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SC-1
4. SERVICE
This section contains calibration and recalibration information, calibration frequencies,
cleaning and maintenance guidelines, troubleshooting guidelines, customer support contact
information, and terms and conditions.
4.1 CALIBRATION
For the SC-1 to make accurate readings of stomatal conductance, the two RH sensors in
the sensor head must behave in a very repeatable manner. The sensors occasionally change
characteristics over time. While the endpoint RH measurement may still be accurate, the
response time of the sensors can change subtly which creates inaccurate conductance
measurements. The best way to ensure accurate conductance measurements is to verify
the accuracy of the SC-1 before taking measurements (Section4.1.1) and calibrate if
necessary (Section4.1.2). The SC-1 may also need recalibration if there are drastic changes
to environmental conditions or if the sensor head is used on an alternate handheld.
4.1.1 VERIFICATION PROCESS
METER recommends verification before every day of use or for every different set of
environmental conditions (e.g., >15 °C temperature change). Also verify the accuracy of the
SC-1 after the desiccant chamber is installed or removed.
Use the following steps to verify porometer performance.
1. Allow the sensor head, DI water, and calibration plate to come to thermal equilibrium
with the measuring environment.
For example, moving the SC-1 from an air-conditioned environment into field conditions
can take 10 min or more to reach equilibrium. A calibration block or bottle of DI water
that has been kept in a pants pocket or hand for extended periods of time will also need
time to reach equilibrium.
Holding the sensor head in the correct manner during verification is very important
for maintaining thermal equilibrium. Figure43 illustrates the correct way to hold the
external sensor.
Figure43 Holding the sensor head
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