Apera Instruments GroStar GS2 User manual

GroStar™
GS2 Premium Soil pH Pen Tester
User Manual
APERA INSTRUMENTS (Europe) GmbH
www.aperainst.de

1
Content
1Main Features ................................................................................................................ 1
2Preparation Before First Use .......................................................................................... 3
3pH Calibration................................................................................................................. 3
4pH Measurement............................................................................................................ 4
5Measure Soil pH Directly................................................................................................ 5
6Making a Soil Slurry........................................................................................................ 6
7Other Functions.............................................................................................................. 6
8Probe Cleaning............................................................................................................... 7
9Probe Storage................................................................................................................ 7
10 Battery Replacement...................................................................................................... 8
11 Probe Replacement........................................................................................................ 8
12 Notes.............................................................................................................................. 8
13 Troubleshooting Guide ................................................................................................... 9
14 Technical Specs............................................................................................................11
15 What’s in the box...........................................................................................................12
16 Accessories...................................................................................................................12
17 Warranty........................................................................................................................12
Thank you for choosing the Apera GroStar™ GS2 Premium pH Pen Tester. This
premium pen has been designed specifically for the horticultural market. Since 1991,
Apera instruments has been dedicated to providing hi-tech, accurate, lab-grade
instruments and sensors. GroStar's intelligent design reduces the guesswork, so you
can easily manage your crops success.
1 Main Features
•The Swiss LabSen® Spear soil pH probe provides accurate results with minimal
maintenance in soil pH test
•Easy to use design and quick two-point calibration adjustment
•3-Color backlit LCD screen gives you clear readings in different modes even in dark
environment
•Durable structure, IP67 waterproof rating, powered by AAA batteries
•The probe is replaceable, so you don't have to discard the entire pen when the probe
reaches its end of life

2
3-Color LCD Screen
•White for measurement mode
•Green for calibration mode
•Red for calibration error
stands for stabilized reading
L/M/H stands for successful
calibration: L is pH 4, M is pH 7 pH is
pH 10. The icon(s) will disappear
after 30 days to remind you for re-
calibration
Probe Cap Ring
Loosen the probe cap ring before
pulling out the probe cap
Short Press
Long
Press
1. Power on
2. Manual hold
Press again to
cancel hold
Power off
In measurement
mode, press to
turn on/off the
backlight.
Start
calibration
In calibration
mode, press to
cancel calibration
Switch
between
°F and °C
Swiss LabSen® Spear Soil pH Probe
Backed by Apera's proprietary sensor
technology from Switzerland, this spear
pH probe is specifically designed for
making soil pH test easier and more
reliable.
•Impact-resistant spear glass tip, 10
times stronger than conventional glass
bulb
•PTFE ring prevents a clogged junction
caused by soil particle
•Long-life reference system ensures
high durability
Probe Cap
•The probe must be soaked in 3M
KCl soaking solution when not in
use
•Fill in 3M KCl soaking solution to
about 1/3 of the probe cap, store
the probe in it, then twist on the
cap ring

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2 Preparation Before First Use
2.1 Pull out the battery insulation slip;
loosen the probe cap ring, then pull out
the probe cap.
2.2 Prepare a bucket of clean water (tap
water is ok. Ideally use RO water).
Rinse the probe in it and shake off
excess water.
2.3 Calibrate the tester at pH 7 and pH 4 before first use. See below for calibration tutorial.
3 pH Calibration
3.1 Power on the pen and remove the probe cap. Always calibrate
7.00 pH first.
3.2 Rinse the probe with clean water and shake off excess water, then
submerge it in the 7.00 pH standard buffer; make a quick stir in
the solution and hold still.
3.3 Hold until screen turns green. The pen starts automatic
calibration. Wait for "Good" to show up (in 10-15 seconds),
indicating the calibration is completed, then the pen returns to
measurement mode.
Short press any key while calibrating (in green screen) to cancel
calibration and return to measurement.

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3.4 icon will show up on the lower left corner of the screen, indicating the pen is
successfully calibrated. Repeat Step 3.2 to 3.3 to calibrate pH 4
using 4.00 pH buffer, then will show up next to . You can
continue to calibrate pH 10 by repeating Step 3.2 to 3.3 using 10.01
pH buffer (sold separately), then will show up to the right of
.
Calibrating pH 10 is usually not necessary unless your estimated target pH is greater than 8.0
pH.
3.5 / / will disappear in 30 days after calibration, reminding
you to recalibrate the tester. We recommend calibrating pH at least
once a month to ensure accuracy. If you feel like the accuracy
might be off, simply test the standard buffers(make sure the buffers
are fresh and clean). If a discrepancy is found, then it’s time to
calibrate again.
3.6 If the calibration fails, the screen will turn red. For details, see
Section 13 Troubleshooting Guide.
Always perform at least a 2-point pH calibration to ensure accuracy. Start
with 7.00 pH, followed by 4.00 pH immediately. If you happened to turn off
the pen before calibrating 4.00 pH, you need to start with 7.00 pH again
after rebooting the pen, then 4.00 pH.
4 pH Measurement
4.1 Power on and remove the probe cap.
4.2 Rinse the probe with clean water and shake off excess water.
4.3 Fully submerge the probe into the solution at least 1 inch deep.
4.4 Hold the pen and wait for the reading to stabilize ( stays on screen),
then record the reading. Press to lock the reading if necessary.
Press it again to cancel the lock.
4.5 After measurement, thoroughly rinse off the probe with clean water,
then put the probe back into the cap with 3M KCl storage solution.

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5 Measure Soil pH Directly
5.1 Remove about 2 inches (5cm) of the top layer soil in the test area,
make sure the soil is wet. If the soil is dry, pH measurement
cannot be performed, and the probe can be damaged. For dry soil,
please add some distilled or RO water to moisten. Ideally, wait 24
hours before measuring.
5.2 Use the dibber to create a pathway for the spear probe at about 4-6 inches (10-15cm) in
depth. This will help minimize the wear and tear of the spear glass probe.
5.3 Remove the probe cap; power on the pen; rinse the probe in the
water bucket and shake off excess water.
5.4 Insert the probe in the hole you just created up until the bottom
where you cannot stick in any further (do NOT use excessive force
to stick in); Wait for the reading to fully stabilize ( stays on screen),
then press to hold the reading. Then take out the pen
and record the measurement.
5.5 After each test, the probe must be thoroughly rinsed in the water bucket. Make sure to
clean off the dirt onthe white PTFE junctionring using the cleaning brush. Avoid brushing
the spear glass tip. After cleaning, shake off excess water. For details of probe cleaning,
refer to Section 8.
5.6 Repeat Step 5.2 to Step 5.5 to record 3-5 measurements in different locations of your
sample area, then calculate the average value. After measurement, put the probe back
in the storage cap and soak in the 3M KCl solution.
The recommended pH range for soil crops is 5.8 to 7.2 pH. And the best pH range for each plant
is different. The factors that are affecting the soil pH include soil type, growth stage of the plant,
use and types of fertilizers, use of pesticides, and the soil’s temperature.
In the practice of direct soil pH testing, as soil is not evenly distributed by its nature, different
locations and different depth will generate slightly different pH readings. Even when the angle
at which you stick in the probe is different, the reading can also be affected. Therefore, selecting
multiple locations while doing your best sticking in the probe at the same depth and angle, then
calculating the average is the best way to compensate such reading errors and maximize the
measurement accuracy.

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6 Making a Soil Slurry
6.1 Remove about 2 inches (5 cm) of the top layer soil and collect different locations’ soil
samples at approximately 6 inches (15 cm) deep.
6.2 Thoroughly mix all collected soil.
6.3 Ideally, dry the soil in the air or bake in an oven at 104 ˚F / 40 ˚C.
6.4 Weigh out 20 g of the mixed soil sample into a glass jar and add 100 g of distilled or
deionized water in it.
6.5 Shake well for 5 minutes or use a magnetic stirrer to automatically stir for 15 minutes.
Leave overnight.
6.6 Shake or stir again next morning, then allow it to settle for 15-30 minutes.
6.7 Power on the tester; Remove the probe cap; Rinse the probe in the water bucket and
shake dry.
6.8 Submerge the probe into the soil solution, shake for a few seconds, and wait for the
reading to fully stabilize. Then record the reading.
6.9 After measurement, put the probe back in the storage cap and soak in the 3M KCl
solution.
7 Other Functions
7.1 If necessary, you can manually hold (lock) the reading by short pressing . Press it
again to cancel the hold.
7.2 Long press to switch temp. unit between °F and °C.
7.3
Out of range reminder for pH Out of range reminder for temperature
7.4 The tester will automatically power off if there is no operation within
10 minutes. If you want to turn off the Auto. Power Off function,
power off the tester, and then hold for 5 seconds until you see
Auto off. Then it will power on and go to measurement mode
automatically.

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8 Probe Cleaning
8.1 The tester is only as accurate as the probe is clean. Always
thoroughly rinse off the probe before and after each measurement
with clean water in a container or with a wash bottle.
8.2 Use the probe cleaning brush with water to clean off all the dirt on
the probe, especially the white
PTFE junction ring. Avoid wiping
or rubbing the blue spear tip.
The white PTFE ring junction will become slightly brownish after the first soil pH test. This is
normal. The slightly brownish ring will not affect the accuracy as long as the soil particles are
eliminated by the cleaning brush in water.
8.3 For tough contaminants, soak the probe in Apera’s cleaning solution or detergent water
for 30 minutes. Then use a soft brush to remove the contaminants. Afterwards, soak the
probe in 3M KCL soaking solution for 1 hour. Rinse it off, then re-calibrate the tester
before using again. These cleaning tools can be found in the Probe Care Kit (refer to
section 15).
9 Probe Storage
9.1 The spear probe must be soaked in 3M KCl soaking solution when not in use. Fill in 3M
KCl soaking solution to about 1/3 of the probe cap, store the probe in it, then screw on
the cap ring tightly.
If you find white crystals inside or outside the probe cap, it is perfectly normal. It is the 3M KCl
soaking solution that crystalizes over time by its nature. Just rinse them off and add in new
storage solution. This chemical is not poisonous nor dangerous, and the probe’s performance
will not be affected at all.

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10 Battery Replacement
①Pull up the battery cap (might take some force).
②Slide the battery cover along the OPEN arrow to open the cover.
③Open the battery cover.
④Insert the batteries (ALL POSITIVE SIDES FACING UP).
⑤Press down the battery cover and hold it.
⑥Slide the battery cover along the LOCK arrow to lock the cover.
⑦Close the battery cap. Make sure to push it all the way down. The tester’s waterproof
rating may be compromised if the battery cap is not tightly closed.
11 Probe Replacement
Screw off the probe ring, unplug the old probe; plug in the new probe
(make sure to align the connector's position properly), and screw on
the probe ring.
pH probes don’t last forever. Every pH probe will eventually age and
fail even if you don't use it that often. The typical service life of GroStar
pH probes is 18-24 months depending on the frequency of usage and
how well you keep it clean and properly stored.
We recommend replacing your probe at least every 18 months to ensure the best accuracy.
The nice thing about GroStar pens is that you can just buy a replacement probe instead of a
whole new tester.
12 Notes
12.1 Never store the probe in pure water such as tap water, RO water, distilled water,
deionized water, etc.
12.2 Never use your finger to touch the glass membrane or use other material to wipe it.

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12.3 Avoid testing in high (>113°F/ 45°C) or low temperature (<41°F/ 5°C) solutions as it will
cause greater measurement error and damage to the probe. Test your samples and
perform calibration close to room temperature as much as possible.
12.4 Never test oily liquids.
12.5 Make sure the battery cap is completely closed with the O-ring. Otherwise, the
waterproof rating could be compromised.
13 Troubleshooting Guide
Trouble
Reason
How to fix
Cannot
calibrate
Incorrect calibration
order
Power on the tester, calibrate pH 7 first, then pH 4. After pH 4
is calibrated, if you want to calibrate pH 7 again, you need to
reboot the tester
Poor quality standard
solutions
Replace with fresh and clean standard calibration solutions
made by legitimate scientific instrument manufacturers
Contaminated probe
Clean the probe with Apera’s cleaning solution or detergent
water
Aged probe
Replace the probe
Dried-out probe
Soak the probe in the 3M KCl soaking solution for at least 1
hour
Probe is not fully
submerged in the
solution
Make sure the probe is fully immersed in the solution at least 1
inch deep
Air bubbles around
the sensor
Make a quick stir in the solution to remove air bubbles
Reading is
alwaysslowly
changing, won’t
stabilize
Contaminated probe
Clean the probe with Apera’s cleaning solution or detergent
water
Clogged junction
Clean the probe with Apera’s cleaning solution, then soak it in
3M KCL soaking solution overnight.
Aged probe
Replace the probe
Testing pH of low
iconic strength
solutions like tap
water, drinking water,
RO water
Be patient, wait for 2-5 minutes to reach a fully stabilized
reading. If still not stabilizing, add 1ml of 3M KCl solution to
1000ml of test solution.

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Display similar
readings in any
solutions or
alwaysdisplay
7.0 pH
Broken probe
Make sure the soil is wet. Testing in dry soil will damage the
probe. If you don’t find any visible damage of the probe and it’s
within the 1-year probe warranty, contact your point of purchase
for warranty fulfillment; If there is visible damage or the probe is
more than 1-year old, replace the probe.
Reading keeps
jumping
Probe is not fully
submerged in the
solution
Make sure the probe is fully immersed in the solution at least 1
inch deep
Air bubbles around
the sensor
Make a quick stir in the solution to remove air bubbles
Probe is not properly
connected, or the pin
connector is broken.
Check the probe’s connector, make sure it’s not broken and is
correctly connected. Align the probe and instrument correctly
before plugging in. Never force it. Ensure that the probe
connector is not exposed in the air too long.
Calibration is
successful, but
reading is not
accurate or
consistent
Contaminated probe
After each measurement, make sure to use a soft brush with
water to clean off all the dirt on the probe, especially the white
PTFE junction ring. Avoid wiping or rubbing the blue spear tip.
Soil difference
Soil in different locations and different depth will have slightly
different pH values. Even when the angle at which you stick in
the probe is different, the measurement can also be affected.
Therefore, selecting multiple locations and sticking in the probe
at the same depth and angle, then calculating the average is
the best way to maximize accuracy.
Aged probe
Replace the probe
Air bubbles around
the sensor
Make a quick stir in the solution to remove air bubbles
Clogged junction
Clean the probe with cleaning solution, then soak it in 3M KCl
soaking solution overnight
Comparison with
other testers, test
strips, or drop tests
To compare with other testers, make sure to perform a 2-point
calibration for all testers in the same standards, then test a 3rd
point. Whichever gives more accurate reading in the 3rd point
standard is the most accurate one.
Test strips or drop tests’ accuracy is not comparable to pH
meters’.

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14 Technical Specs
Range
0.0 to 14.0 pH,
0 to 50˚C (32 to 122˚F)
Resolution
0.1 pH, 0.1˚F/0.1˚C
Accuracy
±0.1 pH,
±1˚C/±1˚F
Temperature Compensation
Automatic
pH Calibration
Automatic 1 to 3 points (7/4/10)
*pH 10.01 solution sold separately
Unit
pH, ˚F, ˚C
Power supply
4-AAA alkaline batteries
Backlight
White (measurement); Green (calibration); Red (errors)
Reading hold
Manual
Warranty
Two years for the instrument, one year for the probe
pH probe
LabSen® Spear Soil pH Probe
Successful calibration
indicators
M (7.00 pH), L (4.00 pH), H (10.01 pH)
Low battery reminder
Waterproof rating
IP67
Reading stabilization icon

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15 What’s in the box
16 Accessories
•pH buffer Kit (pH4/7, 250ml, each), item AI1113
•pH buffer Kit (pH4/7/10, 250ml, each), item AI1115
•3M KCl storage solution 250ml, item Al1107
•GS2-E Soil pH Probe, item Al58020
17 Warranty
How Long Does the Coverage Last?
Apera Instruments® (Apera) warrants the GroStar™ Premium GS2 Soil pH Pen Tester
(Product) for a period of 24 months for the instrument and 12 months for the probe from date
of purchase by original purchaser or consumer. Proof of purchase is required for the
warranty to be effective (store sales receipt for Product showing model number, payment and
date of purchase). This warranty is non-transferable and terminates if the original
purchaser/consumer sells or transfers the Product a third party.
What is Covered?
Apera warrants the Product against defects in material and workmanship when used in a
normal manner, in accordance with Apera instruction manuals. If Apera is provided with valid
proof of purchase (as defined above) and determines the Product is defective, Apera may, in
its sole discretion either (a) repair the Product with new or refurbished parts, or (b) replace
the Product with a new or refurbished Product.
What is NOT Covered?
Laynard
4.00 pH Solution
7.00 pH
Solution
Soaking
Solution
Dibber
Cleaning Brush
GS2 Soil pH Pen

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This warranty does not apply to equipment, component or part that was not manufactured or
sold by Apera, and shall be void if any such item is installed on a Product. Further, this
warranty does not apply to replacement of items subject to normal use, wear and tear and
expressly excludes:
•Cosmetic damage such as stains, scratches and dents
•Damage due to accident, improper use, negligence, careless operation or handling of
Product not in accordance with Apera instruction manuals, or failure to maintain or care
for Product as recommended by Apera
•Damage caused by use of parts not assembled/installed as per Apera instructions
•Damage caused by use of parts or accessories not produced or recommended by Apera
•Damage due to transportation or shipment of Product
•Product repaired or altered by parties other than Apera or its authorized agents
•Product with defaced, missing or illegible serial numbers
•Products not purchased from Apera or an Apera-authorized distributor or reseller.
How Do You Get Service?
To begin a warranty claim you must return the Product to the point of purchase with valid
proof of purchase.
Limitation of Liability & Acknowledgments
TO THE MAXIMUM EXTENT PERMITTED BY LAW, THIS WARRANTY AND THE
REMEDIES SET OUT ABOVE ARE EXCLUSIVE AND IN LIEU OF ALL OTHER
WARRANTIES, GUARANTEES AND REMEDIES (ORAL OR WRITTEN, EXPRESS OR
IMPLIED). EXCEPT AS PROVIDED IN THIS WARRANTY AND TO THE MAXIMUM
EXTENT PERMITTED BY LAW, APERA INSTRUMENTS IS NOT RESPONSIBLE FOR
SPECIAL, INCIDENTIAL OR CONSEQUENTIAL LOSS OR DAMAGES, OR ANY OTHER
LOSS OR DAMAGES RESULTING FROM SALE OR USE OF THE PRODUCT, OR
BREACH OF WARRANTY, HOWEVER CAUSED, INCLUDING DAMAGES FOR LOST
PROFITS, PERSONAL INJURY OR PROPERTY DAMAGE.
IT IS UNDERSTOOD AND AGREED BY CONSUMER UPON PURCHASE OF A PRODUCT
THAT, EXCEPT AS STATED IN THIS WARRANTY, APERA INSTRUMENTS IS NOT
MAKING AND HAS NOT MADE ANY EXPRESS OR IMPLIED WARRANTY OR OTHER
REPRESENTATION REGARDING THE PRODUCT, AND DISCLAIMS ANY WARRANTY
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE TO THE EXTENT
PERMITTED BY LAW. ANY WARRANTIES WHICH ARE IMPOSED BY LAW AND CANNOT

14
BE DISCLAIMED ARE HEREBY LIMITED IN DURATION TO THE PERIOD AND
REMEDIES PROVIDED IN THIS WARRANTY.
SOME JURISDICTIONS (STATES OR COUNTRIES) DO NOT ALLOW EXCLUSION OR
LIMITATION FOR INCIDENTIAL OR CONSEQUENTIAL DAMAGES, OR LIMITATION ON
HOW LONG AN IMPLIED WARRANTY LASTS, SO THE ABOVE LIMITATION OR
EXCLUSION MAY NOT BE APPLICABLE. IF ANY PROVISION OF THIS WARRANTY IS
JUDGED TO BE ILLEGAL, INVALID OR UNENFORCEABLE, THE REMAINING
PROVISIONS OF THE WARRANTY SHALL REMAIN IN FULL FORCE AND EFFECT.
Governing Law; Authority
This warranty is governed by the laws of the state of country where Product is purchased,
without regard to its choice of law principles. Except as allowed by law, Apera does not limit
or exclude other rights a consumer may have with regard to the Product. No Apera
distributor, employee or agent is authorized to modify, extend or otherwise change the terms
of this warranty.
APERA INSTRUMENTS (Europe) GmbH
Wilhelm-Muthmann-Straße 18
42329 Wuppertal, Germany
Contact: [e-mail]
Website: www.aperainst.de
Tel. [phone]