Salinity - Double Dipping Temp Compensation??

niccumec · May 8, 2024

When checking salinity across different devices, how do I ensure I am not double dipping on temp conversions?

Tropic Marin Hygrometer - factory calibrated at 77 deg F, so definitely need to use temp conversions if tank is different than 77.

Milwaukee MA887 - Auto compensates for temp, but does not document standard temperature that it is adjusting to…. Is it 77 deg F as well?

GHL Conductivity Probe - Auto compensates for temp based on temp probe, but does not document std temp it is adjusting to…. Is it 77 deg F as well?

Perhaps I am missing something, but it is not clear based on documentation (other than Tropic Marin) what the reference temp for auto correction is. Is 77 deg F a universal temp standard for all of these devices?

So my assumed process to compare salinity among devices.
1. Adjust Tropic Marin SG based on actual Tank Temp - now have value based on 77 deg F standard.
2. Read Milwaukee SG and compare to above. If Milwaukee auto adjusts to the same 77 deg (not stated in manual), then it should be apples to apples direct comparison, correct?
3. Read GHL Conductivity probe in ms or Density, convert to SG via online salinity calculator. If GHL also auto adjusts to 77 deg, then there should be no need for an added temp adjustment, correct?

I hope this makes sense, if MA887 and GHL Conductivity are automatically temp compensated, there there should be no need to further adjust based on temperature, correct?

Sorry if this is confusing, just not wanting to double dip on temp conversions when comparing readings.

Randy Holmes-Farley · May 8, 2024

You are over thinking it.

Only floating glass hydrometers need corrections by the user.

For an atc refractometer or a conductivity probe, the device corrects itself and temp of calibration does not matter, no matter what the device claims. It is not correcting to any value specifically. salinity in ppt never changes with temp. specific gravity barely changes with reasonable temp changes so it too is unimportant (unlike hydrometer readings regardless of units which do change a lot).