Conductivity variation

[Dan Reef]

Hello,

My conductivity varies from 32.4 to 33.3. Would this variation be considered normal?

Thanks!

 

[Dan Reef]

Up

 

[vhuang168]

32.4 ppt = 1.0244 sg
33.3 ppt = 1.0251 sg

You are within 0.001 sg which is what most refractometers measure up to.

 

[Randy Holmes-Farley]

Hello,

My conductivity varies from 32.4 to 33.3. Would this variation be considered normal?

Thanks!

When you say varies, do you mean minute to minute reporting errors, or possibly with changes over hours to days, potentially due to changes in the salinity due to evaporation?

The former is not normal for conductivity measurements in general, but I can't speak specifically to the Neptune implementation itself.

The latter could happen if you are manually topping off infrequently.

 

[Dan Reef]

When you say varies, do you mean minute to minute reporting errors, or possibly with changes over hours to days, potentially due to changes in the salinity due to evaporation?

The former is not normal for conductivity measurements in general, but I can't speak specifically to the Neptune implementation itself.

The latter could happen if you are manually topping off infrequently.

Thanks for the reply!

This is the variation over 1 day. I use the ATO from Neptune.

 

[Randy Holmes-Farley]

Same time every day?

It could be temp effects improperly implemented in the conductivity measurement reporting, changes in salinity due to evaporation and imperfect ATO action, or electrical interference from something .

To go from 33.2 to 33.6 mS/cm implies that you evaporated out 1.2% of the tank volume (without replacement), which is not unreasonable for a day of evaporation.

 

[spifftempo]

I might also suggest that you compare your change to how your temperature is changing throughout the day. If you do not have temperature compensation enabled in the probe setup, then temperature changes will affect your conductivity readings.

Typically compensation should be between 2.0-2.2%. If/when you decide to enable it, then you'll need to re-calibrate the probe with tank temperature calibration solution at the time of enabling it.

 

[Dan Reef]

Same time every day?

It could be temp effects improperly implemented in the conductivity measurement reporting, changes in salinity due to evaporation and imperfect ATO action, or electrical interference from something .

To go from 33.2 to 33.6 mS/cm implies that you evaporated out 1.2% of the tank volume (without replacement), which is not unreasonable for a day of evaporation.

Yes, same thing. 1.2% could definitely be evaporation although ATK ato from Neptune is quite precise.

Thanks!