{"product_id":"apera-grostar-replacement-probes-gs1-e-gs2-e-gs3-e-gs4-e-gs5-e","title":"Apera GroStar Replacement Probe for GS1, GS2, GS3 and GS4 Pens: pH, Soil pH, EC, pH\/EC or ORP","description":"\u003cdiv id=\"bts-apera-gsp-description\" style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;width:100%;max-width:1400px;margin:0 auto;color:#26332C;font-size:1rem;line-height:1.75;\"\u003e\n\u003csection style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:clamp(20px,4vw,48px);border:1px solid #B7D0BF;background:#F1F7F3;border-radius:14px;\"\u003e\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;display:flex;flex-wrap:wrap;align-items:center;gap:clamp(24px,4vw,48px);\"\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 340px;min-width:0;\"\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.76rem;font-weight:600;letter-spacing:.12em;text-transform:uppercase;color:#245B45;margin:0 0 12px;\"\u003eAPERA INSTRUMENTS \/ GS1-E · GS2-E · GS3-E · GS4-E · GS5-E \/ AI801G \/ AI802G \/ AI803G \/ AI804G \/ AI805G\u003c\/p\u003e\n\u003ch2 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:clamp(24px,4vw,34px);font-weight:600;line-height:1.2;letter-spacing:-.02em;color:#245B45;margin:0 0 20px;\"\u003eSwap probes,\u003cbr\u003ekeep your GroStar pen.\u003c\/h2\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eApera’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.\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eChoose 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 340px;min-width:0;\"\u003e\u003cfigure style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;margin:0;min-width:0;\"\u003e\u003cimg alt=\"Apera GroStar Probes\" decoding=\"async\" height=\"968\" loading=\"lazy\" sizes=\"(max-width:600px) calc(100vw - 80px), 560px\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-main-20261018-mfr.webp?width=968\" srcset=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-main-20261018-mfr.webp?width=360 360w, https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-main-20261018-mfr.webp?width=640 640w, https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-main-20261018-mfr.webp?width=968 968w\" style=\"display:block;width:100%;max-width:420px;height:auto;object-fit:contain;box-sizing:border-box;margin:0 auto;\" width=\"968\"\u003e\u003cfigcaption style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.86rem;line-height:1.65;color:#5D6C63;margin-top:12px;\"\u003eApera GS1-E · GS2-E · GS3-E · GS4-E · GS5-E.\u003c\/figcaption\u003e\u003c\/figure\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/section\u003e\u003cdetails id=\"bts-apera-tester-probe-selector\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;border:1px solid #FF931A;border-radius:10px;padding:0;margin:24px 0;background:#fff;overflow:visible;\"\u003e\u003csummary aria-label=\"Compare Apera replacement probes for pocket testers, pH pens and GroStar pens. Expand or collapse the guide.\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:flex;align-items:center;justify-content:space-between;gap:16px;padding:20px;background:#FF931A;color:#172b4d;cursor:pointer;border-radius:10px;font-weight:600;line-height:1.5;\"\u003e\u003cspan style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:block;flex:1;min-width:0;\"\u003e\u003cspan style=\"display:block;font-size:clamp(17px,2.6vw,21px);font-weight:700;line-height:1.35;\"\u003eChoose your replacement probe\u003c\/span\u003e\u003cspan style=\"display:block;font-size:.88rem;font-weight:400;line-height:1.55;margin-top:5px;\"\u003e\u003cspan class=\"bts-sp-when-closed\"\u003eClick or tap to compare 6 probe families\u003c\/span\u003e\u003cspan class=\"bts-sp-when-open\"\u003eCompare the models below - click or tap here to close\u003c\/span\u003e\u003c\/span\u003e\u003c\/span\u003e\u003cspan aria-hidden=\"true\" class=\"bts-sp-toggle\" style=\"display:flex;align-items:center;justify-content:center;flex:0 0 38px;width:38px;height:38px;border:1px solid rgba(23,43,77,.35);border-radius:50%;background:#fff;color:#172b4d;font-size:27px;font-weight:400;line-height:1;\"\u003e\u003c\/span\u003e\u003c\/summary\u003e\u003cp class=\"bts-guide-availability\" style=\"font-family:'Open Sans',sans-serif;font-size:15px;line-height:1.6;color:#26332C;margin:12px 0;\"\u003eOnly published products are linked. Other cards provide model-comparison information and do not indicate current storefront availability.\u003c\/p\u003e\n\u003cdiv class=\"bts-sp-selector-inner\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;padding:20px;\"\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.95rem;font-weight:300;line-height:1.65;margin:0 0 18px;color:#26332C;\"\u003ePublished families link to their product pages. Other models are shown for comparison only; confirm the exact connector and host before choosing.\u003c\/p\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:flex;flex-wrap:wrap;gap:14px;\"\u003e\n\u003ca class=\"bts-apera-electrode-family-link\" href=\"https:\/\/bluetigerscientific.com\/products\/apera-replacement-ph-probe-ph60-ph60-z-pocket-testers\" rel=\"noopener noreferrer\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:flex;align-items:flex-start;gap:16px;flex:1 1 300px;min-width:0;max-width:100%;padding:18px;border:1px solid #e0e0e0;background:#fff;border-radius:9px;text-decoration:none;color:#26332C;transition:box-shadow .15s ease,transform .15s ease,border-color .15s ease;cursor:pointer;\" target=\"_blank\"\u003e\n\u003cimg alt=\"Apera PH60-E replacement pH probe\" class=\"bts-sp-model-thumb\" decoding=\"async\" height=\"88\" loading=\"lazy\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-ph60-e-main-20261018-mfr.webp?v=1792352315\" style=\"display:block;width:88px;height:88px;flex:0 0 88px;object-fit:contain;background:#fff;border-radius:6px;box-sizing:border-box;\" width=\"88\"\u003e\u003cdiv style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;flex:1;min-width:0;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:1.1rem;line-height:1.3;font-weight:700;color:#245B45;margin:0 0 3px;\"\u003ePocket pH Probes\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.76rem;font-weight:400;line-height:1.5;color:#5D6C63;margin:0 0 9px;\"\u003ePH60-E · PH60F-E · PH60S-E\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.95rem;font-weight:600;line-height:1.5;color:#26332C;margin:0 0 6px;\"\u003ePH60-series pH probes\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.86rem;font-weight:300;line-height:1.65;color:#26332C;margin:0 0 12px;\"\u003eStandard, flat or spear E probes for PH60, PH60F, PH60S and PC60.\u003c\/p\u003e\n\u003cspan class=\"bts-sp-card-cta\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:inline-block;font-size:.85rem;font-weight:700;line-height:1.5;color:#172b4d;background:#FFF0DD;border-radius:5px;padding:6px 9px;\"\u003eView Pocket pH Probes →\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\n\u003ca class=\"bts-apera-electrode-family-link\" href=\"https:\/\/bluetigerscientific.com\/products\/apera-replacement-orp-probe-orp60-zentest-pocket-testers\" rel=\"noopener noreferrer\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:flex;align-items:flex-start;gap:16px;flex:1 1 300px;min-width:0;max-width:100%;padding:18px;border:1px solid #e0e0e0;background:#fff;border-radius:9px;text-decoration:none;color:#26332C;transition:box-shadow .15s ease,transform .15s ease,border-color .15s ease;cursor:pointer;\" target=\"_blank\"\u003e\n\u003cimg alt=\"Apera ORP60-E replacement ORP probe\" class=\"bts-sp-model-thumb\" decoding=\"async\" height=\"88\" loading=\"lazy\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-orp60-e-main-20261018-mfr.webp?v=1792352315\" style=\"display:block;width:88px;height:88px;flex:0 0 88px;object-fit:contain;background:#fff;border-radius:6px;box-sizing:border-box;\" width=\"88\"\u003e\u003cdiv style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;flex:1;min-width:0;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:1.1rem;line-height:1.3;font-weight:700;color:#245B45;margin:0 0 3px;\"\u003ePocket ORP Probe\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.76rem;font-weight:400;line-height:1.5;color:#5D6C63;margin:0 0 9px;\"\u003eORP60-E\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.95rem;font-weight:600;line-height:1.5;color:#26332C;margin:0 0 6px;\"\u003eORP60-E standard probe\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.86rem;font-weight:300;line-height:1.65;color:#26332C;margin:0 0 12px;\"\u003ePlatinum ORP\/temperature probe for ORP60; also listed for PH60, PH60F and PH60S.\u003c\/p\u003e\n\u003cspan class=\"bts-sp-card-cta\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:inline-block;font-size:.85rem;font-weight:700;line-height:1.5;color:#172b4d;background:#FFF0DD;border-radius:5px;padding:6px 9px;\"\u003eView Pocket ORP Probes →\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\n\u003ca class=\"bts-apera-electrode-family-link\" href=\"https:\/\/bluetigerscientific.com\/products\/apera-replacement-conductivity-probe-ec60-ec60-z\" rel=\"noopener noreferrer\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:flex;align-items:flex-start;gap:16px;flex:1 1 300px;min-width:0;max-width:100%;padding:18px;border:1px solid #e0e0e0;background:#fff;border-radius:9px;text-decoration:none;color:#26332C;transition:box-shadow .15s ease,transform .15s ease,border-color .15s ease;cursor:pointer;\" target=\"_blank\"\u003e\n\u003cimg alt=\"Apera EC60-E replacement conductivity probe\" class=\"bts-sp-model-thumb\" decoding=\"async\" height=\"88\" loading=\"lazy\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-ec60-e-main-20261018-mfr.webp?v=1792352315\" style=\"display:block;width:88px;height:88px;flex:0 0 88px;object-fit:contain;background:#fff;border-radius:6px;box-sizing:border-box;\" width=\"88\"\u003e\u003cdiv style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;flex:1;min-width:0;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:1.1rem;line-height:1.3;font-weight:700;color:#245B45;margin:0 0 3px;\"\u003ePocket EC Probe\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.76rem;font-weight:400;line-height:1.5;color:#5D6C63;margin:0 0 9px;\"\u003eEC60-E\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.95rem;font-weight:600;line-height:1.5;color:#26332C;margin:0 0 6px;\"\u003eEC60-E standard conductivity probe\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.86rem;font-weight:300;line-height:1.65;color:#26332C;margin:0 0 12px;\"\u003ePlatinum-black conductivity\/temperature probe for EC60 and PC60; no pH sensor.\u003c\/p\u003e\n\u003cspan class=\"bts-sp-card-cta\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:inline-block;font-size:.85rem;font-weight:700;line-height:1.5;color:#172b4d;background:#FFF0DD;border-radius:5px;padding:6px 9px;\"\u003eView Pocket EC Probes →\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\n\u003ca class=\"bts-apera-electrode-family-link\" href=\"https:\/\/bluetigerscientific.com\/products\/apera-replacement-ph-conductivity-probe-pc60-pc60-z\" rel=\"noopener noreferrer\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:flex;align-items:flex-start;gap:16px;flex:1 1 300px;min-width:0;max-width:100%;padding:18px;border:1px solid #e0e0e0;background:#fff;border-radius:9px;text-decoration:none;color:#26332C;transition:box-shadow .15s ease,transform .15s ease,border-color .15s ease;cursor:pointer;\" target=\"_blank\"\u003e\n\u003cimg alt=\"Apera PC60-E replacement multi-parameter probe\" class=\"bts-sp-model-thumb\" decoding=\"async\" height=\"88\" loading=\"lazy\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-pc60-e-main-20261018-mfr.webp?v=1792352315\" style=\"display:block;width:88px;height:88px;flex:0 0 88px;object-fit:contain;background:#fff;border-radius:6px;box-sizing:border-box;\" width=\"88\"\u003e\u003cdiv style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;flex:1;min-width:0;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:1.1rem;line-height:1.3;font-weight:700;color:#245B45;margin:0 0 3px;\"\u003ePocket pH\/EC Probe\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.76rem;font-weight:400;line-height:1.5;color:#5D6C63;margin:0 0 9px;\"\u003ePC60-E\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.95rem;font-weight:600;line-height:1.5;color:#26332C;margin:0 0 6px;\"\u003ePC60-E standard combination probe\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.86rem;font-weight:300;line-height:1.65;color:#26332C;margin:0 0 12px;\"\u003epH glass plus platinum-black conductivity and temperature sensing for PC60.\u003c\/p\u003e\n\u003cspan class=\"bts-sp-card-cta\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:inline-block;font-size:.85rem;font-weight:700;line-height:1.5;color:#172b4d;background:#FFF0DD;border-radius:5px;padding:6px 9px;\"\u003eView Pocket pH\/EC Probes →\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\n\u003ca class=\"bts-apera-electrode-family-link\" href=\"https:\/\/bluetigerscientific.com\/products\/apera-sx615-sx625-replacement-ph-probe-sx610-sx620-pens\" rel=\"noopener noreferrer\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:flex;align-items:flex-start;gap:16px;flex:1 1 300px;min-width:0;max-width:100%;padding:18px;border:1px solid #e0e0e0;background:#fff;border-radius:9px;text-decoration:none;color:#26332C;transition:box-shadow .15s ease,transform .15s ease,border-color .15s ease;cursor:pointer;\" target=\"_blank\"\u003e\n\u003cimg alt=\"Apera SX Pen Probes\" class=\"bts-sp-model-thumb\" decoding=\"async\" height=\"88\" loading=\"lazy\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-sx615-main-20261018-mfr.webp?width=200\" style=\"display:block;width:88px;height:88px;flex:0 0 88px;object-fit:contain;background:#fff;border-radius:6px;box-sizing:border-box;\" width=\"88\"\u003e\u003cdiv style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;flex:1;min-width:0;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:1.1rem;line-height:1.3;font-weight:700;color:#245B45;margin:0 0 3px;\"\u003eSX Pen Probes\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.76rem;font-weight:400;line-height:1.5;color:#5D6C63;margin:0 0 9px;\"\u003eSX615 · SX625\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.95rem;font-weight:600;line-height:1.5;color:#26332C;margin:0 0 6px;\"\u003eSX610 \/ SX620 pens\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.86rem;font-weight:300;line-height:1.65;color:#26332C;margin:0 0 12px;\"\u003eSlim 10 mm glass bulb probes with temperature sensor.\u003c\/p\u003e\n\u003cspan class=\"bts-sp-card-cta\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:inline-block;font-size:.85rem;font-weight:700;line-height:1.5;color:#172b4d;background:#FFF0DD;border-radius:5px;padding:6px 9px;\"\u003eView SX Pen Probes →\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/a\u003e\n\u003cdiv aria-current=\"page\" class=\"bts-apera-electrode-family-link\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:flex;align-items:flex-start;gap:16px;flex:1 1 300px;min-width:0;max-width:100%;padding:18px;border:2px solid #FF931A;background:#FFF9F0;border-radius:9px;text-decoration:none;color:#26332C;transition:box-shadow .15s ease,transform .15s ease,border-color .15s ease;cursor:default;\"\u003e\n\u003cimg alt=\"Apera GroStar Probes\" class=\"bts-sp-model-thumb\" decoding=\"async\" height=\"88\" loading=\"lazy\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-main-20261018-mfr.webp?width=200\" style=\"display:block;width:88px;height:88px;flex:0 0 88px;object-fit:contain;background:#fff;border-radius:6px;box-sizing:border-box;\" width=\"88\"\u003e\u003cdiv style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;flex:1;min-width:0;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:1.1rem;line-height:1.3;font-weight:700;color:#245B45;margin:0 0 3px;\"\u003eGroStar Probes\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.76rem;font-weight:400;line-height:1.5;color:#5D6C63;margin:0 0 9px;\"\u003eGS1-E · GS2-E · GS3-E · GS4-E · GS5-E\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.95rem;font-weight:600;line-height:1.5;color:#26332C;margin:0 0 6px;\"\u003eGroStar pen probes\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;font-size:.86rem;font-weight:300;line-height:1.65;color:#26332C;margin:0 0 12px;\"\u003epH, soil spear, EC, pH\/EC combo and ORP probes.\u003c\/p\u003e\n\u003cspan class=\"bts-sp-card-cta\" style=\"font-family:'Open Sans',sans-serif;box-sizing:border-box;display:inline-block;font-size:.85rem;font-weight:700;line-height:1.5;color:#172b4d;background:#FFF0DD;border-radius:5px;padding:6px 9px;background:#F1F7F3;color:#5D6C63;\"\u003eCurrent item\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/details\u003e\u003csection style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:clamp(28px,5vw,56px) 0;border-bottom:1px solid #B7D0BF;\"\u003e\u003ch2 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:clamp(24px,4vw,34px);font-weight:600;line-height:1.2;letter-spacing:-.02em;color:#245B45;margin:0 0 20px;\"\u003ePick the version\u003cbr\u003ethat fits your tester.\u003c\/h2\u003e\n\u003cdiv aria-label=\"Version table\" role=\"region\" style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;overflow-x:auto;width:100%;max-width:100%;\" tabindex=\"0\"\u003e\u003ctable style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;width:100%;border-collapse:collapse;font-size:1rem;border:1px solid #e0e0e0;table-layout:fixed;\"\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth scope=\"col\" style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;background:#f5f5f5;text-align:left;padding:12px;font-size:1rem;font-weight:700;border:1px solid #e0e0e0;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eVersion\u003c\/th\u003e\n\u003cth scope=\"col\" style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;background:#f5f5f5;text-align:left;padding:12px;font-size:1rem;font-weight:700;border:1px solid #e0e0e0;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eKey differences\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr style=\"background:#fff;\"\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:32%;font-weight:600;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eGS1-E · AI801G\u003c\/td\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eFits: GS1 (also GS2, GS4); Measures: pH and temperature; Sensor: Lithium glass, double junction, blue gel.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background:#f9f9f9;\"\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:32%;font-weight:600;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eGS2-E · AI802G\u003c\/td\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eFits: GS2 (also GS1, GS4); Measures: pH and temperature; Sensor: Swiss spear pH sensor, PTFE ring junction.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background:#fff;\"\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:32%;font-weight:600;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eGS3-E · AI803G\u003c\/td\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eFits: GS3 (also GS4); Measures: EC, ppm (500), ppm (700), temperature; Sensor: Titanium alloy.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background:#f9f9f9;\"\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:32%;font-weight:600;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eGS4-E · AI804G\u003c\/td\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eFits: GS4; Measures: pH, EC, ppm, temperature; Sensor: Lithium glass (double junction, blue gel) + titanium alloy.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr style=\"background:#fff;\"\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:32%;font-weight:600;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eGS5-E · AI805G\u003c\/td\u003e\n\u003ctd style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:12px;font-size:1rem;line-height:1.6;vertical-align:top;border:1px solid #e0e0e0;width:50%;overflow-wrap:anywhere;min-width:0;\"\u003eFits: GS1, GS2, GS4; Measures: ORP; Sensor: Platinum, double junction, gel KCl.\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\u003c\/div\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;display:flex;flex-wrap:wrap;align-items:center;gap:clamp(24px,4vw,48px);\"\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 340px;min-width:0;\"\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003e\u003cstrong\u003eGS1-E\u003c\/strong\u003e fits the GS1 (and GS2, GS4) pens: \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/apera-instruments-grostar%C2%AE-gs1-ph-pen-tester-gen-ii\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003eGS1\u003c\/a\u003e and \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/apera-instruments-grostar%C2%AE-gs1-p-ph-orp-pen-tester-kit-gen-ii-precision-ph-orp-monitoring-for-growers-hydroponics\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003eGS1-P\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003e\u003cstrong\u003eGS2-E\u003c\/strong\u003e fits the GS2 soil pen (and GS1, GS4): \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/apera-instruments-grostar%C2%AE-gs2-soil-ph-pen-tester-gen-ii\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003eGS2\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003e\u003cstrong\u003eGS3-E\u003c\/strong\u003e fits the GS3 EC\/ppm pen (and GS4): \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/grostar%C2%AE-gs3-ec-ppm-pen-tester-gen-ii\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003eGS3\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003e\u003cstrong\u003eGS4-E\u003c\/strong\u003e fits the GS4 combo pen: \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/grostar%C2%AE-gs4-ph-ec-500ppm-700ppm-temp-5-in-1-combo-pen-tester-gen-ii\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003eGS4\u003c\/a\u003e and \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/apera-instruments-grostar%C2%AE-gs4-p-6-in-1-ph-ec-ppm-orp-combo-pen-tester-gen-ii-advanced-nutrient-water-quality-monitoring-for-growers\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003eGS4-P\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003e\u003cstrong\u003eGS5-E\u003c\/strong\u003e fits the GS1, GS2 and GS4 pens, to add ORP.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 340px;min-width:0;\"\u003e\u003cfigure style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;margin:0;min-width:0;\"\u003e\u003cimg alt=\"Apera GS1-E\" decoding=\"async\" height=\"432\" loading=\"lazy\" sizes=\"(max-width:600px) calc(100vw - 80px), 560px\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-body-2-20261018-mfr.webp?width=432\" srcset=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-body-2-20261018-mfr.webp?width=360 360w, https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-body-2-20261018-mfr.webp?width=432 432w\" style=\"display:block;width:100%;max-width:420px;height:auto;object-fit:contain;box-sizing:border-box;margin:0 auto;\" width=\"432\"\u003e\u003cfigcaption style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.86rem;line-height:1.65;color:#5D6C63;margin-top:12px;\"\u003eApera GS1-E.\u003c\/figcaption\u003e\u003c\/figure\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/section\u003e\u003csection style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:clamp(28px,5vw,56px) 0;border-bottom:1px solid #B7D0BF;\"\u003e\u003ch2 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:clamp(24px,4vw,34px);font-weight:600;line-height:1.2;letter-spacing:-.02em;color:#245B45;margin:0 0 20px;\"\u003eWhat makes it work.\u003c\/h2\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;display:flex;flex-wrap:wrap;align-items:center;gap:clamp(24px,4vw,48px);\"\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 340px;min-width:0;\"\u003e\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;display:flex;flex-wrap:wrap;gap:16px;\"\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 240px;min-width:0;padding:24px;background:#fff;border:1px solid #DCE6DF;border-radius:10px;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1.07rem;font-weight:600;color:#245B45;margin:0 0 12px;\"\u003eTool-free swap\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eUnscrew 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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 240px;min-width:0;padding:24px;background:#fff;border:1px solid #DCE6DF;border-radius:10px;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1.07rem;font-weight:600;color:#245B45;margin:0 0 12px;\"\u003eDouble junction, blue gel\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eGS1-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.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 240px;min-width:0;padding:24px;background:#fff;border:1px solid #DCE6DF;border-radius:10px;\"\u003e\n\u003ch3 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1.07rem;font-weight:600;color:#245B45;margin:0 0 12px;\"\u003eSoil spear (GS2-E)\u003c\/h3\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eMeasures directly in soil, coco coir, rockwool and other media; a PTFE ring keeps soil out of the junction.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/div\u003e\n\u003cdiv style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;flex:1 1 340px;min-width:0;\"\u003e\u003cfigure style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;margin:0;min-width:0;\"\u003e\u003cimg alt=\"Apera GS2-E\" decoding=\"async\" height=\"1600\" loading=\"lazy\" sizes=\"(max-width:600px) calc(100vw - 80px), 560px\" src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs2-e-graphic-2-20261018-mfr.webp?width=1000\" srcset=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs2-e-graphic-2-20261018-mfr.webp?width=360 360w, https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs2-e-graphic-2-20261018-mfr.webp?width=640 640w, https:\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs2-e-graphic-2-20261018-mfr.webp?width=1000 1000w\" style=\"display:block;width:100%;max-width:460px;height:auto;object-fit:contain;box-sizing:border-box;margin:0 auto;\" width=\"1600\"\u003e\u003cfigcaption style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.86rem;line-height:1.65;color:#5D6C63;margin-top:12px;\"\u003eApera GS2-E.\u003c\/figcaption\u003e\u003c\/figure\u003e\u003c\/div\u003e\n\u003c\/div\u003e\u003c\/section\u003e\u003csection style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:clamp(28px,5vw,56px) 0;border-bottom:1px solid #B7D0BF;\"\u003e\u003ch2 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:clamp(24px,4vw,34px);font-weight:600;line-height:1.2;letter-spacing:-.02em;color:#245B45;margin:0 0 20px;\"\u003eCheck the specifications.\u003c\/h2\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eThe 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.\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eThe full specification table, version by version, is in the Product Specifications tab.\u003c\/p\u003e\u003c\/section\u003e\u003csection style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:clamp(28px,5vw,56px) 0;border-bottom:1px solid #B7D0BF;\"\u003e\u003ch2 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:clamp(24px,4vw,34px);font-weight:600;line-height:1.2;letter-spacing:-.02em;color:#245B45;margin:0 0 20px;\"\u003eCare and storage.\u003c\/h2\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eUse 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.\u003c\/p\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eRinse 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.\u003c\/p\u003e\u003c\/section\u003e\u003csection style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:clamp(28px,5vw,56px) 0;border-bottom:1px solid #B7D0BF;\"\u003e\u003ch2 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:clamp(24px,4vw,34px);font-weight:600;line-height:1.2;letter-spacing:-.02em;color:#245B45;margin:0 0 20px;\"\u003eRelated items.\u003c\/h2\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eCalibrate with \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/apera-ph-7-00-calibration-buffer-solution\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003epH 7.00\u003c\/a\u003e and \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/apera-ph-4-00-calibration-buffer-solution\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003epH 4.00\u003c\/a\u003e buffers and \u003ca href=\"https:\/\/bluetigerscientific.com\/products\/apera-1413-us-cm-conductivity-calibration-standard\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003e1413 µS\/cm standard\u003c\/a\u003e for EC.\u003c\/p\u003e\u003c\/section\u003e\u003csection id=\"bts-apera-gsp-faq\" style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:28px 0;line-height:1.15;\"\u003e\u003ch2 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1.1rem;font-weight:600;margin:0 0 16px;\"\u003eGroStar Probes buyer questions\u003c\/h2\u003e\n\u003cdetails style=\"border:1px solid #e0e0e0;border-radius:8px;margin-bottom:10px;background:white;\"\u003e\u003csummary style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:14px 16px;cursor:pointer;font-weight:600;font-size:1rem;line-height:1.15;\"\u003eWhich GroStar probe restores ordinary pH measurement?\u003c\/summary\u003e\u003cdiv style=\"padding:0 16px 14px;\"\u003e\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.97rem;line-height:1.6;margin:0;\"\u003eGS1-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.\u003c\/p\u003e\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #e0e0e0;border-radius:8px;margin-bottom:10px;background:white;\"\u003e\u003csummary style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:14px 16px;cursor:pointer;font-weight:600;font-size:1rem;line-height:1.15;\"\u003eWhich probe is intended for direct soil testing?\u003c\/summary\u003e\u003cdiv style=\"padding:0 16px 14px;\"\u003e\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.97rem;line-height:1.6;margin:0;\"\u003eGS2-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.\u003c\/p\u003e\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #e0e0e0;border-radius:8px;margin-bottom:10px;background:white;\"\u003e\u003csummary style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:14px 16px;cursor:pointer;font-weight:600;font-size:1rem;line-height:1.15;\"\u003eWhat is the difference between GS3-E and GS4-E?\u003c\/summary\u003e\u003cdiv style=\"padding:0 16px 14px;\"\u003e\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.97rem;line-height:1.6;margin:0;\"\u003eGS3-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.\u003c\/p\u003e\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #e0e0e0;border-radius:8px;margin-bottom:10px;background:white;\"\u003e\u003csummary style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:14px 16px;cursor:pointer;font-weight:600;font-size:1rem;line-height:1.15;\"\u003eWhich GroStar pens can use GS5-E for ORP?\u003c\/summary\u003e\u003cdiv style=\"padding:0 16px 14px;\"\u003e\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.97rem;line-height:1.6;margin:0;\"\u003eApera 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.\u003c\/p\u003e\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #e0e0e0;border-radius:8px;margin-bottom:10px;background:white;\"\u003e\u003csummary style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:14px 16px;cursor:pointer;font-weight:600;font-size:1rem;line-height:1.15;\"\u003eAre these probes interchangeable with PH60 or ZenTest probes?\u003c\/summary\u003e\u003cdiv style=\"padding:0 16px 14px;\"\u003e\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.97rem;line-height:1.6;margin:0;\"\u003eNo 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.\u003c\/p\u003e\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #e0e0e0;border-radius:8px;margin-bottom:10px;background:white;\"\u003e\u003csummary style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:14px 16px;cursor:pointer;font-weight:600;font-size:1rem;line-height:1.15;\"\u003eShould all GroStar probes be stored in KCl?\u003c\/summary\u003e\u003cdiv style=\"padding:0 16px 14px;\"\u003e\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.97rem;line-height:1.6;margin:0;\"\u003eNo. 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.\u003c\/p\u003e\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #e0e0e0;border-radius:8px;margin-bottom:10px;background:white;\"\u003e\u003csummary style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:14px 16px;cursor:pointer;font-weight:600;font-size:1rem;line-height:1.15;\"\u003eDo EC and ppm readings come from different sensors?\u003c\/summary\u003e\u003cdiv style=\"padding:0 16px 14px;\"\u003e\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.97rem;line-height:1.6;margin:0;\"\u003eNo. 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.\u003c\/p\u003e\u003c\/div\u003e\u003c\/details\u003e\u003cdetails style=\"border:1px solid #e0e0e0;border-radius:8px;margin-bottom:10px;background:white;\"\u003e\u003csummary style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:14px 16px;cursor:pointer;font-weight:600;font-size:1rem;line-height:1.15;\"\u003eWhat should I do after changing a GroStar probe?\u003c\/summary\u003e\u003cdiv style=\"padding:0 16px 14px;\"\u003e\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:.97rem;line-height:1.6;margin:0;\"\u003eUnscrew 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.\u003c\/p\u003e\u003c\/div\u003e\u003c\/details\u003e\u003c\/section\u003e\u003csection style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;padding:28px;background:#F1F7F3;border:1px solid #B7D0BF;border-radius:12px;\"\u003e\u003ch2 style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:clamp(24px,4vw,34px);font-weight:600;line-height:1.2;letter-spacing:-.02em;color:#245B45;margin:0 0 20px;\"\u003eConfirm the exact configuration before ordering.\u003c\/h2\u003e\n\u003cp style=\"font-family:'Open Sans',sans-serif;font-weight:300;box-sizing:border-box;font-size:1rem;line-height:1.75;margin:0 0 16px;\"\u003eCheck the version and catalog number (AI801G \/ AI802G \/ AI803G \/ AI804G \/ AI805G) against your tester or pen, then return to the live price and ordering controls.\u003c\/p\u003e\n\u003ca href=\"#\" style=\"color:#245B45;text-decoration:underline;font-weight:600;\"\u003eBack to price and ordering ↑\u003c\/a\u003e\u003c\/section\u003e\n\u003c\/div\u003e","brand":"Apera Instruments","offers":[{"title":"GS1-E – pH probe","offer_id":53012058702122,"sku":"BTS-AI801G","price":49.0,"currency_code":"USD","in_stock":true},{"title":"GS2-E – soil spear pH probe","offer_id":53012058734890,"sku":"BTS-AI802G","price":149.0,"currency_code":"USD","in_stock":true},{"title":"GS3-E – EC\/ppm probe","offer_id":53012058767658,"sku":"BTS-AI803G","price":49.0,"currency_code":"USD","in_stock":true},{"title":"GS4-E – pH\/EC combo probe","offer_id":53012058800426,"sku":"BTS-AI804G","price":80.0,"currency_code":"USD","in_stock":true},{"title":"GS5-E – ORP probe","offer_id":53012058833194,"sku":"BTS-AI805G","price":69.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0896\/1579\/4474\/files\/apera-gs1-e-main-20261018-mfr.webp?v=1792352315","url":"https:\/\/bluetigerscientific.com\/products\/apera-grostar-replacement-probes-gs1-e-gs2-e-gs3-e-gs4-e-gs5-e","provider":"Blue Tiger Scientific","version":"1.0","type":"link"}