Hach PHC281, User Manual

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Section 1 Product overview
The Intellical PHC281 series pH probes are digital, combination electrodes that measure the pH of
water samples. The probes are refillable and have a built-in temperature sensor. The probes have
good performance in low ionic strength (LIS) samples (e.g., deionized, reverse osmosis, distilled) and
other clean waters (specific conductance less than 100 µS/cm to ultrapure). The open reference
junction lets the electrolyte flow at a high rate for optimum electrical connection with the sample. The
open reference junction does not become clogged with suspended solids if used in dirty applications.
A 59-mL bottle of 2.44 M KCl reference electrolyte filling solution is supplied with the probe. Refer to
Figure 1 .
Note: Do not use the probe for measurements in organic solvents.
Figure 1 Probe overview
1 Probe soaker bottle with storage solution 5 Cable
2 Glass bulb, reference junction and
temperature sensor 6 Probe soaker bottle holder
3 Filling-hole plug 7 Electrode filling and storage solution
4 Protective tape and filling hole 8 Dispensing cap
Section 2 Specifications
Specifications are subject to change without notice.
Specifications Details
Probe type Digital combination pH probe with refillable electrolyte and built-in
temperature sensor
pH range 0 to 14 pH
pH accuracy ±0.02 pH
Reference type Ag/AgCl
Reference junction Open
Slope –59 mV/pH (90 to 110% at 25 °C (77 °F) per Nernstian theoretical
value)
Isopotential point 0 (±30) mV at 7.0 (±0.5) pH
Sodium (alkalinity) error –0.6 pH at pH 12.6 in 1 M NaOH
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