Campbell CS115 User manual

INSTRUCTION MANUAL
CS115
Barometric Pressure Sensor
3/03
Copyright (c) 2002-2003
Campbell Scientific, Inc.

Warranty and Assistance
The CS115 BAROMETRIC PRESSURE SENSOR 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
CS115 Table of Contents
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1. Introduction.................................................................1
2. Specifications .............................................................2
2.1 Performance..............................................................................................2
2.2 Electrical...................................................................................................2
2.3 Physical.....................................................................................................2
3. Installation...................................................................3
3.1 Venting and Condensation........................................................................3
3.2 Mounting...................................................................................................3
3.3 Jumper Settings.........................................................................................4
4. Wiring ..........................................................................5
5. Programming ..............................................................5
5.1 Period Averaging Measurement Examples...............................................7
5.1.1 Period Averaging Measurement Example for CR10(X)..................7
5.1.2 Period Averaging Measurement Example for CR10(X) in a Slow
Executing Program....................................................................8
5.1.3 Period Averaging Measurement Example for CR23X....................9
5.1.4 Period Averaging Measurement Example for CR5000 in a Fast
Executing Program at 10 Hz....................................................11
5.2 Pulse Count Measurement Example........................................................12
5.21 Pulse Count Measurement Example for 21X .................................12
5.3 Output Resolution...................................................................................13
6. Correcting Pressure to Sea Level............................13
7. Maintenance and Calibration ...................................14
Figures
3-1 Mounting CS115.......................................................................................3
3-2 Jumper Settings on CS115........................................................................4
Tables
4-1 Wiring for Example Programs..................................................................5
5-1 Conversion Factors for Alternative Pressure Units...................................6

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1
CS115 Barometric Pressure Sensor
The CS115 Barometric Pressure Sensor uses the resonant silicon technology pressure
sensor developed by Druck. The sensor outputs a variable frequency which can be
measured using the datalogger's period averaging instruction or pulse count instruction.
The entire process is essentially digital from sensor element to datalogger, ensuring the
highest precision and most accurate reading possible.
1. Introduction
The sensor comprises two elements, one acting as a pressure sensitive
diaphragm and the other acting as a resonator. Pressure variations deflect the
sensitive diaphragm and change the sensor’s resonant frequency. The resonant
frequency is measured, corrected for the effects of temperature and non-
linearity, and then output as a frequency signal. The sensor is characterized
over the full temperature and pressure range, and the corrections are stored in
the sensor's non-volatile memory. It can be operated in a triggered or
continuous mode. In the triggered mode the datalogger switches 12 VDC
power to the barometer before the measurement. The datalogger then powers
down the barometer after the measurements to conserve power.

CS115 Barometric Pressure Sensor
2
2. Specifications
2.1 Performance
Measurement Range: 600 mb to 1100 mb (hPa)
Operating Temperature Range: -40°C to +60°C
Humidity Range: non-condensing
Media Compatibility: non-corrosive gas
Total Accuracy1:
at 20°C ±0.3 mb
-10°C to +50°C ±0.5 mb
-20°C to +60°C ±1.5 mb
-40°C to +60°C ±2.0 mb
Long-term Stability: <0.11 mb per year (100 ppm)
Overpressure Limit: 1375 mb
2.2 Electrical
Supply Voltage: 9.5 V to 24 VDC
Current Consumption: 8 mA nominal
Output Frequency: 600 Hz to 1100 Hz
Frequency Output: -2.5 to +2.5 VDC zero-crossing square wave
External Trigger Voltages: ON 1 to 24 VDC
OFF 0 VDC
Warm-up Time: <2 seconds (-40°C to +60°C)
EMC Compatibility: Emissions – BS EN50081-1
Immunity – BS EN61000-6-2
2.3 Physical
Dimensions (Main Box): 2.36” x 2.36” x 1.15”
(6.0 cm x 6.0 cm x 2.9 cm)
Weight: 4.4 oz (125 g)
Mounting Hole Centers: 3 inches (7.62 cm)
Pressure Connector: 0.16” (0.4 cm) barbed hose
The black outer jacket of the cable is Santoprene® rubber. This
compound was chosen for its resistance to temperature extremes,
moisture, and UV degradation. However, this jacket will support
combustion in air. It is rated as slow burning when tested
according to U.L. 94 H.B. and will pass FMVSS302. Local fire
codes may preclude its use inside buildings.
1Non-linearity, hysteresis, and repeatability over calibrated temperature range
NOTE

CS115 Barometric Pressure Sensor
3
3. Installation
3.1 Venting and Condensation
To prevent condensation, install the sensor in an environmentally protected
enclosure, complete with desiccant which should be changed at regular
intervals. As the sensor must detect the external ambient pressure the enclosure
must not be ‘hermetically sealed’.
Failure to protect the sensor from condensation may result
in permanent damage.
If it is necessary to make a vent hole on the outer wall of an
enclosure, do not make the hole on one of the vertical side walls,
as wind blowing around it can cause transient changes in
pressure.
3.2 Mounting
The mounting holes for the sensor are one-inch-centered, and will mount
directly onto the holes on the backplates of the Campbell Scientific enclosures.
Mount the sensor with the pneumatic connector pointing vertically downwards
to prevent condensation collecting in the pressure cavity, and also to ensure
that water cannot enter the sensor.
FIGURE 3-1. Mounting CS115
CAUTION
NOTE

CS115 Barometric Pressure Sensor
4
As you mount the sensor onto the backplate of the enclosure, place the fork lug
under the mounting screw to accomplish the proper grounding of the sensor as
shown in Figure 3-1.
3.3 Jumper Settings
The CS115 has two operating modes, ‘continuous’ and ‘triggered’. It is normally
shipped in the ‘triggered’ mode, in which the unit is turned on and off by applying
signal to the blue wire (EXT. TRIG.) using a datalogger’s control port. In this
mode, power consumption is minimized, but the sensor is subject to a 2-second
‘warm-up’ delay after it is turned on. You can also configure the unit for the
‘continuous’ mode to avoid the need for the delay, in which the sensor is powered
on continuously. This can be achieved either by connecting the blue wire (EXT.
TRIG.) to a continuous 1 to 24 VDC supply (to 5 V or 12 V channel of the
datalogger) or by changing the jumper position connecting the pins on the circuit
board. See Figure 3-2 below.
FIGURE 3-2. Jumper Settings on CS115
AB
Jumper (blue link) –
Position A = continuous mode
Position B = triggered mode

CS115 Barometric Pressure Sensor
5
4. Wiring
The CS115 wiring instructions for the example programs are shown in
Table 4-1. For dataloggers CR500, CR510, CR10(X), CR23X, and CR5000,
analog channel is used for period averaging measurement. For CR7, 21X and
CR9000 pulse channel is used for pulse count measurement.
TABLE 4-1. Wiring for Example Programs
Wire Color Description CR10(X) CR23X 21X CR5000
Green Frequency Out SE6 SE24 P1 SE33
Red Supply (12Vdc) 12V 12V 12V 12V
Black Power Ground G G G
Yellow Signal Ground AG
Blue External Trigger C8 C1 C6 C1
Clear Shield G G G
5. Programming
There are two ways to measure the output of the CS115. The preferred way is
to use the period averaging instruction available with the CR500, CR510,
CR10(X), CR23X and CR5000 dataloggers. This instruction determines the
period of the output signal averaged over a user-specified number of cycles and
outputs it in kHz.
If you have a datalogger that does not support the period averaging instruction
(e.g., 21X, CR7 or CR9000), a pulse count instruction can be used to measure
the CS115.
Atmospheric pressure changes little with time. In most weather station
applications measuring pressure once an hour is adequate.
In Example 1, the datalogger turns on the CS115 one minute before the top of
the hour with a control port. As in the example, the execution interval must be
one minute or less. The datalogger measures the CS115 on the hour, and then it
turns the CS115 off.
In Example 2, the CS115 is measured every execution interval. The datalogger
turns the CS115 on and waits two seconds for it to warm up before the
measurement is made. The execution interval must be long enough to
accommodate the two-second warm-up delay plus all the other measurements
and processing instructions in the program.
Example 3 resembles Example 1 in every way, but it is for the CR23X.
In Example 4, the CR5000 measures the CS115 once an hour in a program that
runs at 10 Hz. With the CR5000, the period averaging instruction has to be
executed every scan and cannot be inside the “If” statement. The measured
value, therefore, is first written into a temporary variable called "CS115_Freq".

CS115 Barometric Pressure Sensor
6
Once the CS115 is turned on one minute before every hour, and the correct
measurement is made, it is then copied into the current variable called
"Pressure". The sensor is then turned off immediately following the
measurement. In this example, the CR5000 measures the CS115 once every
hour while measuring other sensors at 10 Hz.
In Example 5, the 21X turns on the CS115 one minute before the top of the
hour, and on the hour it measures the CS115 using the pulse count instruction.
The execution interval should be set at 1 second, and the configuration code for
Pulse instruction (P3) should be set at 24, Low Level AC, 16-bit, Output in Hz.
When this option is selected, two adjacent 8-bit pulse counters (Pulse Input
channels 1 and 2) are combined into one input channel (Pulse Input channel 1)
to form a 16-bit accumulator. Therefore, Pulse Input channel 2 cannot be used.
You can also choose to use Pulse Input channel 3, in which case Pulse Input
channels 4 will be combined with Pulse Input channel 3 to form a 16-bit
accumulator. In this mode, the 21X’s execution interval must be less than one
minute. If the execution interval is longer than one minute, you will get an
error, because the 16-bit pulse accumulator will overflow counting the signal
from the CS115 when it outputs close to 1100 Hz (1100 mb of barometric
pressure).
In the example programs above, the pressure is reported in millibars (mb). To
report pressure in different units, multiply the measured pressure by the
appropriate conversion factor using the P37 (Z=X*F) instruction for the
CR500, CR510, CR10(X), CR23X, 21X and CR7, or by adding an expression
for the CR5000 and CR9000. See Table 5-1 below for conversion factors.
TABLE 5-1. Conversion Factors for
Alternative Pressure Units
To Find Multiply by
hPa 1.0
kPa 0.1
mm of Hg 0.75006
in of Hg 0.02953
psi 0.0145
atm 0.00099
torr 0.75006

CS115 Barometric Pressure Sensor
7
5.1 Period Averaging Measurement Examples
5.1.1 Period Averaging Measurement Example for CR10(X)
EXAMPLE 1. Sample Program for CR10(X)
;{CR10X}
;
*Table 1 Program
01: 1 Execution Interval (seconds)
;Turn on CS115 one minute before the hour
;
1: If time is (P92)
1: 59 Minutes (Seconds --) into a
2: 60 Interval (same units as above)
3: 48* Set Port 8* High
;Measure CS115 at the top of the hour
;
2: If time is (P92)
1: 0 Minutes (Seconds --) into a
2: 60 Interval (same units as above)
3: 30 Then Do
3: Period Average (SE) (P27)
1: 1 Reps
2: 14 200 kHz Max Freq @ 2 V Peak to Peak, Freq Output
3: 6* SE Channel
4: 10 No. of Cycles
5: 5 Timeout (units = 0.01 seconds)
6: 1* Loc [ P_mb ]
7: 1000 Mult
8: 0.0 Offset
;Turn off CS115
;
4: Do (P86)
1: 58* Set Port 8* Low
5: End (P95)
6: 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)
7: Real Time (P77)
1: 0110 Day,Hour/Minute (midnight = 0000)

CS115 Barometric Pressure Sensor
8
8: Sample (P70)
1: 1 Reps
2: 1* Loc [ P_mb ]
*Table 2 Program
02: 0.0000 Execution Interval (seconds)
*Table 3 Subroutines
End Program
-Input Locations-
1 P_mb
* Proper entries will vary with program and datalogger channel, and input location assignments.
5.1.2 Period Averaging Measurement Example for CR10(X) in a Slow
Executing Program
EXAMPLE 2. Sample Program for CR10(X)
;{CR10X}
;
*Table 1 Program
01: 10 Execution Interval (seconds)
;Turn on CS115
;
1: Do (P86)
1: 48* Set Port 8* High
;Give 2 second delay for CS115 to settle
;
2: Excitation with Delay (P22)
1: 1 Ex Channel
2: 0 Delay W/Ex (0.01 sec units)
3: 200 Delay After Ex (0.01 sec units)
4: 0 mV Excitation
3: Period Average (SE) (P27)
1: 1 Reps
2: 14 200 kHz Max Freq @ 2 V Peak to Peak, Freq Output
3: 6* SE Channel
4: 10 No. of Cycles
5: 5 Timeout (units = 0.01 seconds)
6: 1* Loc [ P_mb ]
7: 1000 Mult
8: 0.0 Offset

CS115 Barometric Pressure Sensor
9
;Turn off CS115
;
4: Do (P86)
1: 58* Set Port 8* Low
5: 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)
6: Real Time (P77)
1: 0110 Day,Hour/Minute (midnight = 0000)
7: Sample (P70)
1: 1 Reps
2: 1* Loc [ P_mb ]
*Table 2 Program
02: 0.0000 Execution Interval (seconds)
*Table 3 Subroutines
End Program
-Input Locations-
1 P_mb
* Proper entries will vary with program and datalogger channel, and input location assignments.
5.1.3 Period Averaging Measurement Example for CR23X
EXAMPLE 3. Sample Program for CR23X
;{CR23X}
;
*Table 1 Program
01: 1 Execution Interval (seconds)
;Turn on CS115 one minute before the hour
;
1: If time is (P92)
1: 59 Minutes (Seconds --) into a
2: 60 Interval (same units as above)
3: 41* Set Port 1* High
;Measure CS115 at the top of the hour
;
2: If time is (P92)
1: 0 Minutes (Seconds --) into a
2: 60 Interval (same units as above)
3: 30 Then Do

CS115 Barometric Pressure Sensor
10
3: Period Average (SE) (P27)
1: 1 Reps
2: 14 200 kHz Max Freq @ 500 mV Peak to Peak, Freq Output
3: 24* SE Channel
4: 10 No. of Cycles
5: 5 Timeout (units = 0.01 seconds)
6: 1* Loc [ P_mb ]
7: 1000 Mult
8: 0.0 Offset
;Turn off CS115
;
4: Do (P86)
1: 51* Set Port 1* Low
5: End (P95)
6: 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)
7: Real Time (P77)
1: 0110 Day,Hour/Minute (midnight = 0000)
8: Sample (P70)
1: 1 Reps
2: 1* Loc [ P_mb ]
*Table 2 Program
02: 0.0000 Execution Interval (seconds)
*Table 3 Subroutines
End Program
-Input Locations-
1 P_mb 1 1 1
* Proper entries will vary with program and datalogger channel, and input location assignments.

CS115 Barometric Pressure Sensor
11
5.1.4 Period Averaging Measurement Example for CR5000 in a Fast
Executing Program at 10Hz
EXAMPLE 4. Sample Program for CR5000
‘CR5000
'
'Sample Program to Measure CS115 Barometric Pressure Sensor
'
'
Public CS115_Freq, Pressure
Units Pressure = mb
BeginProg
Scan (100,mSec,3,0)
'Turn CS115 ON one minute before every hour
'If (IfTime (59,60,min)) Then WriteIO (1,1)
'Period Avgeraging instruction must be executed every scan, and
'cannot be inside the "If" statement. The measured value, therefore, is
'first written into a temporary variable called "CS115_Freq".
PeriodAvg (CS115_Freq,1,mV5000,33,0,1,10,20,1.0,0)
'Once CS115 is turned on one minute before every hour, and
'the correct measurement is made, it is copied into the current variable
'called "Pressure". The sensor is, then, turned off.
'If IfTime(0,60,min) Then
Pressure = CS115_Freq
'Turns CS115 OFF
' WriteIO (1,0)
EndIf
NextScan
EndProg

CS115 Barometric Pressure Sensor
12
5.2 Pulse Count Measurement Example
5.2.1 Pulse Count Measurement Example for 21X
EXAMPLE 5. Sample Program for 21X
;{21X}
;
*Table 1 Program
01: 1 Execution Interval (seconds)
1: If time is (P92)
1: 59 Minutes into a
2: 60 Minute Interval
3: 46* Set Port 6* High
2: If time is (P92)
1: 0 Minutes into a
2: 60 Minute Interval
3: 30 Then Do
3: Pulse (P3)
1: 1 Reps
2: 1* Pulse Input Channel
3: 24 Low Level AC, 16 Bit, Output Hz
4: 1* Loc [ P_mb ]
5: 1 Mult
6: 0.0 Offset
4: Do (P86)
1: 56* Set Port 6* Low
5: End (P95)
6: If time is (P92)
1: 0 Minutes into a
2: 60 Minute Interval
3: 10 Set Output Flag High
7: Real Time (P77)
1: 0110 Day,Hour/Minute (midnight = 0000)
8: Resolution (P78)
1: 1 High Resolution
9: Sample (P70)
1: 1 Reps
2: 1 Loc [ P_mb ]
*Table 2 Program
02: 0.0000 Execution Interval (seconds)

CS115 Barometric Pressure Sensor
13
*Table 3 Subroutines
End Program
-Input Locations-
1 P_mb 1 1 1
* Proper entries will vary with program and datalogger channel, and input location assignments.
5.3 Output Resolution
When storing the values from the CS115 to a datalogger’s final storage
location, or to a data table, care must be taken to choose suitable scaling of the
reading or to store the value with adequate resolution to avoid losing useful
resolution of the pressure measurement. The default resolution (Low
Resolution) for the Campbell Scientific dataloggers is limited to a maximum of
four digits. Even then the maximum digit value that can be displayed is 6999
(7999 for the CR5000/9000 dataloggers). If you use this option with
barometric data scaled in millibars (hPa), a reading above 699.9 mb (799.9 mb
for CR5000/9000) will lose one digit of resolution, e.g. at 900mb, the
resolution is limited to 1 mb.
To retain 0.1 mb resolution, you either need to deduct a fixed offset from the
reading before it is stored to avoid exceeding the 699.9 (or 799.9) threshold, or
output the barometric reading in high resolution format. This can be done by
using the Resolution (P78) instruction in the CR500, CR510, CR10(X),
CR23X, CR7 and 21X dataloggers, or the IEEE4 format for the CR5000 and
CR9000.
6. Correcting Pressure to Sea Level
The weather service, most airports, radio stations, and television stations reduce
the atmospheric pressure to a common reference (sea level). Equation 1 can be
used to find the difference in pressure between the sea level and the site. That
value (dP) is then added to the offset (0.0 mb) in the measurement instruction.
U. S. Standard Atmosphere and dry air were assumed when Equation 1 was
derived (Wallace, J. M. and P. V. Hobbes, 1977: Atmospheric Science: An
Introductory Survey, Academic Press, pp. 59-61).
dP E =−−















1013 25 1 1 44307 69231
5.25328
..(1)
The value dP is in millibars and the site elevation, E, is in meters. Add dP
value to the offset in the measurement instruction.
Use Equation (2) to convert feet to meters.
Em Eft
ft m
() ()
.
=3 281 (2)

CS115 Barometric Pressure Sensor
14
The corrections involved can be significant: e.g., at 1000 mb and 20°C,
barometric pressure will decrease by 1.1 mb for every 10 meter increase in
altitude.
7. Maintenance and Calibration
Since the sensor is semi-sealed, minimum maintenance is required.
1. Visually inspect the cable connection to ensure it is clean and dry.
2. Ensure that the ground connection (shield) is secure and clean.
3. Visually inspect the casing for damage.
4. Ensure that the pneumatic connection and pipe are secure and undamaged.
The external case can be cleaned with a damp, lint-free cloth and a mild
detergent solution.
Druck recommends recalibrating the CS115 every year. Contact Campbell
Scientific, Inc., phone [phone], for an RMA number before returning
the sensor for recalibration. You may also return the unit directly to Druck
USA for recalibration.
Should you lose the five terminal connector (p/n 16004), the replacement part
can be purchased from Campbell Scientific, Inc. Contact Campbell Scientific,
Inc. to purchase the part.
The CS115 is sensitive to static when the backplate is
removed. To avoid damage, take adequate anti-static
measures when handling.
CAUTION

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