ORP Calibration

[investindy]

Seen a few posts in here indicating there is a constant need to calibrate your PH sensor if you are using it for an automatic feed system so it is reading correctly. I personally have the same problem with our PH sensors we use at work for treating chemicals so they are at appropriate levels before going to the city waste system

I am a controls person so i'm automating my own chlorine dispense system I have it mostly complete but haven't integrated the feedback system. I will need an ORP sensor and a controller that allows me to have 2 setpoints (low and very low sanitizer). I found some reasonable ORP sensors and controllers I could use from the fish tank industry that has contacts I can do my controls from but was curious if they or all ORP sensors exhibit the same need to constantly calibrate as PH sensors do.

If I have to go and constantly tweak my sensor it may not be worth the cost/trouble. I will just fine-tune the daily dispense amounts on my own(flow control). Anyone have any experience with ORP sensors and caibration reliability? Anyone know of any specific low-end brands sensor/controller that are resonable????

 

[JasonLion]

With a good quality ORP sensor you only need to adjust your set point a few times a season and clean the sensor perhaps twice a season. Less expensive ORP sensors tend to fail completely in less than a season, often much less. The better quality sensors, without the electronics, seem to be running $175 to $250 this year, up substantially from last year.

Likewise, there are PH sensors in the same price range that are good for an entire season after one calibration (given that the precision required is not lab quality and can drift by 0.1 or even 0.2 without problems).