Apera Instruments GroStar GS4 User manual

GroStar™
GS4 Premium pH/EC Pen Tester
User Manual
APERA INSTRUMENTS (Europe) GmbH
www.aperainst.de

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Content
1Main Features ................................................................................................................ 1
2Preparation Before First Use .......................................................................................... 3
3pH Calibration................................................................................................................. 3
4pH Measurement............................................................................................................ 5
5EC Calibration................................................................................................................ 5
6EC/500ppm/700ppm Measurement................................................................................ 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............................................................................................................10
15 What’s in the box...........................................................................................................11
16 Accessories...................................................................................................................11
17 Warranty........................................................................................................................12
Thank you for choosing the Apera GroStar™ GS4 Premium pH EC 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
•Premium combo pH/EC probe measures pH, EC, ppm (500/700) all-in-one unit with
minimal maintenance.
•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.

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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
or 2.77 EC, H is pH 10. The icon(s)
will disappear after 30 days to
remind you for re-calibration.
Probe Cap
•Water droplets are added
during production to maintain
the moisture of the probe. This
is normal practice and should
not be attributed to used
product.
•The fill line shows the level to
which you should pour the
soaking solution or sample
solution.
•For details of probe storage, see
Section 9.
Premium pH • EC Combo Probe
•Upgraded double-junction blue pH
sensor, increased durability and easier to
use.
•Titanium alloy conductivity sensor, highly
accurate and requires minimal
maintenance.
•The probe is replaceable, saving money in
the long run.
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
Switch mode:
pH→EC→500p
pm →700ppm
Switch
between °F
and °C
Sensor Shield
Protects the sensitive pH glass
membrane from accidental damage.
Remove it when cleaning the pH sensor.

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2 Preparation Before First Use
2.1 Pull out the battery insulation slip, and take off the probe cap.
2.2 Rinse off the probe in clean water, then shake off excess water.
2.3 Calibrate pH and EC. For calibration tutorial, refer to Section 3 and Section 4.
2.4 If you find the probe cap is dried out, soak the probe in 3M KCL soaking solution for 5
minutes before use.
2.5 If the tester hasn’t been used for a long time (over 1 month), please soak the probe in
the 3M KCL soaking solution for at least 1 hour, then calibrate it before measurement
begins
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; shake the probe
up and down in the solution for a few seconds and let it stand.

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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.
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.

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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,
make a quick stir to remove potential air bubbles around the
probe.
4.4 Hold the pen and wait for the reading to stabilize ( stays on
screen), then record the reading.
4.5 Thoroughly rinse off the probe with clean water, then close the
probe cap.
5 EC Calibration
5.1 Power on and remove the probe cap. Press to switch to EC
measurement mode. Rinse the probe with clean water and
shake-dry, then submerge it in the 2.77 EC standard solution;
shake the probe in the solution up and down for a few seconds
to remove potential air bubbles, then let it stand.
5.2 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.
5.3 icon will show up on the lower left corner indicating the tester
is successfully calibrated. will disappear in 30 days after
calibration, reminding you to re-calibrate EC. We recommend
calibrating the EC once every month to ensure the accuracy. If
you feel like the accuracy might be off, simply test the standard
solution (make sure the standard is fresh and clean). If the reading is greater than 2.8
EC or smaller than 2.7 EC, then it’s time to calibrate again.
5.4 If the calibration fails, the screen will turn red. For details, see
Section 13 Troubleshooting Guide.

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6 EC/500ppm/700ppm Measurement
6.1 Power on and remove the probe cap.
6.2 Rinse the probe with clean water and shake off excess water.
6.3 Submerge the probe into the solution, make a quick stir to remove
potential air bubbles around the sensor. Hold still and wait for the
reading to stabilize ( stays on the screen), then record the
reading.
6.4 Short press to switch from EC → 500ppm → 700ppm
6.5 Thoroughly rinse off the probe with clean water.
What is EC and its relation to 500ppm & 700ppm?
EC (electrical conductivity) is a measure of the nutrients in the solution. Low conductivity
implies a low nutrient concentration, which usually results in nutritional deficiencies and slow
growth rates of your plants.
A higher conductivity is more food for your plants. However, be careful of very high levels as
delicate plants, cuttings, and seedlings can experience fertilizer burn if the conductivity is
excessively high.
EC, 500ppm, and 700ppm are simply different units preferred by different markets. 500ppm
and 700ppm both originate from EC. Therefore, using EC to compare and analyze test result
is the safest way and will minimize confusion. Here is how they convert to each other:
1.0 (EC) = 500ppm (500ppm) = 700ppm (700ppm)
2.6 (EC) = 1300ppm (500ppm) = 1820ppm (700ppm)
3.5 (EC) = 1750ppm (500ppm) = 2450ppm (700ppm)
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 The tester will automatically power off if there is no operation
within 10 minutes. If you want to turn off/on the Auto. Power Off
function, power off the tester, and then hold for 5 seconds
until you see Auto Off or Auto On. 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 For tough contaminants, remove the sensor shield, 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.
9 Probe Storage
9.1 Under regular usage (daily or weekly use), make sure there are several
drops 3M KCL soaking solution in the probe cap, and tightly close the cap
with the O-ring.
9.2 For long-term storage (you are not going to use the product for more than a
month), add 3M KCL soaking solution to the Fill line in the cap and store
the probe in it. Close the probe cap tightly with the O-ring.
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 soaking solution. This chemical is not poisonous nor dangerous,
and the probe’s performance will not be affected at all.
or

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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.
Probes don’t last forever. Every probe will eventually age and fail even
if you don't use it that often. The typical service life of GroStar 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.
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.

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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 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 a fully
stabilized reading. 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
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.

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Out of range reminder for:
pH
temperature
EC
14 Technical Specs
Range
0.0 to 14.0 pH,
0 to 10.0 EC,
0 to 7000ppm (700ppm),
0 to 5000ppm (500ppm),
0 to 50˚C (32 to 122˚F)
Resolution
0.1 pH, 0.1EC, 10ppm (700ppm), 10ppm(500ppm),
0.1˚F/0.1˚C
Accuracy
±0.1 pH,
±0.1 EC
±30ppm (500ppm)
±40ppm (700ppm)
±1˚C/±1˚F
Temperature compensation
Automatic
Calibration
pH: automatic 1 to 3 points (7/4/10) *10.01 pH solution sold
separately; EC: automatic 1 point (2.77 EC)
Unit
pH, EC, 500ppm, 700ppm, ˚F, ˚C
Power Supply
4-AAA alkaline batteries, up to 1000 hours of operation
Backlight
White (measurement); Green (calibration); Red (errors)
Reading hold
Manual
Calibration is
successful, but
reading is not
accurate
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, teststrips, 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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Warranty
Two years for the instrument, one year for the probe
pH probe
Low-resistance lithium glass membrane, double-junction,
blue gel electrolyte
EC probe
Titanium alloy
Successful calibration
indicators
M (7.00 pH/2.77 EC), L (4.00 pH), H (10.01 pH)
Low battery reminder
Waterproof rating
IP67
Reading stabilization icon
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
•2.77 EC Standard Calibration Solution
•3M KCl storage solution 250ml, item Al1107
•GS1-E pH Probe, item Al58010
•GS2-E Soil pH Probe, item Al58020
•GS3-E EC Probe, item Al58030
•GS4-E pH/EC-Combo-Probe, item Al58040
GS4 Combo Pen
Laynard
Soaking Solution
4.00 pH Solution
7.00 pH
Solution
2.77 EC
Solution

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17 Warranty
How Long Does the Coverage Last?
Apera Instruments® (Apera) warrants the GroStar™ GS4 Premium pH/EC Combo 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

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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.
APERA INSTRUMENTS (Europe) GmbH
Wilhelm-Muthmann-Straße 18
42329 Wuppertal, Germany
Contact: [e-mail]
Website: www.aperainst.de
Tel. [phone]