Apex Conductivity Probe

[shafiq_hossain]

Got new Apex system. Calibrated probes. What should the reading on my conductivity probe be? Refractometer shows 1.025 for salinity. What conductivity reading is that equivalent to?

Thanks...

 

[schwaggs]

33.2

Conversion calculator here:

 

[shafiq_hossain]

I'm getting 3.9 on the apex web portal. I guess that means 39, right?

 

[schwaggs]

Not sure... What settings are you using? Have you calibrated it?

 

[shafiq_hossain]

I have calibrated it. When you say settings, what specific setting are you referring to?

 

[schwaggs]

What range do you have it set for? Are you using temperature compensation? What is that set to? Do you have a temperature probe connected to the PM2?

In any event, a reading of 3.9 in not correct. It should be reading in the 30s. If it is reading 3.9, either you have the range set wrong or your calibration didn't work properly.

 

[shafiq_hossain]

The following are the settings on the Conductivity Probe page:
Conductivity Compensation: 0.0
Conductivity Range: Salinity
Offset: 1
Scale: 0.23e

 

[schwaggs]

Looks correct to me. If it is reading 3.9 and you have it set to Salinity, you need to try and recalibtrate. Also, make sure there aren't any air bubbles in the probe when calibrating or wherever it is reading. Bubbles in the probe will make it read low...

 

[shafiq_hossain]

Thanks. I'll pick up a new packet of calibration liquid today. To ensure no bubbles exist, can I let the probe dry out before calibrating?

 

[schwaggs]

The bubbles are a problem when the probe is in the calibration solution or when it is in the tank measuring salinity, not when you are doing the first step of calibration.

 

[schwaggs]

Also, be sure to select the correct calibration fluid as you are calibrating (you should be using the 53,000 microsiemens/cm (53 milisiemens/cm) solution. I use the pinpoint solution because it can be used to calibrate your refractometer too!

 

[shafiq_hossain]

Yep, that's what I used last time. I'll pick up the same type from Pure Reef today.

 

[shafiq_hossain]

I'm not sure if I'm getting much use out of the expensive piece of equipment. It shows the salinity level going down down down to 21 but my refractometer is still spot on at 1.025. It's not even a week old. Any ideas why it would provide not only this type of reading but going down at this rate? I thought Conductivity and Salinity were directly related. Could it be that Conductivity is going down without affecting salinity?

 

[schwaggs]

Nope, salinity and conductivity are directly related. Something is definitely wrong, your salinity reading should not vary that much. Mine moves up an down a few tenths througout the day. The conductivity reading is very sensitive to stray voltage in your tank. Can you correlate the swings with other items turning on or off (lights, heater, etc)?

 

[ripped tide]

Would a stray voltage cause a conductivity level to go down? If anything I would assume that It would cause reading to jump around instead of just dropping.