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Swap probes, keep your GroStar pen.
APERA INSTRUMENTS / GS1-E · GS2-E · GS3-E · GS4-E · GS5-E / AI801G / AI802G / AI803G / AI804G / AI805G
Apera’s GroStar replacement probes attach to compatible GroStar pen testers with a locking ring. GS1-E is the double-junction pH probe; GS2-E is the soil spear for soil, coco coir and rockwool; GS3-E is the EC/ppm probe; GS4-E is the pH/EC combination probe. GS5-E adds ORP to the explicitly listed GS1, GS2 and GS4 hosts; the GS4 manual documents automatic recognition and mV-mode selection.
Choose the version from the menu above. Apera’s warranty: one year from delivery for GS1-E, GS3-E and GS4-E. For GS2-E and GS5-E, each current US page advertises “1-year warranty” but its formal Warranty section states “SIX MONTHS from the delivery.” Coverage for the supplied GS2-E/GS5-E revision is not verified here; neither duration is promised for those two models. If warranty duration determines your choice, obtain the applicable written terms before purchase. This manufacturer-coverage qualification does not change the merchant’s return policy.
Only published products are linked. Other cards provide model-comparison information and do not indicate current storefront availability.
Published families link to their product pages. Other models are shown for comparison only; confirm the exact connector and host before choosing.
PH60-E · PH60F-E · PH60S-E
PH60-series pH probes
Standard, flat or spear E probes for PH60, PH60F, PH60S and PC60.
ORP60-E
ORP60-E standard probe
Platinum ORP/temperature probe for ORP60; also listed for PH60, PH60F and PH60S.
EC60-E
EC60-E standard conductivity probe
Platinum-black conductivity/temperature probe for EC60 and PC60; no pH sensor.
PC60-E
PC60-E standard combination probe
pH glass plus platinum-black conductivity and temperature sensing for PC60.
SX615 · SX625
SX610 / SX620 pens
Slim 10 mm glass bulb probes with temperature sensor.
GS1-E · GS2-E · GS3-E · GS4-E · GS5-E
GroStar pen probes
pH, soil spear, EC, pH/EC combo and ORP probes.
GS1-E fits the GS1 (and GS2, GS4) pens: GS1 and GS1-P.
GS2-E fits the GS2 soil pen (and GS1, GS4): GS2.
GS3-E fits the GS3 EC/ppm pen (and GS4): GS3.
GS4-E fits the GS4 combo pen: GS4 and GS4-P.
GS5-E fits the GS1, GS2 and GS4 pens, to add ORP.
Unscrew the locking ring, align the matching replacement probe and tighten the ring. Select the probe by its documented host models; do not assume every GroStar probe provides every measurement on every pen.
GS1-E and GS4-E use double-junction pH sensing with blue gel. GS2-E uses a spear glass tip and PTFE ring junction for soil and growing media; these are distinct sensor constructions.
Measures directly in soil, coco coir, rockwool and other media; a PTFE ring keeps soil out of the junction.
The probe functions and compatibility differ by model. Match GS1-E, GS2-E, GS3-E, GS4-E or GS5-E to the host listed in the specification table; the host manual determines display ranges, calibration and measurement-system accuracy.
The full specification table, version by version, is in the Product Specifications tab.
Use model-specific storage. GS2-E must remain in 3M KCl when not in use. The GS1 and GS4 Gen II manuals specify a humid cap for daily/weekly use and KCl for long-term storage. The GS3 conductivity manual specifies a humid cap for regular use and clean water for long-term storage - not KCl. Follow the exact host instructions for the installed probe, protect glass from abrasion, and calibrate pH/EC after replacement.
Rinse between samples. Follow the separate pH, conductivity or ORP care instructions for the installed probe; a single soaking procedure is not appropriate for every GroStar sensor.
Calibrate with pH 7.00 and pH 4.00 buffers and 1413 µS/cm standard for EC.
GS1-E is the double-junction pH probe for GS1 and is also explicitly listed for GS2 and GS4. It measures pH with the host; it is not an EC probe.
GS2-E has a spear glass tip and PTFE ring junction for soil, coco coir, rockwool and nutrient solutions. Apera lists it for GS2, GS1 and GS4. Do not force the glass spear against stones or hard material.
GS3-E is the titanium-sensor conductivity probe for GS3 and GS4. GS4-E combines a double-junction pH sensor with titanium-alloy conductivity sensing for GS4, so it preserves both pH and EC functions.
Apera explicitly lists GS1, GS2 and GS4 for the platinum, double-junction GS5-E. The GS4 host manual says the pen recognizes GS5-E and switches to mV mode. GS3 is not on that compatibility list.
No such interchangeability is established here. The GS1-E through GS5-E options are selected by their documented GroStar host models; a similar screw ring or housing is not proof of fit.
No. GS2-E must remain in 3M KCl when not in use. The GS1 and GS4 Gen II manuals specify a humid cap during regular use and KCl for long-term storage. The GS3 conductivity manual specifies a humid cap for regular use and clean water for long-term storage.
No. With GS3-E or GS4-E, the host calculates its ppm 500 and ppm 700 values from conductivity. Those conversions and the displayed range belong to the host tester, not to separate ppm sensors.
Unscrew the locking ring, align and seat the correct replacement, and tighten the ring without tools. Condition and calibrate pH or EC according to the matching host manual; check GS5-E in ORP standard rather than applying a pH calibration.
Check the version and catalog number (AI801G / AI802G / AI803G / AI804G / AI805G) against your tester or pen, then return to the live price and ordering controls.
Operating scope and qualification: GS1-E / GS3-E / GS4-E: one year from delivery. GS2-E / GS5-E: each US page advertises 1 year but its formal Warranty section states six months from delivery; applicability to the supplied revision is unverified, so neither term is promised. If coverage duration is material to your purchase, obtain the applicable written terms first. Merchant return policy unchanged.
APERA INSTRUMENTS, LLC warrants this product to be free from defects in material and workmanship for SIX MONTHS (one year for the GroStar GS1-E to GS4-E probes) from the delivery.
This limited warranty does NOT cover accidental damage, improper use, normal wear and tear, transportation, storage, failure to follow the product instructions, unauthorized maintenance, modification or repair, or external causes beyond Apera's reasonable control.
Verified manufacturer host-tester manuals are provided below for operation, probe replacement and care. These are parent-instrument documents, not standalone probe manuals; select replacement probes by the exact model guidance above.
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