Thinking about no longer calibrating probes

[Tangdora]

As the title states, with the exception of the Neptune temp probe whic lets you set it to a value of your choice, I’m thinking about no longer calibrating my probes. Thought process here would be to stop constantly going through periodic calibrations that shifts the probes offsets to bring it back into a proper reading.

Instead would just reset everything back to factory calibration and simply notate the variance against a calibration solution when a periodic check is performed. This way the setting can remain fix. And you don’t have to worry about a calibration making things better or potentially worse.

So for example if an apex ph probe with the factory calibration is reading 6.85 in a 7.00 solution after testing I would just rename my probe from PH say to PH-M0-15 ie (Minus 0.15). The naming convention would indicate that the probe reads 0.15 less than actual and any additional coding against the PH probe would need to be offset to factor this in difference.

Doing the math on the fly is easy enough only down side would be after each check if the variance changes all outlets using would need to be update. But a quick search can find all outlet pointed to a specific probe. Sorta already do this with orp which Neptune recommends not to calibrate.

 

[BeanAnimal]

I don’t get it? Why adjust various set points and do mental math when looking at charts -vs- just calibrating the probe?

You still have to use the calibration solution to record the offset to begin with.

 

[Randy Holmes-Farley Verified Community Expert]

That fixed correction is not an accurate way to deal with a pH recalibration. It may be close enough for values near 7, especially since many folks do not measure pH at all, but calibration is not a fixed correction.

 

[BeanAnimal]

That fixed correction is not an accurate way to deal with a pH recalibration. It may be close enough for values near 7, especially since many folks do not measure pH at all, but calibration is not a fixed correction.

Good point as well for any probe that has a dual point calibration.

 

[Tangdora]

That fixed correction is not an accurate way to deal with a pH recalibration. It may be close enough for values near 7, especially since many folks do not measure pH at all, but calibration is not a fixed correction.

Would not be calibrating anything though. the probe would being using the factory preset calibrations. All I would be doing is adding a number to the final reported value. So back to my example. If place in the calibration solution with the factory preset calibration and was reporting a value lower by 0.15 is it wrong to say that the probe then placed in the tank now reading 8.00 is not really a value of 8.15 after factoring in how off the preset reading is.

 

[BeanAnimal]

Would not be calibrating anything though. the probe would being using the factory preset calibrations. All I would be doing is adding a number to the final reported value.

Ignoring error (see Randy’s comment, and mine below) using a single offset value, you are still going through the process of dunking probes in calibration solutions and then adding the manual work of adjusting any programming tied to the values and the mental math every time you look at a reading or a chart? I am at a loss as to the benefit even if it were accurate.

So back to my example. If place in the calibration solution with the factory preset calibration and was reporting a value lower by 0.15 is it wrong to say that the probe then placed in the tank now reading 8.00 is not really a value of 8.15 after factoring in how off the preset reading is.

pH uses two points, one to get the offset and the second to get the slope of the line running through that offset. So you can’t simply apply your 0.15 adjustment to every reading.

Conductive is similar, but the two readings form a multiplier, so your measured “offset” at the calibration solution value is also not fixed and only valid at that value.