0871LH1 Freezing Rain Sensor User Manual
Contents
1. Description Colour CR3000 CR1000 CR10X CR510 Control Port Control Port Status Yellow Control Port Control Port Power Reference Case GND Green G G 5V Power Purple 5V 5V Shield Clear G G cannot share control ports Power Connections to Terminal Expander 24 VDC Red V 24V Black V Figure 5 Power Supply Connections part C2155 CR1000 Transformer 0871LH1 220 4 120 VAC eescccces gt NOTE Please contact a certified electrician to properly install the power supply _ 24VDC A 0000 Terminal Expander FIN2PWR L Figure 6 General Hook up Diagram 0871LH1 Freezing Rain Sensor 9 Program Examples 9 1 CR1000 Declare Public Variables Public PTemp batt_volt Public TimeCount Public IceSignal Public StatusSignal ice signal 1 no ice 0 ice status signal 0 okay 1 fault Define Data Tables DataTable Stat True 1 Sample 1 StatusSignal FP2 EndTable DataTable Ice True 1 Sample 1 IceSignal FP2 EndTable DataTable Info 1 1 Datalnterval 0 15 Sec 10 Minimum 1 batt_volt FP2 0 False Sample 1 PTemp FP2 EndTable Main Program BeginProg PortsConfig amp B11 amp B00 Scan 5 Sec 0 0 PanelTemp PTemp 250 Battery Batt_volt TimeCount Timer 1 Sec 0 If TimeCount gt 61 then Portget IceSignal 1 PortGet StatusSignal 2 If StatusSignal 1 then CallTable Stat EndIf If IceSignal 0 the2. is verified by simulating a microcontroller time out and waiting for a reset input e Proper ROM operation is verified by computing a checksum of the ROM contents and comparing against a checksum stored in the ROM e RAM operation is verified by writing and reading test bytes A 3 Appendix A RS 422 Output Format e The Power Interrupt Timer is checked by verifying its transitions to a warm state after performing a cold start e The power fail input is pulled down to verify a power failure is detected Each time the critical data from the Serial EEPROM is read a checksum is read and compared to the checksum computed from the contents Each time critical data is written to the Serial EEPROM a checksum is computed and stored with the data e Resets due to unknown reasons such as reset from the watchdog timer are detected Initiated BIT will examine the RESET EEPROM input If the input is active the STATUS output will be set to FAIL and the ICE output and probe heater will be disabled This feature allows a factory technician to perform the MSO capacitor selection process without activation of the probe heater Activation of the Press to Test PTT input for greater than 100 ms also causes the ice detector to perform Initiated BIT The PTT input is ignored when the ice output is active After PTT is completed the correlation count is restored to its pre test value Initiated BIT is complete within 3 seconds
3. request When returning equipment the Repair Reference Number must be clearly marked on the outside of the package Note that goods sent air freight are subject to Customs clearance fees which Campbell Scientific will charge to customers In many cases these charges are greater than the cost of the repair CAMPBELL SCIENTIFIC EUROPE WHEN MEASUREMENTS MATTER Campbell Scientific Ltd Campbell Park 80 Hathern Road Shepshed Loughborough LE12 9GX UK Tel 44 0 1509 601141 Fax 44 0 1509 601091 Email support campbellsci co uk www campbellsci co uk PLEASE READ FIRST About this manual Please note that this manual was originally produced by Campbell Scientific Inc primarily for the North American market Some spellings weights and measures may reflect this origin Some useful conversion factors Area 1 in square inch 645 mm Length 1 in inch 25 4 mm 1 ft foot 304 8 mm 1 yard 0 914 m 1 mile 1 609 km Mass 1 oz ounce 28 35 g 1 Ib pound weight 0 454 kg Pressure 1 psi lb in 68 95 mb Volume 1 UK pint 568 3 ml 1 UK gallon 4 546 litres 1 US gallon 3 785 litres In addition while most of the information in the manual is correct for all countries certain information is specific to the North American market and so may not be applicable to European users Differences include the U S standard external power supply details where some information for example the AC t
4. 0871LH1 Freezing Rain Sensor User Manual Issued 14 1 09 Copyright 2007 Campbell Scientific Canada Corp Printed under licence by Campbell Scientific Ltd CSL 742 Guarantee This equipment is guaranteed against defects in materials and workmanship This guarantee applies for twelve months from date of delivery We will repair or replace products which prove to be defective during the guarantee period provided they are returned to us prepaid The guarantee will not apply to e Equipment which has been modified or altered in any way without the written permission of Campbell Scientific e Batteries e Any product which has been subjected to misuse neglect acts of God or damage in transit Campbell Scientific will return guaranteed equipment by surface carrier prepaid Campbell Scientific will not reimburse the claimant for costs incurred in removing and or reinstalling equipment This guarantee and the Company s obligation thereunder is in lieu of all other guarantees expressed or implied including those of suitability and fitness for a particular purpose Campbell Scientific is not liable for consequential damage Please inform us before returning equipment and obtain a Repair Reference Number whether the repair is under guarantee or not Please state the faults as clearly as possible and if the product is out of the guarantee period it should be accompanied by a purchase order Quotations for repairs can be given on
5. Loc IceStat If there is ice on the unit start a looping sequence that ends only when ice is no longer detected 17 Timer P26 1 0 Reset Timer 18 End P95 19 End P95 Appendix A RS 422 Output Format A 1 RS 422 Output Format for non Campbell Datalogger Applications This output operates at 9600 BAUD One Start Bit 8 Data Bits No Parity One Stop Bit A 24 byte string is sent once per second See section 10 2 for string definition A two line output provides a bi directional serial port running at 9600 BAUD 8 bits one Start Bit One Stop Bit no parity to allow communication with aircraft electronics and external test equipment NOTE If access to the digital RS422 data is required with a Campbell Scientific datalogger this is possible using an SDM SIO1 Please contact Campbell Scientific for further details A 2 Built In Test BIT Built In Test BIT capabilities of the freezing rain sensor consist of hardware continuous power up and operator initiated tests Whenever a failure is detected and verified the freezing rain sensor stops detecting and annunciating icing conditions and the heaters are disabled Failures detected in Initiated and Continuous BIT are counted and enunciated once they have been verified To eliminate nuisance errors failures are verified by delaying debouncing the failure for a period of time Failures detected in Initiated BIT are latched and power must be cycled on an
6. a a oaa Eep E AE ESAT 1 3 Detailed Principle of Operation 1 4 Physical Description e nennen nennen 3 5 Temperature Considerations 3 6 Power InterruptioNs eee eee eeeeeeeeeees 3 7 Mounting Considerations 4 8 Wiring Diagram tours ae 5 9 Program ExampleSs reee reeree rrenen 6 ILLERA id 6 DD MCR D3 A ees vere OS 7 Figures 1s MSO Circuit SChemMatic iaia ri 2 2 MSO Circuit Sectional View css ccee eee cseeeeessseseeessseaeesesesaeeaeees 2 3 ICE detector mc iia a nana 3 d4 Mount T RATORI RAR 4 5 Power Supply Connections Ee RER 5 6 General Hook up Diagram naciona noncnn cnn cnncncnncnncnos 5 B1 Functional Block Diagram oo ieee sseeseeeeceeceseeseeeeeeeeeesseeaeeeeseee B 1 Tables AL BIT Information een A 2 A2 Serial String Format iii eee A 5 B1 0871KB Ice Detector Qualification Capabilities B 4 B2 Input Output Pin Designations ii B 5 Appendices A RS 422 Output Format B Freezing Rain Sensor 0871LH1 Freezing Rain Sensor 1 Purpose 2 General This document provides detailed information about the Goodrich model 0871LH1 Freezing Rain Sensor for use in ground based meteorological appl
7. ate 1 Heater On 0 Heater Off Ice Output 1 Ice 0 No Ice Status Output 1 Fail 0 OK No Fail 1 2 MSO FREQUENCY MSO Count in Hex ea Oe 3 ERRSTAT1 7 Unused 1 Active 6 MSA Fail Too High 5 MSO Fail Too Low 4 EEPROM Fail 3 RAM Fail 2 ROM Fail 1 Watchdog Fail 0 Power Interrupt Timer Fail 4 ERRSTAT2 7 6 Probe Heater Failure 00 Probe Heater OK 01 Probe Heater Always ON or OPEN 10 Probe Heater Always OFF 11 Probe Heater ON with 1 Enable 5 De Icing Fail 1 Active 4 3 2 Unused 1 Unused 0 Unused 5 7 ON TIME CNT o Un HON 00 01FFFF 8 9 COLD START CNT eee 00 FFFF 10 11 ICE CNT Ice Events 00 FFFF Total Failures 12 FAIL CNT Encountered This 00 FF number is incremented each time the ice detector transitions from OK to fail MSO Frequency Fail 13 FAIL DTL 1 7 4 Count 0 F 3 0 Heater Fail Count 0 F A 5 Appendix A RS 422 Output Format 14 FAIL DTL 2 7 4 Not Used Not Used 3 0 Not Used Not Used 15 LAST ERR 1 See ERRSTAT1 Above 16 LAST ERR 2 See ERRSTAT2 Above 17 2ND LAST ERR 1 See ERRSTAT1 Above 18 2ND LAST ERR 2 See ERRSTAT2 Above 19 PERM ERR 1 See ERRSTAT1 Above 20 PERM ERR 2 See ERRSTAT2 Above 21 Software Version 7 0 lope per 0 FF 22 Correlation Count 7 0 0 01 ice accretion 0 FF increments since power on 23 CHECKSUM Summation 1 byte wide 0 FF of bytes 0 22 A 9 Electrostatic Discharge ESD Consideration The freezi
8. d off to remove a failure If failures detected in Continuous BIT go away the ice detector changes back to normal mode and once again enables all ice detection functions A 3 Hardware Built In Test BIT Hardware BIT is comprised of a watchdog timer that forces the microcontroller to re initialize if it does not receive a strobe every 1 6 seconds An internal voltage monitor forces the microcontroller to the reset state if the internal 5VDC power supply falls below 4 65 VDC and holds it there until the power supply returns above 4 65 VDC When the microcontroller is reset no output string is sent A 1 Appendix A RS 422 Output Format A 4 Continuous Built In Test BIT Continuous BIT consists of verifying the following e The probe heater is in the correct state The return leg of the heater is monitored e The ICE discrete output is in the correct state The ICE discrete output is fed back to the microcontroller through a passive voltage divider and voltage comparator e The MSO is operating correctly Frequencies between 39000 and 40150 Hz are valid e The probe heater is de icing correctly After turn on the probe heater must cause the MSO frequency to return to at least 39970 Hz within the 25 second timeout or it is considered failed e Probe is de iced within 25 seconds De Icing Fail A 5 BIT Failure That Disables Ice Output A 2 The Ice output is disabled due to Continuous and Initiated BIT failure
9. ed Each time 0 020 forms on the probe the 60 second counter is reset In effect the output stays on for 60 seconds after the beginning of the last icing encounter The Status output indicates whether the freezing rain sensor is functioning correctly using tests that are described in more detail in following sections of this document 10 METERS NODE PLATE MAGNETOSTRICTIVE OSCILLATION FEEDBACK 40 000 Hz aL ms DRIVE COIL Be NI SPAN C THIN WALLED TUBE Figure 1 MSO Circuit Schematic ULI KA SONIC VIBRAIING STRUT PROBE 40kHz HEATER FEEDBACK COIL PROBE HEATER TERMINATION DRIVE COIL Figure 2 MSO Circuit Sectional View User Manual 4 Physical Description The freezing rain sensor is an integrated unit containing both the sensor and processing electronics It contains a 7 35 cm 2 9 square faceplate for mounting to the 0871LH1MNT and a 7 28 cm 2 86 diameter housing containing the processing electronics The unit weighs 318 grams 0 7 lbs maximum PROBE STRUT I Figure 3 Ice Detector 5 Temperature Considerations WARNING In the case of unit malfunction causing strut heater lock on the probe temperature can exceed 204 4 C Maintenance personnel should exercise caution when servicing the unit Power Interruptions The freezing rain sensor is qualified to DO 160C power input category Z The unit will remember status through a 200 ms power interruption but the output
10. frequency of the probe With the sensor wired to the datalogger use a digital voltmeter DVM measure DC voltage signal between the Ice signal blue wire in control port and the power reference ground black wire in G terminal The voltage reading should be 4500mvDC to 5000mvDC When the probe tip of the ice detector is squeezed thus changing the frequency and tripping the probe the voltage reading will immediately drop to a reading below 500mvDC Observing this will verify that the probe is operating properly and give the user enough time to release the probe before it reaches its full heating temperature Once initiated the heating de icing sequence will quickly heat the probe to 204 4 C Though bare fingers must be used for a reliable test result there is a danger that you will burn your fingers if you do not let go when heating has been verified A 7 Initiated Built In Test BIT Initiated BIT is performed at initial power up of the freezing rain sensor and following power interruptions of not less than 200 ms Initiated BIT consists of the following tests e The ice and fault status outputs are set in the RS 422 string and on the discrete outputs so monitoring electronics or test equipment can verify activation e The freezing rain sensor heater is turned on for a short period of time to verify correct operation of the heater heater control circuit and heater feedback circuit e Correct operation of the watchdog timer
11. ge The watchdog indicates impending power loss so the ice detector can shut down in a known manner B1 3 Serial EEPROMB The Serial EEPROM stores unit status icing state failure state heater state correlation count which is recovered after power interruptions of 200 ms or less This allows the unit to meet the power interruption requirements of RTCA DC 160C Section 16 Category Z Additionally the Serial EEPROM stores environmental and failure information such as unit elapsed time number of icing encounters number of failures and detailed information on types and quantities of each annunciated failure This information is used by Rosemount Aerospace to confirm and repair failures reported by the end user and also to collect MTBF data Each time the Serial EEPROM is written a checksum is computed and written Each time the Serial EEPROM is read a checksum is computed and compared to the stored value B1 4 Probe Oscillator The probe oscillator is the electronic control portion of the magnetostrictive oscillator MSO used to sense and detect ice This circuit provides the drive and feedback of the ice sensing probe The circuit drives the probe at a nominal 40kHz and converts the feedback into a CMOS compatible square wave that is measured by the microcontroller As ice accretes on the probe the frequency decreases and it is this frequency change that the microcontroller annunciates in the form of Ice Signal 1 B1 5 Heater Co
12. ications Topics covered include requirements qualification categories and methodology and detailed design information The Goodrich 0871LH1 Freezing Rain Sensor is a one piece unit that detects the presence of icing condition Twenty four volts DC input power is provided to the freezing rain sensor The freezing rain sensor outputs include ice detection indication and fault status indication These outputs are provided through an RS 422 interface and discrete outputs One freezing rain sensor is used on each station and provides the primary means of ice detection The ice signal is used to indicate to the operator that an icing condition exists so that appropriate actions can be taken 3 Detailed Principle of Operation The freezing rain sensor uses an ultrasonically axially vibrating probe to detect the presence of icing conditions The sensing probe is a nickel alloy tube mounted in the strut at its midpoint node with one inch exposed to the elements This tube exhibits magnetostrictive properties it expands and contracts under the influence of a variable magnetic field A magnet mounted inside the strut and modulated by a drive coil surrounding the lower half of the tube provides the magnetic field A magnetostrictive oscillator MSO circuit is created with the above components and the addition of a pickup coil and an electronic comparator The ultrasonic axial movement of the tube resulting from the activation of the drive coil cau
13. n CallTable Ice Timer 1 Sec 3 EndIf EndIf CallTable Info NextScan EndProg User Manual 9 2 CR23X he Timer P26 3 Loc Timer he If X lt gt F P89 3 X Loc Timer 3 gt 61 F 30 Then Do DD U Set Port s P20 9999 C8 C5 nc nc nc nc 2 9988 C4 C1 nc nc input input e This Section will read the status of the ports for comparison 4 Read Ports P25 1 1 Mask 0 255 2 2 Loc IceStat 5 Read Ports P25 1 2 Mask 0 255 2 1 Loc FaultStat Check to see if there is a fault in the unit and output it f X lt gt F P89 X Loc FaultStat F 6 1 2 3 4 30 Then Do W ma N Do P86 1 10 Set Output Flag High Flag 0 8 Set Active Storage Area P80 13085 1 Final Storage Area 1 2 10 Array ID he 9 Real Time P77 1712 1 1220 Year Day Hour Minute midnight 2400 10 Sample P70 23951 1 1 Reps 2 1 Loc FaultStat 11 End P95 Check to see if there is Ice on the unit and output it PRISE EIG RISES CRICRICI RICKI ICR ICRICR ACACIA AACR ACA AA IAA 12 If X lt gt F P89 132 X Loc IceStat 2 1 3 1 F 4 30 Then Do 13 Do P86 1 10 Set Output Flag High Flag 0 14 Set Active Storage Area P80 110755 1 1 Final Storage Area 1 2 20 Array ID 0871LH1 Freezing Rain Sensor 15 Real Time P77 8112 1 1220 Year Day Hour Minute midnight 2400 16 Sample P70 5446 1 1 Reps 2 2
14. ng however is only guaranteed when input voltage is 24VDC or greater CAMPBELL SCIENTIFIC COMPANIES Campbell Scientific Inc CSI 815 West 1800 North Logan Utah 84321 UNITED STATES www campbellsci com info campbellsci com Campbell Scientific Africa Pty Ltd CSAf PO Box 2450 Somerset West 7129 SOUTH AFRICA www csafrica co za sales csafrica co za Campbell Scientific Australia Pty Ltd CSA PO Box 444 Thuringowa Central QLD 4812 AUSTRALIA www campbellsci com au info campbellsci com au Campbell Scientific do Brazil Ltda CSB Rua Luisa Crapsi Orsi 15 Butant CEP 005543 000 Sao Paulo SP BRAZIL www campbellsci com br suporte campbellsci com br Campbell Scientific Canada Corp CSC 11564 149th Street NW Edmonton Alberta T3M 1W7 CANADA www campbellsci ca dataloggers campbellsci ca Campbell Scientific Ltd CSL Campbell Park 80 Hathern Road Shepshed Loughborough LE12 9GX UNITED KINGDOM www campbellsci co uk sales Ocampbellsci co uk Campbell Scientific Ltd France Miniparc du Verger Bat H 1 rue de Terre Neuve Les Ulis 91967 COURTABOEUF CEDEX FRANCE www campbellsci fr info campbellsci fr Campbell Scientific Spain S L Psg Font 14 local 8 08013 Barcelona SPAIN www campbellsci es info campbellsci es Campbell Scientific Ltd Germany Fahrenheitstrasse13 D 28359 Bremen GERMANY www campbellsci de info campbellsci de Please visit www campbellsci com
15. ng rain sensor internal components are ESD sensitive class 1 so proper ESD precautions must be observed wrist straps conductive surfaces when handling A 6 Appendix B Freezing Rain Sensor B 1 Freezing Rain Sensor Block Diagram The block diagram in Figure B 1 Functional Block Diagram provides an understanding of the functionality of the freezing rain sensor Feedback Coil Probe Heater Probe Oscillator 24 VDC return Heater Control Voltage Monitor amp DC Power Watchdog Supply Timer Connector Y pal o Y 2 RS 422 Transmit RS 422 Transmit ICE Feedback EEPROM Figure B 1 Functional Block Diagram B 1 Appendix B Freezing Rain Sensor B1 1 Microcontroller The freezing rain sensor uses an Intel 87C51 type microcontroller to control the freezing rain sensor functions This 8 bit microcontroller requires at least 4 Kbytes of on board ROM 128 bytes of RAM and 32 input output ports The freezing rain sensor uses about 75 of these resources Upgraded microcontrollers that provide more resources are available The microcontroller runs at 7 372 MHz B1 2 Watchdog Reset Circuit The watchdog timer reset circuit monitors the microcontroller and provides a reset pulse if not periodically toggled The watchdog also provides reset pulses on initial power up and holds the microcontroller in the reset state if the internal power supply falls below an acceptable volta
16. ntrol B 2 The heater control turns the probe heater on and off as commanded by the microcontroller and monitors the actual heater state ON or OFF for verification by the microcontroller Two outputs are required from the microcontroller to turn on the heater This minimizes the possibility of an unintended heater ON condition The heater control also monitors the state of the heater B1 6 Drive Coil Appendix B Freezing Rain Sensor and provides feedback to the microcontroller so that it can be determined whether the heater is on or off The drive coil modulates the magnetic field of the magnetostrictive oscillator and causes an ultrasonic axial movement of the probe B1 7 Feedback Coil B1 8 Heater The feedback coil senses the movement of the probe and when employed in the probe oscillator circuit completes the feedback portion of the MSO The probe heater de ices the probe It is activated when the nominal icing trip point of 0 020 is reached and is turned off five seconds after the MSO has returned to at least 39 970 Hz the additional five seconds allows the strut probe time to shed the de bonded ice The maximum heater ON time is 25 seconds If the probe frequency has not returned at least 39 970 Hz by that time a de ice failure is declared and the heaters are turned off An open circuit of the heater is detected by the microcontroller B1 9 DC Power Supply The DC power supply provides 24 VDC for the heater circui
17. of initial power up A 8 Correlation Counting A 4 The freezing rain sensor tracks the amount of ice accumulation on the probe during an icing encounter The correlation count is a value tracked by the freezing rain sensor that indicates the amount of ice that has accumulated on the probe during the icing encounter Each correlation count equals 0 010 inches of ice The correlation count ranging from 0 to 255 indicates the number of times the MSO frequency decreases by 65 Hz during an icing encounter A decrease in frequency of 65 Hz correlates to an equivalent 0 25 mm of ice that would have formed on the ice detector probe neglecting the change in collection efficiency caused by ice build up Upon reaching a correlation count of 255 the value is no longer incremented The freezing rain sensor compensates by adding a value ranging from 0 to 6 to the correlation count when the ice detection cycle is completed to account for the ice that would have accumulated if the heater had not been on The correlation count is in the serial string Table A2 Serial String Format The correlation count is initialized to zero at unit power up Appendix A RS 422 Output Format Table A2 Serial String Format Byte 0 First Definition String ID Comments nterpretation Range Presently defined as 00 May add additional strings in future Unused Probe Heater St
18. ransformer input voltage will not be applicable for British European use Please note however that when a power supply adapter is ordered it will be suitable for use in your country Some brackets shields and enclosure options including wiring are not sold as standard items in the European market in some cases alternatives are offered Details of the alternatives will be covered in separate manuals Recycling information At the end of this product s life it should not be put in commercial or domestic refuse but sent for recycling Any batteries contained within the product or used during the products life should be removed from the product and also be sent to an appropriate recycling facility Campbell Scientific Ltd can advise on the recycling of the equipment and in some cases EA arrange collection and the correct disposal of it although charges may apply for some items or territories For further advice or support please contact Campbell Scientific Ltd or your local agent CAMPBELL SCIENTIFIC EUROPE WHEN MEASUREMENTS MATTER Campbell Scientific Ltd Campbell Park 80 Hathern Road Shepshed Loughborough LE12 9GX UK Tel 44 0 1509 601141 Fax 44 0 1509 601091 Email support O campbellsci co uk www campbellsci co uk 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 T PUrDOSe Leica eroi 1 2 A e
19. s as shown in Table A1 BIT Information Ice detection is disabled when these failures occur because the integrity of the ice detection capability has been compromised Table Al BIT Information ve Sees Initiated BIT Continuous BIT MSO Fail High x MSO Fail Low x EEPROM Fail x RAM Fail X ROM Fail X Watchdog Fail X Power Interrupt Timer Fail X Power Fault Monitor Fail X en Reatar Always ON or Active Test Passive Test Probe Heater Always OFF Active Test Nele Probe Heater ON w 1 X Enable De Icing Fail Clear Only Set Only Unknown Reset Failure X ee di Active Test Passive Test Appendix A RS 422 Output Format Note 1 When the failure is enunciated the software no longer provides ice detection capability Note 2 In Continuous BIT the Probe Heater Always OFF failure is set when the heater is ON and a de icing failure has been detected If the frequency indicates that the ice has been removed within the expected time the software will not annunciate the probe heater failure The actual failure is most likely due to a problem in the heater feedback circuitry rather than heater control circuitry The failure will be enunciated the next time IBIT is performed A 6 Operator Initiated Tests CAUTION The operator can test the freezing rain sensor functionality by squeezing the tip of the probe between the index finger and thumb This simulates icing by decreasing the
20. ses a current to be induced in the pickup coil The current from the pickup coil drives the comparator that in turn provides the signal for the drive coil The oscillation frequency of the circuit is determined by the natural resonant frequency of the sensor tube which is tuned to 40 kHz With the start of an icing event ice collects on the sensing probe The added mass of accreted ice causes the frequency of the sensing probe to decrease in accordance with the laws of classical mechanics A 0 5 mm 0 020 thickness of ice on the probe causes the operating frequency of the probe to decrease by approximately 130 Hz Freezing Rain Sensor software monitors probe frequency and detects and annunciates this frequency decrease At the same time the internal probe heater power is applied until the frequency rises to a predetermined set point plus an additional delay factor to assure complete de icing 0871LH1 Freezing Rain Sensor Once de iced the sensing probe cools within a few seconds and is ready to sense ice formation again When ice forms on the sensing probe again to the point where the MSO frequency decreases by 130 Hz the sensor de ices itself again This cyclic process is repeated as long as the freezing rain sensor remains in an icing environment The ice signal activates at 0 020 ice accretion and stays on for 60 seconds after the end of the icing encounter Specifically when the output is activated a 60 second timer is start
21. sh Safety DO 160C Shock Salt Spray DO 160C Cat S Humidity DO 160C Cat B Icing Performance Rosemount Aerospace Inc Test Procedure Power Input DO 160C Cat Z 18 29 5 VDC Voltage Spike DO 160C Cat A Magnetic Effect DO 160C Cat A 1 deflection at 0 5m Bonding 2 5 mQ Max Mounting Plate to Aircraft Structure 10 mQ Max Connector Shell to Mounting Plate Dielectric Withstanding MIL STD 202 500 VAC 60 Hz EMI Filters Disconnected Insulation Resistance MIL STD 202 500 VDC 1000 MQ EMI Filters Disconnected Fluid Susceptibility DO 160C Cat F Waterproofness DO 160C Cat W Fungus Resistance DO 160C Cat F Sand and Dust DO 160C Cat D Direct Lightning Strike DO 160C Cat 1A Software DO 178B used as a guideline B 4 Appendix B Freezing Rain Sensor Table B 2 Input Output Pin Designations Signal Name Con Input or Definition Current Wire nector Output Gauge Pin 1 5 Amp Max at ene Input 18 29 5 VDC 28VDC 20 24VDC Ret B eturn ip o Case Ground C Input ane 20 RS 422 High D Output Per RS 422 Spec Per RS 422 Spec 20 24 RS 422 Low E Output Per RS 422 Spec Per RS 422 Spec 20 24 Ice F Output Ground Active 1 5 VDC Max 0 5 50 mA 20 24 Open Inactive Status G Output Ground Active 1 5 VDC Max 0 5 50 mA 20 24 Open Inactive Ice will be correctly detected between these voltages Proper probe de ici
22. string will cease during the interruption The freezing rain sensor uses a power fail monitor to verify the supply voltage If a power fault is detected the freezing rain sensor is halted with a failure indication on the STATUS discrete output 0871LH1 Freezing Rain Sensor 7 Mounting Considerations Prevailing Wind Se 20 30 degrees ee Figure 4 Mounting part 0871LH1 MNT The freezing rain sensor should be mounted to a sturdy crossarm located away from buildings or other obstacles that could shadow the sensing element from freezing rain The sensor should be installed so that the sensing probe is a minimum 36 inches above the ground 1 Remove the protective tube from strut 2 Attach the freezing rain sensor to the mounting bracket using the supplied Y4 20 screws and lock washers Position the freezing rain sensor on the mounting pole with the sensing probe pointing upward with the bracket inclined at a 20 30 angle above horizontal to ensure proper drainage of melted ice 3 Attach to a vertical or horizontal pipe using the supplied V bolts nuts and washers NOTE The sensor should be mounted so as to be oriented into the prevailing wind 4 Connect cable to connector 5 Secure cable to bracket with cable ties 6 Remove shipping cover and protective cap prior to powering on the unit User Manual 8 Wiring Diagram using cable Part 0871LH1CBL L Datalogger Connections
23. tected to meet RTCA DO 160C lightning requirements and to prevent stray high voltage from coupling into the unit and damaging the output transistor The ice output has feedback to the microcontroller for software to verify it is in the correct state for more built in test coverage The software in the 0871KB2 model uses this feedback to verify that the ice output is operating correctly However in the 0871KB1 model the software does not use this input To interface to the 0871 KB the power supply must provide a pull up to 5 to 28 volts When the ice output is inactive open the nominal resistance to ground is 13 4 KQ The power supply should source at least 0 250 mA to provide the proper signal to the Ice Signal feedback circuitry When the output is active closed it is capable of sinking 50 mA and is guaranteed to be no more than 1 5 VDC with respect to Signal Return Table B 1 0871KB Ice Detector Qualification Capabilities Test Name Test Requirement EMC DO 160C Audio Freq Susc Cat Z Induced Signal Cat Z Susc Chg Notice 3 Cat R RF Susceptibility Cat Z RF Emissions Cat Z Lightning Induced Susceptibility DO 160C Multiple Burst Multiple Stroke Waveform 3 amp 4 Level 3 Waveform 3 Level 3 Temperature Variation DO 160C Cat A Temperature Altitude DO 160C Cat D2 40 C to 71 C Vibration DO 160C Cat E Random 7 9 grms Operation Shock Cra
24. to obtain contact information for your local US or International representative
25. try Internal circuitry converts the 24 VDC input power to 5 VDC for use by the microcontroller and associated circuits It employs a large input capacitor to provide enough time between detection of input power loss and actual loss of DC power for the microcontroller to store the current unity status in the non volatile memory The DC power supply provides input transient protection to meet RTCA DO 160C power input voltage spike and lightning requirements B1 10 Status Output The status output provides a ground output when the freezing rain sensor is operating correctly and high impedance 200 KQ minimum when the unit has detected a failure Failures are detected through continuous and initiated tests The Status output is capable of sinking 50 mA and is guaranteed to be no more than 1 5 VDC with respect to Signal Return when active This output is transient protected to meet RTCA DO 160C lightning requirements and to prevent stray high voltage from coupling into the unit and damaging the output transistor B1 11 Ice Signal Output The Ice Signal output provides a ground output for 60 6 seconds when the ice detector has detected the presence of ice B 3 Appendix B Freezing Rain Sensor frequency drop of 130 Hz equivalent to approximately 0 020 ice formation If the frequency subsequently decreases by 130 Hz while the Ice Signal output timer is non zero the timer is reinitialized to 60 seconds The output is transient pro
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