continuous measurement changes.
⚫3.7V rechargeable lithium battery can supply power for over 20 hours of continuous measurement.
The battery life is 5 times longer compared with tungsten lamp turbidimeter in the market using AA
alkaline batteries.
⚫Meets IP67 rating, ideal for use under harsh environment and field.
⚫Comes with a carrying case, which includes the meter, calibration solutions, and other accessories,
convenient for use and carry.

- 2 -
2TECHNICAL SPECIFICATIONS
Measurement
Method
90° scattering measurement
Light Source
Tungsten (400 – 600nm) filament lamp, compliant with US EPA 180.1 Method
Measuring Range
0 to 1000 NTU (FNU), automatic range switch
0.01 to 19.99 NTU (FNU)
20.0 to 99.9 NTU (FNU)
100 to 1000 NTU (FNU)
Accuracy
≤ ±2% of reading+ stray light
Repeatability
≤ ±1% of reading or 0.02 NTU(FNU) (whichever is greater)
Resolution
0.01/0.1/1 NTU (FNU)
Stray Light
≤0.02 NTU (FNU)
Calibration
Standard
AMCO Polymer solution or Formazin Solution: 0, 20, 100, 400 and 800 NTU
(FNU)
Detector
Silicone photovoltaic
Measuring Mode
Normal measurement; Average Measurement
Display
TFT color screen
Sample Cuvette
Φ25×60 mm, high borosilicate glass with lid
Sample Cuvette
Volume
18 ml
Power supply
3.7V Rechargeable lithium battery
Working Condition
Temperature: 0 to 50°C（32°F to 122°F）； Relative humidity：
0 to 90% at 30°C, 0 to 80% at 40°C, 0 to 70% at 50°C, no condensation
Storage Condition
Instrument: -40 to 60°C (-40 to 140°F)
Calibration Solution: 5 to 30°C (41 to 86°F)
Instrument sealing
grade
IP67
Certificates
CE and RoHS
Limited Warranty
2 years
Dimension and
Weight
Meter: (90×203×80) mm/385g
Test Kit: (310×295×110) mm/1.5kg

- 3 -
3INSTRUMENTATION ILLUSTRATION
3.1Overview
①
Flip cover of the sample cuvette holder
(Close the cover when measuring)
⑦
Dust-proof plug (Take off the plug when
measuring)
②
Housing
⑧
Sample cuvette holder
③
Display
⑨
Calibration cuvettes or sample cuvettes
④
Keypad
⑩
Positioning mark (Align the mark with the
mark on the calibration cuvette or sample
cuvette)
⑤
USB Port
⑪
Built-in lithium battery (Rechargeable)
⑥
Lamp cover
Diagram-1
⑪
⑩
⑦
⑧
⑨
④
①
②
③
⑥
⑤

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3.2 Configuration
3.3 Display Mode
Measuring
Mode
Calibration
Mode
①
Calibration Solutions：
0.0, 20.0, 100, 400, 800 NTU
②
Carrying case
③
TN420 Turbidimeter
④
Microfiber cloth
⑤
Power adaptor (5V 1A)
⑥
Silicone oil (10 ml)
⑦
Sample cuvettes×6
⑧
USB Cable (under the meter)
⑨
User Manual
①Calibration solution
②Measurements and unit
③Progress bar
④Operation guide
①Measurement Mode
②Measurements and unit
③Operation Guide
④Battery icon
Diagram-2
⑨
①
②
③
④
⑤
⑧
⑦
⑥

- 5 -
Calibration
Menu
3.4 Keypad
Keypad
Functions
⚫Power on/off
⚫In measurement mode: press to enter calibration mode
⚫In calibration mode: press to exit calibration mode
⚫In measurement mode: long press to switch measurement units NTU-FTU
⚫In measuring mode: Short press the key to perform normal measurement; long
press the key to perform average measurement
⚫In calibration mode: press the key to confirm the calibration.
⚫In calibration mode, press the key to select standard solution.
Diagram 3
①Calibration mode
②Standard values
③Operation guide
④Finished calibration indicator

- 6 -
3.5 Power Supply
The instrument adopts 3.7V rechargeable lithium battery. Fully charge the battery before first-time
use.
a) Charging mode
·Charge via Power adaptor: connect instrument and power adaptor with a USB cable. Adaptor
specification: AC110 to 240V, 50/60Hz, output: 5V/1A.
·Charge via Computer: connect instrument and a computer with a USB cable.
Under normal circumstances, it is recommended to use the power adapter to charge the lithium
battery to ensure the performance. When the lithiumbattery voltage is lower than 3V, the instrument
will shut down, and it’s time to recharge it.
b) Battery capacity indication
·Battery capacity icon: , please recharge the battery when
icon displays to ensure measuring accuracy; when icon displays, the battery must be
recharged, otherwise the instrument cannot work properly.
·If charging the instrument when it is turned on, icon will be displayed. Users can continue
using the instrument while it is being charged.
·If charging the instrument when it is turned off, "Charging......" will be displayed, and "Charging
is completed" will be displayed after a full charge.
4METER CALIBRATION
4.1Preparation for Calibration
a) Calibration Point
The instrument has 5 calibration points: 0 NTU, 20 NTU, 100 NTU, 400 NTU, and 800 NTU. Among
them, 0 NTU point uses AMCO 0.0 NTU calibration solution or laboratory distilled water, and the
remaining 4 calibration points use AMCO polymer solutions. Note that the cap of the 0.0 NTU solution
cuvette can be unscrewed. After the solution is invalidated, users can replace the 0.0 NTU calibration
solution or use fresh laboratory distilled water. The AMCO 0.0 NTU calibration solution refill can be
purchased from the supplier; For the remaining 4 calibration solutions, their cuvette caps cannot be
opened. Simply dispose the solutions after they are expired or invalidated and buy new ones from
your supplier to replace. See the detail in Section 8 Replacement Parts.
b) Replace zero turbidity solution
•Open the 0.0 NTU cuvette cap, pour out the original solution, add 1/2 distilled water, screw on
the cap and shake the cuvette to rinse it off and pour out the water. Repeat it 3 times. Shake off
the distilled water in the cuvette. Pour in new AMCO 0.0 NTU calibration solution or fresh
laboratory distilled water. Then close the cuvette cap.
•AMCO 0.0 NTU calibration solution has 6 to 12 months of shelf-life, distilled water is only valid for
a couple of days.

- 7 -
AMCO 0.0 NTU solution is provided in the default kit. For purchase details, please refer to Section 8
Replacement Parts.
c) Clean cuvette surface
Apply a small drop of silicone oil on the surface of the cuvette and wipe it off with a lint-free cloth to
evenly distribute the silicone oil on the surface in order to cover smudges and scratches, whichhelps
light scattering. But please pay attention to the following points:
①The silicone oil applied should not be too much. After wiping with lint-free cloth, please wipe with
filter paper or high-quality tissue paper to clean off. Excessive residual silicone oil on the cuvette
surface will affect the measurement accuracy.
②It's not necessary to use silicone oil for each calibration and measurement. Apply silicone oil
every several days or once a week. In between, just clean the surface with filter paper or high-
quality tissue paper.
③Clean the calibration cuvette and sample cuvette together and keep the steps and actions
consistent to achieve same degree of cleanliness.
④Stability of calibration solutions
The U.S EPA approved AMCO polymer standard calibration solution is very uniform and stable.
It does not precipitate, drift or condense. Generally, it can be used directly without shaking or
flipping the cuvette (to make the solution even). For AMCO polymer calibration solutions that
have not been used for a long time, slowly flip the cuvette twice and let it stand for 2 minutes.
Be careful not to shake the solution vigorously, as this will create air bubbles which will
destabilize the measurement; For 0.0 NTU calibration solution, do NOT shake or flip. If using
Formazin calibration solution, as it tends to precipitate easily, each time users must flip and
shake the cuvette to make the solution even. But sediment can still occur during tests and would
make the measurement unstable. Users need to have rich experience handling Formazin
calibration solutions.

- 8 -
4.2 Calibration Procedure (Take 0 NTU and 20 NTU as an example)
1) Instrument warm up (only required for low-range or high-accuracy measurement): Power on the
instrument, set parameter P2 (continuous measurement time) to 5 times. Long press to
start continuous measurement (don't insert the cuvette), then wait for 3 to 5 minutes.
2) Open the flip cover and place the 0.0 NTU calibration
cuvette. Align the arrow on the cuvette lid with the arrow
on the sample cuvette holder and close the flip cover.
3) Press to enter the calibration menu, the cursor is
at 0 NTU. Press to start calibration.
4) After calibration is done, press to confirm.
The instrument will return to the calibration menu (see
Diagram on the right side). The OK sign indicates that 0
NTU has been calibrated and prompt to calibrate 20
NTU.
5) Place the 20.0 NTU calibration cuvette in the sample
cuvette holder, press to start 20 NTU calibration.
After calibration is done, press to confirm. The
instrument will return to the calibration menu (see
diagram on the right side). The OK sign indicates that
20 NTU has been calibrated.
6) If you want to continue to calibrate 100, 400 and 800 NTU, place the 100 NTU calibration cuvette
in the sample cuvette holder and press to calibrate. After calibration is done, press
to confirm; repeat the steps to calibrate 400 NTU and 800 NTU. After calibration is done,
press to return to measurement mode.

- 9 -
7) Press to exit calibration mode, the instrument will
return to measurement mode as shown in Diagram on the
right side.
4.3 Notes for Calibration
a) Calibration point verification: The calibration point can be verified after the calibration is
completed. If the calibration point has a large error, enter the calibration mode and repeat the
calibration. For calibration point accuracy, users can refer to the following standards:
b) Calibration point selection: The instrument has been calibrated at full range before leaving the
factory. For subsequent use, you can select 2 or more points as needed, as long as the estimated
measurement range is between the two calibration points. In calibration setup mode, press
or to select the calibration point.
c) Low turbidity calibration requirement
a) For low turbiditymeasurements (measurement less than 2 NTU), please test 0.0 NTU calibration
solution. If the accuracy is not meeting requirements, calibrate the instrument at 0.0 NTU and
20.0 NTU before test; then use 1#or 2#sample cuvette for measurement.
b) Using the same sample cuvette to calibrate and measure can eliminate the error caused by
different cuvettes, thus achieving higher accuracy. For example, add laboratory distilled water
to 1#cuvette for calibration and then add sample solution to 1#cuvette for measurement. Note
that the solution cuvette should be rinsed thoroughly when changing solutions.
d) High turbidity calibration requirement: For turbidity measurement greater than 2 NTU, it is
recommended to calibrate once a week, or to test a calibration solution close to the sample solution.
If the error is large, the instrument needs to be recalibrated.
e) The instrument does not automatically recognize the calibration solution. If the wrong solution is
selected for calibration, the measurement will be completely wrong. In this case, it can be restored
by recalibrating with the correct calibration solutions.
f) Place the instrument on a flat and level surface. Do not hold the instrument in hand while operating.
g) If using Formazin standards for calibration, please make sure to use the freshly made Formazin
standard to ensure calibration accuracy.
Calibration point
Accuracy for reference
0 NTU
≤0.05 NTU
20 NTU
≤±0.2 NTU
100 NTU
≤±2 NTU
400 NTU and 800 NTU
≤±5 NTU

- 10 -
5TURBIDITY MEASUREMENT
5.1 Sample Cuvette Handling
a) 6 sample cuvettes are included in the test kit. The cap is marked with 1#to 6#, and the bottom of the
cuvette also has the same number. The number of the cuvette and the cap should always be the
same. *Pay attention that 1#and 2#cuvettes are only for low turbidity solution measurement. (< 2
NTU)
b) The cuvette has been rigorously cleaned and sterilized. They can be used directly for the first time.
For subsequent uses, follow the steps below to perform a thorough cleaning.
⚫Clean the sample cuvette inside and outside with detergent → rinse with distilled water or
deionized water multiple times → Rinse the cuvette twice with the sample solution → Pour the
sample solution into the cuvette → Close the cap.
5.2 Measurement Preparation
a) Collect the sample solution with a clean container and add the
solution to the 4/5 of the cuvette (about 18ml), see Diagram 4.
Then close the lid.
b) Before the measurement, users can slowly flip the sample
cuvette a few times and let it stand for 2 to 5 minutes to eliminate
potential air bubbles (see Diagram 5).
c) Clean off the surface of the cuvette to ensure it is dry, clean and free of stains. Apply a small drop
of silicone oil on the surface of the cuvette and wipe it off with a micro-fiber cloth. Then wipe again
with filter paper or high-quality tissue paper. See section 4.1(c) for details.
5.3 Measurement Mode
a) Normal Measurement Mode
Press , the screen will display the progress bar, and the measured value will be
displayed in 20 seconds. To take the next measurement, press again.
b) Average Measurement Mode
Long press button, release it until you hear a beep, then the instrument enters average
reading mode. In this mode, the instrument will perform 10 times continuous measurement, measure
and display 1 data every 20 seconds, and displays the average value at the end, see diagram 6. The
average measurement mode can be used for observing the stabilizing process of turbidity, and is
ideal for testing rapid-settling solutions.
Diagram 4
Diagram 5

- 11 -
5.4 Notes for Measurement
a) Keep the sample stable: After the cuvette is placed into the sample cell, it is recommended to wait
for 1 to 2 minutes before calibration, as the solution will experience some shaking when the cuvette
moves, which may result in inaccurate measurements.
b) Sample Cuvette cleaning requirement: Sample cuvette must be rigorously cleaned and free from
smudges and scratches. When wiping, user should grip the cap and bottom to avoid leaving
fingerprints on the surface of the cuvette. Its surface should be applied with a drop of silicone oil be
wiped with a micro-fiber cloth. After that, please clean with filter paper or high-quality tissue paper.
See section 4.1(c) for details.
c) Mixing and Degassing: Samples should not be vigorously shaken or vibrated. It is recommended
thatusers gentlyshakethesample cuvettetomake solutionevenlydistributed.Airbubbles in solution
will cause big error to turbidity measurement. So, the cuvette should be left stand still for 2 to 5
minutes to eliminate potential air bubbles before measuring. But mixing and degassing
simultaneously is a difficultprocess to handle, especially for solution with precipitates, which requires
some operating experience or making some limits in test conditions, for example, limiting the mixing
condition and waiting time for degassing to be the same before comparing measurements.
d) Other Requirements
⚫On the premise of ensuring evenly distributed samples, sample solution should be measured
immediately to prevent temperature changing and precipitates from affecting measurements.
⚫Avoid sample dilution for measurement as much as possible.
⚫Avoid operating under direct sunlight.
⚫Do not pour solution into the cuvette holder. Sample cuvettes must be used for measurement.
⚫Please do not wash the cuvette holder as this may damage its optical structure.
Diagram 6

- 12 -
6 LAMP REPLACEMENT
6.1 Light Source Check
Observe the light source on the left side of the sample cuvette holder as in Diagram 11. Turn on the
instrument, and press . The light source will light up for 5 seconds. If it’s not lighting up or it’s
flashing, please replace the lamp.
6.2 Lamp Replacement
The tungsten filament lamp module (sold separately) is shown as in Diagram 12. The lamp hole and
socket are as in Diagram 13. Diagram 14 shows you how to replace the lamp.
Diagram 12
Tungsten filament lamp module
Diagram 13
lamp hole and socket
Diagram 11
Check light source
socket
lamp hole
lamp
cover
gasket
tungsten
filament
lamp
Socket
Light source
Unscrew the lamp cover
with a coin
Use a tweezer to
unplug the socket
Use a tweezer to
unscrew the lamp cover.
Take out the old tungsten
filament lamp module
Install the new tungsten
filament lamp module.
Close the lamp cover and
screw tight with a tweezer.
Use a tweezer to plug
wire into the gap and plug
in the socket
Screw on the lamp
cover tightly

- 13 -
7 WARRANTY
We warrant this instrument to be free from defects in material and workmanship and agree to repair or
replace free of charge, at the option of APERA INSTRUMENTS, LLC, any malfunctioned or damaged
product attributable to the responsibility of APERA INSTRUMENTS, LLC for a period of TWO YEARS for
the instrument from the delivery.
This limited warranty does NOT cover any issues due to:
⚫Accidental damage
⚫Improper use
⚫Normal wear and tear
⚫Transportation
⚫Storage
⚫Failure to follow the product instructions
⚫Unauthorized maintenance, modifications, combination or use with any products, materials,
processes, systems or other matter
⚫Unauthorized repair
⚫External causes or other actions beyond our reasonable control.
8 REPLACEMENT PARTS
Model
Name
Description
Quantity
T500-2
AMCO 0.0 NTU calibration
solution
0.0 NTU/100mL
1 bottle
T500-1
20/100/400/800 NTU
AMCO polymer
Compatible with TN500&TN420
4 bottles
T500-3
Sample cuvettes with lid
Φ25×60mm，1# to 6#
6 pcs
T500-5
Tungsten filament lamp
/
1 pc
T500-4
Rechargeable lithium battery
3.7 V
1 pc
TN400-S3
Silicone oil
10mL
1 bottle

- 14 -
APERA INSTRUMENTS, LLC
Address: 6656 Busch Blvd, Columbus Ohio 43229
Tel: [phone]
Email: [e-mail]
Website: aperainst.com