Pinpoint vs. Milwaukee ORP Probe

[mstgkillr]

I've been running the red Pinpoint ORP probe on my Hydros system for close to a year now. Before I added ozone, the ORP usually hovered around 350 mV. However, I noticed that the readings could swing quite a bit (250 to 450 mV) depending on whether I moved or cleaned the probe. That made me start to question the consistency of the readings.

A few weeks ago, I added a Poseidon 200 ozone generator to my 210-gallon display, running it at level 5 for 15 minutes every hour. Shortly after starting ozone, the Pinpoint probe reading jumped up to around 400 mV.

Given that the Pinpoint probe was about a year old and already showing some questionable behavior, I figured it was time to try a new one. I recently picked up a Milwaukee MA21B/2 double junction ORP probe and installed it three days ago. It's already stabilizing a bit, but I'm seeing some odd behavior, it's reading much lower than the Pinpoint, hovering around 126 mV, and trends inversely to pH. Meanwhile, the Pinpoint is now reading 416 mV.

I have calibration solution on the way, but I wanted to reach out to see if anyone has run into similar discrepancies between ORP probes, especially between these two brands. Could this just be a calibration or break-in issue with the new Milwaukee, or is one of them possibly faulty?

Any input or tips are appreciated!

 

[KrisReef]

I don't have probe comparison experience, but I do think that ozone in the water could easily create confounding results if the probes are downstream of the ozone in the sump.

Maybe post a picture or diagram of the system to help others see what is happening in the sump.

Otherwise, bump!

 

[mstgkillr]

I don't have probe comparison experience, but I do think that ozone in the water could easily create confounding results if the probes are downstream of the ozone in the sump.

Maybe post a picture or diagram of the system to help others see what is happening in the sump.

Otherwise, bump!

Both the probes are in the same holder, upstream of the ozone reactor.

 

[mstgkillr]

I received a fresh pouch of the Pinpoint 400 mV ORP/Redox reference solution and did a quick check. The older Pinpoint probe read 502 mV, and the new Milwaukee probe came in at 414 mV. I didn’t adjust any offsets or attempt to calibrate, just a straight 20-min dip into the solution.

After returning the probes to the probe holder, the old Pinpoint dropped to 482 mV, but the Milwaukee dropped significantly to 164 mV.

From what I can tell, the old Pinpoint seems to be reading on the high side, while the Milwaukee may be reading low. I’ve got a brand-new Pinpoint probe on the way.

Curious to hear if anyone else has seen similar discrepancies between different ORP probes or has advice on interpreting this kind of variance. Thanks in advance!

 

[X-37B]

I received a fresh pouch of the Pinpoint 400 mV ORP/Redox reference solution and did a quick check. The older Pinpoint probe read 502 mV, and the new Milwaukee probe came in at 414 mV. I didn’t adjust any offsets or attempt to calibrate, just a straight 20-min dip into the solution.

After returning the probes to the probe holder, the old Pinpoint dropped to 482 mV, but the Milwaukee dropped significantly to 164 mV.

From what I can tell, the old Pinpoint seems to be reading on the high side, while the Milwaukee may be reading low. I’ve got a brand-new Pinpoint probe on the way.

Curious to hear if anyone else has seen similar discrepancies between different ORP probes or has advice on interpreting this kind of variance. Thanks in advance!

I run the Milwaukee orp probe and controller. Probe is in the return where the skimmer is and the probe is stable.
I run the Posiedon at level 3 and my system is 150g's.
What I have found is you need to use cleaning solution and a brush to clean the probe once a month.
Any time you clean the probe the orp will fall due to the probe being clean. I just verify with the 400 standard and it's always within 20-30mv which is close enough for me.
I run 24/7.

 

[mstgkillr]

I received the new Pinpoint ORP probe on Tuesday, so it has had 5 days to settle. Unfortunately, now I have three ORP probes that all read something significantly different.

• 12-month old Pinpoint ORP = 495
• New Milwaukee MA21B/2 ORP = 170 mV
• New Pinpoint ORP = 325 mV

I assume the older Pinpoint ORP needs to be replaced, but which one of the new probes is accurate? The new Pinpoint seems to be the closest to expected readings.

What to do now?

 

[X-37B]

I received the new Pinpoint ORP probe on Tuesday, so it has had 5 days to settle. Unfortunately, now I have three ORP probes that all read something significantly different.

• 12-month old Pinpoint ORP = 495
• New Milwaukee MA21B/2 ORP = 170 mV
• New Pinpoint ORP = 325 mV

I assume the older Pinpoint ORP needs to be replaced, but which one of the new probes is accurate? The new Pinpoint seems to be the closest to expected readings.

What to do now?

What do they read in the standard?

 

[mmorrison55]

What ever became of this? Did the OP figure it out or just gave up worrying about Orp?

Im kind of in the same boat with my Neptune apex probe. I may need a new or ori may have something else going on like electrical interference due to a power cable crossing the Orp probe wire somewhere along the route.

I was recently concerned as I to run ozone, and I noticed my reading for Orp on the apex was getting close to 450. I thought maybe due to a dirty sump where the probe resided, so I cleaned the sump and did a 20% water change and the Orp reading went way down to around 265 for a few days, but now has jumped back up (overnight) to 400.

Possible that it took it a few days to settle after the sump cleaning and water change? Idk… maybe… and my reading is accurate and i actually went from 450 to 400 after the cleaning vs the 450 to 265 that I got immediately after the cleaning.

I did order a pouch of the 400mv pinpoint solution and I guess I will wait and test the probe and decide if I need a new probe.

Note, I bought this apex system second hand and have no idea how old the probes are. I’ve been using it almost a year, so I’d guess they are at least 2- 4 years old.

 

[reefernc02]

Milwaukee all the way