Buck 1011C Bedienungsanleitung
MODEL 1011C HYGROMETER
OPERATING MANUAL
December 2008
BUCK RESEARCH INSTRUMENTS, LLC
PO Box 19498
Boulder, CO 80308
Copyright 2008. Buck Research Instruments, LLC All rights reserved.
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TABLE OF CONTENTS
1.0 INTRODUCTION p.5
1.1 General Operational Description
1.2 Brief Physical Description
1.3 Specifications
1.4 List of improvements from the 1011B
1.5 Acknowledgment
2.0 CONTROLS, CONNECTORS, AND MAJOR COMPONENTS p.11
2.1 Sensing Unit
2.2 Control/Indicator Unit
2.3 Power Unit
2.4 Cables
2.5 Optional Accessories
3.0 INSTALLATION
p.18
3.1 Unpacking Procedure
3.2 Initial Operation Check
3.3 Installation on Aircraft
3.4 Leak Check
3.5 Pressure Within Sensor
3.6 Cabling
4.0 OPERATING INSTRUCTIONS p.24
4.1 Initial Setup
4.2 System Operation
4.2.1 Time Response
4.2.2 Mirror Cleanliness
4.2.3 Supercooled Dew Points
4.2.4 Low Frost Points
4.2.5 Pressure Effects
4.2.6 Typical Response to Humidity Changes
4.2.7 Mirror Flooding
4.3 Operation while Parked or off the Aircraft
5.0 PREVENTIVE MAINTENANCE AND TROUBLESHOOTING p.29
5.1 Periodic Inspection
5.2 Cleaning System Optics
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FIGURES
Number Title
1 Model 1011C Dew Point Hygrometer System p.7
2Depression capability p.9
3Dew Point Sensing Unit p.12
4 Control/Indicator Unit p.14
5 Power Unit, External p.15
6 Power Unit, Internal p.17
7 Sensing Unit: Mounting and Assembly p.20
8 Sensing Unit, Internal p.22
9 Flow Test Fixture Hookup p.23
10 System Response Characteristics p.28
Appendix Figures:
11. 1011C Wiring Diagrams p.31-2
12 Water Vapor Conversions p.33
13 Vapor pressure vs. dew/frost point p.34
14 Absolute humidity vs. dew/frost point p.35
15 Effect of pressure on dew point p.36
16 Aspirating Fixture Hookup p.37
17 1011C Hygrometer Complete p.38
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LIST OF TABLES
Number Title
1 1011C Connectors p.39
2 Dew Point to Frost Point Conversions p.40
3 Dew Point Error Due to Pressure Change in Sampling System p.41
APPENDIXES
1 1011C Pin Out p.30
2 Humidity Conversion Equations p.42
3 Warranty p.44
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SECTION 1. INTRODUCTION
1.1 GENERAL OPERATIONAL INSTRUCTIONS
The 1011C is a high performance condensation type hygrometer designed for airborne
measurement of dew and frost point temperatures. The system is capable of measuring
dew/frost points between -75°C and +50°C, over a wide range of temperatures, pressures,
and airspeeds. The 1011C is a complete update of the 1011B hygrometer, incorporating
many new features described below.
The instrument operates on the chilled-mirror principle. A mirror is thermoelectrically
cooled until it reaches a temperature at which condensation begins to form (the dew or
frost point), and is then held at that temperature; the presence of condensation is sensed
optically. The signal output is a voltage corresponding to the temperature of the mirror.
The 1011C consists of three distinct units – a Sensor unit, a Power unit and a
Control/Indicator unit. The Sensor unit contains a three-stage thermoelectric cooler (TEC)
capable of reaching frost points normally encountered at altitudes up to 45,000 feet.
ALL PARTS OF THE 1011C CAN ONLY BE USED WITH THE 1011C. NONE OF
THE 1011B COMPONENTS CAN BE INTERCHANGED WITH THE 1011C.
The 1011C features a microcontroller-based Power unit. It features both voltage and 9600
baud RS-232 serial data outputs. Optionally, it includes a power switch and a pressure
sensor input.
The Control/Indicator unit features LEDs that indicate mirror cleanliness, an LED display
that shows dew/frost point temperature, and a blue LED that indicates whether the
instrument is controlling on a dew or a frost point.
The instrument will operate well in most environments, both on and off aircraft. Although
the standard configuration is designed for in-flight operation, an optional aspirating kit
enables use while the aircraft is on the ground, as well as off the aircraft in a lab or other
environment.
Startup and operation are normally very simple. Excluding extreme humidity
environments, no in-flight adjustments are required.
Note: An aircraft is an exceedingly difficult platform from which to make
humidity measurements, because of the extreme range of environmental
conditions which can occur, the abruptness of changes encountered, and
various thermodynamic and aerodynamic considerations. While the 1011C
is designed using the highest standards in this type of instrument, in-flight
situations can be encountered which will tax its limits. To help assure
consistently good performance, a number of cautionary factors are
discussed in this manual.
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1.2 BRIEF PHYSICAL DESCRIPTION
Physically, the system (Figure 1) consists of a sensing unit, a control/indicator unit, a
power unit, associated cabling, and a maintenance unit.
The Sensing Unit (A) is the moisture-detecting device. It contains a right or left hand inlet
fitting, a mirror, sensing/control optics, a thermistor, a TEC, and associated electronics.
The Control/Indicator Unit (B) is the user interface component, and contains the on/off
function switch, balance control, and displays.
The Power Unit (C) distributes operating power to the system components and contains the
circuitry that controls the thermoelectric cooler and converts mirror temperature to a
suitable output signal (provided at rear of unit). The unit is equipped with quick-remove
shock mount.
The Maintenance kit: Consisting of bottles for water and acetone, cotton swabs and spare
gaskets and o-rings. Unlike the 1011B, the 1011C does not come with a calibration plug.
This is because the 1011C uses an ultra-stable thermistor instead of an RTD, which
improves speed of response and is far less susceptible to drift. Additionally, the
temperature is measured with an analog-to-digital converter (ADC) that is calibrated each
time the instrument is turned on and is not susceptible to drift like the analog electronics in
the old 1011B instrument, and therefore does not need a calibration plug.
Three Cables or six Connectors, a Data Connector, and a Power Connector connect the
various system components and provide input power.
Optional Accessories, which further increase versatility and ease of use, are described in
Section 2.6.
Note:The 1011B hygrometer was originally developed and produced by
General Eastern Instruments. This operating manual originated at General
Eastern, and many of the drawings are reproduced by their courtesy.
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C
B
A
Figure 1. Dew Point Hygrometer System
(shown with optional cables)
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1.3 SPECIFICATIONS
Dew point range: -75 to +50 °C nominal
(see also Figure 2)
Accuracy ± 0.1° C RS-232
± 0.3° C LED display
Response time: Variable
(see Sect. 4.2.1)
OutputsAnalog:
Dew point: 0.08 v/°C, 6v = 0°C
Control voltage: 0 – 10 vdc
Minimum load impedance 5 K ohms
Digital display resolution: 0.1 °C
Power Input 28 vdc, 2.5 A max
Operating Limits
Operating temperature range
Sensing Unit: -80 to +60 °C
Control/Indicator Unit: -40 to +60 °C
Power unit: -40 to +60 °C
Airspeed (nominal): 450 knots
Altitude (nominal): 45,000 feet
Pressure Limit: 1.5 atmospheres
Dimensions in inches
Sensing Unit
Diameter (max): 2.50
Length (with inlet fitting): 4.25
Control/Indicator unit
Height: 3.26
Width: 3.26
Depth: 5.88
Power unit, including shock mount
Height: 6.38
Width: 6.06
Depth: 12.0
Weight, lbs.
Sensor: 1.5 lbs.
Control/Indicator: 1.25 lbs.
Power unit: 3.25 lbs.
Cables: 8.0 oz.
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1.4 NOTE TO USERS OF 1011B SYSTEMS
The following is a list of improvements made:
1. 28 VDC operation.
2. RS-232 data output
3. Improved accuracy, ± 0.1 degree C over entire range*
4. Improved servo control, reducing oscillations be a factor of 10.
5. Improved cooling of at least 10 degrees C
6. Faster and more accurate response at low dew points
7. Software-upgradeable by end user.
8. Optional pressure sensor input and mixing ratio output
9. Autobalance feature automatically compensates for reduced mirror reflectivity
caused by contamination.
10. Service Mirror LED illuminates to indicate mirror contamination is too great
and mirror needs to be cleaned.
11. D/F Point LED, which illuminates when a dew or frost point is reached
*RS-232 output only
1.5 ACKNOWLEDGMENT
David M. McFarland at the National Center for Atmospheric Research initially developed
the flow test fixture and the aspirating fixture. We acknowledge with appreciation Mr.
McFarland's contribution in making these devices available to the user community.
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