Humidity Sensor Protocol

Materials and Equipment Needed

  1. Deionized water
  2. Replacement wicks (shoelaces-the round kind that are hollow in the middle after the end is cut off)

Safety Issues

Use caution when working with chamber parts underneath the chamber floor as some of the metal edges are sharp.

Time Required

5-15 minutes depending on problem

Procedure

Step Image
The growth chamber determines relative humidity by measuring the temperature difference between wet and dry bulb thermometers.  The wet bulb sensor is covered by a wick kept wet with deionized water.

The chamber reads 99 when the wick dries out.  The chamber then begins heating (not good for thrips or plants). 

Possible reasons the wick may have dried out are 1) the deionized water is off, 2) the deionized water line to the sensors may be plugged, 3) the wick may be old. 

Check to see if the deionized water is working at the sink in the growth chamber room.  If not working, notify a graduate student or the greenhouse staff and wet the wick with water from a beaker.  Check on the chamber frequently until the water is back on.
To locate the humidity sensors, remove the front section of the chamber floor.
Remove the fan and cover (chambers 1 and 2) or the lid on the sensor container (chamber 3).
Open water flow valve (on left in photo) to flush out debris, then return water to a drop by drop flow (chambers 1 and 2) or depress float valve (chamber 3).
If the wick appears to be old or slimy, or none of these steps fixes the problem, notify Daniel.