{"product_id":"bluelab-onepen-replacement-probe","title":"OnePen Replacement Probe by Bluelab — pH, EC \u0026 Temperature Sensor","description":"\u003cdiv style=\"font-family: 'Helvetica Neue', Arial, sans-serif; max-width: 860px; margin: 0 auto; color: #1a1a1a;\"\u003e\n\n\u003cp style=\"font-size: 1.05rem; line-height: 1.7; margin-bottom: 1.5rem;\"\u003eThe Bluelab OnePen Replacement Probe restores pH, conductivity (EC) and temperature accuracy to your Bluelab OnePen in one quick swap. When the probe wears out — or can no longer be calibrated — you replace the sensor, not the whole meter. With a double-junction pH probe and titanium EC electrodes, it brings your OnePen back to the precision it shipped with.\u003c\/p\u003e\n\n\u003cdiv style=\"background: #fdecea; border-left: 4px solid #c0392b; padding: 1rem 1.3rem; border-radius: 6px; margin-bottom: 2rem;\"\u003e\n\u003cstrong style=\"color: #c0392b; display: block; margin-bottom: 0.5rem;\"\u003eCheck Compatibility Before Ordering\u003c\/strong\u003e\n\u003cspan style=\"font-size: 0.93rem; line-height: 1.6;\"\u003eThis probe fits the Bluelab OnePen (PENONE) only. It does not fit the pH PenPlus, the standard pH Pen, or any BNC-connector Bluelab meter or monitor. The OnePen only accepts genuine Bluelab probes — imitation probes are rejected by the pen.\u003c\/span\u003e\n\u003c\/div\u003e\n\n\u003cdiv style=\"display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 1rem; margin-bottom: 2rem;\"\u003e\n\u003cdiv style=\"background: #f4f9f4; border-left: 4px solid #2e5e2e; padding: 1rem 1.2rem; border-radius: 6px;\"\u003e\n\u003cstrong style=\"display: block; margin-bottom: 0.3rem; color: #2e5e2e;\"\u003eThree Measurements, One Swap\u003c\/strong\u003e\u003cspan style=\"font-size: 0.9rem; color: #444;\"\u003eRestores pH, EC and temperature readings in a single replacement — the full sensor package of the OnePen renewed at once.\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background: #f4f9f4; border-left: 4px solid #2e5e2e; padding: 1rem 1.2rem; border-radius: 6px;\"\u003e\n\u003cstrong style=\"display: block; margin-bottom: 0.3rem; color: #2e5e2e;\"\u003eLab-Grade Accuracy\u003c\/strong\u003e\u003cspan style=\"font-size: 0.9rem; color: #444;\"\u003eRestores the OnePen's full ±0.05 pH and ±0.1 EC accuracy with readings down to two decimal places.\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background: #f4f9f4; border-left: 4px solid #2e5e2e; padding: 1rem 1.2rem; border-radius: 6px;\"\u003e\n\u003cstrong style=\"display: block; margin-bottom: 0.3rem; color: #2e5e2e;\"\u003eTitanium EC Electrodes\u003c\/strong\u003e\u003cspan style=\"font-size: 0.9rem; color: #444;\"\u003eCorrosion-resistant titanium conductivity electrodes and a double-junction pH probe built for nutrient-rich solutions.\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"background: #f4f9f4; border-left: 4px solid #2e5e2e; padding: 1rem 1.2rem; border-radius: 6px;\"\u003e\n\u003cstrong style=\"display: block; margin-bottom: 0.3rem; color: #2e5e2e;\"\u003eCheaper Than a New Meter\u003c\/strong\u003e\u003cspan style=\"font-size: 0.9rem; color: #444;\"\u003eExtends the life of your OnePen and keeps a $395 instrument out of landfill — replace the consumable, keep the electronics.\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003ch2 style=\"font-size: 1.1rem; font-weight: 700; border-bottom: 2px solid #2e5e2e; padding-bottom: 0.4rem; margin-bottom: 1rem;\"\u003eSpecifications\u003c\/h2\u003e\n\u003cdiv style=\"display: grid; grid-template-columns: 1fr 1fr; gap: 0.5rem 2rem; margin-bottom: 2rem; font-size: 0.95rem;\"\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eCompatible With:\u003c\/strong\u003e Bluelab OnePen (PENONE) only\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eMeasures:\u003c\/strong\u003e pH, conductivity (EC) and temperature\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003epH:\u003c\/strong\u003e 0.0 – 14.0 pH, ±0.05 at 25°C, double-junction probe\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eConductivity:\u003c\/strong\u003e 0 – 10.0 EC, ±0.1 EC, titanium electrodes (factory calibrated)\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eTemperature:\u003c\/strong\u003e 0 – 50°C, ±1°C, with automatic temperature compensation\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eOperating Environment:\u003c\/strong\u003e 0 – 50°C, IP68 dustproof and waterproof\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eInstallation:\u003c\/strong\u003e Tool-free — arrow-to-notch alignment, threaded collar\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eAverage Probe Life:\u003c\/strong\u003e Approximately 18 months with good care\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eWarranty:\u003c\/strong\u003e 6-month limited warranty\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cstrong\u003eBluelab SKU:\u003c\/strong\u003e PROBONE\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cdiv style=\"background: #fff8e1; border-left: 4px solid #f9a825; padding: 1rem 1.3rem; border-radius: 6px; margin-bottom: 2rem;\"\u003e\n\u003cstrong style=\"color: #e65100; display: block; margin-bottom: 0.5rem;\"\u003eGrow Guys Tip — Hydrate the Bulb, Not the Electrodes\u003c\/strong\u003e\n\u003cul style=\"margin: 0 0 0 1.2rem; padding: 0; font-size: 0.93rem; line-height: 1.7;\"\u003e\n\u003cli\u003eHydrate the pH glass bulb via the storage cap: place a few drops of KCl storage solution on the sponge inside the cap, fit it, and leave for 24 hours before first calibration. A dehydrated bulb drifts, reads stuck near pH 7 and can break.\u003c\/li\u003e\n\u003cli\u003eDo not soak the titanium EC electrodes in KCl solution for any length of time — Bluelab warns against it. The cap-sponge method hydrates the bulb without bathing the electrodes.\u003c\/li\u003e\n\u003cli\u003eNever use RO, distilled or deionised water anywhere near the probe — pure water permanently damages it. KCl only.\u003c\/li\u003e\n\u003cli\u003eClean with Bluelab pH Probe Cleaner and a soft brush on the EC electrodes — never Bluelab Conductivity Probe Cleaner, which Bluelab states is not compatible with the OnePen, and never abrasive cleaners.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\n\u003ch2 style=\"font-size: 1.1rem; font-weight: 700; border-bottom: 2px solid #2e5e2e; padding-bottom: 0.4rem; margin-bottom: 1rem;\"\u003eHow to Replace the Probe\u003c\/h2\u003e\n\u003cdiv style=\"margin-bottom: 2rem;\"\u003e\n\u003cdiv style=\"display: flex; align-items: flex-start; gap: 14px; padding: 12px 0; border-bottom: 1px solid #edf3ed; font-size: 0.93rem; line-height: 1.6;\"\u003e\n\u003cspan style=\"background: #2e5e2e; color: #fff; font-weight: 700; font-size: 0.85rem; min-width: 28px; height: 28px; border-radius: 50%; display: flex; align-items: center; justify-content: center; flex-shrink: 0; margin-top: 1px;\"\u003e1\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eRemove the old probe.\u003c\/strong\u003e Remove the storage cap, turn the pen upside down so the batteries stay in place, unscrew the threaded collar and remove the old probe from the pen body.\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"display: flex; align-items: flex-start; gap: 14px; padding: 12px 0; border-bottom: 1px solid #edf3ed; font-size: 0.93rem; line-height: 1.6;\"\u003e\n\u003cspan style=\"background: #2e5e2e; color: #fff; font-weight: 700; font-size: 0.85rem; min-width: 28px; height: 28px; border-radius: 50%; display: flex; align-items: center; justify-content: center; flex-shrink: 0; margin-top: 1px;\"\u003e2\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eFit the new probe.\u003c\/strong\u003e Remove the protective cap, line up the arrow on the probe with the notch on the pen body, push it all the way in and secure the threaded collar until fully tightened.\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"display: flex; align-items: flex-start; gap: 14px; padding: 12px 0; border-bottom: 1px solid #edf3ed; font-size: 0.93rem; line-height: 1.6;\"\u003e\n\u003cspan style=\"background: #2e5e2e; color: #fff; font-weight: 700; font-size: 0.85rem; min-width: 28px; height: 28px; border-radius: 50%; display: flex; align-items: center; justify-content: center; flex-shrink: 0; margin-top: 1px;\"\u003e3\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eHydrate for 24 hours.\u003c\/strong\u003e Place a few drops of KCl storage solution on the sponge inside the storage cap, refit the cap and leave for 24 hours so the glass bulb is active. Never use RO, distilled or deionised water, and don't soak the titanium electrodes in KCl.\u003c\/span\u003e\n\u003c\/div\u003e\n\u003cdiv style=\"display: flex; align-items: flex-start; gap: 14px; padding: 12px 0; font-size: 0.93rem; line-height: 1.6;\"\u003e\n\u003cspan style=\"background: #2e5e2e; color: #fff; font-weight: 700; font-size: 0.85rem; min-width: 28px; height: 28px; border-radius: 50%; display: flex; align-items: center; justify-content: center; flex-shrink: 0; margin-top: 1px;\"\u003e4\u003c\/span\u003e\u003cspan\u003e\u003cstrong\u003eCalibrate pH — always 7.0 first.\u003c\/strong\u003e Rinse the tip in fresh tap water, then run a full 2-point pH calibration with fresh pH 7.0 then 4.0 (or 10.0) solution. EC is factory calibrated — verify against 2.77 EC standard if you want to confirm.\u003c\/span\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003ch2 style=\"font-size: 1.1rem; font-weight: 700; border-bottom: 2px solid #2e5e2e; padding-bottom: 0.4rem; margin-bottom: 1rem;\"\u003ePairs Well With\u003c\/h2\u003e\n\u003cdiv style=\"display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 1rem; margin-bottom: 2rem;\"\u003e\n\u003ca href=\"\/products\/one-pen-by-bluelab-1\" style=\"text-decoration: none; color: inherit; background: #f4f9f4; border: 1px solid #c8dfc8; padding: 1rem; border-radius: 6px; display: block;\"\u003e\u003cstrong style=\"color: #2e5e2e; display: block; margin-bottom: 0.3rem;\"\u003eBluelab OnePen\u003c\/strong\u003e\u003cp style=\"font-size: 0.85rem; margin: 0;\"\u003eThe 3-in-1 pH, EC and temperature meter this probe belongs to — one pen for the whole reservoir check.\u003c\/p\u003e\u003c\/a\u003e\n\u003ca href=\"\/collections\/ph-control-calibration-ph-ec\" style=\"text-decoration: none; color: inherit; background: #f4f9f4; border: 1px solid #c8dfc8; padding: 1rem; border-radius: 6px; display: block;\"\u003e\u003cstrong style=\"color: #2e5e2e; display: block; margin-bottom: 0.3rem;\"\u003eCalibration \u0026amp; pH Control\u003c\/strong\u003e\u003cp style=\"font-size: 0.85rem; margin: 0;\"\u003eGrab pH 7.0 and 4.0 calibration sachets plus KCl storage solution — you'll need them to hydrate and calibrate the new probe.\u003c\/p\u003e\u003c\/a\u003e\n\u003ca href=\"\/collections\/bluelab-1\" style=\"text-decoration: none; color: inherit; background: #f4f9f4; border: 1px solid #c8dfc8; padding: 1rem; border-radius: 6px; display: block;\"\u003e\u003cstrong style=\"color: #2e5e2e; display: block; margin-bottom: 0.3rem;\"\u003eMore From Bluelab\u003c\/strong\u003e\u003cp style=\"font-size: 0.85rem; margin: 0;\"\u003eProbes, monitors and meters from the New Zealand brand growers have relied on for over 30 years.\u003c\/p\u003e\u003c\/a\u003e\n\u003c\/div\u003e\n\n\u003ch2 style=\"font-size: 1.1rem; font-weight: 700; border-bottom: 2px solid #2e5e2e; padding-bottom: 0.4rem; margin-bottom: 1rem;\"\u003eFAQ\u003c\/h2\u003e\n\u003cdetails style=\"margin-bottom: 0.8rem; border: 1px solid #e0e0e0; border-radius: 6px; padding: 0.8rem 1rem;\"\u003e\u003csummary style=\"font-weight: 600; cursor: pointer;\"\u003eDoes this probe fit the pH PenPlus or other Bluelab meters?\u003c\/summary\u003e\u003cp style=\"margin: 0.6rem 0 0; font-size: 0.93rem; line-height: 1.6;\"\u003eNo. This replacement probe fits the Bluelab OnePen only. The pH PenPlus uses the separate pH ProbePlus, and Combo Meters, pH Meters and Guardian Monitors use BNC-connector probes.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails style=\"margin-bottom: 0.8rem; border: 1px solid #e0e0e0; border-radius: 6px; padding: 0.8rem 1rem;\"\u003e\u003csummary style=\"font-weight: 600; cursor: pointer;\"\u003eWill a cheaper non-genuine probe work in the OnePen?\u003c\/summary\u003e\u003cp style=\"margin: 0.6rem 0 0; font-size: 0.93rem; line-height: 1.6;\"\u003eNo. The OnePen detects and rejects non-genuine probes with a \"PROBE INVALID\" error — only official Bluelab OnePen Replacement Probes will function.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails style=\"margin-bottom: 0.8rem; border: 1px solid #e0e0e0; border-radius: 6px; padding: 0.8rem 1rem;\"\u003e\u003csummary style=\"font-weight: 600; cursor: pointer;\"\u003eDoes it replace pH, EC and temperature sensing?\u003c\/summary\u003e\u003cp style=\"margin: 0.6rem 0 0; font-size: 0.93rem; line-height: 1.6;\"\u003eYes. The probe carries all three sensors — a double-junction pH probe, titanium EC electrodes and the temperature sensor — so one swap restores every measurement the OnePen takes.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails style=\"margin-bottom: 0.8rem; border: 1px solid #e0e0e0; border-radius: 6px; padding: 0.8rem 1rem;\"\u003e\u003csummary style=\"font-weight: 600; cursor: pointer;\"\u003eDo I need to hydrate the new probe before using it?\u003c\/summary\u003e\u003cp style=\"margin: 0.6rem 0 0; font-size: 0.93rem; line-height: 1.6;\"\u003eYes. Bluelab recommends hydrating the pH glass bulb for 24 hours before initial calibration — a few drops of KCl storage solution on the sponge inside the storage cap, cap fitted. Don't soak the titanium electrodes in KCl, and never use RO, distilled or deionised water.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails style=\"margin-bottom: 0.8rem; border: 1px solid #e0e0e0; border-radius: 6px; padding: 0.8rem 1rem;\"\u003e\u003csummary style=\"font-weight: 600; cursor: pointer;\"\u003eHow long does an OnePen probe last?\u003c\/summary\u003e\u003cp style=\"margin: 0.6rem 0 0; font-size: 0.93rem; line-height: 1.6;\"\u003eApproximately 18 months on average, according to Bluelab. pH probes are charged with reference material that expends through use — good hydration and regular cleaning stretch the lifespan, but every probe eventually fails to calibrate and needs replacing.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails style=\"margin-bottom: 0.8rem; border: 1px solid #e0e0e0; border-radius: 6px; padding: 0.8rem 1rem;\"\u003e\u003csummary style=\"font-weight: 600; cursor: pointer;\"\u003eCan I use Bluelab Conductivity Probe Cleaner on it?\u003c\/summary\u003e\u003cp style=\"margin: 0.6rem 0 0; font-size: 0.93rem; line-height: 1.6;\"\u003eNo. Bluelab states its Conductivity Probe Cleaner is not compatible with the OnePen or this replacement probe. Clean with Bluelab pH Probe Cleaner and a soft brush on the EC electrodes, never abrasives, and recalibrate pH after every clean.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails style=\"margin-bottom: 0.8rem; border: 1px solid #e0e0e0; border-radius: 6px; padding: 0.8rem 1rem;\"\u003e\u003csummary style=\"font-weight: 600; cursor: pointer;\"\u003eDoes calibration solution come included?\u003c\/summary\u003e\u003cp style=\"margin: 0.6rem 0 0; font-size: 0.93rem; line-height: 1.6;\"\u003eNo. The probe ships on its own — add pH 7.0 and 4.0 calibration solution and KCl storage solution to your order so you can hydrate and calibrate before first use.\u003c\/p\u003e\u003c\/details\u003e\n\n\u003cdiv style=\"background: #1c3a1c; color: #fff; padding: 2rem; border-radius: 10px; text-align: center; margin-top: 2rem;\"\u003e\n\u003ch2 style=\"color: #fff !important; margin: 0 0 0.5rem; font-size: 1.3rem;\"\u003eReplace the Probe, Keep the Pen.\u003c\/h2\u003e\n\u003cp style=\"color: #aed1ae !important; margin: 0 0 1.5rem; font-size: 0.95rem;\"\u003eRestore pH, EC and temperature accuracy to your OnePen — shipped fast Australia-wide.\u003c\/p\u003e\n\u003cdiv style=\"display: flex; justify-content: center; gap: 1rem; flex-wrap: wrap;\"\u003e\n\u003cbutton id=\"btn-add-to-cart\" style=\"background: #b67317 !important; color: #fff !important; padding: 0.85rem 2rem !important; border: none !important; border-radius: 6px !important; font-size: 1rem !important; font-weight: 700 !important; cursor: pointer !important;\"\u003eAdd to Cart\u003c\/button\u003e\n\u003ca href=\"\/products\/one-pen-by-bluelab-1\" style=\"background: transparent !important; color: #fff !important; padding: 0.85rem 2rem !important; border: 2px solid #fff !important; border-radius: 6px !important; font-size: 1rem !important; font-weight: 600 !important; text-decoration: none !important; display: inline-block !important;\"\u003eShop the OnePen\u003c\/a\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\n\u003cscript\u003e\ndocument.addEventListener('DOMContentLoaded', function() {\n  var btn = document.getElementById('btn-add-to-cart');\n  if (!btn) return;\n  btn.addEventListener('click', function() {\n    fetch('\/cart\/add.js', {\n      method: 'POST',\n      headers: {'Content-Type': 'application\/json'},\n      body: JSON.stringify({id: parseInt('52066658189610', 10), quantity: 1})\n    }).then(function(response) {\n      return response.json();\n    }).then(function(data) {\n      if (data.status \u0026\u0026 data.status !== 200) { throw new Error(data.description); }\n      btn.textContent = 'Added to Cart';\n      btn.style.background = '#2e5e2e';\n      setTimeout(function() {\n        btn.textContent = 'Add to Cart';\n        btn.style.background = '#b67317';\n      }, 2000);\n    }).catch(function() {\n      btn.textContent = 'Error — Try Again';\n      btn.style.background = '#c0392b';\n      setTimeout(function() {\n        btn.textContent = 'Add to Cart';\n        btn.style.background = '#b67317';\n      }, 2500);\n    });\n  });\n});\n\u003c\/script\u003e\n\n\u003c\/div\u003e","brand":"Bluelab","offers":[{"title":"Default Title","offer_id":52066658189610,"sku":"BL-MTR-PROBE-ONE","price":159.95,"currency_code":"AUD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0847\/1573\/3290\/files\/BL_Image_Product_PROBONE_OnePen_Replaceable_Probe_013.png?v=1783730792","url":"https:\/\/www.thegrowguys.com.au\/products\/bluelab-onepen-replacement-probe","provider":"The Grow Guys","version":"1.0","type":"link"}