pH 

pH governs metal solubility and toxicity, the fraction of ammonia present in its un-ionized form, disinfection and coagulation performance, and corrosivity. Because the scale is logarithmic, a one-unit shift is a tenfold change in hydrogen ion activity.

RAECO Rents supplies pH instruments and sensors with NIST-traceable calibration included. Free ground shipping and free return shipping are included on every rental.

YSI ProDSS Multiparameter Digital Water Quality Meter
Frequently Asked Questions
Common questions about ph
How many calibration points does pH need?
Two covers most work — buffer 7 plus either 4 or 10, chosen to bracket the values you expect in the field. Use all three when the in-situ pH is unknown or when you expect readings on both sides of neutral. Buffer 7 should be included regardless of how many points you run, though it does not have to be first.
Do I have to enter the buffer values manually?
Not if you are using a standard USA (4, 7, 10) or NIST (4.01, 6.86, 9.18) buffer set — the instrument recognizes those automatically and compensates the calibration value for temperature. Just make sure the correct buffer set is selected in the sensor setup menu, because the wrong one selected is a common cause of a questionable calibration warning.
What millivolt readings indicate a healthy pH sensor?
Buffer 7 should read 0 mV plus or minus 50 mV. Buffer 4 should sit +165 to +180 mV from the buffer 7 value, and buffer 10 should sit -165 to -180 mV from it. If the span between points drops below about 160 mV, clean the sensor and recalibrate before trusting the data.
My pH sensor is responding slowly. What should I do?
If it takes more than about 90 seconds to stabilize in buffer, clean and recondition it. Start gently: a moistened lens tissue or cotton swab on the glass bulb, then carefully clear the reference junction. Escalate to a mild detergent soak only if that does not restore response.
How should a pH sensor be stored between jobs?
Moist, never dry. pH 4 buffer makes a good storage solution. If a sensor has been allowed to dry out, or has been sitting in distilled or deionized water for a long period, soaking it in buffer 4 overnight will often bring it back. Typical working life is roughly 12 to 24 months depending on how it is used and stored.
Does pH affect my other measurements?
Yes, in two directions. pH governs how much of the total ammonia present exists in the far more toxic un-ionized form, and it controls metal solubility — so it changes how other results should be interpreted. It also works the other way: the high ionic content of pH buffers causes real but temporary drift in ammonium, nitrate and chloride sensors, so plan the calibration order around that.
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YSI ProDSS Multiparameter Digital Water Quality Meter
Water Quality Meter

YSI ProDSS Multiparameter Digital Water Quality Meter

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