pH Meter Maintenance_Flairform

8/7/2019 pH Meter Maintenance_Flairform

http://slidepdf.com/reader/full/ph-meter-maintenanceflairform 1/3104 MAXIMUM YIELD USA - September 2008

Electronic pH MetersH ms mloyg glss lod usul o s H msum

bu qu qu lbo, o sog d hdlg o su uy

d lbly. Th l o whh suh ms o s bsd o h

h wh glss o omoso ss wo quous soluos hvg

d hydog o oos, volg s dvlod bw h wo

s o h glss. Th lo m sl s smly vy ssv volm,

whh msus h volg bu s lbd ms o H us sd o vols.

Maintenance

by Bob Taylor - Chemist or Flairorm Australia

Figure 1: Popular styles o pH meters: availability

ranges rom the more expensive laboratory

grade (let), to the cheaper pocket sized (right).

C o p y r i g h t © 2 0 0 8 w w w . f a i r o

r m . c o m

pH Meter


http://slidepdf.com/reader/full/ph-meter-maintenanceflairform 2/3105MAXIMUM YIELD USA - September 2008

Accuracy problems with pH Meters

No h ds bg oly lbd hs b my

qu x h d H ms wll odu

sgly d H dgs o h sm soluos. Ths

s slly u o low quly lods bus hy

sod o oh ss h lohmlly sml o

hydog os, suh s sodum. Fo hs so gow g

H dgs dg by mo h 0.5 us wh sg

u sml wh wo d H ms h hv b

oly lbd. No h H dos o gv ls

dgs wh ololss smls bus hy wll oly sod

o hydog os.

Storage of pH Electrodes

Fo H m wh sgl ombo lod o wok

oly h mus b ll oo bw h

lod llg soluo (usully ossum hlod – whh s

llly oduv) d h sml soluo. Ths s hvd

Calibration of pH Meters

To su h uy, H ms mus b gully lbd

o uy usg sdd H bu soluos h md o

olly gd . Ths sbl soluos h

ossss s H vlu. I s ssl o lb usg

ls wo H bus h d H by ls h H us

ov h g bg usd. Fo hydoos H bu 4.0 dH bu 7.0 h dl lbo sdds o us.

Som muus lm h H ms qu oly

sgl o lbo. Howv, h lm s smly o

jusbl uy s ds. Th us o wo H bu

sdds sus h h lbo slo s obd. I hs

uo s o k wh h lod s l ld

H bu 4.0 soluo, h m wll ylly d, o xml,

4.4, sd o 4.0. Ths ol oblm b vodd by

usg boh h H 7.0 d 4.0 bus.

How to Calibrate

Follow you H m muu’s suos.

Alvly, su o lb s wh H bu 7.0

ollowd by H bu 4.0. To do hs, s h lod

dslld w d gly shk o h xss w. Th,

mms h lod H bu 7.0 soluo o ls wo

mus bo djusg so h ds 7.0. Flly h

odu wh H bu 4.0 djusg so h ds 4.0. To

v omo o h H bus, d oo o

smll o o om h bov lbo, d dsd

o usd.

Common Mistakes Made WhenUsing Electronic pH Meters

1. Bo msug h H, su h h u s wll

sd, slly H u d dow usd. Ths s o

o h mos ommo msks md wh sg H o

oduvy. Also, su h smlg o s l.

2. See Figure 2 - Wh h H lod s ld sml,

you my o h h dg vs o som m (myb

svl mus) bo sg o l vlu. Th my b

d xss o 1.0 H u bw h l d

l H vlu. S h l vlu wll b h mos u,

mk su you w log ough o h dg o sblz.

Howv, o h so o lg.

Figure 3:

Do not immerse the electrode deeper than 20mm.

Figure 4:

Always clean the electrode

with distilled water ater use

- No. 1 maintenance tip or

prolonged electrode lie!

Figure 5:

Always keep pH electrodes

immersed in a “ storage”

solution when not in use.

Figure 2:

Stir nutrient tank well beore sampling.

Then leave the electrode in the sample

or a ew minutes beore switching the

meter on and taking the measurement.

Copyright ©2008 www.fairorm.com



3. Do o mms h lod h sml o dh h

xds h lvl o h llg soluo sd h lod

(Figure 3). S s o ossbl o vw h dh o

h llg soluo my ok szd ms, mms

h lod o dh o o mo h 20 mllms.

Exdg hs dh m h sml soluo o w

bk o h lod sl sulg u dgs.

4. O h dg hs b k, mmdly mov h

lod om h sml d s wh dslld w

(Figure 4). Flu o do so wll us d doo

o h lod d s h d d quy o

ou m – s so o lg. Whls o

us, su o so h lod (Figure 5) oly

omuld sog soluo – s so o sog.


http://slidepdf.com/reader/full/ph-meter-maintenanceflairform 3/3106 MAXIMUM YIELD USA - September 2008

v h us o oous o wk (Figure 6) h glss wll

sg h llg soluo hmb om h sml.

Boh hs dvs llow h (vy slow) fow o h llg

soluo o h sml soluo.

Th mos ommo us o H m lu s du o

blokg o hs oous o wk. Ths s usully usd by

dy sog o h lod o lvg h lod mmsd

o oo log od soluos. Dy sog uss

dhydo o boh h glss lod d o

o sls wh h ss o h sl (Figure 7). Th

osqus dg d, slow sos ms d

dsd ssvy sulg (loss o uy d so).

To vod hs oblms h lod mus b mly

sod (Figure 5) slly omuld sog soluo.

No h w o H bus o subl o sog o

H lods.

Rgul lg wll mxmz lod om d

su log wokg l. Som subl ls :

• Og omo - us mld lqud dg,

o*, mhyld s o oluol*. I oluol s ssy,

s subsquly wh o o mhyld ss d

lly w. • Iog omo – us dlu o

hydohlo d.

I hydoos, bus boh og d og

omos d o o-ou, s bs o us ll-

uos l.

* No h som ls my k lod hdw

- ully ls. Tho, su o hk wh h

lod’s muu bo odg.

pH Indicators

Alhough H dos my o lwys dsgush

bw H o, sy, 5.2 d 5.3, wd g olo

H dos hvg good olo soluo b:

• Fs

• Exmly u

• Sml

• Rlbl

• Us dly

• Eooml

As od, H ms qu os

u-k. Clg, lbg d o

sog mus b do o gul bss,bu v h my o gv lbl

dgs.

pH Meter Maintenance

Figure 6:

Schematic layout o glass pH

electrode. Loss o accuracy is

invariably explained by dierent

degress o blockage o the ‘rit’ or

‘wick’ - oten caused by dry storage.

Testing o oily or harsh chemicals

(eg. pH Up or concentrated

nutrient), or ailure to rinse the

electrode properly ater use.

Figure 7:

Arrow highlights contamination on

this ‘rit’ (or wick). The hydrogen

ion sensitive glass ‘bulb’ containing

the measuring cell electrode can be

seen to the right o the arrow.



Cleaning pH Electrodes

Th d glss o H m lods vbly bom

omd wh mus (Fg 1.8b) usg symoms suh

s dg d, slow sos ms d dsd ssvy

(loss o uy d so). Como my b so

sv h -lbo s o ossbl whou o lg.

Mmz hs oblm by lg olly oblm

w smls (.. gsy o hghly ubd) o o omg

H msum. Avod lg lods oly soluos

s hy o h lod. Fuhmo, vod msug

(o lvg lods o oo log) hsh hmls h

hghly us (H U, sl ddvs) o od soluos

lk w us. Ths dmg lods d/o s

h d o lod m.

MY

Documents

pH Meter Maintenance_Flairform