I need to build a ph monitor. In the past I have done this with isolation transformers because of interference from from things like pumps and other electrical devices that share same commons.
The noise from waterpumps would cause issues with readings. The isolstion transformers helped tremendously but it still resulted in fouled electrodes.
I need only to analyze ph of liquid solution once my automated system mixes solution, 1 or 2 times a day.
I need to come up with a solution to get stable reading from my ph sensor board. It uses analog 0-5v. I was thinking about using a battery that charges/stays charged when arduino/esp CPU is in "sleep" mode. I would need the device to awake during a mixing event
switch power battery - take reading- send reading through optoisolation or wirless communications.
I am open to suggestions. Also I would have to figure out how to use interrupt without a galvinic connection.
I'm looking for suggestions how to create this module. Thanks
We use the products from Atlas Scientific. They are a bit expensive, but they "just work" when plugged together. Useful when you want to get on with the research rather than messing with hardware. We use the T1 for isolation of a collection of sensors. For isolation products see.. https://atlas-scientific.com/electrical-isolation/
I am trying to look at the schematic for the T1. i would like to see how it isolates the signals. from the picture it looks like it may be using isolated serial. I am concerned with the circuit sharing the same ground path as the pumps or other electronics in the liquid mixture. I may be wrong but wouldn't this at minimum require an AC isolation transformer? Even isolation transformers that provide isolation up to 100Mohm there will still be noise because of transformer coil saturation creating induction etc.
when i build this module im concerned with stable vRef signals for adc. I think pH probes are in the Mohm range. so a slight fluctuation in ref voltage would cause big drifts.
Maybe i should have posted this in General Electronics
I need a plan to get stable readings. im not sure that module can do it because there's no schematic for the circuit. The company don't mention how the isolation/where the isolation is provided.
I think battery power would be fool proof IF i can figure out how to get a very stable adc when CPU is on battery power.
Lets not forget temp compensations because of how sensitive these electrodes and opamp circuits are. I need some guidance lol
I dont understand how a DC-DC convert could be enough isolation for a pH sensor amp. Do they provide galvanic isolation? i have used these isolation modules when i used more than one sensor.
Is there another way to galvanically isolate the sensor/signal GND from the pumps/other electronics. I have not left any details about how the pumps are powered sorry.
The pumps are powered by 120vac so are other things in the solution. I think the only way for the signal ground to be isolated from PWR/120vac is to power the ph module with a transformer or a battery?
Are you talking about the T1 boards? or just in general. I really would like to use my own pH modules. Ill have to dig them out and get the model#. but the look like these exactly
If your talking about the T1 then i know what you mean the dc-dc converter gnd has to be isolated
I use a dual channel opto relay to isolate my EC and TDS sensor so the can work in close proximity as they conflict with each other, the schematic for the PH sensor is on page two Hydro-motherboard-schematic, its just a LTV-827 and a resistor, and they are rated for 40Ma and the module use 10Ma and my PCB has been working fine for years.
The Tentacle T1 uses a si8600 for signal isolation and an r1se isolated dc/dc converter for power isolation. The probes and signal conditioning electronics are totally isolated from the rest of the system.
But the device is NOT isolated "totally" unless you use a battery. You still have to power the dc -dc converter. You could power the dc dc with a battery and that would provide good isolation. Even ac isolation transformers don't provide perfect isolation.