hi friends i need help .
Here i have pH transmitter and arduino uno board as well as current simulator which will provide 4-20 mA. My intention is to read pH values. The pH Transmitter provides 4-20 mA output when pH electrode (sensor) connected to it . The output of Transmitter’s current will be varied based on liquid.
Now i have dipped the sensor in 4 pH liquid. The output of transmitter converted into 1-5v by adding 250 ohm resistor. then the output voltage was connected to Arduino uno’s Analog ‘0’ pin. but the ADC readings are FLUCTUATING . For conforming the current , i connected multi-meter in series to transmitter. i was getting 8.44 to 8.78 mA fluctuations . but the ADC of arduino uno is reading values always fluctuating 0 to 1023 .
For above( pH transmitter) circuit diagram , it is available in attachments.
The pH range is 0 to 14.
first ADC bits are converted to voltage by using below formula.
then i converted voltage to pH.
And i have replace the pH transmitter with current simulator. i have adjusted output is to 8.4 mA. then output voltage is connected Analog ‘A0’ pin. that time i was getting constant ADC output.
For current simulator circuit diagram , it is available in attachments.
so if u find anything wrong in circuit or procedure pls let me know.