Teledyne 4220 installation and operation guide Flow Meter Options and Accessories

4220 Flow Meter

Section 5 Options and Accessories

pH measurement is affected significantly by temperature, like any other chemical reaction. Consequently, temperature compen- sation is provided. in the flow meter. The Isco pH probe has a built-in temperature sensor that is exposed for faster response.

The pH probe connects to a Parameter Module that plugs into the Parameter Port on the flow meter. The probe has a 25 ft. (7.6

m)cable. For greater distances, contact the factory. The maximum distance between the module and the flow meter is 1,000 ft. (304.8 m).

When the ion-selective electrode and the reference electrode are connected to a high-impedance voltmeter and submerged in sa olution, ions move to the surface of the membrane. The electrical charge on the ions creates a potential difference across the barrier between the solution and the membrane. This potential, or voltage difference, is proportional to the activity of the ions in the solution.

The potential, when read by a sensitive voltmeter, translates into a reading of pH. With an Isco flow meter, the voltage is sent first to a preamplifier inside the probe to reduce the impedance of the circuit and improve the signal-to-noise ratio, and then on to the parameter module to allow greater operating distance from the flow meter. The flow meter determines the pH value and displays it.

5.9.1pH Probe Calibration The 4220 provides a two- or three-point calibration for the pH probes with commercially-prepared calibrated buffer solutions. Calibrations of 4 and 7, 7 and 10, and 4, 7, and 10 are all pos- sible. For accurate readings you must clean and re-calibrate the probe on a regular basis. How often you need to do this depends on the condition of your flow stream. Flow streams with a high grease content will coat the sensing surfaces of the probe quickly, clogging them and slowing the response time or stopping it alto- gether. Installation in very greasy flow streams is not recom- mended.

Note

For pH probe calibration, Teledyne Isco recommends that you use a glass container for the buffer solutions to ensure that the following conditions are met:

The probe must be properly submerged in solution, and there must be no air trapped under the probe membrane, or the reading may become incorrect and/or erratic.

Do not touch the probe until after you have performed step 6.

1.To calibrate the pH probe with the flow meter, first go to program Step 1: PROGRAM, SETUP. Select PROGRAM.

2.Step through the units of measure with the Enter key until you reach the menu that says pH UNITS - NOT MEASURED, pH. Select pH. You must do this in step 1 or the pH menu will not appear later.

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