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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2answers
54 views

Using multiple sensors on the same i2C circuit

It’s possible to control multiple pH probes with one single i2C ph circuit (like this https://www.atlas-scientific.com/product_pages/circuits/ezo_ph.html) ? Rather than buying I2C circuit for each ...
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Why does an ISFET need a reference electrode?

I'm trying to understand why an ISFET needs a reference electrode. I have looked up several answers online but still dont understand. I have drawn out the doping, a MOSFET and the ISFET: In my mind, ...
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95 views

pH sensor voltage versus pH

I am currently in the process of making an ultra-low power pH captor and I'm running in a problem. The voltage I get from my pH probe does not fallow the Nernst equation (which states that the voltage ...
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117 views

pH measurement in cascaded tanks — Ground loop

I am doing a mini waste water plant with cascaded PVC tanks (and PVC fittings) for my university project. Each tank has a mixer (the motor is grounded). I made a pH amplification PCB which works with ...
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472 views

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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161 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
139 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 ...
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1answer
419 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
91 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
143 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,...
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1answer
205 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
254 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
217 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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602 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
80 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
11k 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
208 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
58 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
355 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
361 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
543 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
335 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
154 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
95 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
1k 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 ...
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1answer
396 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 ...
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3answers
566 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 ...
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1answer
590 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 ...