Grow Mediums My new HM Digital pH meter does not work. Help!

[Pyru]

So i splurged on a new digi pH meter on amazon, was torn between the Oakton and the HMD both roughly $50 but seemed the more recent reviews on the HMD was better plus it was like 5 bucks cheaper so i went with it.

HMD: http://www.amazon.com/HMDPHM80-Digital-pH-Temperature-Meter/dp/B0096N8OWI
Oakton: http://www.amazon.com/Oakton-EcoTestr-Waterproof-Tester-Range/dp/B004G8PWAU

got it today..

instructions say to add storage solution in the cap and wait at least 15min, so i waited about an hour then calibrated it using the ph 7.0 buffer packet and 0 TDS water from my zero water filter pitcher in the fridge (instructions say distilled, but the zero water pitcher pretty much makes tap water distilled.

I then tested the buffer solution and it went to 7 then down to 6.9

I then tested my res water and it stabilized at 6.4

I then added 1 drop of General Hydro pH down and tested it with the GH drop vial and immediately the color turned red so I knew it must be in the pH 4 range...

Tested with the HMD pen and it again climbed and stabilized at 6.4

..added 2 more drops of pH down and again.. pen says 6.4

tested the pH buffer solution and it went to 6.9.


in conclusion, seems like any time I test my res it reads 6.4, unless i add too much pH up.. i did record a 7.0 on the pen at that point.. but no matter how much pH down I add it always reads 6.4


needless to say I just ordered the Oakton and hope to test it on saturday. Cant really afford the $100+ testers like the Blue Labs one:dunno:

 

[DWCocha]

Hey bud ,you could test the meter a few different ways rather than just testing the res .Get some tap water ,filtered water ect & test ...then add a drop or two of up & test again ,grab another glass of water & put some down in .If the readings change & the meter works ok it could be something wrong with the nute mix in the res ?.If the meter reads the same after adding up or down to water in a glass as well than the meter is broke & you can send it back :Sharing One:

 

[KsjAuto]

Sounds like the junction aint working right..
These things happend when they arent used much,,,"new"
i whoud leve it in a ph4 solution for 15 to 30 min.
put it back in the kcl solution (storage solution) for 30 min..
And tjeck again.

Some junction needs a little work to get going,
Cheap batteries can also be a problem..

Just my to pennnies
:smoke:

Edit:
Junction:Short version
http://www.all-about-ph.com/reference-junction.html

 

[namvet25]

I have used the oakton2 for three years and nevere had a problem.You need calibrating solution to make sure it is accurate and check it every month or so.

 

[Pyru]

I think I figured it out!

ive been adding the pH drops directly in the res and stirring it in and taking readings directly from res

i just emptied solution into a big kettle and added the ph down til meter said 5.5, tested with droppers and it came out red, added 3 drops of up and meter said 5.8, tested with drops and color is a light orange!!! Bingo

so I'm not sure these drop testers are totally accurate in the lower range, looks like according to the meter that I've been running my res solution at pH 6.5-6.9!! Yikes no wonder my girls are like 4+ weeks old and still look like seedlings