Subject: pH Meter
Date: 26 dec 02
For Checker 1 - Stick model ?Checker? with replaceable HI 1270 screw-type, 
combination, pH electrode see 
http://www.hannainst.com/products/testers/checker.htm
I have found the above pH meter to be the most cost effective and best for use 
with, plant source water, water from soil (soil ph), urine, and saliva testing.   
This unit costs $25 and I recommend it for after PS use.  The batteries will 
last about 3,000 hours of use and are easy to change.   pH paper may be 
impractical for a while after the PS during rain and wet weather.  This unit 
will not last forever but neither does pH paper.

The unit is not temperature compensated.  However, I have found that if one 
calibrates the unit for room temperature (about 70 deg F) and is measuring urine 
or saliva (at 98.6 deg F) that if one adds .2 to the ph reading it will be very 
close to accurate.  The way to occasionally check this is to let the solution 
cool off to room temperature and take the difference between the readings. 

 I also recommend you check the calibration at regular intervals (about every 
month).  This would depend on the use.  I keep small 2 oz plastic bottles of 
standard buffer solution for ph 7.0, 10.0, and 4.0 for use with calibration.  
One tests and adjusts the unit to 7.0 washing the electrode off between 
solutions.  Then use 4.0 or 10.0 depending on whether measuring mostly acid or 
base.   When the unit is calibrated (changing trim pots to match the buffer 
solution) the measurements are more accurate than pH paper. 

Once in use one keeps the electrode wet with storage solution or distilled 
water.  I keep the unit upright ready to use with the electrodes constantly kept 
wet.  This can be done by drilling a hole in the cap of a small bottle (plastic 
pill bottle will work).  

Clarkson Lab and Supply Inc has the units listed as:
Part number                                              Price
HAN HI98103  Checker 1 pH Tester W/electrode          At $25.00
BS0170-07F   Buffer standard solution pH 7.00 1 qt.   At  $8.50
BS0170-04F   Buffer standard solution pH 4.00 1 qt.   At  $8.50
BS0170-10F   Buffer standard solution pH 10.00 1 qt.  At  $8.50

Phone# 619 425-1932
http://www.clarksonlab.com/contact.htm
http://www.clarksonlab.com/

