lecture 13 chemical sensors. 2 of 17 ph sensor ph indicates how acidic or alkaline a solution is ph...
TRANSCRIPT
Lecture 13
Chemical sensors
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pH sensor
• pH indicates how acidic or alkaline a solution is
• pH term translates the values of the hydrogen ion concentration
• Solutions with pH < 7 are acidic, with pH > 7 alkaline (basic), pH = 7 is said to be neutral.
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pH sensor• pH is defined as the negative logarithmic
value of the Hydrogen ion (H+) concentration
pHIon Concentration (gram equivalent
per liter)Type of Solution
0 1.0
Acid Solution
- Hydrogen ions -
H+
1 0.1
2 0.01
3 0.001
4 0.0001
5 0.00001
6 0.000001
7 0.0000001 Neutral Solution
8 0.000001
Basic (alkaline) Solution
- Hydroxide ions -OH-
9 0.00001
10 0.0001
11 0.001
12 0.01
13 0.1
14 1.0
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Examples of substancesProduct pH
Battery Acid 0
HCl in stomach acid 1
Lemon juice, vinegar 2-3
Orange juice 3-4
Acid rain 4
Black coffee 5
Urine, salvia 6
Pure water 7
Sea water 8
Baking soda 9
Ammonia solution 10-11
Soapy water 12
Bleach 13
Oven cleaner 13-14
Drain cleaner 14
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pH sensor
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pH sensor - properties
• electrical resistance of the circuit is very high (around 400M Ω)• Temperature dependent• Requires regular calibration
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pH sensor
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Density - tanks
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Density - pipes
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Density – vibrating fork
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Oxygen sensor (Lambda sensor)
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Oxygen sensor (Lambda sensor)
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Blood glucose sensorglucose oxidase
2 2 2 2Glucose + 2H O+O Gluconic Acid + 2H O
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Blood glucose sensor
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Heated alcohol sensor
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Heated alcohol sensor
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Pyroelectric infrared-detector for Gas Analysis