PH meter

[Steve_hi]

Looking for schematic and parts list to make pH meter capable of measuring 0 to 14 ph preferably with a 12 vdc power supply Thank you

[audioguru]

Hi Steve,
Look in Google for pH Meter Circuit. There are plenty.

[Steve_hi]

I have one but there are some parts that when i try to order them from futurlec they dont seem to have them there are all kinds of resistors that dont have the same values and a diode too

[audioguru]

Digikey and Newark would have the parts.
1) The opamps are Cmos from National Semiconductor.
2) The "diode" is actually a 2.5V voltage reference IC that is much better than a zener diode.
3) The resistors have 1% values.

[Steve_hi]

I checked digi key for part LM4040D1Z-2.5but they have no listing for it is there some thing that could be substituted for it

Also the resistors that are listef for sale do not match those asked for by the schematic what does one do for this situation choose the closest one to it or is there a different solution.
Thank you

[Steve_hi]

also it is asking for 100k resistor + 3500 ppm Note 12
style 144 I dont know what this means

[audioguru]

Digikey has thousands of LM4040 2.5V reference ICs in stock. In different packages and from different manufacturers. Enter LM4040 in a search then enter 2.5V.

Didn't you see the entire pH meter project on the datasheet for the LMC6001 IC? It tells you all about pH and why R1 is a temperature compensating resistor. I don't know where to get R1.
The datasheet also tells you how to setup and calibrate the circuit.

[Steve_hi]

A suggestion for new projects to whoever is responsible for this department!!

A pH-METER
Thanks

[audioguru]

Hi Steve,
Anybody can post a project.
Why don't you?

[Steve_hi]

I didn't know I could!  I will try to figure out how,  get it ready and do it.
Thanks  :)

[audioguru]

Design a circuit or steal it from another site or from a datasheet.
Make a clear schematic, parts list and description about its parts and how the circuits works.
Then see "Publish Your Circuit" instructions on the Home page.