Campbell CS805 User manual

INSTRUCTION MANUAL
CS805 Heated-Needle
Anemometer
6/02
Copyright (c) 2002
Campbell Scientific, Inc.

Warranty and Assistance
The CS805 HEATED-NEEDLE ANEMOMETER is warranted by
CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and
workmanship under normal use and service for twelve (12) months from date of
shipment unless specified otherwise. Batteries have no warranty. CAMPBELL
SCIENTIFIC, INC.'s obligation under this warranty is limited to repairing or
replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products.
The customer shall assume all costs of removing, reinstalling, and shipping
defective products to CAMPBELL SCIENTIFIC, INC. CAMPBELL
SCIENTIFIC, INC. will return such products by surface carrier prepaid. This
warranty shall not apply to any CAMPBELL SCIENTIFIC, INC. products
which have been subjected to modification, misuse, neglect, accidents of
nature, or shipping damage. This warranty is in lieu of all other warranties,
expressed or implied, including warranties of merchantability or fitness for a
particular purpose. CAMPBELL SCIENTIFIC, INC. is not liable for special,
indirect, incidental, or consequential damages.
Products may not be returned without prior authorization. The following
contact information is for US and International customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle repairs
for customers within their territories. Please visit www.campbellsci.com to
determine which Campbell Scientific company serves your country. To obtain
a Returned Materials Authorization (RMA), contact CAMPBELL
SCIENTIFIC, INC., phone [phone]. After an applications engineer
determines the nature of the problem, an RMA number will be issued. Please
write this number clearly on the outside of the shipping container.
CAMPBELL SCIENTIFIC's shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____
815 West 1800 North
Logan, Utah 84321-1784
CAMPBELL SCIENTIFIC, INC. does not accept collect calls.

i
CS805 Table of Contents
PDF viewers note: These page numbers refer to the printed version of this document. Use
the Adobe Acrobat® bookmarks tab for links to specific sections.
1. General Description....................................................1
2. Specifications .............................................................1
3. Calibration and System Accuracy.............................2
3.1 Angular Sensitivity....................................................................................2
3.2 Pressure Change with Elevation................................................................3
3.3 Coupled Error of CE805...........................................................................3
4. Calibration...................................................................4
5. Installation...................................................................4
6. Wiring ..........................................................................6
7. Example Programs .....................................................7
Appendix
A. Secondary Error Considerations ..........................A-1
A.1 Pressure Validation..............................................................................A-1
A.2 Conductive Heat Transport across the Boundary Layer.......................A-1
A.3 Reference.............................................................................................A-3
Figures
1. Angular Response of CS805.......................................................................2
2. Pressure and Elevation................................................................................3
3. Plane of Calibrated Sensitivity....................................................................5
4. CS805, Sensor and Wiring Figure ..............................................................6
A-1. Changes in Kair with Temperature and Humidity................................A-2

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1
CS805 Heated-Needle Anemometer
1. General Description
The CS805 Heated-Needle Anemometer is a dual-needle sensor containing a
heater element and two type T (copper-constantan) thermocouples. The -L
option on the model CS805-L indicates that the cable length is user specified.
This manual refers to the sensor as the CS805 and applies to the CS805-L as
well. The CS805 is meant for use with a current source, such as the CE805,
and a data acquisition system, such as the CR500, CR510, CR10(X), 21X,
CR23X, CR7, CR9000, and CR5000 dataloggers, all available from Campbell
Scientific. The CE805 is a four-channel current excitation device, outputting
31.1 milliamps across a maximum of 9.0 volts, used to power the CS805.
The CS805 measures wind speeds in low-flow applications. Its small size and
lack of moving parts makes it superior to cup, propeller, and sonic
anemometers in space-constrained environments. The CS805 uses stainless
steel hypodermic tubing to add durability to and resist corrosion of the
measurement circuitry. The interface of the needles and cable are
mechanically supported and chemically protected within a potting compound
forming the base of the probe.
The CS805 works on the principle of fluid heat transport from a cylinder. A
heater element is located in the tip of the long needle. The temperature
difference between the two needles is referenced to an external air temperature
measurement. Measuring the change of the temperature difference between the
two needles makes it possible to calculate wind speed.
2. Specifications
CS805
Specified Range: 5-500 cm/s (0.1-11 mph)
Calibrated Range: 5-500 cm/s
Precision Over Calibrated Range: 0.5 cm/s (0.01 mph)
Accuracy Over Calibrated Range: ±5 cm/s (±0.1 mph) or 5% of reading
Operating Temperature: -20 to 50°C
Storage Temperature: -20 to 50°C
Total Probe Length: 10.5 cm (4 in)
Probe Base Diameter: 0.95 cm (0.375 in)
Needle Length:
Long: 5 cm (2 in)
Short: 2 cm (0.8 in)
Needle Diameter: 1 mm (0.025 in)
Power Consumption: ~100 mW @ 31.1 mA
Heater Resistance: 101-102.5 Ohms
Thermocouple: Type T (Copper-Constantan)
Settling Time After Power is Switched On: 15 seconds
Cable Properties: See Belden Inc., cable number 8723
CE805
Channels: 4
Supply Current: 31.1 mA
Current Accuracy: ±2%
Maximum Voltage Output: 9 Volts
Power Consumption:
~25 mA plus 31.1 mA per channel being used
~150 mA when all 4 channels are used

CS805 Heated-Needle Anemometer
2
3. Calibration and System Accuracy
As listed in the previous section, the CS805 has been calibrated and tested in a
controlled environment at 25°C, 646 mmHg (861 mbar, 0.85 atm), and 31.100
mA of constant current. This sensor is going to be exposed to many
applications deviating from the calibration environment, and will continue to
work well. Concerns with calibration and sensor accuracy as the application
environment changes temperature, pressure, and humidity are discussed in
detail in Appendix A. To follow, are the major concerns needing to be dealt
with for proper use, in the order of decreasing error to system accuracy.
3.1 Angular Sensitivity
The CS805 has been calibrated to measure winds in the plane orthogonal to the
axis of the needle. The sensor loses response as the angle between air flow and
axis of the needle decreases. This is quantified with the graph below. The
performance constraints of the CS805 need to be understood in order to make
the desired measurements. If the sensor is not oriented properly upon
installation, it could introduce as much as a 50 percent error into the
measurement. This is further discussed in the installation section.
FIGURE 1. Angular Response of CS805

CS805 Heated-Needle Anemometer
3
3.2 Pressure Change with Elevation
FIGURE 2. Atmospheric Pressure Change with Elevation
The calibration of the CS805 took place in Logan, Utah, at an elevation of
1.384 km (4500 ft.) above sea level. Unless the sensor is being used at this
elevation, the calibration will need to be adjusted for a pressure change due to
elevation. The heat transport from the needle anemometer is a function of the
fluid passing over the heated cylinder. Thermodynamically, this is a gas, and
the energy transport is being done by mass. The mass and volume of a gas are
directly proportional. As the pressure increases with lower elevations, there
will be more air molecules per volume and more energy transport from the
cylinder. The calibration needs to be adjusted by a ratio of calibration pressure
(Pcalib) to that of the use pressure (Puse). We see this in Equation 1, where u is
wind speed, B is the slope, ∆T is the temperature difference, and A is the
offset.
2/1
use
calib
2/1 P
P
T
B
Au 












∆
+= (Eq. 1)
Atmospheric pressure does not usually change enough from day to day to be
concerned about the effects on the measurement. Experimental validation of
the above theory can be viewed in Appendix A.
3.3 Coupled Error of CE805
The calibration for the CS805 was done with a BK Precision (model 1646)
power supply and a Keithly (model 197A) digital multimeter adjusted to keep
the current 31.1 ±0.005 mA. The CE805 has an accuracy error of 2% over the
full temperature range. It has been bench tested to be within 1% at 25°C.

CS805 Heated-Needle Anemometer
4
Changes in the current delivered to the CS805 will directly contribute to the
error of the wind speed measurement. When the CS805 is being used with the
CE805 at a temperature different from 25°C the inaccuracy of the current
delivery will alter the measurement. This deviation will show up in the square
root of wind speed domain, and the error will actually double in the wind speed
domain.
For example, if you are operating over a range –20 to 50°C, with the CE805
delivering current to the CS805, that will introduce a 2% inaccuracy in your
current (sqrt (wind speed) domain) and will show up as a 4% inaccuracy in
your wind speed measurement. This would add to the 5% inaccuracy specified
in the CS805.
4. Calibration
As mentioned in the previous section, calibration was done in a controlled
environment at 25°C, 646 mmHg (861mbar, 0.85 atm), and 31.100 mA of
constant current. The calibration is done in a wind tunnel, using Sierra
Instruments’ mass flow meters (700 series) to calculate the wind speed. Each
sensor has been calibrated over the specified range to deliver accurate and
precise measurements within the specifications.
As previously noted, the best fit calibration curve is linear, of the form:
2/1
use
calib
2/1 P
P
T
B
Au 












∆
+= ,
where u is the wind speed, A is the offset, B is the slope, ∆T the temperature
difference, Pcalib the calibration pressure, and Puse is the use pressure, which will
be site specific to the user.
Each sensor comes with a serial number specific calibration giving the user the
slope and offset of the calibrated fit. Pcalib is a function of the elevation in
Logan, Utah, and is: 646 mmHg, 861 mbar, or 0.85 atm, depending upon
preferred units. The calibration is done to output wind speed in cm/s. If the
desired unit is mph, a multiplier of 0.0224 mph/cms-1 needs to be used as the
final adjustment.
For the provided calibration to work in use, the ∆T measurement should be
referenced to an external air temperature measurement. Because of the
datalogger’s thermocouple measurement algorithm, the reference temperature
will need to be subtracted from the original CS805 temperature measurement
to determine ∆T. This is further discussed in the installation and program
example sections of the manual.
5. Installation
The CS805 is most sensitive to wind perpendicular to the axis probe. The
sensitivity deviates as the angle of wind changes from normal, as discussed in
Section 3.1. The probe will also be affected by the free flow of air at the
sensor; any wind shielding by a leaf or building will affect the measurement. It
is suggested to think carefully about the desired measurement and
measurement constraints of the sensor.

CS805 Heated-Needle Anemometer
5
FIGURE 3. Plane of Calibrated Sensitivity
For example, if the desired measurement were horizontal wind in a desert, the
preferred installation would be to have the probe positioned vertically, the
needles pointing toward the sky. This orientation would provide the greatest
sensitivity to transverse wind. In addition, the contribution of the vertical wind
component to the total wind vector is generally less than the horizontal
components. The probe should be installed free from shrubbery or any nearby
equipment that may inhibit air flow.
Secondly, the differential temperature of the CS805 needs to be referenced to a
separate air temperature measurement. This separate measurement needs to be
made in a vicinity representative of the air temperature at the CS805. This can
be done with any method of temperature measurement, such as a 107 probe or
thermocouple.
Finally, this sensor is fragile and should be treated appropriately. The
protective tip should be used at all times when transporting and installing the
probe. If installed in a rugged environment, such as a plant canopy, care
should be taken to keep leaves from hitting into and damaging the probe. The
CS805 measurement and calibration rely on the needles being kept straight.
Any bending may reduce the sensitivity and damage or break the probe.

CS805 Heated-Needle Anemometer
6
6. Wiring
FIGURE 4. CS805, Sensor and Wiring Figure
Below is listed the wiring needed for your CS805/CE805/Datalogger system.
The wiring between the CE805 and the Datalogger is not provided by
Campbell Scientific.
CR7, 21 X, CR23X CE805 CS805
H------------------------------------------------------------------------------Green
L ------------------------------------------------------------------------------White
-----------------------------------------------------------------------------Shield
1 -----------------------------------Red
---------------------------------Black
C ---------------------------------------- CTRL
+ 12------------------------------------- +12V
---------------------------------------
CR10(X or T)/CR510 CE805 CS805
HI-----------------------------------------------------------------------------Green
LOW -------------------------------------------------------------------------White
AG----------------------------------------------------------------------------Shield
1 -----------------------------------Red
---------------------------------Black
C ---------------------------------------- CTRL
12 V ------------------------------------ +12V
G ---------------------------------------
Thermocouple + Green
Thermocouple - White
Heater + Red
Heater - Black
Shield - Clear

CS805 Heated-Needle Anemometer
7
CR5000, CR9000 CE805 CS805
H ------------------------------------------------------------------------------Green
L-------------------------------------------------------------------------------White
-----------------------------------------------------------------------------Shield
1 -----------------------------------Red
---------------------------------Black
C ---------------------------------------- CTRL
12 V------------------------------------- +12V
G ----------------------------------------
7. Example Programs
Wiring for Example Programs
Color Function Datalogger CE805
Green Thermocouple + 6 High
White Thermocouple - 6 Low
Clear Shield Ground
Red Heater + 1
Black Heater -
Yellow Control C1 Ctrl
Blue CE805 Power + +12 V +12 V
Orange CE805 Power -
In addition, the program uses a 107 probe or a Type E thermocouple for a
separate temperature measurement. This is connected to channel 1 of the
datalogger.
Example 1. CR10X Program
(continually powered; time series ~1 or 2 s with 107 probe)
;{CR10X}
; This program is written to work with the CS805,
; being used in conjunction with the CE805 and a
; CS107 temperature probe as an air temperture
; reference.
; This program is designed to measure the sensor
; once every execution interval (1 second), and
; dump the measurement to final storage.
*Table 1 Program
01: 1 Execution Interval (seconds)
; For this program the CS805 is going to be
; continually powered. The best way to do this
; trigger the CE805 at the beginning of the program.

CS805 Heated-Needle Anemometer
8
1: If Flag/Port (P91)
1: 21 Do if Flag 1 is Low
2: 30 Then Do
; Set Control Port 1 High to trigger CE805
2: Do (P86)
1: 41 Set Port 1 High
; Note:
; The CS805 takes about 15 seconds to settle
; upon inital power up. The first 15 measurement
; are not going to be correct.
; Set Flag 1 High, not to enter the IF again.
3: Do (P86)
1: 11 Set Flag 1 High
4: End (P95)
; Begin making measurements
; The 107 probe for air temperature reference
; for the CS805 thermocouple measurement.
5: Temp (107) (P11)
1: 1 Reps
2: 1 SE Channel
3: 3 Excite all reps w/E3
4: 1 Loc [ Air_Temp ]
5: 1.0 Mult
6: 0.0 Offset
; Measure the CS805
6: Thermocouple Temp (DIFF) (P14)
1: 1 Reps
2: 1 2.5 mV Slow Range
3: 6 DIFF Channel
4: 1 Type T (Copper-Constantan)
5: 1 Ref Temp (Deg. C) Loc [ Air_Temp ]
6: 2 Loc [ ndl_Temp ]
7: 1.0 Mult
8: 0.0 Offset
; Begin processing the measurement for wind speed
; The measurement made above has been referenced
; to air temperature. The way the datalogger
; works adds the reference on to the temperature
; measurement that is made. To get the actual
; temperature difference between the needles the
; reference needs to be subtracted.
7: Z=X-Y (P35)
1: 2 X Loc [ ndl_Temp ]
2: 1 Y Loc [ Air_Temp ]
3: 3 Z Loc [ delta_T ]

CS805 Heated-Needle Anemometer
9
; Begin working through the calibration adjustments
8: Z=1/X (P42)
1: 3 X Loc [ delta_T ]
2: 4 Z Loc [ Inv_dT ]
; Slope adjustment
9: Z=X*F (P37)
1: 4 X Loc [ Inv_dT ]
2: 255.1 F
3: 5 Z Loc [ wnd_spd ]
; Offset adjustment
10: Z=X+F (P34)
1: 5 X Loc [ wnd_spd ]
2: -2.38 F
3: 5 Z Loc [ wnd_spd ]
; Now we need to adjust for the pressure
; change due to elevation. For this
; example let the Puse be 1 atm. at sea
; level. This will be an adjustment
; from 0.85 atm. calibration pressure
; in Logan, Utah. Since the adjustment
; is site specific, but will not change
; from day to day, the math will be done
; in a subroutine.
11: If Flag/Port (P91)
1: 22 Do if Flag 2 is Low
2: 2 Call Subroutine 2
; Adjust for the pressure multiplier
12: Z=X*Y (P36)
1: 5 X Loc [ wnd_spd ]
2: 8 Y Loc [ P_adj ]
3: 5 Z Loc [ wnd_spd ]
; Now adjust for the square root
; of wind speed
13: Z=X*Y (P36)
1: 5 X Loc [ wnd_spd ]
2: 5 Y Loc [ wnd_spd ]
3: 5 Z Loc [ wnd_spd ]
; Finally, output the measurement
14: If time is (P92)
1: 0 -- Minutes (Seconds --) into a
2: 1 Interval (same units as above)
3: 10 Set Output Flag High (Flag 0)
15: Real Time (P77)^19852
1: 111 Day,Hour/Minute,Seconds (midnight = 0000)
; Note:
; Remember, the first 15 seconds of measurements
; are not going to be correct.

CS805 Heated-Needle Anemometer
10
16: Sample (P70)^11916
1: 1 Reps
2: 5 Loc [ wnd_spd ]
*Table 2 Program
02: 0.0000 Execution Interval (seconds)
*Table 3 Subroutines
; Subroutine 2 will make the adjustment
; multiplier for pressure, and store
; it in an input location.
1: Beginning of Subroutine (P85)
1: 2 Subroutine 2
; Set flag 2 High, so that we do not enter
; this subroutine again.
2: Do (P86)
1: 12 Set Flag 2 High
; The adjustment will be from calibration
; pressure of .85 atm to a use pressure
; of 1 atm.
3: Z=F x 10^n (P30)
1: 0.85 F
2: 0 n, Exponent of 10
3: 6 Z Loc [ P_calib ]
4: Z=F x 10^n (P30)
1: 1 F
2: 0 n, Exponent of 10
3: 7 Z Loc [ P_use ]
; Create the ratio
5: Z=X/Y (P38)
1: 6 X Loc [ P_calib ]
2: 7 Y Loc [ P_use ]
3: 8 Z Loc [ P_adj ]
; Create the multiplier that will
; be used in the rest of the program.
6: Z=SQRT(X) (P39)
1: 8 X Loc [ P_adj ]
2: 8 Z Loc [ P_adj ]
7: End (P95)
End Program
-Input Locations-
1 Air_Temp 1 2 1
2 ndl_Temp 1 1 1
3 delta_T 1 1 1
4 Inv_dT 1 1 1
5 wnd_spd 1 5 4
6 P_calib 1 1 1
7 P_use 1 1 1
8 P_adj 1 2 2

CS805 Heated-Needle Anemometer
11
Example 2. CR10X Program
(with delay; with average; with 107 probe)
;{CR10X}
; This program is written to work with the CS805,
; being used in conjunction with the CE805 and a
; CS107 temperature probe as an air temperture
; reference.
; This program is designed to measure the sensor
; once every execution interval (30 seconds), and
; average the measurement every hour in final storage.
; Because the execution interval is slow, the probe
; will not need to be on all the time. It will
; be powered up with a delay each time. This will
; save the power used.
*Table 1 Program
01: 30 Execution Interval (seconds)
; For this program the CS805 is going to be
; intermintantly powered. The best way to do this
; trigger the CE805 at the beginning of the execution
; interval with subroutine 1.
1: Do (P86)
1: 1 Call Subroutine 1
; Begin making measurements
; The 107 probe for air temperature reference
; for the CS805 thermocouple measurement.
2: Temp (107) (P11)
1: 1 Reps
2: 1 SE Channel
3: 3 Excite all reps w/E3
4: 1 Loc [ Air_Temp ]
5: 1.0 Mult
6: 0.0 Offset
; Measure the CS805
3: Thermocouple Temp (DIFF) (P14)
1: 1 Reps
2: 1 2.5 mV Slow Range
3: 6 DIFF Channel
4: 1 Type T (Copper-Constantan)
5: 1 Ref Temp (Deg. C) Loc [ Air_Temp ]
6: 2 Loc [ ndl_Temp ]
7: 1.0 Mult
8: 0.0 Offset
; Now that the measurement has been made
; set control port 1 Low. This will
; cut power to the sensor.

CS805 Heated-Needle Anemometer
12
4: Do (P86)
1: 51 Set Port 1 Low
; Begin processing the measurement for wind speed
; The measurement made above has been referenced
; to air temperature. The way the datalogger
; works adds the reference on to the temperature
; measurement that is made. To get the actual
; temperature difference between the needles the
; reference needs to be subtracted.
5: Z=X-Y (P35)
1: 2 X Loc [ ndl_Temp ]
2: 1 Y Loc [ Air_Temp ]
3: 3 Z Loc [ delta_T ]
; Begin working through the calibration adjustments
6: Z=1/X (P42)
1: 3 X Loc [ delta_T ]
2: 4 Z Loc [ Inv_dT ]
; Slope adjustment
7: Z=X*F (P37)
1: 4 X Loc [ Inv_dT ]
2: 255.1 F
3: 5 Z Loc [ wnd_spd ]
; Offset adjustment
8: Z=X+F (P34)
1: 5 X Loc [ wnd_spd ]
2: -2.38 F
3: 5 Z Loc [ wnd_spd ]
; Now we need to adjust for the pressure
; change due to elevation. For this
; example let the Puse be 1 atm. at sea
; level. This will be an adjustment
; from 0.85 atm. calibration pressure
; in Logan, Utah. Since the adjustment
; is site specific, but will not change
; from day to day, the math will be done
; in a subroutine 2.
9: Do (P86)
1: 2 Call Subroutine 2
; Adjust for the pressure multiplier
10: Z=X*Y (P36)
1: 5 X Loc [ wnd_spd ]
2: 8 Y Loc [ P_adj ]
3: 5 Z Loc [ wnd_spd ]

CS805 Heated-Needle Anemometer
13
; Now adjust for the square root
; of wind speed
11: Z=X*Y (P36)
1: 5 X Loc [ wnd_spd ]
2: 5 Y Loc [ wnd_spd ]
3: 5 Z Loc [ wnd_spd ]
; Finally, output the measurement
12: If time is (P92)
1: 0 Minutes (Seconds --) into a
2: 60 Interval (same units as above)
3: 10 Set Output Flag High (Flag 0)
13: Real Time (P77)^19852
1: 111 Day,Hour/Minute,Seconds (midnight = 0000)
14: Average (P71)^31556
1: 1 Reps
2: 5 Loc [ wnd_spd ]
*Table 2 Program
02: 0.0000 Execution Interval (seconds)
*Table 3 Subroutines
; Subroutine 1 is to trigger the CE805
; with a delay of 15 seconds to allow
; the CS805 to warm up.
1: Beginning of Subroutine (P85)
1: 1 Subroutine 1
; Set Control Port 1 High to trigger CE805
2: Do (P86)
1: 41 Set Port 1 High
; Note:
; The CS805 takes about 15 seconds to warm
; up upon initial power up.
3: Excitation with Delay (P22)
1: 1 Ex Channel
2: 0 Delay W/Ex (0.01 sec units)
3: 1500 Delay After Ex (0.01 sec units)
4: 0 mV Excitation
4: End (P95)
; Subroutine 2 will make the adjustment
; multiplier for pressure, and store
; it in an input location.
5: Beginning of Subroutine (P85)
1: 2 Subroutine 2
; Set flag 2 High, so that we do not enter
; this subroutine again.

CS805 Heated-Needle Anemometer
14
6: Do (P86)
1: 12 Set Flag 2 High
; The adjustment will be from calibration
; pressure of .85 atm to a use pressure
; of 1 atm.
7: Z=F x 10^n (P30)
1: 0.85 F
2: 0 n, Exponent of 10
3: 6 Z Loc [ P_calib ]
8: Z=F x 10^n (P30)
1: 1 F
2: 0 n, Exponent of 10
3: 7 Z Loc [ P_use ]
; Create the ratio
9: Z=X/Y (P38)
1: 6 X Loc [ P_calib ]
2: 7 Y Loc [ P_use ]
3: 8 Z Loc [ P_adj ]
; Create the multiplier that will
; be used in the rest of the program.
10: Z=SQRT(X) (P39)
1: 8 X Loc [ P_adj ]
2: 8 Z Loc [ P_adj ]
11: End (P95)
End Program
-Input Locations-
1 Air_Temp 1 2 1
2 ndl_Temp 1 1 1
3 delta_T 1 1 1
4 Inv_dT 1 1 1
5 wnd_spd 1 5 4
6 P_calib 1 1 1
7 P_use 1 1 1
8 P_adj 1 2 2

CS805 Heated-Needle Anemometer
15
Example 3. Program with CR Basic
(continually powered; with average; with FWTC)
'CR5000
'This program is written to measure the CS805
'needle anemometer. It works with the CE805,
' and a Type E themocouple as a temperature
' reference. The CS805 will be continually powered.
'These are the constants for the program.
' First,'the pressure adjustment constants, and secondly,
' the slope and offset constants for the calibration.
const P_calib=646 'In mmHg @ Logan, Utah
const P_use=760 'In nnHg @ sea level
const B=255.1 'The slope constant
const A=-2.39 'The offset constant
'Make the public variable what needs to be measured
'such as the Temperature of the logger, Temp. of the
'air, Temp. of the needle, and the temperature
'difference of the two needles, and wind speed.
Public Tpanel(1), T_air(1), T_ndl(1), delta_T(1), wind(1)
units Tpanel(1)= C
units T_ai(1)r= C
units T_ndl(1)=C
units delta_T(1)= C
units wind(1)= cm/s
DataTable(wind, true, -1)
DataInterval (0,1,Min,0) '! min average
Average(1, wind(1), ieee4, false) 'average wind speed
StdDev(1,wind(1), ieee4, false) 'std. dev on the wind speed
EndTable
BeginProg
'As we begin the program, trigger the CS805 to stay on
'after it scans it will stay High the rest of the program
Scan(1,mSec,1, 1)
Portset(1,1) 'Trigger with port 1 High
NextScan
'Now begin the loop for measurement
Scan (2 ,Sec,3,0) '2 second execution interval
PanelTemp (Tpanel,250) 'measure the panel temp for TC ref
'measure the TC of the wind tunnel
TCDiff(T_air(1),1,mV20, 1, TypeE, Tpanel, True, 0,250, 1.0, 0)
'measure the CS805
TCDiff(T_ndl(1), 1, mV20, 6,TypeT, T_air, true, 0,250, 1, 0)
'Now begin processing the measurement
'Subtract T_air from T_ndl, to adjust for the datalogger
'adding on the referece temperature.
delta_T=T_ndl-T_air
'Process the calibration for wind speed
wind= ( A+ (B/delta_T) ) * sqr(P_calib/P_use)

CS805 Heated-Needle Anemometer
16
'Process for the sqr. root of wind speed
wind= wind * wind
'Call the table for final storage
CallTable wind
NextScan
EndProg