Ph Sensor

Is it linear.... this shouldn't matter.. the point of a control system is to control therefore your ph shouldn't vary over the 0 to 14 range, it should hunt slightly around the control level according to the hysteresis and reaction time of the control system.

(I don't think it is linear...but I don't actually know....)

I wouldn't think a Cell Phone would effect it...after all the instrumentation should meet EMI regulations.
It would be easy enough to test it..... observe the reading while someone goes near with a cell phone.
I'd be more worried about some maintenance guy using an arc welder in the vicinity!
Del

Good answer PWS. I also would also like to point out the yours was the only post that correctly used small p and capital H. pH.

It is a constant reminder that we are measuring the negative log of the hydrogen ion concentration. or a range of 1 to 14,0000,000,000,000. It seams we get lost looking through the window the instrument lets us view the process through.

How do i ensure that the Ph is varying linearly over 0 to 14 range

When I first played with pH, I also asked this question. We calibrated with pH 4 and pH 7 and assumed that the reading above pH 7 would be accurate as well.

Just to reassure myself, I had them purchase a pH 10 buffer solution. After doing the usual calibration with 4 and 7, I checked the reading with the pH 10 buffer. Watta ya know! It read correctly! It took more time to settle at pH 10 but it did read correctly.

How to adjust the slope in case of any deviation

Most pH meters I've seen have a facility for making adjustments, usually a zero and span. This can be two potentiometers or, in the case of digital instruments, a couple of buttons.

does Ph electrode show any difference in its output mv when subjected to Electromagnetic Interference

I haven't tried this with pH meters or probes but I've noticed that some instruments can be affected if the phone is right next to the instrument (the instrument's cover needs to be off too).

Hi,

As the topic is about the pH Sensor, I would like to add my question here.

We have a pH Electrode dipped in our Aqueous Washing Tank with

Ultrasonic Frequency at 40kHz and 70% of 2kW Power Rating.

Water Temperature is at 55°C ± 5°C.

My problem is the the glass sensor always breaks. We are using signet pH Electrode.

My initial thought is that, the glass breaks due to the ultrasonic wave in the tank?

Is this correct?

And is there any ways to protect the glass from breaking?

I'm also thinking of putting the sensor in-line and not in the tank itself but the cost my concern.

Any help/advice please?

Thanks..

I've used pH sensors with ultrasonic cleaning devices right next to them. The purpose of the device was specifically to keep the probe clean, not to clean anything else. I don't know precisely what the power rating of the device was but it probably wasn't 2kW.

It's possible that your pH probe isn't designed to handle such high levels of ultrasonic power. I'd advice trying a different type of probe, like a plastic lined one, instead of a glass type. Inquire from your supplier if they have any alternatives.

If I guess right, you just bought a pH probe and stuck in the tank without informing the supplier of what you were going to use it for.

Hi Vulcan,

Thanks. But the probe has been there before i join the company so i don't know the history. Now I'm trying to correct this to avoid losses and interuption to our washing line.

I'll try to get some plastic types.

I have some from mettler toledo which they say will not break coz their glass is thicker but i'm not that confident.

i'm not that confident

I wouldn't be confident either. Here's what you can do.

If they give you assurance that it will survive for, say, three months, get it in writing and have them put it in. They have to be the one to do it so that they can't claim that you installed it improperly. If it survives the specified time period, you pay them. If it breaks before that time, they take it as a loss.

We call these "trial orders". We never pay them until it proves itself. If it doesn't work, they just get their equipment back (in whatever condition it is in) and walk away with a loss. It's not applicable in all cases but it works.

Based on this discussion i would like to ask the forum members, we are actualy facing a similar situation in our factory. we are using using mettler toledo glass ph electrode which often break while removing them and dipping. this has to be done frequently to ensure correctness. Is there any alternative to this. I mean any non-contactive type ph electrode or a much rugged one other than glass.

thnx