Pessl Instruments iMETOS - Temperature and Relative Humidty Sensor; Maintenance; Troubleshooting

iMETOS Maintenance & troubleshooting 7
5. TEMPERATURE AND RELATIVE HUMIDTY SENSOR
5.1 Maintenance
The temperature sensors of iMETOS are free of any maintenance as long as they are used in a proper way
and the cables are not damaged. Long-term stability is better than 1 %RH per year. Depending on the condi-
tions of measurement, the lter should be checked from time to time. Corroded, discolored or clogged lters
should be replaced. Applications where the probe is exposed to contaminants may require more frequent
verications. The relative humidity sensor is aected by pollution in dependence of the severity of the pollu-
tion. It is recommended to recalibrate the sensor based on the type of application, in particular:
• In scientic research studies every 2-3 years.
• In agricultural application, every 5-8 years. Keep the readings checked, under frequent copper sprays it
may give inaccurate high readings after some years of use.
In this case the sensor has to be changed for a new calibrated one. Recalibration can be done through Pessl
Instruments and it means to receive a new calibrated sensor head and to send back the replaced one. Be-
fore request for calibration please check, if the lter covering the sensor element is clean. If it is dirty at your
glance, a new lter can be ordered (order no. A660622).
Radiation shield: (aka: convection cup) must be cleaned at the beginning of the season. At least three lamel-
lae (plates) must cover the top of the sensor.
5.2 Troubleshooting
• RH always 100% (long periods): replace the lter or clean the lter, replacement lter available with ord. no.
A660622. It can also be checked by looking at the leaf wetness data.
• RH drops down to 0%: sensor is damaged by condensated water: replace the head of the sensor.
• iMetos 3.3 no data of Temperature, RH, dew point and Serial Number: cable is damaged, change the cable
and check the sensor.
• Head/Sensor replacement of old HC: If it has a metal ring between sensor and cable you can change just
the head. If it is plastic than it is the HC1 and you have to change the sensor and the cable. If it is an iMe-
tos1, you need a new HC + cable + voltage converter. iMetos 3.3 works only with HC2.