How can I assure I get accurate TDS readings?

“Refer to your TDS device manual for detailed instructions and remember that TDS meters can vary. Shake:
Always make sure to shake excess water off the meter before dipping it into a water sample, even if it’s the same water.

Stir/tap:
After dipping the meter in the water, always lightly tap it against the side and stir the meter to remove any lingering air bubbles or electrical charges.

Positioning:
When taking the reading, always make sure to hold the meter straight up without it touching the sides or bottom of the glass/beaker/cup. The probes should be suspended as close to the center of the water sample as possible.

Time:
The longer the meter is in the water, the more accurate the reading will be.

Temperature:
25 degrees Celsius is the ideal temperature for conductivity readings, even if the meter has ATC.

Rinse:
If switching between very low and very high ppm water, always rinse the probes with distilled water to avoid any build-up.”