--- title: CI-340 that is reading 100% humidity description: CI-340 that is reading 100% humidity --- [Skip to content](https://knowledgebase.cid-inc.com/ci-340-that-is-reading-100-humidity#main-content) English Show submenu for translations [![CID green](https://knowledgebase.cid-inc.com/hs-fs/hubfs/CID%20green.png?width=350&height=77&name=CID%20green.png)](https://knowledgebase.cid-inc.com/?hsLang=en) Open main navigation Close main navigation - English Show submenu for translations - [Submit a Support Ticket](https://cid-inc.com/plant-science-tools/leaf-area-measurement/ci-110-plant-canopy-imager/support/#SubmitaTicket) [Submit a Support Ticket](https://cid-inc.com/plant-science-tools/leaf-area-measurement/ci-110-plant-canopy-imager/support/#SubmitaTicket) How can we help you? - There are no suggestions because the search field is empty. 1. [CID Knowledge Base](https://knowledgebase.cid-inc.com/?hsLang=en) 2. [Photosynthesis Analysis CI-340](https://knowledgebase.cid-inc.com/photosynthesis-analysis-ci-340?hsLang=en) 3. [CI-340 Handheld Photosynthesis System](https://knowledgebase.cid-inc.com/photosynthesis-analysis-ci-340?hsLang=en#ci-340-handheld-photosynthesis-system) # CI-340 that is reading 100% humidity ## How to resolve CI-340 that is reading 100% humidity CI-340 that is reading 100% humidity? It is possible that the temperature sensor and PAR sensor are disconnected or malfunctioning. If the temperature sensor is not plugged in or malfunctioning, the unit will read 100% humidity and negative VPD Similarly, after having calibrated the unit, the PAR showing zero value indicates that the PAR sensor is either disconnected or malfunctioning. If the PAR sensor is working correctly, you should be able to see movement in the PAR readings with a flashlight pointed at the unit from above. Note that the transpiration rate being 0 could be a result of the humidity sensors not reading properly (i.e., reading the same at the outlet as the inlet) Stomatal conductance will always be 0 if transpiration is reading 0, but if transpiration is reading a non-zero number and stomatal conductance is always reading 0 then that’s likely an issue with the leaf temp sensor. If the unit is stuck “warming up” and will not take measurements, there is a possibility that the unit’s pump is no longer functioning properly. You can place the unit in “development mode” to confirm the pump voltage and flow and if needed. To place the unit in development mode: Hold down the UP arrow button and then press POWER. The unit will display DEVELOPMENT MODE on the screen. Then press shift. Then press enter several times until the device powers off and back on again. The unit will display the pump voltage (VPUMP) and flow (FLOW DIFF.) with a message saying “warming up”. - [Root Analysis](https://knowledgebase.cid-inc.com/root-analysis?hsLang=en#main-content) - [CI-602 Narrow Gauge Root Imager](https://knowledgebase.cid-inc.com/root-analysis?hsLang=en#ci-602-narrow-gauge-root-imager) - [CI-600 In-Situ Root Imager](https://knowledgebase.cid-inc.com/root-analysis?hsLang=en#ci-600-in-situ-root-imager) - [Canopy Analysis CI-110P](https://knowledgebase.cid-inc.com/canopy-analysis-ci-110p?hsLang=en#main-content) - [CI-110 Plant Canopy Imager](https://knowledgebase.cid-inc.com/canopy-analysis-ci-110p?hsLang=en#ci-110-plant-canopy-imager) - [Photosynthesis Analysis CI-340](https://knowledgebase.cid-inc.com/photosynthesis-analysis-ci-340?hsLang=en#main-content) - [CI-340 Handheld Photosynthesis System](https://knowledgebase.cid-inc.com/photosynthesis-analysis-ci-340?hsLang=en#ci-340-handheld-photosynthesis-system) - [Leaf Analysis CI-202/203/710s](https://knowledgebase.cid-inc.com/leaf-analysis-ci-202-203-710s?hsLang=en#main-content) - [CI-710s SpectraVue Leaf Spectrometer](https://knowledgebase.cid-inc.com/leaf-analysis-ci-202-203-710s?hsLang=en#ci-710s-spectravue-leaf-spectrometer) - [CI-203 Handheld Laser Leaf Area Meter](https://knowledgebase.cid-inc.com/leaf-analysis-ci-202-203-710s?hsLang=en#ci-203-handheld-laser-leaf-area-meter) - [CI-202 Portable Laser Leaf Area Meter](https://knowledgebase.cid-inc.com/leaf-analysis-ci-202-203-710s?hsLang=en#ci-202-portable-laser-leaf-area-meter) - [Software](https://knowledgebase.cid-inc.com/software?hsLang=en#main-content) - [Rootsnap!](https://knowledgebase.cid-inc.com/software?hsLang=en#rootsnap) [![felix logo 8-15-2019 transparent-1](https://knowledgebase.cid-inc.com/hs-fs/hubfs/felix%20logo%208-15-2019%20transparent-1.png?width=150&height=92&name=felix%20logo%208-15-2019%20transparent-1.png "felix logo 8-15-2019 transparent-1")](https://knowledgebase.cid-inc.com/?hsLang=en) 123 Waverly Pl., Boston, MA 02135 [mailto:sales@cid-inc.com](mailto:sales@cid-inc.com) Copyright © 2024, CID Bio-Science