Hach EC1000, Инструкция по эксплуатации

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1.4 Hach One Process pH Electrode
The Hach One pH Electrode features a continuous, free-flowing reference junction to
assure a constant long-lasting reference potential. The electrode contains a replaceable
pH glass sensor (in bulb or flat configuration) a reference half cell, a temperature sensor,
and an internal preamp. The internal preamp produces two current loop signals, one for
mV and the other for temperature. The preamp allows for up to 1000 feet of separation
between the electrode and meter, and is operable up to a depth of 40 feet. The
electrode housing works in any of the sample handling systems described in Section 1.7
Sample Handling System.
1.4.1 Sodium Error
Acid error is negligible; negative sodium error, usually present in alkaline solutions, is low
even at pH values as high as 12. To determine the sodium error in pH units, measure the
apparent pH and sodium concentration of the test solution and determine the error from
Figure 3. Locate the point (on the appropriate pH horizontal grid line) representing the
sodium concentration based on the extrapolation between the 229, 2,290, and
22,900 = mg/L Na plots. Add the vertical grid line at that point to the apparent pH meter
reading. For example, a sample that reads pH 12 with a Na+ concentration of 0.5M has a
negative sodium error of approximately 0.12 pH units. Therefore, the actual pH of the
sample is 12.12.
Figure 3 Sodium Ion Error Graph
1.5 Hach One ORP Electrode
The Hach One ORP Electrode also features the continuous, free-flowing reference
junction, a temperature sensor, and a preamp. It is housed in the same electrode body as
the pH flat configured electrode (see Figure 4 on page 22). The replaceable sensor is a
Platinum disc sealed in glass. Select the mV readout for ORP applications.
TYPICAL SODIUM ERROR FOR
HACH ONE COMBINATION pH
ELECTRODE (AT 25 °C)