Thermocouple Conditioner Setpoint Controller AD596*/AD597* GENERA

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Thermocouple Conditioner Setpoint Controller AD596/AD597 GENERA

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FEATURES Cost Operates with Type (AD596) Type (AD597) Thermocouples Built-In Point Compensation Temperature Proportional Operation Temperature Setpoint Operation ON/OFF Programmable Switching Hysteresis High Impedance Differential Input
Thermocouple Conditioner Setpoint Controller AD596*/AD597*
GENERAL DESCRIPTION
AD596/AD597 monolithic temperature setpoint controller which been optimized elevated temperatures such those found oven control applications. device cold junction compensates amplifies type thermocouple input derive internal signal proportional temperature. internal signal then compared with externally applied setpoint voltage yield impedance switched output voltage. Dead-Band switching hysteresis programmed using single external resistor. Alternately, AD596/ AD597 configured provide voltage output mV/°C) directly from type thermocouple signal. also used stand-alone voltage output temperature sensor. AD596/AD597 powered with single supply from dual supplies total span Typical quiescent supply current which minimizes self-heating errors. AD596/AD597 package option includes thermocouple failure alarm that indicates open thermocouple lead when operated temperature proportional measurement mode. alarm output flexible format which used drive relays, LEDs logic. device packaged reliability qualified, cost effective 10-pin metal can, 8-pin plastic mini-DIP SOIC trimmed operate over ambient temperature range from +25°C +100°C. Operation over extended ambient temperature range possible with slightly reduced accuracy. AD596 will amplify thermocouple signals covering entire -200°C +760°C temperature range recommended type thermocouples while AD597 accommodate -200°C +1250°C type inputs. AD596/AD597 calibration accuracy ambient temperature 60°C ambient temperature stability specification 0.05°C/°C from +25°C +100°C. higher accuracy, lower ambient operating temperature required, either AD594 thermocouple) AD595 thermocouple) should considered.
*Protected U.S. Patent 029,974.
PRODUCT HIGHLIGHTS
AD596/AD597 provides cold junction compensation high gain amplifier which used setpoint comparator. input stage AD596/AD597 high quality instrumentation amplifier that allows thermocouple float over most supply voltage range. Linearization required thermocouple temperatures close 175°C (+100°C +540°C AD596). Cold junction compensation optimized ambient temperatures ranging from +25°C +100°C. stand-alone mode, AD596/AD597 produces output voltage that indicates temperature.
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Information furnished Analog Devices believed accurate reliable. However, responsibility assumed Analog Devices use, infringements patents other rights third parties which result from use. license granted implication otherwise under patent patent rights Analog Devices.
Technology Way, P.O. 9106, Norwood, 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703
AD596/AD597-SPECIFICATIONS unless otherwise noted)
Model ABSOLUTE MAXIMUM RATINGS Common-Mode Input Voltage Differential Input Voltage Alarm Voltages +ALM -ALM Operating Tcmperature Range Output Short Circuit Common TEMPERATURE MEASUREMENT (Specified Temperature Range +25°C +100°C) Calibration Error1 Stability Temperature2 Gain Error Nominal Transfer Function AMPLIFIER CHARACTERISTICS Closed Loop Gain3 Input Offset Voltage Input Bias Current Differential Input Range Common Mode Range Common Mode Sensitivity-RTO Power Supply Sensitivity-RTO Output Voltage Range Dual Supplies Single Supply Usable Output Current4 Bandwidth ALARM CHARACTERISTICS VCE(SAT) Leakage Current Operating Voltage Short Circuit Current POWER REQUIREMENTS Operating Quiescent Current
NOTES
Type (AD596), Type (AD597) Thermocouple,
AD597AH AD597AN/AR (-VS +36) +125
AD596AH (-VS +36) +125
(-VS +36) +125
Units Volts Volts Volts Volts Volts
(-VS 0.15) Indefinite
(-VS 0.15) Indefinite
(-VS 0.15) Indefinite
-1.5
0.02
0.05 +1.5
-1.5
0.02 245.5 41.27
0.05 +1.5
-1.5
0.02 245.5 41.27
0.05 +1.5
°C/°C mV/°C Volts mV/V mV/V Volts Volts Volts Volts
180.6 53.21 (-VS 0.15) (+VS (-VS 2.5) (+VS (+VS -VS) (+VS (+VS
(+VS 0.15) (-VS 2.5)
(+VS (+VS (+VS
(-VS 0.15) (-VS 2.5)
(+VS (+VS (+VS
Alarm Function Pinned (+VS (+VS -VS) (+VS -VS)
Volts
This measure deviation from ideal with measuring thermocouple junction 175°C chip temperature 60°C. ideal transfer function given AD596: VOUT 180.57 (ambient 53.21 µV/°C AD597: VOUT 245.46 (ambient 41.27 µV/°C where represent measuring ambient temperatures taken from appropriate thermocouple table. ideal transfer function minimizes error over ambient temperature range 25°C 100°C with thermocouple temperature approximately 175°C. Defined slope line connecting AD596/AD597 errors measured 25°C 100°C ambient temperature. shorted Current Sink Capability single supply configuration limited current drawn ground through resistor output voltages below Alarm function available package option only. Specifications subject change without notice. Specifications shown boldface tested production units final electrical test. Results from those tests used calculate outgoing quality levels. specifications guaranteed, although only those shown boldface tested production units.
ORDERING GUIDE
Model AD596AH AD597AH AD597AN* AD597AR*
Package Description TO-100 TO-100 Plastic SOIC
Package Option H-10A H-10A
*Consult factory availability.
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AD596/AD597
Table Output Voltage Thermocouple Temperature (Ambient
Thermocouple Temperature -200 -180 -160 -140 -120 -100 Type Voltage -7.890 -7.402 -6.821 -6.159 -5.426 -4.632 -3.785 -2.892 -1.960 -.995 -.501 .507 1.019 1.277 1.536 2.058 2.585 3.115 4.186 5.268 6.359 7.457 8.560 9.667 10.777 11.887 12.998 14.108 15.217 16.325 17.432 18.537 19.640 20.743 21.846 22.949 24.054 25.161 26.272 AD596 Output -1370 -1282 -1177 -1058 -925 -782 -629 -468 -299 -125 1006 1203 1401 1600 1800 2000 2201 2401 2602 2802 3002 3202 3402 3601 3800 3999 4198 4398 4598 4798 Type Voltage -5.891 -5.550 -5.141 -4.669 -4.138 -3.553 -2.920 -2.243 -1.527 -.777 -.392 .397 .798 1.000 1.203 1.611 2.022 2.436 3.266 4.095 4.919 5.733 6.539 7.338 8.137 8.938 9.745 10.560 11.381 12.207 13.039 13.874 14.712 15.552 16.395 17.241 18.088 18.938 19.788 AD597 Output -1446 -1362 -1262 -1146 -1016 -872 -717 -551 -375 -191 1005 1207 1407 1605 1801 1997 2194 2392 2592 2794 2996 3201 3406 3611 3817 4024 4232 4440 4649 4857 Thermocouple Temperature 1000 1020 1040 1060 1080 1100 1120 1140 1160 1180 1200 1220 1240 1250 Type Voltage 27.388 28.511 29.642 30.782 31.933 33.096 34.273 35.464 36.671 37.893 39.130 40.382 41.647 42.283 AD596 Output 5000 5203 5407 5613 5821 6031 6243 6458 6676 6897 7120 7346 7575 7689 Type Voltage 20.640 21.493 22.346 23.198 24.050 24.902 25.751 26.599 27.445 28.288 29.128 29.965 30.799 31.214 31.629 32.455 33.277 34.095 34.909 35.718 36.524 37.325 38.122 38.915 39.703 40.488 41.269 42.045 42.817 43.585 44.439 45.108 45.863 46.612 47.356 48.095 48.828 49.555 50.276 50.633 AD597 Output 5066 5276 5485 5694 5903 6112 6321 6529 6737 6944 7150 7355 7560 7662 7764 7966 8168 8369 8569 8767 8965 9162 9357 9552 9745 9938 10130 10320 10510 10698 10908 11072 11258 11441 11624 11805 11985 12164 12341 12428
TEMPERATURE PROPORTIONAL OUTPUT MODE
AD596/AD597 used generate temperature proportional output mV/°C when operated with type thermocouples shown Figure Thermocouples produce level output voltages which function both temperature being measured reference cold junction temperature. AD596/AD597 compensates cold junction temperature amplifies thermocouple signal produce high level mV/°C voltage output which function only temperature being measured. temperature stability part indicates sensitivity output voltage changes ambient device temperatures. This typically 0.02°C/°C over +25°C +100°C recommended ambient temperature range. parts will operate over extended ambient temperature ranges from -55°C +125°C, thermocouple nonlinearity reference junction will degrade temperature stability over this extended range. Table list ideal AD596/AD597 output voltages function Celsius temperature type ANSI standard thermocouples with package reference junction 60°C. normally case, REV.
these outputs subject calibration temperature sensitivity errors. These tables derived using ideal transfer functions: AD596 output (Type voltage 301.5 180.57 AD597 output (Type voltage) 245.46
Figure Temperature Proportional Output Connection
offsets gains these devices have been laser trimmed closely approximate thermocouple characteristics over measurement temperature ranges centered around 175°C with
AD596/AD597
AD596/AD597 ambient temperature between 25°C 100°C. This eliminates need additional gain offset adjustments make output voltage read: VOUT mV/°C (thermocouple temperature (within specified tolerances). Excluding calibration errors, above transfer function accurate within from +80°C +550°C AD596 -20°C +350°C AD597. different temperature ranges differences type thermocouple curves. European FE-CuNi thermocouple vary slightly from ANSI type thermocouples. Table does apply when these types thermocouples used. transfer functions given previously thermocouple table should used instead. Figure also shows optional trimming network which used change device's offset voltage. Injecting sinking from will offset output approximately (1°C). AD596/AD597 operate from single supply from from split supplies totalling less shown. Since output only swing within positive supply, usable measurement temperature range will restricted when positive supplies less than AD597 AD596 used. AD596/AD597 used indicate negative Celsius temperatures, then negative supply required. Common-mode voltages thermocouple inputs must remain within common-mode voltage range AD596/ AD597, with return path provided bias currents. thermocouple remotely grounded, then dotted line connection shown Figure must made thermocouple inputs. there return path bias currents, input stage will saturate, causing erroneous output voltages. this configuration, AD596/AD597 package option circuitry which detects presence open thermocouple. thermocouple loop becomes open, both inputs device will deprived bias current causing output saturate. this saturation which detected internally used activate alarm circuitry. output this feature flexible format which used source sink current. collector (+ALM) should allowed become more positive than (-VS however, permitted more positive than +VS. emitter voltage (-ALM) should constrained such that does become more positive than below +VS. alarm feature used, this should connected Pins shown Figure alarm function unavailable AN/AR package option.
SETPOINT CONTROL MODE
input impedance setpoint AD596/AD597 approximately temperature coefficient this resistance ppm/°C. Therefore, ppm/°C shown Figure will only introduce additional degradation temperature stability over +25°C +100°C ambient temperature range.
Figure Setpoint Control Mode
Switching hysteresis often used setpoint systems this type provide noise immunity increase system reliability. reducing frequency on-off cycling, mechanical component wear reduced leading enhanced system reliability. This easily implemented with single external resistor between Pins AD596/AD597. Each current injected into when output switches will cause about hysteresis; that
RHYST °CHYST
setpoint configuration, AD596/AD597 output saturated times, alarm transistor will regardless whether there open circuit not. However, -ALM must tied voltage below (+VS proper operation rest circuit.
STAND-ALONE TEMPERATURE TRANSDUCER
AD596/AD597 configured stand-alone Celsius thermometer shown Figure
AD596/AD597 connected setpoint controller shown Figure thermocouple voltage cold junction compensated, amplified, compared external setpoint voltage. relationship between setpoint voltage temperature given Table temperature controlled within operating range (-55°C +125°C) device, monitor temperature shorting inputs ground. setpoint voltage with thermocouple inputs grounded given expressions: AD596 Setpoint Voltage mV/°C AD597 Setpoint Voltage 10.1 mV/°C
Figure Stand-Alone Temperature Transducer Temperature Proportional Output Connection
Simply omit thermocouple connect inputs (Pins common. output will reflect compensation voltage hence will indicate AD596/AD597 temperature. this three terminal, voltage output, temperature REV.
AD596/AD597
sensing mode, AD596/AD597 will operate over full extended -55°C +125°C temperature range. output scaling will with AD596 10.1 with AD597. Additionally there will offset with AD596 causing read slightly high when used this mode.
THERMOCOUPLE CONNECTIONS
deviation from temperature-voltage characteristic Table 5.75°C, 100°C maximum (see Figure offset error removed with single offset adjustment, these errors will reduced 1.75°C max. optional trim circuit shown Figure demonstrates ambient offset error adjusted zero.
connection thermocouple wire normal wire printed circuit board traces going AD596/AD597 forms effective reference junction shown Figure This junction must kept same temperature AD596/ AD597 internal cold junction compensation work properly. Unless AD596/AD597 thermally stable enclosure, thermocouple leads should brought directly Pins
Figure Drift Error Temperature
THERMAL ENVIRONMENTAL EFFECTS
Figure Connections
ensure secure bonding, thermocouple wire should cleaned remove oxidization prior soldering. Noncorrosive resin flux effective with iron, constantan, chromel, alumel, following solders: tin-5% silver, tin-10% lead.
SINGLE DUAL SUPPLY CONNECTIONS
single supply configuration used setpoint controller Figure convenient voltage from used, with self-heating errors being minimized lower supply levels. this configuration, connection tied ground. Temperatures below zero accommodated single supply setpoint mode, single supply temperature measuring mode (Figure reconnected single supply). Temperatures below zero only indicated negative output voltage, which impossible single supply mode. Common-mode voltages thermocouple inputs must remain below positive supply, more than 0.15 more negative than minus supply. addition, return path input bias currents must provided. thermocouple remotely grounded, then dotted line connections Figures mandatory. AD596/AD597 specified maximum error ambient temperature 60°C measuring junction temperature 175°C. ambient temperature stability specified maximum 0.05°C/°C. other words, every degree change ambient temperature, output will change more than 0.05 degrees. 25°C maximum REV.
STABILITY OVER TEMPERATURE
inherent power dissipation AD596/AD597 keeps self-heating errors minimum. However, device output capable delivering external load alarm circuitry supply Since typical junction ambient thermal resistance free 150°C/W, significant temperature difference between package pins (where reference junction located) chip (where cold junction temperature measured then compensated) exist when device operated high dissipation mode. These temperature differences will result direct error output. temperature proportional mode, alarm feature will only activate event open thermocouple system transient which causes device output saturate. Self-Heating errors will effect operation alarm cases need considered. First, after fault corrected alarm reset, AD596/AD597 must allowed cool before readings again accurate. This take minutes more depending upon thermal environment seen device. Second, junction temperature part should allowed exceed 150°C. alarm circuit AD596/ AD597 made source sink with across junction temperature will 90°C above ambient causing temperature exceed 150°C when ambient above 60°C. this case, either load must reduced, heat sink used lower thermal resistance. TEMPERATURE READOUT CONTROL Figure shows complete temperature indication control system based AD596/AD597. Here AD596/AD597 being used closed-loop thermocouple signal conditioner external used implement setpoint. This important advantages. provides high level mV/°C) output panel meter also preserves alarm function open thermocouples. panel meter easily offset scaled shown read directly degrees Fahrenheit. temperature calibration scheme used, dominant residual errors will arise from sources; ambient temperature rejection (typically over 25°C 100°C range) thermocouple nonlinearity typical +1°C from 80°C 550°C type +1°C from -20°C 350°C type
AD596/AD597
external voltage reference used both increase stability converter supply stable reference setpoint voltage. traditional requirement design setpoint control thermocouple systems been configure system such that appropriate action taken event open thermocouple. open thermocouple alarm with flexible current-limited output format supports this function when part operates temperature proportional mode. addition, thermocouple remotely grounded, possible program device either positive negative full-scale output event open thermocouple. This done connecting bias return resistor directly high output voltage desired indicate fault condition. Alternately, bias return provided thermocouple lead connected open circuit will result output reading. Figure shows ground return connected that thermocouple fails, heater will remain off. same time, alarm circuit lights signalling need service thermocouple. Grounding would lead output voltage saturation, this circuit would result potentially dangerous thermal runaway under fault conditions.
Figure Temperature Measurement Control
OUTLINE DIMENSIONS
Dimensions shown inches (mm).
Package TO-100
Package 8-Lead Small Outline (SOIC)
Package 8-Lead Plastic
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PRINTED U.S.A.
C831a-5-11/85