[Ray47]

Hi All, just brought a Hanna HI98201 ORP meter as I have Trichodina and have treated pond with P&P for 3 hours of purple water at 450 mv reading on the meter as per Duncan Griffiths book. after checking the readings for 45 mins still the reading was 450 mv but the water was turning brown. I checked the meter after rinseing it with tap water and tried again still 450 mv, I then checked the meter with Hanna's redox solution 200 to 275 mv and that gave me a reading of 250 mv. as PP has stopped working once water is brown but still reading 450 mv I could not add more PP to keep the purple water up thus aborted the treatment. any ideas?
Ray

[pondy]

at the risk of sounding condesending.... are you sure you have calibrated it correctly? if you have , did you have it running for about an hour before putting the pp in your pond? what did it rise from and to or was it always reading that one figure?

[Ray47]

Hi Pondy, the meter should be already calibrated according to Hanna, but no to the 30 mins, I went by the instuctions that came with the meter, they nothing about leaving it pond for 30 mins except (quote) (for more accrate readings condition the meter in HI7091 or HI7092) these I dont have but do have the storage and redox solutions which when I tested the meter gave me a correct reading, also when I aborted the treatment I did a water change and this brought the reading down. which section BKKS are you from ? im Crouch Valley.
Ray

[Davej]

ORP (Oxidation-Reduction Potental) meters can be temperamental - well the probes can!!

I use Pinpoint meters rather than the Hanna with Aquamedic probes which I have found more responsive than the Pinpoint probes.

Cleaning solutions such as the 7092 solution are helpful but probe will always need a gentle brush over with a soft toothbrush.

If you scooped a bucket of water out when you had a reading of 450mv and added a couple of drops of HP then you should see an immediate response!!

Dave

[pondy]

Ray,
both Davej and myself are crouch valley but i would have thought you should know that! im not exactly inconspicuous!
try the bucket test as Dave has suggested and hopefully you should see wether your meter is functioning properly or not

[Ray47]

Hi All, I've only been a member of CVKS for 3mths and dont know members that well. so ok I'll try with hydrogen peroxide ?
Ray

[Ray47]

phoned Hanna today, no help at all, they say the fact that the meter reading falls when washing in tap water and using redox solution gives correct reading means the meter is working and if it stays at 450mv in the pond after using PP then thats the correct reading. so I cant add more PP to keep purple water as I may overdose, seems I will have treat pond 3 times every 4 days. not to impressed with Hanna.
Ray

[Ray47]

yes after adding HP to water meter readings do drop. But that still leaves the problem

[ochiba110]

Ray47 I think you may find this interesting reading on ORP.
ORP notes

[Ray47]

Hi, thanks for the info I changed the Hanna for a Pinpoint and all is fine, but good info about ORP
Thanks Ray