Apera Instruments GroStar GS1 User manual

GroStar™

GS1 Premium 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............................................................................................................ 5 
5Other Functions.............................................................................................................. 5 
6Probe Cleaning............................................................................................................... 5 
7Probe Storage................................................................................................................ 6 
8Battery Replacement...................................................................................................... 6 
9Probe Replacement........................................................................................................ 7 
10 Notes.............................................................................................................................. 7 
11 Troubleshooting Guide ................................................................................................... 7 
12 Technical Specs............................................................................................................. 9 
13 What’s in the box............................................................................................................ 9 
14 Accessories...................................................................................................................10 
15 Warranty........................................................................................................................10 
 
Thank  you  for  choosing  the  Apera  GroStar™  GS1 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 
•Premium pH probe with double-junction and sensor shield, increased reliability, and 
durability. 
•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 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

•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 7.

Premium pH Probe

•Built with low-resistance lithium glass

membrane with double-junction and blue

gel electrolyte, ensuring accuracy and

durability.

•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

measurement

mode, press to

turn on/off the

backlight.

Start calibration

In calibration

mode, press to

cancel

calibration.

Switch between

°F and °C

Sensor Shield

Protects the sensitive pH glass

membrane from accidental damage.

Remove it when cleaning the pH sensor.

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 Perform a 2-point calibration at pH 7 and pH 4. For calibration tutorial, refer to Section

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.

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 11 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,

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 Other Functions

5.1 If necessary, you can manually hold (lock) the reading by short pressing . Press it

again to cancel the hold.

5.2 Long press to switch temp. unit between °F and °C.

5.3 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.

6 Probe Cleaning

6.1 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.

6.2 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 at least 1

hour. Rinse it off, then re-calibrate the tester before using again.

7 Probe Storage

7.1 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.

7.2 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.

8 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.

9 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.

10 Notes

10.1 Never store the probe in pure water such as tap water, RO water, distilled water,

deionized water, etc.

10.2 Never use your finger to touch the glass membrane or use other material to wipe it.

10.3 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.

10.4 Never test oily liquids.

10.5 Make sure the battery cap is completely closed with the O-ring. Otherwise, the

waterproof rating could be compromised.

11 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

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.

Calibration

successful,

butreading

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, 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’.

Out of range reminder for pH

Out of range reminder for temperature

12 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

pH: automatic 1 to 3 points (7/4/10)

*10.01 pH 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

Low-resistance lithium glass membrane, double-junction,

blue gel electrolyte

Successful calibration

indicators

M (7.00 pH), L (4.00 pH), H (10.01 pH)

Low battery reminder

Waterproof rating

IP67

Reading stabilization icon

13 What’s in the box

GS1 pH Pen

Laynard

Soaking Solution

4.00 pH Solution

7.00 pH

Solution

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