Humidity sensor
The Smart Sense Humidity sensor is designed to indicate humidity between 10% to 90% relative humidity (R.H.). The sensor connects to any one of the analogue sensor inputs. Once connected the Smart Move software will display the name of the sensor and label the appropriate input ‘HUMIDITY’. The screen will display the current reading from the sensor.
The graph (Fig.1) shows the sensor response for a given R.H. The sensor will return readings between 0 and 255 for a change in humidity between 0% and 100% R.H but will not produce accurate readings outside the range 10% to 90% R.H. The shaded band indicates that the sensor will follow the actual humidity to within 5% R.H. The reading from the sensor can be converted to R.H. by dividing by 2.55. The Smart Move INT function can be used to indicate the R.H. to the nearest whole number i.e. PRINT INT (HUMIDITY /2.55). The sensor will typically respond to changes in humidity within 3 minutes. The sensor is designed to be used between 5°C to 40°C.
As with most humidity sensors variations in temperature will produce errors so changes in humidity should be measured at the same temperature whenever possible. Errors of up to 5% R.H. may be caused by variations in temperature between 5-40°C.
Warning
- Do not expose to temperatures outside the sensor's working range.
- Do not expose the sensor to organic solvents or vapours.
- Do not immerse in any liquid.
- Do not breathe directly onto the sensor or allow condensation to form on the sensor.
Example procedures[edit]
As a room fills with people the temperature and humidity can change dramatically. The procedure "Humid" monitors the room once every minute and prints the current temperature and humidity values. This procedure could be extended by using the STORE command to store the readings to a disk file. The data file could then be loaded into a spreadsheet and a graph of the changes produced.
Procedure: Humid[edit]
REPEAT LET a=HUMIDITY PRINT "Humidity is";a/2.55;"R.H." PRINT "temperature is";TEMP;"deg C" WAIT 60 LET b=HUMIDITY IF b>a THEN PRINT "Humidity is rising" ELSE PRINT "Humidity is falling" FOREVER
The second example "Drying" allows the action of silica gel to be observed. Place a sachet of silica gel desiccant and the sensor into a polythene bag. Seal the bag just before running the procedure.
Procedure: Drying[edit]
RESET CLOCK START CLOCK FILE 1, "Drying" REPEAT STORE 1, HUMIDITY WAIT 10 UNTIL HUMIDITY IS LESS THAN 25 CLOSE 1