Good morning. Does anyone here use a blue lab pH pen? Mines been working fine up until today. Right after I calibrate in the solution, it starts off at 4.8 after the rinse. This is after I run though calibrating in both solutions, 7 then 4. After power up, at starts at 5.2. it should power on and default at around 7. I always store properly and keep the sensor moist with the storage solution. Any ideas? Thanks!
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How old is it and is the sensor dirty?
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It’s about a year old & I keep it as cleas as possible since it’s technically considered lab equipment. I’m gonna try wiping the sensors off or try keeping submerged in the storage solution for a while.
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Does it still read accurately otherwise? Like once calibrated and put into a 4 or 7 solution does it still read correctly? It’s just the storage solution/default that’s the issue?
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KCL storage solution tends to be around 4-5. Try remeasuring the PH of the calibration solution(s) or alternatively, measure some tap water. Also, watch for the response time, it should be stable fairly rapidly … maybe several seconds.
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The solutions read properly, however, when I initially begin to calibrate, it starts at 4 until I dunk in the solution. I’m just gonna try soaking in the storage solution overnight and change the batteries. Thanks folks
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That’s what I would do too. Could be dying batteries or dirty probe/bulb.
Here’s the instructions from blue lab on cleaning their ph pens (in case you need them):
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Edit: It calibrates at 7 and 4.
This is what I use.
The solution is just to keep the sensor moist.
https://amzn.to/3PC4QmT
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It calibrate at 7 and 4
PH probes measure the solute PH by measuring a voltage potential between the solute and a gel within the glass bulb probe.
As you place the probe into a solution, hydrogen ions will diffuse either into or out of the gel layer. This exchange develops a measurable voltage differential. Storing the probe in an acidic solution will diffuse hydrogen ions into the gel layer also known as hydration.
The hydration of the bulb determines it’s base measurement. Calibration offset and slope is determined in conjunction with the base measurement and the measurements points from a calibration solutions with known PH.
The storage solution is acidic, supplies h+ ions, and is then biased with an abundance of hydrogen ions (when using KCL).
I believe what you are reading is the hydrated gel layer (with no ion exchange) which tends to indicate that the gel layer is hydrated in equilibrium to the storage solution ion density and is ready for use. FWIW, the probe I have does the same. It is fine and is accurate.
Some other generic thoughts:
- bulb hydration is essential for longevity
- store it in a solution with high H+ ions. Keep the bulb moist.
- allowing the bulb gel layer to dehydrate will eventually deplete ions in the solution interior to the bulb. Sealed probes will be at their end of life as that occurs.
- never store the probe in deionized / distilled water
- pick a storage solution depending on the type of probe. KCL is common in the US.
- allow time for the bulb to hydrate in the storage solution
- if you change the storage solution formulation, different vender, etc the probe should be recalibrated after hydration (couple of days, maybe).
- Sealed bulb probes will eventually fail.
- Measurements of a solute that never stabilize or have significant drift indicate that something is going wrong.
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I went to calibrate and it flashed “7.”
Yep and you press the calibrate button again after the 7 and it’ll show 4. It’s in the manual. I just had to rehydrate and calibrate mine last week.
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Thank you. That is good to know because I have a fresh 4.0 bottle, never used.
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Ph sensors usually have about a 1 year life if stored properly. You can get some extra life out of them for sure. When you start having calibration problems or have to calibrate more frequently it may be time for a replacement probe/sensor.
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My first Bluelab pen lasted 5 years. The 2 replacements got water into the screen and died within a few months of buying them. So I switched to Apera.
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Wow, 5 years is a long time. Glad it worked that long for you. My ph meter is from my brewing hobby and is a Milwaukee ph102. I like it because it has a separate probe and temperature sensor. I usually get a few years out of a probe. Unless I’m brewing a beer and testing ph at a high temperature. Oddly enough when tested against the ph strips the strips are spot on accurate.
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My Apera has been going strong since Dec 2022 so have had great luck with it.
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My blue lab Ec has been going 5 years, my ph went 4 and died last year. Trying a Hanna now as it was given to me by a good friend
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Maybe I was wrong about how long ph meters last. In the mead hobby they mention a 1 year lifespan on the probe. It appears that The Bluelab or Apera ph meters last quite a bit longer. Something to think about when getting a new PH meter. 
*edit Just checked and my ph probe is 3 years old. Time flies. haha
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