
 | Description The YSI 6561 pH Sensor provides long life, good response time, and accurate readings in most environmental waters, including freshwater of low ionic strength.
Features Sealed gel reference eliminates refilling, saves time Carefully designed to perform under all ionic strength conditions Field-replaceable

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Details:
The YSI 6561 pH sensor features a 'long-life' sealed gel reference, eliminating the need to refill. For high-fouling applications, the 6561FG 'flat glass' sensor is available for wiped antifouling protection on the 6600EDS V2.
YSI pH sensors have been carefully designed to perform under all ionic strength conditions, from seawater with a conductivity of 53,000 uS/cm, to "average" freshwater lakes and rivers with conductivities of 200 to 1500 uS/cm, to pure mountain streams with conductivities as low as 15 uS/cm, which has historically been the most difficult medium with respect to accuracy, quick response to pH changes, and minimal flow dependence.