Difference between revisions of "Team:NCKU Tainan/pH meter"
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| Line 63: | Line 63: | ||
<ul> | <ul> | ||
| − | <li>Experiment 1:Instrument calibration</li> | + | <li>Experiment 1:Instrument calibration</li></br> |
<ol> | <ol> | ||
| − | <li>Experimental purpose</li> | + | <li>Experimental purpose</li></br> |
<ul> | <ul> | ||
<li>Because the buffer solution wouldn’t change too much in the | <li>Because the buffer solution wouldn’t change too much in the | ||
environment, we used the buffer solution to calibrate the pH meter to | environment, we used the buffer solution to calibrate the pH meter to | ||
| − | ensure that the deviation would the same every time.</li> | + | ensure that the deviation would the same every time.</li></br> |
</ul> | </ul> | ||
| − | <li>Experimental method</li> | + | <li>Experimental method</li></br> |
<ol type="a"> | <ol type="a"> | ||
<li>Insert pH meter into pH 7 buffer solution, wait about 1 min, it | <li>Insert pH meter into pH 7 buffer solution, wait about 1 min, it | ||
will achieve a stable | will achieve a stable | ||
| − | value.</li> | + | value.</li></br> |
<li>Minus the value with pH 7, and it will get the offset value. For | <li>Minus the value with pH 7, and it will get the offset value. For | ||
| − | instance, 7-7.09=-0.09.</li> | + | instance, 7-7.09=-0.09.</li></br> |
<div id="centerimg" class="pic1"> | <div id="centerimg" class="pic1"> | ||
| Line 87: | Line 87: | ||
</div> | </div> | ||
| + | </br> | ||
<li>Write the offset value into code, upload the code into Arduino | <li>Write the offset value into code, upload the code into Arduino | ||
| − | again.</li> | + | again.</li></br> |
<div id="centerimg" class="pic2"> | <div id="centerimg" class="pic2"> | ||
| Line 94: | Line 95: | ||
</div> | </div> | ||
| + | </br> | ||
<li>After rinsing the pH meter, insert it into pH 4 buffer | <li>After rinsing the pH meter, insert it into pH 4 buffer | ||
| − | solution.</li> | + | solution.</li></br> |
<li>If it is found to be too different from the error of pH=4, you | <li>If it is found to be too different from the error of pH=4, you | ||
should adjust the knob. | should adjust the knob. | ||
After inserting pH = 4, it is found that the error with 4 is very | After inserting pH = 4, it is found that the error with 4 is very | ||
| − | large.</li> | + | large.</li></br> |
<div id="centerimg" class="pic3"> | <div id="centerimg" class="pic3"> | ||
| Line 105: | Line 107: | ||
</div> | </div> | ||
| + | </br> | ||
<li>Adjust the knob. (Remark: Because the change of the knob is small, | <li>Adjust the knob. (Remark: Because the change of the knob is small, | ||
it may have to turn a | it may have to turn a | ||
| − | few more times until display pH 4.)</li> | + | few more times until display pH 4.)</li></br> |
<div id="centerimg" class="pic4"> | <div id="centerimg" class="pic4"> | ||
<img class="oneimg" src=""> | <img class="oneimg" src=""> | ||
</div> | </div> | ||
| − | + | </br> | |
| − | <li>Finally, it can be found that the measured pH is 4.</li> | + | <li>Finally, it can be found that the measured pH is 4.</li></br> |
<div id="centerimg" class="pic5"> | <div id="centerimg" class="pic5"> | ||
| Line 122: | Line 125: | ||
</ol> | </ol> | ||
| − | + | </br> | |
| − | <li>Formula calculation</li> | + | <li>Formula calculation</li></br> |
<ol type="a"> | <ol type="a"> | ||
| − | <li>voltage = analog value*5/1024</li> | + | <li>voltage = analog value*5/1024</li></br> |
| − | <li>pH value = 3.5*voltage+offset</ | + | <li>pH value = 3.5*voltage+offset</li></br> |
</ol> | </ol> | ||
| − | <li>Experiment 2: Precision measurement</li> | + | <li>Experiment 2: Precision measurement</li></br> |
<ol> | <ol> | ||
| − | <li>Purpose</li> | + | <li>Purpose</li></br> |
<ul> | <ul> | ||
<li>We assume that pH 4 to 7 is linear, so we want to verify | <li>We assume that pH 4 to 7 is linear, so we want to verify | ||
whether it is linear between pH | whether it is linear between pH | ||
4 to 7. By measuring the solution of pH 4.7, compare its | 4 to 7. By measuring the solution of pH 4.7, compare its | ||
| − | deviation.</li> | + | deviation.</li></br> |
</ul> | </ul> | ||
| − | <li>Method</li> | + | <li>Method</li></br> |
<ul> | <ul> | ||
<li>Mixing a solution with pH=4.7 and measure with a calibrated pH | <li>Mixing a solution with pH=4.7 and measure with a calibrated pH | ||
| − | meter.</li> | + | meter.</li></br> |
</ul> | </ul> | ||
| − | <li>Result</li> | + | <li>Result</li></br> |
<ul> | <ul> | ||
| Line 157: | Line 160: | ||
value was stable at pH 4.83 | value was stable at pH 4.83 | ||
with an error of about 0.13, which roughly met the error of | with an error of about 0.13, which roughly met the error of | ||
| − | this pH meter ± 0.1 pH.</li> | + | this pH meter ± 0.1 pH.</li></br> |
</ul> | </ul> | ||
| Line 164: | Line 167: | ||
</div> | </div> | ||
| − | + | </br> | |
| + | <li>Materials used</li></br> | ||
<ol> | <ol> | ||
| − | <li>Arduino UNO</li> | + | <li>Arduino UNO</li></br> |
| − | <li>pH sensor | + | <li>pH sensor</li></br> |
<ol type="a"> | <ol type="a"> | ||
<li>Module Power : 5.00V</li> | <li>Module Power : 5.00V</li> | ||
| Line 175: | Line 179: | ||
<li>Accuracy : ± 0.1pH (25 ℃)</li> | <li>Accuracy : ± 0.1pH (25 ℃)</li> | ||
</ol> | </ol> | ||
| − | </ | + | </br> |
| − | <li>pH buffer solution</li> | + | <li>pH buffer solution</li></br> |
| − | <li>Arduino code</li> | + | <li>Arduino code</li></br> |
</ol> | </ol> | ||
Revision as of 12:49, 30 September 2018
pH Meter
About this section, we are showing how to use the pH meter in arduino.
Motivation
Because E. coli is sensitive to pH value, and according to the experiment of the pH sensor by WET members. We know that E. coli can’t grow below pH value of 6, and generally grow the best about pH 7.
Experiments
- Experiment 1:Instrument calibration
- Experimental purpose
- Because the buffer solution wouldn’t change too much in the environment, we used the buffer solution to calibrate the pH meter to ensure that the deviation would the same every time.
- Experimental method
- Insert pH meter into pH 7 buffer solution, wait about 1 min, it will achieve a stable value.
- Minus the value with pH 7, and it will get the offset value. For instance, 7-7.09=-0.09.
- Write the offset value into code, upload the code into Arduino again.
- After rinsing the pH meter, insert it into pH 4 buffer solution.
- If it is found to be too different from the error of pH=4, you should adjust the knob. After inserting pH = 4, it is found that the error with 4 is very large.
- Adjust the knob. (Remark: Because the change of the knob is small, it may have to turn a few more times until display pH 4.)
- Finally, it can be found that the measured pH is 4.
- Formula calculation
- voltage = analog value*5/1024
- pH value = 3.5*voltage+offset
- Experiment 2: Precision measurement
- Purpose
- We assume that pH 4 to 7 is linear, so we want to verify whether it is linear between pH 4 to 7. By measuring the solution of pH 4.7, compare its deviation.
- Method
- Mixing a solution with pH=4.7 and measure with a calibrated pH meter.
- Result
- After inserting the solution with pH=4.7, we found that the value was stable at pH 4.83 with an error of about 0.13, which roughly met the error of this pH meter ± 0.1 pH.
- Materials used
- Arduino UNO
- pH sensor
- Module Power : 5.00V
- Measuring Range:0-14pH
- Measuring Temperature :0-60 ℃
- Accuracy : ± 0.1pH (25 ℃)
- pH buffer solution
- Arduino code
Experiments
Reference
- Boywhy Chen.(2016).[Arduino] PH meter. Retrieved from http://boywhy.blogspot.com/2016/07/arduino-ph-meter.html(Augest 28,2018)