User Guide

6 TDS CALIBRATION

IMPORTANT: When Calibration mode is entered, controller automatically goes into

a “HOLD” mode where the 4-20 mA output freezes and relays are de-activated (if it

was in an activated condition). Upon return to measurement mode, both 4-20mA

output and relay activities resume, depending on settings.

The αlpha TDS 190 controller includes 8 TDS measurement ranges. One-point

slope calibration is possible, in each range.

Choose fresh standard solutions, whose value is reasonably close to the

measurement value.

Before calibration, make sure electrode is clean. Use iso-propyl alcohol followed by

thorough rinsing in distilled water to clean electrode.

Important: To achieve a successful TDS calibration, two conditions must be

satisfied:

1. Difference between measured value of standard solution, and actual

value of standard solution, must be within ± 40 %.

(e.g. if value of standard solution is 1500 ppm, then allowable

measured values by controller must be within 2100ppm {+ 40%} and

900 ppm {- 40%}); and

2. The lowest possible value must be at least 10% of full scale

(e.g. if range of 0 to 100.0 ppm selected, min. measured value at

calibration, must be at least 10.0 ppm).

If any or both conditions are not satisfied, controller will display ERR 1 (blinking).

1. Press CAL / ENTER key to directly access the Calibration mode when the

unit is in conductivity measurement mode. Controller displays the value of

the standard solution.

NOTE: Instead of pressing the CAL/ENTER key, you can also enter the Calibration

mode using the password code procedure as explained in Section 5.

2. Use electrode to agitate standard solution to obtain a homogeneous solution

and to dislodge any bubbles. Allow electrode time to stabilize with solution

temperature.

3. Use ▲/ ▼keys to adjust displayed readings to the value of the standard

solution. Press ENTER.