Checking Calibration - Omega RH650 User Manual

If the primary readout shows 0.0% with the meter in your hand (and not touching anything), the
meter is ready to make measurements. To measure the moisture level of a material, press the
pinless sensor on the back of the meter (Fig. 1, Callout L) against it. The moisture level, as
percentage, will appear on the primary readout.
If the primary readout shows a value other than 0.0%, you should reset the baseline of
measurements in MOIST INT mode. To do so, continue to hold the meter in your hand (touching
nothing) and press the ZERO button. Immediately after the term ZERO appears briefly below the
bar graph at the left of the display, the primary readout will show 0.0% and the measurements
will again be accurate in MOIST INT mode.

CHECKING CALIBRATION

Although you cannot calibrate the RH650 yourself, you can check the meter's calibration
periodically to assure yourself of the accuracy of humidity-related readings (RH, absolute
humidity, dew point and mixing ratio). Factory calibration should minimize the humidity sensor's
drift for several years—well beyond the warranty period.
At a minimum, a calibration check should entail immersing the slotted structure protecting the
humidity sensor in two bottles containing saturated salts. One reference salt should produce a
reading of a 33%; the other should produce a reading of 75%.
Depending on the size and shape of the calibration salt bottle that you use, you may have to
remove the hanger tab (Fig. 1, Callout B) from the meter to provide sufficient clearance for the
bottle to fit snugly over the slotted structure protecting the humidity/temperature sensor (after
removing the dust cap). The hanger tab is removable for that reason.
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To obtain accurate readings in MOIST INT mode, you should reset
the readout to 0.0% each time you re-enter that mode from
another mode.