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Questions tagged [ph]

In chemistry, pH is a measure of the activity of the (solvated) hydrogen ion. Pure water has a pH very close to 7 at 25°C. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline.

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pH sensor box - ADS1115

I made a pH sensor box to monitoring my hydroponic culture. I built a PH sensor box (see Frtitzing) to use for my hydroponics system with: - Esp8266 - ADS1115 - BNC + pH probe (2X) Unfortunately the ...
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3answers
85 views

AD620 pH probe has a positive voltage offset!

I am a chem eng. but little background in electronics. I'd like to interface a pH probe with an AD620A, the original PCB that came with pH probe was damaged by a current leak in the solution. I made ...
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1answer
70 views

Stable 200uA Current source by cascading REF200's Current source and Current mirror

I am trying to work on above circuit. A common operating point of ISFET pH sensor is a drain-source current of 100 uA and a drain-source voltage of 500 mV. I am using REF200 current source to feed ...
2
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1answer
156 views

PH Probe Unstable Measurement

I've recently set up a small circuit for PH measurement using a BNC PH electrode. A picture of my circuit can be seen below: The linear reference REF1 alongside opamp U1A serve to generate a 2.5V ...
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2answers
60 views

What pH sensor have a long-term use with non-calibrated?

I have a project that use some water monitoring sensors (pH, oxygen, conductivity...). But my project are facing a problem: My device can not be touch within 3 months. And as my knowledge, those ...
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1answer
137 views

stable DC converter for PH analog reading [closed]

i have purchased a small board to measure pH with a MCU. I am using a ADS1115 as ADC that have an internal Vref, that should be precise enough for my purpose. Now, if i connect my Vin to the ADC pin,...
2
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1answer
160 views

pH sensor buffering, gain, and offset with one inverting opamp

I'm working on the above mentioned circuit. I'm a hobbyist with little electronics training so don't laugh if something terribly dumb comes out of my keyboard please. Anyway, a different question on ...
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1answer
197 views

How to prevent pH-sensor from maxing out, when pump is turned on?

I am a bioproces engineer currently working with setting up a pH control system in a bioreactor (basically a large vessel filled with water). Hence, my electronics knowledge is quite limited. ...
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2answers
175 views

how to offseting voltage for ph electrode?

is it necessary to use circuit below for offseting? and what is the difference if I connect directly 512mv Voltage to my ph electrode?
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1answer
438 views

Amplifier for a ph sensor [closed]

I am going trying to interface with a ph sensor. For this work I realize I need to connect to an amplifier for an impedance buffer. After searching I found some op amps that have high impedance, which ...
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1answer
72 views

pH Sensor with current loop

I have a ph sensor(S272CD) that give the output from -2000mV to +2000mV. I need to interface it into a current loop converter(XTR117). The current loop ic will accept only 0 to 5v. How can i connect ...
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3answers
9k views

Building a pH meter circuit - is it feasible?

Let's say I have a budget of $15-20 to build a pH meter. I will then read the analog values from a microcontroller or such, but I want to first focus on somehow getting a reliable pH value on a ...
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2answers
188 views

I2C sensor not detected on Raspi3

I am trying to set up a pH sensor from Atlas Scientific using a Raspi3. I am using this Tutorial to set it up. I have set the sensor to I2C as the LED is blue. The circuit is shown here. I am now ...
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1answer
57 views

digital pH indicator

Those who work in industries will understand this question better. A pH electrode has pH vs mV table will be somewhat similar to this image. Our company has a digital pH indicator showing input as -...
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1answer
304 views

dual pH sensor system

I am working on the development of a dual pH and dual Pt100 sensor interface for a fish farm tank control system. The tank is expected to have about 75m3 of water, a number of pumps, and feeding ...
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2answers
318 views

OP amp output can't go below below 1.8V

I'm kind a new in electronics so pardon me if i ask a stupid question. I'm trying to follow this schematic but i'm using op07 as buffer and LM336 as voltage reference. What happens is that the op-amp ...
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1answer
517 views

interface two wire pH sensor with arduino

I have purchased this pH/EC sensor from https://www.cooking-hacks.com/ph-sensor however it does not have a BNC connector and just two wires, black and read. How could i interface this to an Arduino? ...
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2answers
267 views

pH sensor ground loop alike problem

I experienced the same as described in this question: A AD8603 is used as voltage follower to amplify the pH sensor signal to a microcontroller. As this opamp has a single supply and thus cannot ...
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1answer
139 views

pH sensor, is the cebo-lc device suitable?

I would like to interface a pH probe. I know there are various threads on this topic. If found this two most interesting: Miceuz suggests two suitable instrumentation amplifiers (INA 116 and AD549). ...
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1answer
90 views

how to setup a ph sensor probe

I have a INA126 IN-Amp. I hope to use it with a ph probe. But I am not sure exactly how to do that. should I put the probe in series with a branch of a resistive wheat stone bridge, or just tie it to ...
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1answer
969 views

Tactics for stable unity-gain op-amp

The circuit given below is typical pH meter op-amp circuit. But here LMC6001 is not configured as unity gain. My question is this, I want to make this circuit with unity-gain buffer op-amp. What ...
3
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1answer
364 views

pH sensor project: trouble with RF interference

I built this pH sensor project on a breadboard and I'm having a big problem. The output on the voltmeter is completely erratic, and I'm pretty sure it's due to RF interference. When I connect the ...
4
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3answers
527 views

ESD protection for pH measurement electrode input

I want to puild a pH meter, which uses a normal glass electrode. Such an electrode behaves as a pH dependend voltage source (<+-500mV) with very high internal resistance (10MOhm - 1GOhm, depending ...
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3answers
1k views

Ground loop when measuring in process pH

I have been experiencing a very difficult to solve ground loop problem with my pH measuring system. My basic setup is a standard pH electrode running through an op-amp to an ADC which communicates ...
4
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1answer
532 views

Assistance with schematic notation “R@2V” for pH monitor

I've been building a circuit I found online for a pH monitor, while most of the circuit seems straight forward I get caught on the "R@2V" notation, a guess would be maybe resistance at 2 volts? I'm ...
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3answers
2k views

How do I hijack a reading from the circuit of my digital meter

I have a tri - meter (ph, ppm, temp) that reads and displays readings on three LCD screens. I'm trying to hijack the measurement at some point in the circuit and read it in through on of the inputs on ...
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1answer
1k views

pH sensor with DS18B20 temp compensation on PIC

I am trying to build a circuit that interfaces a standard pH electrode to a PIC (18F4550). I need the PIC to also use a DS18B20 for temp reading and use that data to correct the pH reading. I ...