Correcting Continuous Data Accumulation

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Instructions for correcting continuous data accumulation.

On occasion, the LI-3000C Portable Leaf Area Meter may continuously accumulate values. This may happen while nothing is inside the Sensors Head. There are a few things to check to try and correct this irregular behavior. See the suggestions listed below.

Check the rubber strip along the front edge and ensure that it’s not leaning over the front area where the LED and Sensors are. If it is not over this area, then this is probably not the problem. It would need to be torn or extremely bent to be in the path of the LED's, but it is certainly possible.

It is more probable that there is some dirt and/or debris somewhere along the LED and/or Photodiode Sensor strip. Specifically examine the two corners of each window strip. It is fairly common for dust to collect in the little grooves on the end soft hose strips (essentially where LED/Sensor #1 is located...and where #128 is located). Make sure that the entire strip is clean; otherwise it will accumulate 'area' randomly.

Similarly, examine the window strip on the base of the Head. Again examine the two corners of the window strip. Check for dust in the grooves on the each end of the strip (essentially where LED/Sensor #1 is located...and where #128 is located). Make sure that the entire strip is clean; otherwise it will accumulate 'area' randomly.

Remove the seven (7) screws from the top cover of the Head to access the internal components.

The Encoding Cord is the black 'cord' that is pulled to make the Encoder Wheel for measurements. It is possible that an older thread will lose some of its coefficient of friction with the wheel. If this is the case, then it may not turn the encoder wheel very evenly, and my sometimes be slipping rather than spinning. A new length of this cord (LI-COR part number 214-17616) can be ordered to replace it.

Check that the Encoding Wheel is spinning smoothly when the cord is pulled. If not, test to see if this is because of the 'Encoder Wheel' itself or due the 'Take Up Reel'. Unwrap the thread from around the Encoder Wheel. Now that the Encoder Wheel can spin freely, give it a spin. Twist it and see if it spins around easily in both directions. Without much force, this should easily spin the Wheel. If it does not, there may be something in the Encoder Wheel's bearings that is not allowing it to spin easily.

If the previous test works well and the Encoder Wheel spins nicely, then the problem is probably with the Take Up Reel. This is a spring-loaded wheel and has been known to fail over long periods of usage. This is a replacement kit that is user serviceable. It is possible to replace this if working with tools and small parts is not a problem. This part can be ordered from LI-COR and shipped for replacement.

Progressing through the steps above may locate the LI-3000C’s problem. If not, then the issue may be with the Cable connection between the Console and the Head. Occasionally a wire within the cable may break due to strained cable movements and needs to be reconnected. This usually happens where the Cable connects to the Head. This is not so easy to repair, so we would recommend a return trip to LI-COR to fix this.

If it is not feasible to perform these troubleshooting steps, the instrument can be returned to LI-COR for the Factory Technicians to service and repair. Contact LI-COR for an RMA number to ship the instrument back to us.