ca monitor

[Mr_Quality]

Originally posted by Randy Holmes-Farley
I'd contact Lou. That sounds like maybe you pushed the wrong buttons or the meter is defective. Any time such a meter reads zero suggests a problem to me.

FWIW, I finished my testing and submitted my article.

Here's my conclusion:

Conclusions

My conclusion based on limited testing of two Pinpoint Calcium monitors, and from the information that I have received from several other aquarists who have them, is that they can be a useful way to measure calcium, but are not without issues that aquarists must become familiar with. Given the time to calibrate and equilibrate them to each new solution, such a monitor is not faster than a test kit. Since I have not tested the accuracy of any calcium test kits, I cannot compare the accuracy of the calcium monitor to typical commercial kits.

I was pleasantly surprised by the fact that the response does not seem likely to be thrown off by the ranges of different water chemistries encountered in reef aquaria. Temperature seems to be the only big concern, and that is something that aquarists can control.

The monitor is warranteed for 2 years, and it is recommended to replace the electrode after 18-24 months, or when it can no longer be calibrated. Pinpoint has replaced monitors for some folks that had problems (unable to calibrate). All of the measurements that I took were using the 9 volt battery, although one of the meters did come with an AC adapter.

The section below gives some tips for using the Pinpoint calcium selective electrode in reef aquaria. Pinpoint includes many other recommendations in their User’s Guide, which is well written and easy to follow. I have only listed those things here which are not listed there, or which I consider most important:

1. The calcium monitor will probably not give reliable readings for any solution other than seawater. I would not use it for fresh water, limewater (kalkwasser), or calcium supplement solutions (at least not using the Pinpoint seawater standards). It may or may not work properly in the low pH/high alkalinity solutions found in the effluent of a calcium carbonate/carbon dioxide reactor.

2. Temperature is critically important. Make sure that the calibration temperature and the measurement temperature are the same to within 1-2 ºF.

3. The electrode takes a while to equilibrate to the new solution. The longer it is left in, the more reliable will be the reading (within reason, very long times of a day or more may start to encounter some drift). The directions say to equilibrate during calibration until the meter gives 4-5 flashes of the concentration without stopping, but I would suggest leaving it in until it flashes steady without stopping. In taking measurements, I would leave it in for at least 10 minutes and watch the reading to see that it is not changing.

4. Do not tough the tip directly. It can be easily damaged.

5. The directions say to rinse the probe in fresh water between measurements or calibrations. If you are measuring a large volume, like a reef system, that isn’t important. If you are measuring in a small container (like a cup), it is more important to not transfer water between samples. Bear in mind, however, that some fresh water clinging to the probe will alter a measurement more than will the 100 ppm standard if you are going to read seawater. My suggestion is to gently shake the electrode between solutions to remove big drops, and possibly wipe the sides gently with a paper towel if you are taking careful measurements.

6. Turn off the meter between uses. It remembers the previous calibration, so there is no need to run down the battery.

Disclosure: American Marine/Pinpoint supplied the two calcium meters that I tested at no cost.

Gosh Randy, no numbers? No regression, no precision, just words. That's disapointing for us data-hounds.

[Randy Holmes-Farley]

You need to wait for the April reefkeeping to see the test results.

[Mr_Quality]

Oh, you tease you!

[Boomer]

You need to wait for the April reefkeeping to see the test results

People have been beating on me on other forums "how'd you get that before it is published "

[gbr]

Ironically I have not checked this forum in a while. The information that Randy put out about the temp would have been invaluable.

I received a replacement probe tip from Lou Dell at American Marine due to the fact that the original probe tip would not hold its calibration. It would read above the calibration fluids by up to 50% within minutes of the original calibration. I had called Lou and he informed me that the probe tip should not have been soaked in tap water due to inconsistencies in tap water around the country and should only be soaked the 100ppm calibration solution.

1. If you buy this unit, get the new instructions from the American Marine USA web site.

I also spoke to Lou about other things that I had noticed with the unit. These are not quotes from Lou but are "gists" of the conversation and impressions that I got. Lettered below:

a. The unit has the ability to read in the 10ths but jumps by large numbers. My personal observation is that it changes by about 2.3% of he reading. At 100ppm, the next reading will be 102.3, at 400 the next reading will ~409. (sorry I don't remember actual numbers here at work) Lou explained this as necessary due to the way the meter measures (something about a logarithm which was over my head)

b. The probe tip does not need to be kept wet.

c. The sleeve was originally supposed to be kept open during calibration and testing which would affect how the reference solution interacted with the probe tip. Lou said that it was ok to keep the sleeve closed and that it would not significantly affect the readings and would slow evaporation.

d. Flow did not have as large of an effect on the unit as I had believed. At the time I was testing changes due to flow, I was having problems due to temp changes which I was not aware of at the time of testing.

e. Do not put the probe in RO/DI. The lack of ions is not good for the probe. A quick rinse is ok.


Once I was done calibrating the new tip. I put the tip in a shot glass with aquarium water in it. (By Salifert my Ca is always 380)
The reading increased to 570 over 2 minutes. I was of course upset but decided to let it sit for a while to stabilize. I came back down (my sump is in my crawl space) after an hour and to my surprise the unit read 389. Wow...fixed...right. I put the probe tip in the sump and back up to 550 it went. So I assumed it was a flow problem. I went out to the garage a quickly built an acrylic add-on for my sump that was welded on to one of the baffles. It is a box with about 15 - 3/16" holes drilled in it that all of my probes can hang in to really reduce flow. Once to probe was place in that box...570. Obviously not flow. So back into a new shot glass of water. This time I sat with it and watched as it slowly decreased from 550 to 389. AH HA This thing is temp dependent. So I floated the calibration fluids for 1/2 hour, recalibrated and put the probe in the sump box. 389. Fixed for now...

2. This unit is very temperature dependent. (had Randy not gone on vacation and figured this out earlier, he'd be getting a box of cookies...but he didn't...so he doesn't )
Randy recommend 1-2 degrees, I recommend 0. From what I can tell my sump area is at 63 degrees and my aquarium is at 80. A 17 degree change made at least 30% change in reading. I would assume that a 2 degree change could lead to a 3.5% change in reading. That's a guess of course.

Having figured out the temperature problem I left the probe in the sump. 24 hours later the unit read 370. 48 hours later 330 72 hours later 310. At this point I put the probe back into the 1000ppm cal fluid and got a reading of 970. Only a 3% difference. At this point I email American Marine and asked to return the unit. Which I have done.
I have been contacted again by Lou asking if the Magnesium could be very low. My Mg is at 1150 which is low but not very low. Also, according to a post reply to Habib, a low Mg would actually raise the reading, not lower it, and only by 1-2%.

3. The unit is obviously affected by other ions. I cannot even begin to speak intelligently here. Interestingly in a reply earlier to Habib Lou says "I've always said that this meter is really not for the beginning aquarist and if the system was an ionic nightmare results may be off." I didn't read that on the write up from MarineDepot or the American Marine web site.

This review was really is meant to help other people with the unit. I would say that if you are willing to calibrate the unit (2-4 minutes assuming the fluids are floated) and take a reading and be willing to accept that reading and recalibrate often that it does have merits.

Honestly though, as can be seen earlier in this thread, the advanced aquarist probably only measures Ca monthly at most which makes this unit unnecessary. The only reason I got the unit was to do accurate analysis of day to day fluctuations of Ca in my system. Basically to determine the amount of Kalk needed based upon a daily decrease in Ca. This is not possible with this unit.

Travis

[Randy Holmes-Farley]

Thanks for the feedback.

The unit is obviously affected by other ions.
i
I tested a number of other ions, including magnesium sulfate, sodium chloride, magnesium chloride, pH (with HCl, H2SO4, and NaOH) and organics, and didn't see a big difference. Perhaps ones perception is all in the degree to which one expects accuracy. IMO, if it is good to +/- 20 ppm, it is adequate for reefers.

[mrkrispy]

Sounds like one should float the calibration fluid in the tank before calibrating, in addition to equilibrating the probe.

Nice work everyone.

[Randy Holmes-Farley]

Yes, that would be a good way to do it.

[Fastmarc]

Ok, I just received my calcium monitor.
I will report later tonight on how it works.

[Fastmarc]

Ok, Randy et al, here in my experience.
The instruction, which seems modified from what was described earlier in this thread, were very clear and easy.

I soaked the probe in the 100 ppm fluid for an hour.

I went the route of setting up a monitoring station as suggest in the instructions and then did calibration.

As instructed, I did the 100 ppm first, but instead of 5, I waited for it to flash 10 times.

I gave it a quick rinse in DI water along with a light pat down with a paper towel to get rid of any droplets and then did the same with the 1000 ppm.

This completed the calibration process. It didn't take long to do.

I then check the to calibration fluids to see if the calibration held. After about 2 mins in each they both showed the correct readings.

I then check my sample water which I had taken out about an hour earlier to allow it to be the same temp as the calibration fluids.
Interestingly, the instruction now states that all calibration fluids should be 77 deg for greatest accuracy. My room temp was 82 deg.
I waited the same 2 mins and the sample water read 457.1 ppm.

I re-did the calibration process and checked the sample again. It read 457.1 ppm.

I then took the same sample around to a friend for him to check it with a salifert test kit. He got 440 ppm.

When I returned home (1 hour and a half later), I did the test again with new water and it read 457.1.

If the probe is left in it for a long time, it may jump 2%.

As far as I see it, basically, this will do just fine for me. I wanted to be able to occasionally check on my calcium and this allows me to do so

You guys think of any other questions, let me know.

Below is my testing station.

[Randy Holmes-Farley]

Thanks for the info. It seems as if it worked well for you!

[Fastmarc]

Yes. I'm happy with the purchase.

[SEAREEF]

glad to hear it fast marc

[Randy Holmes-Farley]

My review of the Pinpoint Electronic Calcium monitor has posted at:

Electronic Calcium Monitoring
http://reefkeeping.com/issues/2005-04/rhf/index.htm

the contents:

How Ion Selective Electrodes Work
Possible Complications of Using Calcium Selective Electrodes
Experimental Testing of the Pinpoint Calcium Monitor
Calcium Spike Experiments
Response Time
pH Effects
Effects of Other Ions in Solution
Temperature Effects
Long Term In-Tank Use
Water Movement
Effect of Organics
Conclusions

[Fastmarc]

It is a good read as usual Randy, though I will have to read over the more technical info a bit more to fully grasp it.
It's good to know exactly how it comes up with the readings.

[Randy Holmes-Farley]

Thanks.

[Fastmarc]

For those like myself, who had purchased this monitor early, there are updates to the instructions on the American Marine site that addresses storage and maintenance.

[Randy Holmes-Farley]

That's good to hear.

Thanks for the update!