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Dwyer 641B Air Velocity Transmitter Manual PDF

1. 4 31 32 126 21 1 2 a 1 23 32 43 66 The Series 641B Air Velocity Transmitter uses a heated mass flow sensor technology It has 4 user selectable ranges from 250 FPM to 2000 FPM with corresponding metric ranges of 1 25 MPS to 10 MPS The 641B provides an isolated 4 20 mA output proportional to the velocity INSTALLATION Location Select a location where the temperature will be within 32 to 140 F O to 60 C The transmitter may be located any distance from the receiver provided that the total loop resistance does not exceed 600 ohms The probe should be located where conditions are representa tive of the overall environment being monitored Avoid loca tions where turbulence stagnation or rapidly fluctuating velocities or temperatures are present as these conditions may affect the readings The filter setting may be used to average velocity readings in turbulent conditions Position The transmitter is not position sensitive and may be mounted in any orientation Mounting The 641B should be connected to conduit or other connection means with the 1 2 NPT conduit con nection Ensure connection is installed properly so that dust and debris can not enter housing Airflow The 641B is intended for use with dry air Dust accumulation on sensor may impair the velocity measure ment and will require probe cleaning See maintenance section for additional cleaning details DWYER INSTRUMENTS INC P O
2. BOX 373 MICHIGAN CITY INDIANA 46361 U S A Phone 219 879 8000 Fax 219 872 9057 Bulletin E 66 B 9 1 4 235 0 SPECIFICATIONS Service Air and compatible non combustible gases Accuracy 5 FS Process gas 32 to 122 F 0 to 50 C 6 FS Process gas 40 to 32 F amp 122 to 176 F 40 to 0 C amp 50 to 80 C Response Time Flow 1 5 seconds to 95 of final value Output filter set to minimum Temperature Limits Process 40 to 176 F 40 to 80 C Ambient 32 to 140 F O to 60 C Humidity Limit Non Condensing Power Requirements 12 35 VDC 10 16 VAC Output Signal 4 20 mA isolated 24V source 3 or 4 wire connection Output Filter Selectable 0 5 15 Seconds Loop Resistance 600 ohms max Current Consumption 300 mA max Electrical Connections Screw terminal Enclosure Rating Designed to meet NEMA 4X Mounting Orientation Unit not position sensitive Weight 12 6 oz 857 2 9 A brief current transient exceeding 300 mA may be seen on startup www dwyer inst com e mail info dwyer inst com A A Page 2 NOTE Where conduit connections are not made a 1 2 NPT cable seal should be used to prevent contaminants from entering the case Where conduit connections are made make sure that any possible condensation within the conduit will not flow into the transmitter housing ELECTRICAL CONNECTION The 641B has been designed for easy and flexible connec tion
3. or span settings have been changed The RUN LED will otherwise remain on MAINTENANCE In general the 641B should require very little maintenance In some installations dust may accumulate on the sensor over time This can be removed by carefully brushing the probe with a small camel hairbrush A jet of air may also dis lodge the accumulated buildup Technical grade denatured or isopropyl alcohol may be used where the dust accumu lation does not respond to brushing Always disconnect the power when performing a cleaning operation Aside from the adjustments described above the 641B cannot be field calibrated Because of specialized comput er instrumentation required these units must be returned to Dwyer Instruments for factory calibration FR 02 443205 20 www dwyer inst com e mail info dwyer inst com
4. to power and loop receivers Electrical connection is made inside the body of the device with a Euro style ter minal block The device features a current loop that is fully isolated from the power source The current loop has an internal 24V isolated supply so no external loop power is required With full isolation loop grounding is not a concern The input power requirements are also very flexible The device may be powered from either an AC or DC power source 3 or 4 Wire Connection POWER SUPPLY AC OR DC F E RECEIVER 4 WIRE DC SUPPLY DC SUPPLY ONLY ONLY R EITHER FITHER POLARITY 6 G POLARITY o E o EA fe RECEIVER RECEIVER 3 WIRE 3 WIRE RECEIVER NEGATIVE RECEIVER POSITIVE COMMON COMMON CAUTION Do not exceed the specified supply voltage rat ing Permanent damage not covered by the warranty may result Do not use an external power source on the current loop connection Receiver Transmitter Connection The 641B is designed as a three or four wire 4 20 ma device The cur rent loop output is isolated from the power supply input and provides an internal 24 volt loop supply With a DC power supply a three or four wire connection may be used Do not use a three wire connection with an AC power source In a three wire connection either power supply wire may be used as the common The tot
5. al loop resistance should not exceed 600 Ohms CAUTION Do not use a receiver with an internal power supply or use an external supply in the current loop The current loop is powered from within the 641B Connecting an external supply to the current loop may destroy the transmitter Using an external supply voids the warranty Power Supply Connection The power supply may be either AC or DC The DC power may be from 12 to 35 Volts The power connection is not polarity sensitive so the posi tive and negative connections may be made to either power terminal The AC connection may be from 10 to 16 VAC RMS Do not exceed 20 VAC When selecting a transformer please note that the specified output for transformers is at some specified current With a load current less than the specified current transformer output may be significantly higher than the specified voltage Transformers with sec ondary voltages of 10 to 16 VAC are recommended CAUTION Do not use transformers with a secondary volt age rating greater than 16 VAC RMS Wire Type and Length The wire selection for an instal lation is often overlooked or neglected and may contribute to improper or even intermittent operation In all cases ensure that the connection meets all applicable national and local electrical codes Although the 4 20 mA current loop systems are relatively immune to wire or wiring related problems selection of the wire for some installations will be an imp
6. as been designed for easy setup It has five configuration parameters that may be adjusted by the user These parameters are Output Filter Range In English or Metric span 4 mA set point and 20 mA set point All of these may be adjusted at any time in the field These adjustments may also be easily returned to factory default Interior Label Diagram A set of controls and indicators are provided within the unit consisting of the select button enter button adjustment control and six LED indicators When operating normally only the RUN LED indicator will be illuminated During the setup operation the LED indicators will indicate the para meter selected when it is being adjusted and status of the adjustment process If the unit is left in the setup mode for several minutes without any activity it will return to the normal operating mode Two buttons and a potentiometer control the setup process The SELECT button is used to scroll between the setup parameters The ENTER button allows access to each parameter for adjustment The ADJUST potentiometer is used to change the value of the parameters Holding the ENTER button for 2 5 seconds saves the new parameter value Making Adjustments The adjustment process has three steps select the para meter adjust the parameter save the new value These are described in the following steps 1 Sele
7. ct the parameter Each time the SELECT but ton is pressed the LED indicator will advance to the next parameter When the last parameter SPAN is selected the next time the SELECT is pressed the unit will return to RUN mode Press the SELECT button until the LED indicator illuminates the desired parameter Press ENTER The selected indicator will begin to blink show ing the parameter may now be adjusted If the unit is left in the setup mode after several minutes it will reset to the operate mode 2 Adjust the parameter Turn the ADJUST poten tiometer until the desired setting is made This may be adjusted using a small screwdriver or similar tool Be careful not to force the control past its stops or damage will result 3 Save the Parameter To save the new parameter press and hold the ENTER button The LED indicator will begin to flash at a faster rate After about 2 5 seconds all of the LED indicators will flash when the parameter is saved If you do not want to save the parameter press the SELECT button without entering the parameter The adjusted value will be discarded and next LED indicator will be illuminated Adjusting the Output Filter The output filter may be adjusted to smooth the readings when measuring turbulent flow The time constant may be adjusted from 0 5 seconds to 15 seconds To adjust the fil ter time constant select the FILTER indicator Press ENTER to enable adjustment Turn the ADJUST until the desired amo
8. ff Page 4 Span Setting The 641B has been calibrated for standard sea level condi tions As a mass flow device it will always read the air veloc ity for standard conditions Density changes due to baro metric or absolute pressure are not corrected automatically The span setting allows correction for altitude or other stat ic pressure conditions that affect the density of the process air This parameter allows for a 50 adjustment in the span value To make the span adjustment you will need to know either the absolute static pressure or the corrected velocity of the process air Set the air velocity to a known value ideally about 3 4 of the full scale range value Press SELECT until the SPAN LED indicator is illuminated then press ENTER The SPAN LED will begin to blink Adjust the control for the desired velocity then press and hold the ENTER button until all of the LED s flash indicating the new value was saved If you know the absolute static pressure you can compute the corrected velocity using the following equation Po Voor PA Vra g Where PO is the standard pressure of 29 9 in Hg or 760 mm Hg PA is the absolute pressure reading Vrdg is the indicated velocity Vcor is the corrected velocity 4 mA Setting To make this setting you will need a milliammmeter connect ed in the current loop Press SELECT until the 4 mA LED indicator is illuminated then press ENTER The milliammmeter will now read appro
9. ortant factor in ensuring satisfactory system opera tion Twisted conductors will usually be immune to most stray electric and magnetic fields and to some extent elec tromagnetic fields such as interference from RF transmit ters With twisted pair wiring the current loop and the power connections should be separate pairs Avoid using flat or ribbon cable that has no regular conductor twist Where interference is possible it is recommended that shielded wire be used The shield must not be used as one of the conductors and should be connected to ground at only one end generally at the power supply Similarly if the installation uses conduit the conduit should be connected to protective ground as specified by the applicable code and the signal wiring must not be connected to the conduit at more than one point or as specified by the code The maximum length of wire connecting the transmitter and receiver is a function of the wire resistance and receiv er resistance The total loop resistance must not exceed 600 Ohms including the receiver resistance and wire resis tance The power supply connection must be designed so that the worst case voltage drop due to wire resistance will not cause the power supply voltage at the transmitter to drop below the specified value Provided the power supply voltage is maintained within the specified voltage range the 641B is not affected by variations in power supply voltage TRANSMITTER SETUP The 641B h
10. unt of damping is achieved To save the value press and hold the ENTER button until the LED indicators all flash indi cating the value was saved To discard the adjustment press SELECT before pressing the ENTER button OUTPUT FILTER RESPONSE values in seconds of Full Velocity Filter Setting on Adjust Dial Min Mid Max 0 5 Page 3 Range Selection The range selection allows you to select one of four ranges in either feet per minute FPM or meters per second MPS Ranges FPM 250 500 1000 2000 MPS 1 25 2 5 5 10 Select the RANGE indicator by pressing ENTER when the RANGE LED indicator is illuminated The A B C LED indi cators will display which range setting is currently active Press ENTER to enable adjustment Turn the ADJUST until the desired range indication is achieved If you want to dis card the adjustment press SELECT If you want to save the range press and hold ENTER The RANGE LED will blink at a faster rate for about 2 5 seconds then all of the LEDs will flash indicating the value was saved The range setting is displayed with the LED indicators The function of these indicators is summarized on the control label inside the unit The following table summarizes the indicator status for each range setting Range units nun Finer Range i a Span A 0 0 0 0 0 0 0 0 0 0 0 0 1 j 1 1 3oO00O0 00 0oO 0 0 0 1 Indicator on O Indicator o
11. ximately 4 0 mA Adjust the control for a 4 0 mA reading on the milliammeter Press and hold ENTER to save the new setting Pressing SELECT before pressing ENTER will restore the previous calibration value 20 mA Setting With the milliammeter connected in the current loop press SELECT until the 20 mA LED indicator is illuminated Press ENTER to begin adjustment of the 20 mA set point The 20 mA LED will now be blinking Adjust the control until the mil liammeter reads 20 0 mA Press and hold ENTER to save the new setting Pressing SELECT before pressing ENTER will restore the previous calibration value Copyright 2005 Dwyer Instruments Inc DWYER INSTRUMENTS INC P O BOX 373 MICHIGAN CITY INDIANA 46361 U S A Printed in U S A 2 05 Phone 219 879 8000 Fax 219 872 9057 Restoring Factory Default Settings The 4 mA 20 mA and Range settings override factory default values To restore these to the factory default set tings start with the unit in the RUN mode Press and hold the ENTER button The RUN LED indicator will begin to blink After about 2 5 seconds all LED indicators will flash indicating the factory settings have been restored Range and Filter settings are not affected by this operation If you are unsure whether any have been altered press the SELECT button six times to sequence through all settings When you return to the RUN mode the RUN LED indicator will blink several times if either the 4 mA 20 mA

Dwyer 641B Air Velocity Transmitter Manual PDF

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