(a) Set range switch to S (internal standard).
(b) Remove bottom plate to gain access to master calibration control.
(c) Press indicator button and hold it in.
(d) Adjust the master calibration control with your finger until meter reads same as the value
stamped on the bottom plate for the water you will be treating (442 for fresh water and NaCl for seawater).
(e) Release indicator button.
(f) Replace bottom plate.
(3) Recalibration instructions for meters with only 442 internal standard stamped on bottom
(a) Obtain a standard sodium chloride (NaCl) solution and note the ppm (parts per million)
value printed on bottle.
(b) Remove snap-in disc on bottom cover of TDS meter to gain access to the master
(c) Rinse cell cup three times with the standard sodium chloride (NaCl) solution, then fill
(d) Set range switch to the 1000 scale.
(e) Press indicator button and hold it in.
(f) Adjust the master calibration control until the meter reads the value on solution bottle,
then release indicator button. Remember to multiply meter reading by 1000.
(g) Set range switch to S (internal standard).
(h) Press indicator button, and hold it in.
(i) Note the dial reading and write it down for future reference, then release indicator
button. This value is the internal standard for a sodium chloride (NaCl) solution.
(j) Replace snap-in disc in bottom cover.
(4) Calibration Check:
(a) Set range switch to S (an internal standard).
(b) Press indicator button. Read the 0 to 5 scale to the nearest tenth.
(c) For fresh water, meter is ready for use if it matches the 442 ppm internal standard
marked on bottom plate. For seawater or brackish water, meter is ready if its reading matches the NaCl internal
standard, which if not stamped on bottom plate, was noted in step (3)(i).
(d) If reading is not the same, notify unit maintenance to replace TDS meter.
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