HACH - Formula for water analysis.
SensION2 Portable pH/ ISE Meter, with Platinum pH Electrode

Hach Advanced sensION2 Meters feature:

•  Large, readable digits
• Fast response to changes in pH; true pH averaging
•  All-in-one 5-pin connector, for easy determination of temperature and your chosen parameter
• Automatic buffer recognition
•  Resolution to 0.1, 0.01 and 0.001, for the right accuracy when you need it
•  Measures/ compensates temperature in ° C or ° F
• Electrode holder
•  Backlit screen
  

Specifications
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Range:
pH: -2.000 to 19.999
Concentration: 0.000 to 19, 900
mV: ± 2000
Temperature: -10 to 110 ° C
( -50 to 230 ° F)
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Resolution:
pH: 0.1; 0.01; 0.001 ( selectable)
Concentration: 0.1; 0.01; 0.001 selectable
mV: 0.1 mV
Temperature: 0.1 ° C
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Accuracy:
pH: ± 0.002
Concentration: ± 0.5% of reading
mV: ± 0.2 mV or ± 0.05% of reading ( whichever is greater)
Temperature: ± 1.0 ° C
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Output
One-way RS232 via docking station
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Inputs:
( 1) BNC; ( 1) 5-pin connector; ( 1) 2mm single-pin reference connector
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Power Requirements:
4 AA batteries or 110 to 220 Vac line power through docking station
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Input Impedance:
> 1012 Ohms
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Buffer Recognition:
Auto; 4.01, 6.86, 7.00, 10.01; or manual input
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Display: Custom LCD
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Calibration Points: pH: 1, 2 or 3 ( 1 uses previous calibration slope and adjusts offset; 2 and 3 create new slope)
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Calibration Review: User-activated; shows last calibration slope, date and time, buffers/ standards used, and mV in each
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Serial Data Output: RS232 through docking station, recall 99-point memory
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Battery Life: 6 months typical use
( approx. 500 hrs. continuous)
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Low Battery Indicator: Yes
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Dimensions 21.2 x 8.7 x 4.2 cm
( 8.35 x 3.43 x 1.65" )