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FuzzyLogic
11/05/2010, 10:29 AM
The question I have concerns the calibration process of the PM2 conductivity probe and the reading that is displayed. If the calibration range of 'High' is chosen during the process the result is that the display with show the reading of conductivity in mS, right? If the range of 'Salinity' is chosen will the resultant display show the reading in ppt? The display does not specificaly show the unit of measure which leads to my confusion.

schwaggs
11/05/2010, 10:44 AM
See the table on Page 3 of the manual http://www.neptunesys.com/PM2-20104031_WEB.pdf

If you select "High" the reading will be from 0-85 mS/cm

If you select "Salinity" the reading will be from 0 - 45 PPT

Both are calibrated with 53 mS/cm solution

FuzzyLogic
11/05/2010, 01:12 PM
Thank you very much for the answers and the link to the manual. My manual that came with the the PM2 that i had received is a little different from that one.

I had chosen 'Salinity' for my calibration range and when I was prompted to place the probe into my 53 mS/cm solution the number that the PM2 settled on was 35.0. I had assumed that was 35ppt. But when I place the probe into my tank water the displayed reading of 52.3 came up and stayed there! Could that be 52.3ppt? My refractometers tell me my tank is at 35.5ppt. Could my fractos be off that much?

schwaggs
11/05/2010, 05:15 PM
52.3 is a Sg of 1.04... I doubt your refractometer is that far off. Your tank would be dead if your Sg was that low... I would re-calibrate

FuzzyLogic
11/05/2010, 05:54 PM
Good idea.... Will do. Do you know if the number that is displayed during calibration of the high point is the actual measurement of the calibration solution?

schwaggs
11/05/2010, 05:57 PM
I'm not sure with the Conductivity probe. I know that the displayed number is not the calibration solution value when you calibrate a pH probe.

bazineta
11/05/2010, 06:01 PM
Note that with temperature correction activated on the PM2, you must have a temperature probe plugged into the PM2; the probe in the base unit is not referenced by the PM2. If correction is activated with no probe present in the PM2, readings will be nonsensical.

In my case, I simply moved the temperature probe from the base module to the PM2; it'll be named tmpx4 on the PM2. This was a minor annoyance until the recent new microcode release, which allows for probe renaming.

aqua80
11/05/2010, 06:06 PM
and if you have only a temperature probe in the pm2 you can use it for heater control exactly like if it was on the base module right ?
then why I have read that someone bought anothe temp probe juste for the pm2 ?

FuzzyLogic
11/05/2010, 06:08 PM
Yeah I did get that part right. I have a temp probe connected to my PM2 with temp compensation enabled and set to 2.2c. I'm going to recalibrate and post back with the results.