Dear All,
I have a pH electrode of BNC probe type ,which will give the output as mV .Can any one help me to convert sensor mV values into respective pH values .
Any suggestions /help is highly appreciated .
pH=7 - millivolt current=0
For growing ph, remove roughly 57.14 mV per unit of pH (ph=8, millivolt current=-57.14)
For curbing ph, add roughly 57.14 mV per unit of pH
If you are lazy, use (for example):
http://www.traditionaloven.com/conversions_of_measures/ph-voltage.html
I am afraid there might be a misunderstanding... I give you some examples:
pH5 --> mV: 114.29
pH6 --> mV: 57.14
pH7 --> mV: 0
pH8 --> mV: -57.14
ph9 --> mV: -114.29
And so on...
No Michel there is no misunderstanding ,I understood what you meant .
In my formula ,I can also able to calculate fractional values .
Formula --- pH = 7 - mV/ 57.14 .
For example when mV value = 57.14 i will get pH value of 6 by substituting mV value in the formula i .e pH = 7 - (57.14/57.14) = 7-1 = 6 .
lly for -57.14 pH = 7 -(-57.14/57.14) = 8
for -114.29 pH = 7 -(-114.29/57.14) = 9
This can also help to get fractional values of pH.
for 64.2 mV the pH value will be pH = 7 -(64.2/57.14) = 5.88
Kindly let me know if i am wrong .
1. Choose two buffers, let say pH1 = 7.00 and pH2 = 4.00 and measure the corresponding E1 and E2 (in mV).
2. For a sample with pHx, you measure Ex.
3. Calculate pHx = pH1 + (Ex – E1)(pH2 – pH1)/(E2-E1)
Important notes:
- all buffers and samples must be measured at the same temperature
- use a stabilisation time of about 1 minute for the electrode response
- the instrument must have a very high impedance (500 Gohm, not used in common voltmeters; use a pH/mV-meter in "mV" mode to test the equation)
- use a 3rd known buffer as sample (e.g., pH= 9.00 or 10.00) to verify if the sensor response is linear).
- at pH=7.00 , the common measured E is not zero; in the given equation, (Ex – E1) is the correction for this asymmetry
- in the given equation, (pH2 – pH1)/(E2-E1) is the electrode slope.
First, find out the slop of the graph you are getting for E vs pH value.
if the relation is linear then proportion will help to find pH for any mV value available, but if it is not so then need to adopt some other methods.
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