Hanna Checker(s) Issues

[Hanna Instruments]

I agree with the OP. I fill mine with known 10ml and it is absolutely above the line. I also have a quick question regarding the phosphate test. After you put the powder in, or at least as much as you can get from the stupid packet lol. You have to mix for 2/3 mins till its all dissolved then press button to start countdown. Problem is the checker has turned off
by itself and when I hit the button it wants to start over with the C1. What am I doing wrong here? Do you hold the button down? Eric

The phosphate test has a very specific window of time for the chemical reaction to take place. This autoshut-off prevent over mixing of reagent that might throw off the reading.

1. Prior to turning on your meter, fill the cuvette with 10 mL of unreacted sample and replace the cap. Cut open one packet of HI 713-25 reagent and set aside.

1. Turn the meter on by pressing the button. All segments will be displayed. When the display shows “Add”, “C.1” with “Press” blinking, the meter is ready

3. Place the cuvette with 10ml of unreacted sample into the meter and close the meter’s cap.

4. Press the button. When the display shows “Add”, “C.2” with “Press” blinking the meter is zeroed.

5. Remove the cuvette from the meter and unscrew the cap. Add the content of one packet of HI 713-25 reagent. Replace the cap and shake gently for 2 minutes until the powder is completely dissolved. Place the cuvette back into the meter.

6. Press and hold the button until the timer is displayed on the LCD (the display will show the countdown prior to the measurement) or, alternatively, wait for 3 minutes and press the button.

7. The instrument directly displays the concentration of phosphate in ppm. The meter automatically turns off after 2 minutes.

 

[jdinovo]

I agree with the OP. I fill mine with known 10ml and it is absolutely above the line. I also have a quick question regarding the phosphate test. After you put the powder in, or at least as much as you can get from the stupid packet lol. You have to mix for 2/3 mins till its all dissolved then press button to start countdown. Problem is the checker has turned off by itself and when I hit the button it wants to start over with the C1. What am I doing wrong here? Do you hold the button down? Eric

Regarding the 3 minute turn off issue: I set my phone stopwatch to 3 minutes and start it as soon as the display turns to C2 so I know how close I am to the 3 minutes elapsing. I've found that there is enough time as long as I have the packet opened, creased, and ready to pour into the vial, and I typically have the top off the vial when I do the C1 calibration. And yes you do need to hold the button down until the C2 display changes to 3:00. This is not the way the other Hanna checkers work so one time out of ten I press and release and blow the whole test.

Regarding the measurement: I recall from high school chemistry that the measurement is not made where the top edge of the liquid meets the line, but where the lowest part of the little dip in the liquid (called the meniscus I think) meets the line, so the top edge of the liquid will be a little above the line.

 

[RajV]

The right measure i have understood is to use the 10 ml line on the cuvette . The miniscus ie the bottom curve must line up . Hence it needs to be on a level surface and checked at eyelevel .