Apera Instruments GroStar GS2 User manual

GS2 Premium Soil pH Pen Tester
AI31020
User Guide
contents page
Main Features
Preparation Before First Use
pH Calibration
Measure Solution's pH
Measure Soil pH Directly
Making a Soil Slurry
Other Functions
Probe Cleaning
Probe Storage
Battery Replacement
Probe Replacement
Notes
Troubleshooting Guide
Technical Specs
Accessories
Warranty
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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?
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 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.
Address: 6656 Busch Blvd, Columbus Ohio 43229
Tel: [phone]
Email: [e-mail]
Website: aperainst.com
®
®

Lab-Grade Instruments Designed Specifically For Growers Lab-Grade Instruments Designed Specifically For Growers
Thank you for choosing the Apera GroStar™ GS2 Premium Soil 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.
• 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 enviroment.
• Durable structure, IP67 waterproof rating, powered by AAA batteries.
• The pH probe is replaceable, so you don't have to discard the entire pen when the probe reaches its end of life.
3-Color LCD Screen
stands for stabilized reading
Probe Cap
Probe Cap Ring
L/M/H stands for successful
calibration: Lis pH 4, Mis pH 7, H
is pH 10. The icon(s) will disappear
after 30 days to remind you for re-
calibration.
• 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 screw on the
cap ring tightly.
Loosen the probe cap ring before
pulling out the probe cap.
Short Press Long Press
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 particles.
• Long-life reference system ensures high
durability
2.1 Remove the battery slip; Loosen the probe cap
ring, then pull out the probe cap.
2.3 Calibrate the tester at pH 7 and pH 4 before first use. See below for calibration tutorial.
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.
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Main Features
Preparation Before First Use
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-dry, 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.
7.00
pH
7.00
pH
03
pH Calibration
Power off
Start
calibration
Switch
between
°F and °C
In measurement
mode, press to turn
on/off the backlight.
In calibration mode,
press to cancel
calibration.
1. Power on
2. Manual hold
Press again to cancel hold.
• White for measurement mode
• Green for calibration mode
• Red for calibration error

Lab-Grade Instruments Designed Specifically For Growers Lab-Grade Instruments Designed Specifically For Growers
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.
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.
Remove the probe cap; Power on the pen; Rinse the probe in the
water bucket, and shake off excess water.
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.
After each test, the probe must be thoroughly rinsed in the water
bucket. Make sure to clean off the dirt on the white PTFE junction
ring 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.
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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Measure Soil pH Directly
After measurement, thoroughly rinse off the probe with clean water, then put the probe
back into the cap with 3M KCL storage solution.
Wait for the reading to stabilize ( stays on screen), then
record the reading.
Fully submerge the probe into the solution at least 1 inch deep.
Rinse the probe with clean water and shake off excess water.
Power on and remove the probe cap.
Measure Solution's pH
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4.1
4.2
4.3
4.4
4.5
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5.1
5.2
5.3
5.4
5.5
5.6
3.4 icon will show up on the lower left corner of the screen indicating the
tester 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 re-calibrate 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.
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 tester
before calibrating 4.00 pH, you need to start with 7.00 pH again after rebooting
the pen, then 4.00 pH.
3.6 If the calibration fails, the screen will turn red. For details, refer to Section
13 Troubleshooting Guide.

Lab-Grade Instruments Designed Specifically For Growers Lab-Grade Instruments Designed Specifically For Growers
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.
8.1 The tester is only as accurate as the probe is clean.
Always thoroughly rinse off the probe 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.
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 storage solution for at
least 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).
9.1 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.
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Other Functions
Probe Cleaning
Probe Storage
Remove about 2 inches (5cm) of the top layer soil and collect different locations’ soil samples at
approximately 6 inches (15cm) deep.
Thoroughly mix all collected soil.
Ideally, dry the soil in the air or bake in an oven at 104˚F / 40˚C.
Weigh out 20g of the mixed soil sample into a glass jar and add 100g of distilled or deionized water in it.
Shake well for 5 minutes or use a magnetic stirrer to automatically stir for 15 minutes. Leave overnight.
Shake or stir again next morning, then allow it to settle for 15-30 minutes.
Power on the tester; Remove the probe cap; Rinse the probe in the water bucket, and shake dry.
Submerge the probe into the soil solution, shake for a few seconds, and wait for the reading to fully
stabilize. Then record the reading.
After measurement, put the probe back in the storage cap and soak in the 3M KCL solution.
Making a Soil Slurry
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6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
7.1 If necessary, you can manually hold (lock)
the reading by short pressing . Press
it again to cancel the hold.
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, then hold for
5 seconds until you see Auto off.
Then it will power on and go to
measurement mode automatically.
7.2 Long press to switch temp. unit
between °F and °C.
7.3
Out of range reminder for temperatureOut of range reminder for pH
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.

Lab-Grade Instruments Designed Specifically For Growers Lab-Grade Instruments Designed Specifically For Growers
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 solutionsmade 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 1inch deep.
Air bubbles around the sensor Make a quick stir in the solution to remove air bubbles.
Reading is always
slowly 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 afully stabilizedreading. If still not stabilizing, add
1ml of 3M KCL solution to 1000ml of test solution.
Display similar
readings in any
solutions or always
display 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 1inch 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 asoft 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 maximizeaccuracy.
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’.
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.
12.1 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.
12.3 Avoid testing in high (>113°F) or low temperature (<41°C) solutions as it will cause greater measurement
error and cause 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.
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Battery Replacement
Probe Replacement
Notes
Troubleshooting Guide
① Pull up the battery cap (might take some force).
② Slide the battery cover along the OPEN arrow to open the cover.
③ Open the battery cover.
④ Insert the batteries (ALL POSITIVE SIDES FACING UP).
⑤ Press down the battery cover and hold it.
⑥ Slide the battery cover along the LOCK arrow to lock the cover.
⑦ Close 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.

Lab-Grade Instruments Designed Specifically For Growers Lab-Grade Instruments Designed Specifically For Growers
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
What’s in the box
GS2Premium Soil pH Pen Tester, pH 7.00/4.00 (50mL each),
3M KCL storage solution (10ml), dibber, probe cleaning brush,
user manual, lanyard.
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Technical Specs
pH buffer kit (4&7, 8oz. each) pH buffer kit (4,7&10, 8oz. each)
Replacement Probes
GS2-E Soil pH Probe
Probe Care Kit
includes 3M KCL storage solution
(4oz.), cleaning solution (8oz.),
a CalPod solution organizer, a probe
cleaning brush, and a wash bottle
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Accessories
GS2 Soil pH Pen
Lanyard
Dibber
Cleaning Brush
Soaking
Solution
7.00 pH
Solution
4.00 pH
Solution
What's in the box