ICA5 - Load and Force Cells, Indicators and Signal Conditioners at
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1. 6 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 Chapter 4 Calibration Figure 4 1 Connection Details for Calibration ICA5 Connection Details for Calibration PSU 7 5 28V Load cell or load cell simulator Low drift Load resistor N B For optimum EMC performance bolt the ICAS to the load cell chassis via this hole An optional 0603 calibration resistor can be fitted here and S connected across the Exc Voltmeter display and Output arm of the bridge by the adjacent solder blob pads 1 Apply the low calibration conditions weight force or mV V Set the output to 4mA using the Z potentiometer 2 Apply the known high calibration conditions ideally between 75 and full scale and adjust the S potentiometer to give the required output current for the known input e g 16mA for 4 20mA final calibration with 75 input or 20mA if 100 input Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 Chapter 5 Linearisation Many bridge sensors are inherently non linear With the addition of one external resistor it is possible to compensate for parabolic non linearity resulting in up to 20 1 improvement over an uncompensated bridge output Figure 5 1 Bridge Non Linearity BRIDGE TRANSDUCER TRANSFER FUNCTION WITH PARABOLIC NONLINEARITY NONLINEARITY vs STIMULUS o 8 3 l Positive Nonlinearity2. The cable should have single pair twisted cables Table 2 1 Supplier PartNo Description UK RS 367 533 Braided screened twisted multipair cable 7 0 2mm 1 pair Miniature twin round Diameter 4 8 mm Impedance 62 Ohms Capacitance m core to core 120 pF 8 core to screen 210 pF Note For easy connections the above 1 pair cable is recommend however the ones below can be used UK Farnell 148 539 Individually screened twisted multipair cable 7 0 25mm 2 pair Tinned copper drain Individually screened in polyester tape Diameter 4 19 mm Impedance 54 Ohms Capacitance m core to core 115 pF 8 core to screen 203 pF UK Farnell 585 646 Individually screened twisted multipair cable 7 0 25mm 3 pair Tinned copper drain Individually screened in polyester tape Diameter 6 86 mm Impedance 62 Ohms Capacitance m core to core 98 pF amp core to screen 180 pF The earth connection conductor should have sufficient cross sectional area to ensure a low impedance path to attenuate RF interference Output Connections The ICA5 analogue output is 4 to 20mA The power and signal are combined in a single pair cable simplifying installation N B Neither connection to the output load is electrically common to the load cell The following formula gives the suitable range of shunt resistance for low supply voltage operation Output Shunt Resistance Formula The shunt resistance must be less than Vsupply 7 5 20mA Rwir
3. within the sensor limits taken as linear and no linearity compensation is required within the ICA The input corresponding to a one unit change in the least significant digit of the data acquisition display equipment Good resolution is not necessarily equal to good accuracy That part of the Transducer which reacts directly in response to the input Sensitivity This is the relationship between the change in Strain Gauge input to the level or magnitude of the output Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 13 Signal Conditioner Single Card Assembly A circuit module that offsets attenuates amplifies linearizes and or filters the signal The ICA is essentially a Signal Conditioner more specifically known as a Strain Gauge Amplifier in that it CONDITIONS alters the input signal from a load cell to an electrical output The ICA has only the one Printed Circuit Board assembly on which all the components are mounted The assembly is then mounted inside an environmentally rugged enclosure Span Span Adjustment Span is otherwise identified as GAIN It relates to the proportional output to the sensor input Calibration of the ICA is determined by setting the Span Gain and Zero Offset The ability to adjust the gain of a process or strain meter so that a specified display span in engineering units corresponds to a specified signal span Stability Strain Gauge The quali
4. 7 Figure 4 1 Connection Details for Calibrati0N oooonoccccnonoccccononooooncnononnnnnnnnnrroncnnnannnnno 7 Chapter 5 Lin aris ation iaa s andato nudone saare w dasare anane eaa ninina adaa cias 8 Figure 5 1 Bridge Non Linearity cccoooccnnnonononcncncccccnonananonnnonnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnns 8 Figure 5 2 Link Options amp RLin Locations oocccooocccccnooocnnonooononcnnononnnnnnnononononnnnonnnnnnnnnnnnnnns 8 Chapter 7 Product Care ui coceccccscsueseceecScadechaadivcaanetcaczahaacevcdacessateasitectesvasuiadabiaceucested 12 Chapter 8 Glossary siu taosdasnansia noona rdnana miraiet saioan aidian 13 Chapter 9 Specife ON Sa a aa a a a ced a aa a aaa a a et Eea EES ASSE Eas 15 Table 9 1 Specifications sisina aa ai a a a a Aa ea ibaa 15 Environmental Approvals ooooococccccccccccccnonononoononnnnnncncccnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnrrnnnnnnnnnnnnnnnes 15 Other Mantracourt Products sssssssssssuusssusenunnnunnnunnnnnsnnunnnnnnnnnnnnnnnnunnnnnnnnnnnnnnnnunnnnnnnnnn ennnen 16 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 1 Chapter 1 Introduction to The ICA Range Figure 1 1 Block Diagram POWER y SUPPLY INPUT gt AMPLIFIER DON inn pey ICA1 0 1 10V Load Cells 0 1 Strain Gauges ICA2 pal Torque Transducers ICA3 110V Pressure Transducers ICA4 4 20mA g ICA5 4 20mA 2 wire The ICA is a Strain Gauge Amplifier converting a strain gauge input to a
5. calibrate and much more 4 to 20 mA Output Programmable via keypad FIELDBUS CONNECTIVITY IN TWO EXCELLENT PACKAGES DSC The Digital Strain Card D Cell The in cell Digital Strain Puck Mount this package adjacent to the strain Mount this package directly into the strain gauge gauge pocket Plug in and go sensor High accuracy e Integrate the electronics with the load cell e A quantum leap in the quality of measurement e remove the cost space and bother of additional electronics and have a direct output e provided in e REAL ENGINEERING UNITS Accuracy 1 part in half a million Unwanted Signal noise filter Temperature compensated Sensor specific calibration Elimination induced noise on signals ISO 9001 REGISTERED FIRM In the interests of continued product development Mantracourt Electronics Limited reserves the right to alter product specifications without prior notice 9E Doc No ME 0131 MD 4D Code No 517 167 Issue 1 3 09 12 02 16 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3
6. installed i e mV source and output as required Ensure the temperature and other environmental parameters are within specification and where necessary taken into account when calibrating should such parameters have an effect on the calibration 10 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 6 Fine Span Gain and Zero Offset Adjustment Problems If the adjustment cannot reach the maximum output desired then check the tare is not too high If the potentiometer does not alter the output the unit must be repaired remove from service Itis always wise to check a known good ICA against the problem Installation before rejecting the suspect ICA Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 11 Chapter 7 Product Care A worn out component excessive use in harsh environments an overly zealous operator regrettably some circumstances necessitate repair At Mantracourt Electronics Ltd we can t guarantee that a product will never require repairing We can however promise a repair service of exceptional quality one which is governed by a rigorous procedure Detailed below is our pledge to you a defined set of ground rules and procedures to which we will adhere All we ask in return is that you assist us with our procedure such that we can maintain our promise to you Please note that warranty repairs may not be available on overdue accounts and that a strict interpretation of our
7. Preliminary ICAS 2 wire 4 20mA Miniature In Cell Amplifier For Strain Gauges www mantracourt co uk User Manual Instructions ICA5 Manual Contents Chapter 1 Introduction to The ICA RanQ6 coonocccccnccncccconocaccnonnnanononanannnnnnnnnnnnnnananan rr rnnanernnnnnans 2 Figure 1 1 Block Diagram 2 id 2 Pre Installation a ees 3 Figure 2 11 DIMENSIONS 3 Power Connections tilo toalla rip acid ete 4 Figure 2 2 Connection Details oooooooccccnonoccncncooooccnononannnononononnnnnnnnnnnnnnnn no nnnnnnnnnnncnnn nn nnnnnns 4 Figure 2 3 Connection Details for Best EMC ImmunNity oocccccnocccnnnoccooncccnononnnnnnnonnnncnonannnnnos 4 Table 22 eere a a a dee be Munch 5 Output Connections 2 2 4 42 dot eee a o E EE 5 Output Shut Resistance FOrmMulla cccccscsccccssssscceesssceeccsseeeececssseeeeceseeeeeesseeeeeeseseeeeesessaes 5 Chapter 3 Setting Gain and Offset Values cccecceeeeeeeeeeeeeeeneeeeeeeeeeeeeseeeeeseeaeeeseeeeeeeneseeee 6 Calculating the Gain Resistor R4 ccccscccessseeeceeeseseeeeesceeeeeecsseseeeeeccneeeeeessaaeeeseeeeeeeeesaea 6 Offset ReSistor R1 ccccccccccsssecccssssseeeeesseeeeesseeeeeeesseseeesseesaeeesecesseessceeeeeescssseeesseeneeeeeesaaes 6 Figure 3 1 Calibration Resistor cc ccccecceeeeceeeeeceeeeeeeeeeeeeseaeeecaeeceaeeeeeaeeeeeaeeeseeetsnneeseates 6 Chapter 4 Cal pra Orra aaa a aa as p aaa aa Saa araa aaa a ar aa aao Era aidean aaea Sitea
8. RLin pin connected directly to Vreg this is as supplied Using the resulting sensor non linearity B values for Rg and RLin are calculated using equations 1 and 2 A second calibration measurement is then taken to adjust Rg to account for the offsets and mismatches in the linearisation Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 9 Chapter 6 Troubleshooting 1 No Output a Check power supply is present and the correct polarity b Check the output connections are correct with no open circuit connections c Check terminations ensure there are no dry joints d Check the sensor is connected with the power off Impedance check e Check the Excitation voltage is correct f Check the load is connected and is not open or short circuited g Check Span and Gain calibration 2 Low Output This is when an output is present but not of sufficient magnitude to meet the required value Remember to allow for Tare Weight and ensure it is measured and allowed for in the output from the ICA a Check power supply is within specified limits i e is not low Impedance check b Check the sensor is connected typically reading 350 Ohm across output amp with the power off c Check the Excitation voltage is at 1 08V dc for a 1k load cell 0 55V for 350R d Check the calibration e Check the Zero offset is correct for the sensor this too is a common reason for low outputs 3 High Output This is when an
9. Volt or mA output otherwise known as a Signal Conditioner The ICA provides a wide range of signal conditioning for Strain Gauges Load Cells Pressure and Torque Transducers Offered in 5 versions e ICA1 3 wire 0 1 to 10 volts ICA2 3 wire 0 1 to 5 volts ICA3 4 wire 10 volts ICA4 3 wire 4 to 20 mA ICA5 2 wire 4 to 20mA Special unique features to the 2 wire 4 20mA amplifier ICA5 Auto zero amplifier giving very high stability Linerisation Screw mounting 8 earth bonding for EMC Shunt calibration option Operating voltage from as low as 7 5 volts dc Low profile option 7 0mm 0 275 high ICA5L N B The ICA5 is designed for a 1k bridge however 350R can be used with a reduced performance This manual only deals with the ICA5 version separate manuals exist for versions ICA1 2 ICA3 and ICA4 Transducer SENSITIVITY of between 0 5 mV V and 6 mV V are possible It is optimized to 2 5 mV V Sensitivity adjustment is achieved by a combination of gain span resistor R4 change and associated fine adjustment by potentiometer Similarly transducer ZERO can be compensated for in the module This adjustment is to compensate for slight errors in the strain gauge and not to offset tare The value of R1 Figure 2 2 can be modified to increase the trim range of the zero point A high stability resistor R11 Figure 5 2 can be fitted to give a greater positive offset e g 12mA output at zero inpu
10. ame potential as the surrounding earth Linearity Load The closeness of a calibration curve to a specified straight line Linearity is expressed as the maximum deviation of any calibration point on a specified straight line during any one calibration cycle The electrical demand of a process expressed as power watts current amps or resistance ohms Load Impedance Load Cell The impedance presented to the output terminals of a transducer by the associated external circuitry The load cell is one of a series of STRAIN GAUGE sensors that the ICA input is designed to accept Torque Sensor Pressure amp temperature transducers Millivolt One thousandth of a volt 10 volts symbol mV Noise An unwanted electrical interference on the signal wires Null Potentiometer A condition such as balance which results in a minimum absolute value of output Offset is otherwise identified as ZERO Calibration of the ICA is determined by setting the Offset Zero and Gain Span Two potentiometers variable resistors are used in the ICA for fine calibration Pressure Transducer Proportional Outputs Resolution Sensing Element The Pressure Transducer is one of a series of Strain Gauge sensors that the ICA input is designed to accept Torque Sensor Load Cell and Temperature Transducers The Voltage or Current outputs are calibrated to be directly proportional to the input from the sensor The output is
11. ance 9 7 5 0 02 10 65 Ohms NOTE Recommended bridge impedance is 1 000 Ohms Environmental Approvals EMC Emissions EN 50 081 1 1992 Light industrial EMC Emissions EN 50 081 2 1992 Heavy industrial EMC Immunity EN 50 082 1 1992 Light industrial RF Fields Test 500 ppm of reading over 30 to 500MHz EN 50 082 2 1992 Heavy industrial RF Fields Test 6000 ppm of reading over 30 to 500MHz Low Directive IEC 1010 EN 61010 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 15 Other Mantracourt Products www mantracourt co uk Signal Conditioning SGA RCA15 STRAIN GAUGE AMPLIFIER RACK MOUNTED INTELLIGENT Connect up to 4 strain gauges STRAIN GAUGE AMPLIFIER Proportional mA and or Voltage output Complete MULTI CHANNEL system for Strain Simple DIL switch configuration gauges Set Sensitivity and Low pass filter and Relay and or serial outputs per channel output Multidrop serial link Simple Reliable Rugged 19 Eurorack x 3U high Capability similar to the ADW 15 High integrity compact Data acquisition unit LCA ADW15 Mantraweigh IN LINE INTELLIGENT 72 mm DIN Module Display amp Controller STRAIN GAUGE AMPLIFIER 10 mm LED Display Configurable 2 Set Points Sensitivity from 0 5 mV to 200 mV V 4 to 20 mA AND 0 to 10 V isolated outputs 10 V 0150 mA Excitation RS 232 485 Communications port Isolated 1 0100mSec sample rate On Board easy to use Programmer Set Point Relays Auto tare Auto
12. conditions of trading invalidates warranty claims where late payment has occurred Please refer to Customer Repair Service Procedure document contact your supplier for a copy In the unlikely event you have problems with the ICA module we would advise that you take the following precautions The unit is installed as instructed Recommended spares are kept in stock We can assist Sufficient expertise available for first line maintenance Routine maintenance checks are performed annually is recommended The necessary documentation for the product is available to the maintenance personnel We recommend you keep on file as a minimum e This Manual e The calibration figures for the attached sensors e A record of the normal output if applicable e Acalibration record of the ICA e A contact phone number from the supplier for assistance 12 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 Chapter 8 Glossary AWG Background Noise American Wire Gauge The total noise floor from all sources of interference in a measurement system independent of the presence of a data signal See Noise Bipolar The ability of a signal conditioner to display both positive and negative readings Bridge Resistance The resistance measured across the excitation terminals of a Strain Gauge Calibration CMR Common Mode Rejection Common Mode Rejection Ratio Drift Excitation Fine Adjust
13. ent which measures a load of a 100kG Span from 400kG to 500kG is said to have 400kG Zero Suppression Hz Hertz Frequency kHz kilohertz Frequency mA milliamps SC Signal Conditioner ICA Strain Gauge Amplifier V Volts mV millivolts 14 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 Chapter 9 Specifications Table 9 1 Specifications Parameter Minimum Typical Maximum Units Power supply reverse protected 7 5 24 28 V dc Bridge excitation 1 1 V 1k bridge Bridge resistance 350 1000 5000 Ohms Bridge sensitivity 0 5 2 5 6 mV V t 1k bridge Gain adjustment Pot fine adj 3 FS Zero adjustment Pot fine adj 8 FS Output load 800 Ohms Bandwidth 0 2000 Hz Zero temperature stability at 2 5mV V 0 001 0 005 FS C 1k bridge Span temperature stability at 2 5mV V 0 007 0 014 FS C 1k bridge Linearity 0 02 FS Operating temperature range 40 85 C Humidity 0 95 RH FS Full scale set by calibration resistor 24V supply Connections Solder pads 4 strain gauge 2 for power signal N B The voltage between either of the power supply connections and the load cell chassis should not exceed 50V Any leakage will be greater than 10M Ohms For low supply voltage operation the shunt resistor must be less than Vsupply 7 5 20mA Rwiring e g assuming 10 Ohms wiring resistance and 9V supply Max shunt resist
14. ime may result in damage to the PCB If changing resistor R1 or R4 do so at a workbench and not on site Check the relevant details for model ICA5 ensure the module matches the instructions Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 3 The ICA5 solder pads are as shown 4 pads for the strain gauge 4 pads for fitting and linking a calibrating 2 pads for power supply signal resistor 1 pad for earth bolt to chassis this is important for best EMC performance Power Connections The power supply for the ICA5 should be between 7 5 and 28V Figure 2 2 Connection Details ICA5 Connection Details PSU 7 5 28V Strain Gauge N B For optimum EMC performance bolt the ICA5 to the load cell chassis via this hole The strain gauge cable should be attached to the solder pads as illustrated N B The voltage between either of the power supply connections and the load cell chassis should not exceed 50V Any leakage will be greater than 10M Ohms Figure 2 3 Connection Details for Best EMC Immunity ICA5 Connection Details for Best EMC Immunity PSU 7 5 28V ve The securing bolt should be used to provide a good electrical ground and mechanical support This is important for optimum EMC performance 4 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 This typical cable data is provided for information only
15. ing e g assuming 10 Ohms wiring resistance and 9V supply Max shunt resistance 9 7 5 0 02 10 65 Ohms Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 5 Chapter 3 Setting Gain and Offset Values The ICA5 4 to 20mA In Cell strain gauge amplifier is supplied un calibrated but optimized for a sensitivity of 2 5mV V To accommodate other sensitivities the gain resistor R4 as shown in Figure 2 2 can be changed according to the following formulae N B a high quality component e g 1 50 ppm metal film device should be used for optimum performance It may be necessary to use an E96 value for optimum trim range Calculating the Gain Resistor R4 Rg E mV IV Vexc 0 048 0 95 114 mV V Vexc 0 016 Where mV V is the sensitivity of the load cell and Vexc is the excitation voltage Rg comprises R4 in parallel with 919 Ohms lt R4 919 Rg 919 Rg e g For 2 5mV V and Vexc 1V Rg 285 Ohms e 413 Ohms nearest preferred value is 412 Ohms E96 919 285 Offset Resistor R1 The value of R1 can be changed to offset the zero point if outside of the normal range 3 Figure 3 1 Calibration Resistor There is provision on the PCB to add a 0603 high stability calibration resistor and a solder blob link High stability 0603 calibration resistor Solder blobs to connect calibration resistor across Exc and Output arm of bridge
16. ment Full Bridge Adjustment of an instrument or compiling a deviation chart so that it s reading can be correlated to the actual value being measured The ability of an instrument to eliminate the effect of AC or DC noise between signal and ground Normally expressed in dB at DC to 60 Hz One type of CMR is specified between SIG LO and PWR GND In differential meters a second type of CMR is specified between SIG LO and ANA GND METER GND The ability of an instrument to reject interference from a common voltage at its input terminals with relation to ground Usually expressed in db decibels Change of a reading set point value over periods due to several factors including change in ambient temperature time and line voltage The external application of electrical voltage current applied to a transducer for normal operation Zero and Span calibration have a Fine Adjustment to give accuracy to the calibration These are potentiometers P1 and P2 for Span and Zero respectively A Wheatstone Bridge configuration utilizing four active elements or Strain Gauges Full Range Output Ground Earth The algebraic difference between the minimum output and maximum output Gain is otherwise identified as SPAN It relates to the proportional output to the sensor input Calibration of the ICA is determined by setting the Gain Span and Offset Zero The amount of amplification used in an electrical circuit The electrical neutral line having the s
17. output is present but higher in span or zero than expected High output is not normally a problem It is most likely to be incorrect connections and as such the output would be high and fixed a Check the sensor is connected Impedance check with the power off b Check the Excitation voltage is at 1 08V dc assuming a 1k load cell c Check the Zero offset d Check the calibration 4 Unstable Output This is when the output is unstable or varies The cause could be a poor installation or b a noisy environment Poor Installation This is when an output is present but higher or lower in span or zero than expected a Check the installation for problems and repair where necessary b Poor termination c High resistance on cable leads d Low insulation impedance e Proximity to High Voltage Equipment Transformers Contactors Motors etc Noisy Environment a Check if the source can be found and remove noise b Check the cable screening and ensure it is correctly installed and terminated 5 Calibration This section assumes that the unit is providing an output that is not stuck at top or bottom of the scale See paragraphs 1 3 if this is the case Ensure you are connected to the correct sensor and not to another adjacent unit Ensure you have the correct calibration data from the sensor manufacturer This must include a certified table with offset zero and linearity Ensure you have the calibration set up correctly
18. s 7 B 0 025 E 5 5 6 a o 3 5 E o 4 2 2 3 m 3 K H o a Negative Nonlinearity 2 5 z 1 Negative Nonlinearity B 0 019 0 0 01 02 03 04 05 06 07 08 09 1 0 01 02 03 04 05 06 07 08 09 1 Normalized Stimulus Normalized Stimulus Linearity correction is accomplished by signal dependant variation of the bridge excitation voltage This can be tailored to correct for sensor non linearity between 5 and 2 5 Either positive or negative bridge non linearity errors can be compensated for by proper connection of the polarity pads A B and C Figure 5 2 The ICA5 as supplied is set for negative non linearity downward bowing To correct for positive non linearity upward bowing cut the link connecting pads A and B and join pads B and C with a solder blob Figure 5 2 Link Options amp RLin Locations If no linearity correction is desired do not cut the link or remove the resistor RLin RLin is the external linearisation resistor To determine the value of RLin the non linearity of the bridge sensor with constant excitation voltage must be known The linearity circuit can only compensate for the parabolic shaped portions of a sensors non linearity Optimum correction occurs when maximum deviation from linear output occurs at mid scale See Figure 5 1 Sensors with non linearity curves similar to that shown in Figure 5 1 but not peaking exactly 8 Mantracourt Electronics Limited Preliminary ICA5 User Manual Iss
19. t 2 Mantracourt Electronics Limited Preliminary ICA5 User Manual Issue 1 3 Chapter 2 Installing The ICA5 Pre Installation See Specification Details in Chapter 9 for details of Environmental Approvals Carefully remove the ICA unit from its shipment box Check that the unit is complete and undamaged Check The Model Type 1 2 3 4 or 5 they look similar The ICA units can operated in any industrial environment providing the following limits are not exceeded Operating Temperature 40 C to 85 C Humidity 95 non condensing Storage temperature 40 C to 85 C The following installation practices are advised Minimise vibration Do not mount next to strong electrical fields transformers power cables Ensure easy access to the module Install electrical protection device as the unit is not internally fused Always ensure the package is secure and protected Figure 2 1 Dimensions 19 5mm 0 77 iimm 7 0mm 0 45 0 275 Miniature size as standard Low profile option ICA5L The module is designed to fit in the strain gauge pocket The low profile ICA5L version has single turn gain potentiometer to reduce the height Use a bolt through the 2mm hole to secure the unit and to provide a good ground connection Take care soldering cables to the pads Use a temperature controlled soldering iron set to a maximum 330 C for no longer than 2 seconds per pad Excessive heat or increased soldering t
20. ty of an instrument or sensor to maintain a consistent output when a constant input is applied The Strain Gauge is a resistance bridge device where the bridge value alters linearly and proportionally to the force exerted on it be it pressure torque or load The ICA is designed to convert this change in the Strain Gauge to a proportional electrical signal Strain Gauge Amplifier Torque Transducer Wheatstone Bridge Zero Adjustment Zero Offset Zero Suppression The ICA1 amp 2 is essentially a type of Signal Conditioner that it conditions alters the input signal from a strain gauge to an electrical output The Torque Transducer is one of a series of Strain Gauge sensors that the ICA input is designed to accept A network of four resistance s an emf source and a galvanometer connected such that when the four resistance s are matched the galvanometer will show a zero deflection or null reading Zero is otherwise identified as OFFSET It relates to the proportional output to the sensor input Calibration of the ICA is determined by setting the Span Gain and Zero Offset The ability to adjust the display of a process or strain meter so that zero on the display corresponds to a non zero signal The difference between true Zero and an indication given by a measuring instrument See Zero Suppression The Span is Offset from Zero Zero Suppressed such that neither limit of the Span will be Zero For example an instrum
21. ue 1 3 at mid scale can be substantially improved A sensor with an S shaped non linearity curve equal positive and negative non linearity cannot be improved with existing correction circuitry The value of RLin is chosen according to equation 1 4B Ohms 2B 1 RLin KLin h Where KLin 9905 Ohms B is the sensor non linearity relative to Vfs e g for 2 5 non linearity B 0 025 Vfs is the full scale bridge output Vex mV V The sensor s non linearity term B relative to full scale is positive or negative depending on the direction of the bow The gain is affected by the varying excitation voltage used to correct bridge non linearity The corrected value of the gain resistor is calculated from equation 2 e Rg 282M 128 ohms 0 4 1 2B When using linearity correction care should be taken to ensure that the sensor s output common mode voltage remains within the amplifier s input range of 1 1V to 3 5V Equation 3 can be used to calculate the amplifier s new excitation voltage 1 2B 3 VExc Adj VExc Initial ES Volts The common mode voltage of the bridge output is simply half of this value if no common mode resistor is used Exceeding the common mode range may yield unpredictable results For high precision applications errors lt 1 a two step calibration process can be employed Firstly the non linearity of the sensor bridge is measured with the initial gain resistor and RLin 0
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