Help / Aquamedic LF2001C / mS of natural seawater

[Brucey]

Hi chaps, can anybody help . . . . !!!!!

My latest gadget arrived this morning, an Aquamedic LF2001 C salinity controller. All good so far. OK, so I turned it on and read the instructions and that's where I got lost. Not good. It's not a salinity controller really, more a measurer of electrical resistance within seawater represented as a mS (Millisiemens) figure. Not as one might hope, as a specific gravity measure which of course would be well handy.

So two questions.

1. What is the desired level for this device. ie, what mS figure should I be aiming for ? What do other people have theirs set to ?
2. The instructions talk about calibrating the probe in a solution of seawater measuring 50mS. How on earth do you go about making up this solution to calibrate it or should you believe in the calibration out of the box. My current reading is 31.5 mS. using my old hydrometer my salinity measurement is 1.022

Thanks in advance (if anyone can help that is)
Brucey

 

[NaH2O]

Brucey - I'm surprised the probe didn't come with calibration solution. I know when using a conductivity probe, a salinity of 35ppt (SG=1.026) the conductivity is 53mS/cm. That is what you would shoot for, if you want NSW values. From the looks of your initial results, you will want to calibrate it, however, I am not sure what would be the best calibration solution to use for conductivity.

OK - nevermind...LOL - I knew there was an article about this. RH-F's article discusses homemade calibration standards, and the last part of the article talks about conductivity and a homemade calibration fluid. Hope you find it helpful: Reef Aquarium Salinity: Homemade Calibration Standards

 

[Woodstock]

That's a very good article. I once attempted to make a calibration fluid for my refractometer using its instructions. It is tough to do without scales!

How to Use a Conductivity Standard

How to best use a conductivity standard depends a bit on the meter involved. If the meter can be calibrated, then my suggestion is to get the solution to about 25ºC (exactly that temperature if the meter doesn't automatically compensate for temperature, but that would be unusual) and then adjust the meter until it reads 53 mS/cm or S=35 (depending on the output).

Many meters, however, do not allow such calibration. In that case, measure the conductivity or salinity of the standard, and then set up a correction ratio that is applied manually. For example, if the standard reads 56 mS/cm, then multiply all readings on that meter by 53/56 (0.946) to get a corrected reading. The same correction could apply to salinity. For example, if it reads S=38 (or 38 ppt), then multiply every reading by 35/38 = 0.921.

Alternatively, the simplest way is to use the value that is found from the standard as the target for the aquarium, and not worry about calibrations or corrections.

 

[Mad Mike]

You guys don't zero out the refractometer with distilled water to calibrate?

 

[Brucey]

Thanks guys . . . if I tried to make my own I'm so rubbish at it I'd probably put the probe further out than it already is. I'll order some up tomorrow from my LFS.

Hey Nikki. Thanks for the links mate. I had a real good read and I reckon I'm running my salinity WAY too low, so I'm going to adjust.

Brucey

 

[Woodstock]

You guys don't zero out the refractometer with distilled water to calibrate?

...well, actually yes, I use distilled water to calibrate my refractometer but only because finding the correct calibration fluid is very difficult.