Nightmarecreature
Active Member
I'm posting this to help solve the problem of calibrating the HM TDS-3. It's calibrated from the factory but it can go out of wack. I went to the hydro store and I bought some calibration fluid. The store owner told me that the Hanna 1100ppm soultion works just fine. Boy was he wrong. I calibrated it with the Hanna solution and it was way off. First off the HM TDS-3 works great and it's cheap. The problem is that most meters use KCL calibration solution. KCL is what is used in the Hanna solution. The HM TDS-3 uses NaCl, that means you must use NaCl NOT KCl! Also 1100ppm is way to high for our hobby. The ppm needs to be calibrated in the mid 350ppm range. Calibrating it at 1100ppm even with NaCl will cause an inaccurate calibration. I bought the HM digital 342ppm factory calibration fluid. After several batches of homemade solution I have a recipe. Now to calibrate your meter at home use:
12 cups of distilled water (PPM must be near zero)
0.5 gram of Morton salt (1/2 gram)
Throughly mix and set temps to 77 F
The PPM will be close to 350ppm (My solution is dead on at 350ppm)
This will allow you to get your meter within an acceptable range.
Make sure your scale is accurate. Place a nickel on your scale. It should read 0.5g if not don't use it.
If measured correctly the solution will be within 340-360 range.
12 cups of distilled water (PPM must be near zero)
0.5 gram of Morton salt (1/2 gram)
Throughly mix and set temps to 77 F
The PPM will be close to 350ppm (My solution is dead on at 350ppm)
This will allow you to get your meter within an acceptable range.
Make sure your scale is accurate. Place a nickel on your scale. It should read 0.5g if not don't use it.
If measured correctly the solution will be within 340-360 range.