[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

ISFET Ph pens and controllers

About those Ph pens: For the last 20 years I have checked my Ph the chemical way. 
Last X-mas I was in the JLFS ( Japanese Local Fish Store, meaning, no english 
communication only my "beer and fish" japanese). I saw this  "Ph-boy II" pen hanging there.
( ISFET probe, Ion-Sensitive Field Effect Transistor)
 I thought it would be less hassle than a chemical test and with a pen you can take 
a really quick peak at you Ph morning and evening. Great! ( so far ). 
I couldn't get too much details out of the shop guy( language problem, he knew a lot though)
  Bought the pen, calibrated, measured , Dirk happy. Only a couple of weeks later the pen 
needs continuous calibration. And after 6 months it went completely crazy. I could make 
3 successive measurements on the same water: 5.9 / 6.2 / 6.5 Even with calibrating I don't 
thrust the thing anymore. One time my Ph measurement was lower in the evening than in the 
morning although I seriously inject Co2 in a heavily planted tank.  It looks like filled 
with soda in the afternoon. I haven't found any service parts for the pen. It came with 
only one 6.9 calibration solution. ( Isn't there a hysteresis on the measuring equipment????) . 
Ok, this is the story, I don't like the pen and surely not its' price. 
All the calibration and worries take longer than to test the chemical way. 
Currently I inject  Co2 continuously. But in December I will move from ADA 
country back to Belgium. As you can imagine, a project is in the planning stage. 
I'm planning a 75-100 Gallon/ 300-400 Liter VERY green display tank in the living room in 
which I want to incorporate all my knowledge. ( previous max size was a 50 gallon). 
I have always been fascinated by the Ph controlled Co2 systems.
 But know I am getting my doubts: The buffering capacity of the water changes along with 
water changes, leaching of driftwood, use of humic acid containing substrate etc…. 
So the Co2 input of such a system is far from stable. Imagine your Ph goes below 7 
without C02 ( ADA soils do that ) . How can the controller add Co2? Increase hardness??? 
The probes need to be adjusted continuously, and the spare parts are expensive and 
may not always be available. I am really starting to wonder if it is worth the investment.
 I can also build a continuous pressure/ flow system that I adjust by measuring Ph
 chemically.  Does it make such a difference if a controller regulates your system? 
Is it going to make a significant difference in plant growth? 
Right now, my tank is like filled with soda in the afternoon and I don't have a controller.
 I can't imagine my Rotala w. or Cabomba spp. growing faster (don't want to).  
Please let me in on your experiences, good and bad ones so I can get a better understanding
 about the reality regarding these controllers and probes.  The salestalk I heard already.
 Since I have a technical after-sales job I know exactly what nonsense are spread on 
boxes and pamphlets/catalogues or which "inconvenient" information is missing and why 
some customers did not get what they expected. 
How many ways of measuring Ph electronically are there anyway? 
Are professional probes more reliable/usable or worth the expense? 
Are there any ISFET based PH controllers for aquarium use?
Can ISFET based probes resist continuous submerging? 
Thanks for your time, I know it's been long but the answers may wel be worth it.

From Dirk  "Sakanaman"
Suiso-man (RS): My new set-up is doing great, I'll write you later)

Get free personalized email at http://www.iname.com