Conductivity Meters: pinpoint vs used lab grade units

[Velcro]

hi randy,
I'm thinking about picking up a conductivity meter. Pinpoint originally came to mind, but after reading some I understand that it's temp compensation is quite slow. I see several used older Orion 105 handhelds on eBay for the same price as a new pinpoint. How resilient are the probes on these things? Should I just buy a new pinpoint and deal with the slower comp?

 

[Randy Holmes-Farley]

My Pinpoint was definitely slower than my Orion 128. Not more than a couple of minutes or so, but slower.

The probes are pretty tough, relative to probes like pH.

Hard to know which way to go.

 

[Velcro]

My Pinpoint was definitely slower than my Orion 128. Not more than a couple of minutes or so, but slower.

The probes are pretty tough, relative to probes like pH.

Hard to know which way to go.

Thanks for the reply. I ended up going with a thermo orion 105A+ that was about $20 less than a new pinpoint. Definitely some cosmetic use, but I'm told it works well

 

[Randy Holmes-Farley]

Do you know if it is a 4 electrode probe?

 

[Velcro]

Do you know if it is a 4 electrode probe?

Unsure, can you tell from the connection?

 

[Velcro]

Crap, it looks like there's a chance that the included probe is only for up to 20 mS/cm!!!

 

[Velcro]

@Randy Holmes-Farley I think i dodged a bullet. Looks like the cell that only goes to 20mS/cm has a 1m cord while mine clearly is longer which narrows it down to just one possible conductivity cell.

Here's a picture of the same meter but with the 1m cord and the 20mS/cm cell:

 

[Velcro]

I managed to get the probe info. It is a 4 electrode with a range from 1 microS/cm to 200 milliS/cm

 

[Randy Holmes-Farley]

Nice!

 

[Velcro]

Nice!

Now if I could just find a manual!

 

[Randy Holmes-Farley]

lol

My 128 was more simple, with the only user adjustable setting was the range, plus an on/off switch.

 

[Velcro]

lol

My 128 was more simple, with the only user adjustable setting was the range, plus an on/off switch.

Cole palmer came through with a PDF of the manual!

 

[Velcro]

@Randy Holmes-Farley
Is this a reliable conversion from conductivity to salinity?

 

[Randy Holmes-Farley]

@Randy Holmes-Farley
Is this a reliable conversion from conductivity to salinity?

yes

53 mS/cm = 35 ppt.

See table 1 in my article:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

or this calculator (use 25 deg C):

https://web.archive.org/web/20040629190547/http://ioc.unesco.org/oceanteacher/resourcekit/M3/Converters/SeaWaterEquationOfState/Sea Water Equation of State Calculator.htm

 

[Velcro]

yes

53 mS/cm = 35 ppt.

See table 1 in my article:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

or this calculator (use 25 deg C):

https://web.archive.org/web/20040629190547/http://ioc.unesco.org/oceanteacher/resourcekit/M3/Converters/SeaWaterEquationOfState/Sea Water Equation of State Calculator.htm

Sweet, thanks again!

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.

 

[Velcro]

I got the meter, it works GREAT! One interesting thing that I found though.

I got a new bottle of Pinpoint salinity calibration solution. This is supposed to be able to be used for conductivity meters as well as refractometers. Being that it says 53.0mS = 1.026 SG = 35.0ppt I can only assume that it must not be pure KCl, as my understanding is it would not be possible for KCl to show all of these things on both devices without being two different concentrations. This meter works by entering the cell constant in the settings and then measuring a known standard. If it is off, you adjust the cell constant by a percentage until your meter reads the correct conductivity for the corresponding standard. All said and done, I had to adjust the meter down about 1.04%. I didn't really believe this number to be honest, because I tested it on a fresh batch of saltwater I'm mixing and it was showing 32ppt.

Here's where it gets interesting. I used your conductivity calibration solution DIY and made up a pure KCl standard. I used a jewelers balance which reads to 0.01gm. I weighed the appropriate amount of RODI and KCl USP. I then reset the meter to it's default cell constant and tested the DIY KCl solution. BAM 35.0 ppt EXACTLY. I didn't write down the exactly mS/cm... 35.0ppt is close enough for me.

Also this thing is stupid fast. Temp adjusts in 5-10 seconds. I guess you get what you pay for when the probe was over $500 new!

 

[Randy Holmes-Farley]

The Pinpoint fluid is supposed to be 53 mS/cm. It is a seawater mimic, so is good for most devices.

Glad the standard worked!

 

[Tim Olson]

The Pinpoint fluid is supposed to be 53 mS/cm. It is a seawater mimic, so is good for most devices.

Glad the standard worked!

To clarify ... I currently use the Pinpoint fluid to calibrate my Pinpoint Salinity Monitor to 53 mS/cm. Is that the most accurate method or should I use your DIY solution, like Velcro did?

Thanks

 

[Randy Holmes-Farley]

To clarify ... I currently use the Pinpoint fluid to calibrate my Pinpoint Salinity Monitor to 53 mS/cm. Is that the most accurate method or should I use your DIY solution, like Velcro did?

Thanks

Assuming the Pinpoint solution is made as claimed (and not left open to the air to evaporate, etc.), then it is perfect for calibration.