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Meteorological Instruments SLC Module D5 RECORDING THERMOMETER -IDENTIFY AND KNOW PURPOSEThe bimetallic coil contracts and expands with changes in temperature which causes the pen to move accordingly. The timer drum moves around slowly so that a week of temperature recordings can be made by the pen on the circular paper chart. SOIL THERMOMETER -IDENTIFY AND KNOW PURPOSEThe soil thermometer consists of a strip of two metals (e.g., brass and steel) which have different expansion rates when heated. Because they are connected lengthwise, this differential expansion of one metal vs. the other causes the strip to coil or bend, and this movement is registered by the pointer on the dial. SOIL THERMOMETER -IDENTIFY AND KNOW PURPOSE- The soil thermometer is typically inserted 4 inches into soil where it instantaneously reads the temperature of the soil. VOLTMETER WITH THERMOCOUPLE -IDENTIFY AND KNOW PURPOSE- The two small wires, when paired, form a “thermocouple”, and measuring the voltage difference across the two wires yields a temperature measurement when you convert voltage to Celsius (can be done using a standard table). VOLTMETER WITH THERMOCOUPLE -IDENTIFY AND KNOW PURPOSE- Thermocouples are commonly used in research and industry because they are accurate, cheap, and extremely durable. They can be used in relatively corrosive and/or extreme temperature applications. MINIMUM-MAXIMUM THERMOMETER -KNOW HOW TORead Current Temperature, Read Maximum and Minimum Temperatures. MINIMUM-MAXIMUM THERMOMETER The probe is meant to be used under normal, non-extreme conditions The tip of the probe contains a thermistor which consists of an electrical resistor that changes resistance based on temperature. This change is transduced into the temperature reading on the LED display. MINIMUM-MAXIMUM THERMOMETER (Readout) Current Temperature: Ambient with Probe attached Record of Maximum Reading Record of Minimum Reading Alarm Control Normal/Alarm Mode Selector MINIMUM-MAXIMUM THERMOMETER (rear control panel) In Normal Display Mode Use to reset either MIN or MAX Fast Sampling Rate = 10 sec Normal Sampling Rate = 60 sec Select Temp Scale Displayed In Alarm Display Mode Use to reset either LO or HI MINIMUM-MAXIMUM THERMOMETER (reset unit) Insert a slender object and push RESET gently. Necessary to do this whenever a change is made between oC/oF, FAST/NORMAL, Probe inserted/removed. Note that HI/LO alarm settings and MIN/Max readings will be cleared! YSI TELE-THERMOMETER WITH PROBE -KNOW HOW TO- Identify and Operate The YSI Tele-Thermometer also uses a thermistor probe for measuring temperature. This measurement device is the analog version (or older version) of the MinimumMaximum Thermometer, and it just indicates the current temperature without recording previously measured Min or Max temperatures. YSI TELE-THERMOMETER WITH PROBE -KNOW HOW TO- Identify and Operate The probe cannot be submerged or placed in corrosive environments. YSI TELE-THERMOMETER WITH PROBE -Taking a Reading Start to take a reading by turning the knob to the port # the probe is inserted in (in this picture, #1) YSI TELE-THERMOMETER WITH PROBE -Taking a Reading Then, turn the knob to the minimum part of the 10°C range the probe is measuring For example, if the temperature the probe is measuring is 23°C, then the knob should be turned to “20°”, and the pointer will point to “3” YSI TELE-THERMOMETER WITH PROBE -Taking a Reading If the temperature the probe is measuring is 23°C, the pointer will point beyond 11 when the knob is set to “0°”or “10°”, indicating that you’ve set the knob too low and the actual temperature is higher. The pointer will point to 0 or farther left when the knob is set to “30°” or “40°” and the actual temperature is 23°C. RADIOTRANSMITTER -IDENTIFY AND KNOW PURPOSE- The transmitter emits sound pulses (‘chirps’) at a particular wavelength, and the frequency of the pulses is correlated with temperature. Thus, you can measure the temperature of things remotely by tracking the frequency of emitted pulses with a receiver when the transmitter is inside something or glued onto something, etc. Temperature (°C) # Chirps Per Minute THERMOHYGROGRAPH -KNOW HOW TORead Relative Humidity and Temperature for Given Time and Day and Convert to OC. [OF-32] X 5/9 = OC [OC X 9/5] + 32 = OF THERMOHYGROGRAPH A length of hair (typically blonde human or horse hair) expands or contracts in reaction to changes in humidity. The hair is connected to one end of a pen arm through a series of levers, and the expansion or contraction causes the pen to move up or down with respect to humidity changes. A bimetallic coil consists of 2 joined metals that expand or contract slightly differently from each other when temperature increases or decreases, respectively. These relative changes in the metals cause the coil to expand or contract and make the pen move up or down accordingly to indicate temperature changes. THERMOHYGROGRAPH (Details of chart recorder) The drum can be wound to make one complete revolution over the length of 1 week Temperature Scale Relative Humidity Scale The top strip records the measured temperature in °F for one week. The bottom strip records the measured relative humidity in % for one week. Example Thermohygrograph Chart AU 70 THERMOHYGROGRAPH (Details of chart recorder) Temperature Scale Note that the temperature scale is in °F. Be aware that you may need to convert to °C. °C = 5/9 x (°F – 32) °F = (9/5 x °C) + 32 BENDIX PSYCHROMETER -KNOW HOW TORead Wet and Dry Bulb Temperatures and, from the TRe Diagram, Determine % Relative Humidity and Dew Point Temperature BENDIX PSYCHROMETER Please Note: The Wet and Dry Bulb Thermometers are on the side (instead of the top) of the new Bendix Psychrometer. BENDIX PSYCHROMETER Wet Bulb Thermometer (covered in cloth sleeve that can be wetted) Dry Bulb Thermometer The Bendix Psychrometer has an internal fan that is turned on by rotating the knob clockwise one click. The benefit of the internal fan is that the device can be used to measure humidity in enclosed spaces. BENDIX PSYCHROMETER The Wet Bulb Thermometer measures the temperature reached after forced evaporation from the wick. The fan creates air movement which speeds up evaporation. Drier air results in lower wet bulb temperatures. The Dry Bulb Thermometer measures ambient temperature. Taking a Reading: 1. Wet the sleeve of the wet bulb thermometer 2. Turn knob clockwise to turn on fan. Leave Bendix Psychrometer standing upright so that fan does not hit the sides of the device. 3. Leave fan on until wet bulb temperature has stabilized (~1 minute) Taking a Reading: 4. Record the value of the Wet Bulb and Dry Bulb Thermometers. 5. Turn off fan by rotating the knob clockwise one click. Psychrometric Slide Rule Taking a Reading: 1. Now use a Psychrometric Slide Rule to convert Wet Bulb and Dry Bulb Temperature readings into Relative Humidity. 2. Line up the Wet Bulb and Dry Bulb Temperatures on the left-hand side. 3. Then look over to the right-hand side at where the arrow points on the “Per Cent Relative Humidity” scale. Wet Bulb reading = 15.0oC Dry Bulb reading = 22.5oC Relative Humidity = 43% TRe Diagram You could alternatively use a TRe Diagram to convert Wet and Dry Bulb Temperature measurements into Relative Humidity. You can also use the TRe Diagram to convert Dry Bulb and Relative Humidity measurements into the Dew Point Temperature. TRe Diagram Constant Relative Humidity curved lines Constant Temperature vertical lines Constant Vapor Pressure horizontal lines *Note that the “100% sat curve” is the curved line for Dew Point. To find Relative Humidity, take your Wet Bulb Temperature, for example, 70°F, and follow that vertical temperature line up to the “100% sat curve”. Then go from the point of intersection downward and to the right – parallel with the black guide lines – until you hit the Dry Bulb Temperature vertical line at, for example, 80°F. Finally, read the curved Relative Humidity line at the point of intersection which, in this example, is 60%. Another Example: Your Wet Bulb Temperature is 15°C. If your Dry Bulb Temperature is 25°C, then your Relative Humidity is… 31%. Dew Point: To obtain the Dew Point, start with the measured Dry Bulb Temperature, for example, 80°F. Move up vertically along the Dry Bulb Temperature line until it intersects with the measured Relative Humidity curved line, for example, 60%. Then move horizontally to the left along a line of constant vapor pressure until you hit the curved “100% sat curve”. Drop straight down to the x-axis, and this value is the Dew Point in °F or °C. In this example, 64 °F. SLING PSYCHROMETER -KNOW HOW TOIdentify The Sling Psychrometer is a method of measuring Wet and Dry Bulb Temperature, and, hence, Relative Humidity and Dew Point, that does not require a battery. Dry Bulb Wet Bulb The thermometers have been removed from the example Sling Psychrometer in the SLC, but the essential principles of its function were demonstrated already for the Bendix Psychrometer. The Sling Psychrometer cannot be used in enclosed spaces because it uses a spinning, or “slinging” motion to increase the wind speed across the Wet Bulb and speed up evaporation. You must wet the sleeve (or put water in the reservoir at the base of the sleeve) before slinging the psychrometer to obtain a Wet Bulb Temperature measurement. https://csdailyblog.wordpress.com/2013/09/06/phenology-at-conserve-school-part-i Relative Humidity Pen -IDENTIFY AND KNOW PURPOSE- The newer relative humidity measurement devices, like this ‘pen’, measure humidity from a change in capacitance due to a change in the amount of water present. Relative Humidity Pen Front panel controls Temp Scale Selector HYGRO MIN/MAX Recall Press once to view and again to return to Current. Top panel controls TEMP MIN/MAX Recall Press once to view and again to return to Current temp. POWER On/Off EVAPORIMETER -IDENTIFY AND KNOW PURPOSE- The timer drum and paper strip allow you to record evaporation rates over the course of a week. Evaporation rate through time is recorded via the pen. The porous plate allows for the measurement of evaporation across the plate’s surface. RAIN GAUGE -KNOW HOW TORead Rainfall in Inches (and Convert to Centimeters) Detailed View of Measurement 3.00 inches 3 in. x 2.54 cm/in. = 7.62 cm CUP OR CONTACT ANEMOMETER -IDENTIFY AND KNOW PURPOSE- Wind rotates the cups, and the rotations over time cause a counter to increase. The counter on the anemometer in the SLC is designed to count the number of rotations, and hence the wind speed, over long (e.g., a month, several months) periods of time. DWYER ANEMOMETER -IDENTIFY AND KNOW PURPOSE- To measure high wind speed (>10 M.P.H.), place your finger over the red opening at the top while making your measurement. Try turning on the fan and making a wind speed measurement. The Dwyer Anemometer makes instantaneous measurements of wind speed. The left-side scale is for wind speeds between 2 and 10 M.P.H. The right-side scale is for wind speeds around 10 M.P.H. to 60 M.P.H. Wind blowing past openings in the Dwyer anemometer is drawn into the central, vertical chamber causing the ball to float upward. The higher the ball floats, the higher the wind speed. DIGITAL HOT-WIRE THERMOANEMOMETER -KNOW HOW TODetermine Wind Speed The Hot-Wire Anemometer is very useful for measuring low wind speeds because of its sensitivity. However, it’s not durable enough to use in applications where it might be exposed to rain or particulates. DIGITAL HOT-WIRE THERMOANEMOMETER After turning the instrument on, wait for it to count-down, and then note that it tells you the wind speed in m/s and the temperature in °C DIGITAL HOT-WIRE THERMOANEMOMETER If you examine the head of the probe closely you can see the “hot-wire” part in an inlet. Do NOT touch! It’s expensive and delicate. The head of the probe is where the measurements are actually made. The body of the probe telescopes to allow you to measure wind speeds in vents or high in the air. DIGITAL HOT-WIRE THERMOANEMOMETER By placing the head of the probe in line with the flow of air, for example, in front of a running fan, the Hot-Wire Anemometer will display the wind speed and temperature simultaneously. The Hot-Wire Anemometer measures wind speed by using electrical current to either (1) heat up a small, exposed platinum or tungsten wire, and monitor the change in wire temperature due to wind stripping heat away or (2) maintain the wire at a constant temperature and monitor the amount of current needed to maintain that temperature through time. More current will be needed at higher wind speeds. LIGHT METER (GE TRIPLE RANGE) -KNOW HOW TORead Light Intensity at Indicated Place The light meter consists of a sensitized selenium cell that converts light energy into electrical voltage. The red pointer indicates the change in voltage and the 3 scale ranges allow for interpreting the voltage change in light intensity units called “footcandles”. 1 footcandle = 1 lumen/ft.2 LIGHT METER (GE TRIPLE RANGE) -KNOW HOW TORead Light Intensity at Indicated Place The side sliding button has 3 positions corresponding to each of the 3 scales on the dial (all scales have the unit “footcandles”). If the button is all the way down, read the measurement of the red pointer on the bottom scale (10 – 50 footcandles) LIGHT METER (GE TRIPLE RANGE) -KNOW HOW TORead Light Intensity at Indicated Place If the red pointer is reading all the way to the left, then the position of the button is too high. If the red pointer is all the way to the right, then the position of the button is too low. Experiment with taking measurements under ambient fluorescent lighting or turning on the desk incandescent lamp, or covering the top of the device with your hand and change the button position to get a reading. PYRHELIOMETER -IDENTIFY AND KNOW PURPOSE- The drum with the chart strip can be wound so that it makes one complete revolution over 1 week, and thus a recording of weekly solar intensity. Direct, shortwave solar radiation is received through the glass dome onto the metallic strips inside. One strip is coated to reflect the incoming radiation, and the other is painted optical black and absorbs the incoming radiation. The resulting change in conformation of the u-shaped metal joining the plates changes the position of the pen to indicate incident solar intensity.