Pm2 temp?

[jamiequ]

Hi guys
I have a pm2 , I see it has a temp socket, what would you use the second temp probe for , the sump and display? Also how is it displayed on the dashboard, sorry a bit new with this
thanks

[zombie]

It's used for temperature compensation for the salinity probe. You can either add a second temp probe in the same rough location as the cond probe or move the temp probe from your main unit to the PM2 to improve the accuracy of the cond probe (note: heater/chiller code would need to be updated if you do).

The reason this is important is because conductivity varies about 2.2 ppt per degree Celcius. If your tank temperature varies more than about a half a degree, You will see some pretty substantial fluctuations in conductivity even though it is actually constant and can skew your programming responses.

You might be an engineer if...You have no life and can prove it mathematically.

[jamiequ]

Thank Z, that makes sense, does it come up on dashboard as temp2 or something

[zombie]

I think so. Don't remember the default name. If you don't see it, check the unused tile bin. If it's not there either make sure it is enabled (module setup page of the PM2 in the classic dashboard)

You might be an engineer if...You have no life and can prove it mathematically.

[jamiequ]

Many thanks

[jamiequ]

One other thing, where do I get the composition numbers from , I clips on the web saying 2.2 where are they getting that from
thanks

[zombie]

It varies depending on the total salinity and the relative concentration of NaCl to other elements including Magnesium, dKH, calcium, etc. It's incredibly difficult to calculate so trial and error will be your best friend here.

Start at 2.2. If you notice salinity goes down when temp goes down and up when temp goes up, add another 0.1 to it until it stays relatively consistent. If you have the inverse relationship, subtract 0.1 to it until it becomes consistent.

You might be an engineer if...You have no life and can prove it mathematically.