Instrumentation Temperature Controller Instruction Manual
Contents
1. BANDWIDTH AD VOLT READING LTR DESCRIPTION DATE INITIATED J Hw REPLACE ReAB FOR TRIM POT 10K R9 3 1 89 5 du B ECN 2050 UPDATE DRAFTING STANDARDS 4AUG94 JDURR A L C ECN43334 CORRECT SCHEMATIC 7AUG96 JDURR RN3 100K TP2 RN3 100K e AAA 10 10K 5 COMPARE 6 1 WS RN2 RN3 2 1 1 100K 10K R3 100K Aas 15 2 2 2Meg m RN2 12V 715 8 100K 9 NANG Cii 4 100K 13 6 R4 ud TP3 10 ach O HEAT 1014 12V 221 B 47uf 7 22 gt 14 5 eee FRONT END V 12V 16 mua 1 1 5 NA 2 Di tob NES 10K Tc RN2 Bele 1N914 21 R12 1K 1MF R5 10K 100K 12V E 14 NAL 13 am Y ilan v e il R6 2 AD 5 C7 958 N 3159 6 c8 022uf TPA 27pF 4 10 0224 2 AN m8 TCPL TEMP 12 v 100 022uf R70 TPS THERMOCOUPLE FAULT 10 00 DC REFERENCE 100K 12V VOLTAGE z7 REF 1 100 NOT INSTALLED 12V FRONT PANEL MOC E 2 01 10 8 CONTROLS H 5 A13 41 gt 18 lt TEMPERATURE L4 lt 3 7 gt 19 SELECTOR 12V gt 20 lt l 10K Rio 10K m 45 a 91 TTENUATOR 9 ATTENI Q2 Q3L7 gt 5 15 SELECTOR 00 aa 5 5 o6 162. BROWN 220V las ON BOTTOM 2 1 GREEN 9 GREENYELLOW 220V WHITE Ne BLUE 220V Ne L A o f 2 L U 314 VIGI Valco Instruments Co Inc INSTRUMENTATION TEMPERATURE CONTROLLER f S 5 M 0 31119 T o sm lees L PWR ON HTR AT D ADJUST HEIGHT OF COVER BY TURNING SCREW REVISIONS LTR DESCRIPTION DATE APPROVED A ITC BD ASSY REV MN 20FEB89 B ENCLOSURE C 21527 REV G 22FEB89 c 2050 CLARIFY DWG 8AUGS4 JDURR D ECN 4668 CLARIFY 220V VERSION 22MAR99 JDURR PARTS LIST ITEM DESCRIPTION VALCO QTY 1 ENCLOSURE ITC 10 121527 1 1 4 2 ASSY ITC 10 1 22218 1 3 STANDOFF 4 40 1 4 THREADED NYLON HWSO 4050 3 4 SCREW PLMS 4 40 1 4 Ig PANHD PH SS HWSC PL4 4 9 5 STANDOFF 4 40 1 4 SWAGE THREADED HWSO 1650 2 3 6 SWITCH ASSY ITC TEMP CTRL 399 DEG C 1 21280 02 1 7 POWER CORD GREY 6 18 3 SVT W CS 21 1 8 STRAIN RELIEF SRR 10 HEYCO 5 4 1147 HWSRR 10 1 9 LUG FEMALE SLIP ON 16 14 AWG HWLUG 4218B 6 10 THERMOCOUPLE ASSY 102 ITC K TYP 21014 01 1 11 FE
3. Valco Instruments Co Inc Instrumentation Temperature Controller Instruction Manual MAN ITC Rev 8 96 Printed in USA P O Box 55603 Houston TX 77255 713 688 9345 Sales toll free 800 367 8424 Fax 713 688 8106 Table of Contents Page 1 GENERAL 2 0 1 1 1 Standard Features 1 11 1 12 1 13 1 14 1 15 1 16 Thermocouple Sensor Proportional Heater Power Control Power Attenuation Zero Crossover Power Application Digital Temperature Setting Compact Rugged Construction and Functional Layout 1 2 Specifications and Model Codes 1 8 Technical Description 1 31 1 32 1 33 1 34 Thermal System Overview ITC Block Diagram by Function 1 321 Input Amplifier 1 322 Thumbwheel Switches and D A Converter 1 323 Differential Comparator 1 324 Heater Power Switch 1 325 Thermocouple Break Detection 1 326 Proportional Power Control 1 327 Power Attenuation Proportional Power Control Power Attenuation 2 OPERATION X 10 2 1 PHYSICAL LAYOUT OF THE ITC 2 2 Thermocouples 2 3 Setpoint Set C 2 4 Proportioning Bandwidth 2 41 Bandwidth Defined 2 5 Installation 2 6 Troubleshooting and Schematic Diagram 2 61 2 62 2 63 Situation PWR ON indicator fails to illuminate instrument does nothing Situation TCPL indicator ON continuously no power applied to heater Situation No power being applied to
4. 5 5 ZERO CROSSING 12 1210 aspis dis 52 Qe gt 8 8 ae 6 04 2 Q TP6 13 9911 gt 9 02 2 2 01 REGIS a 721V DC I ATTENUATOR n HEAT zs as 13 TP7 12 5 43 14 WA Hv 2 8 m NAME gt 15 HVO m 16 510 10K gt 14 4013 9 13 4 13 8 gt 1 R13 R14 220V BNI oz2ut 32 gt RA ok MODLES ONLY ciet JUMP FOR 110V MODELS 14 Me 5 12 or EP E 100K 12V 7812 co L c4 n acp rr aed N BN 040151 BLACK 022uF i SWI P T1 0504 24 F2 5A F1 10A R14 TRI are ars w 12 BOARD ASSY 1 22218 6 THIS DOCUMENT AND THE INFORMATION WHICH CONTAINS SHALL NOT BE USED EXPLOITED OR SOLD AND SHALL BE REVEALED OR DISCLOSED OTHERS WITHOUT THE EXPRESSED 7 WRITTEN PERMISSION OF VALCO THIS DOCUMENT SHALL REMAIN THE PROPERTY OF VALCO BRI NEUTR AND SHALL BE RETURNED UPON DEMAND 25k_4 p ws WHITE fences y T pa ak na KA Valco Instrumenis Co Inc Ns MT4 mE we xn 42v MT2 MTI e ee n SCHEMATIC 7912 gt TOLOAD APPROVED DATE CUT amp JUMP FOR 27 Te 220V MODLES lol GG se REVP BOWER N B Ul DESIGNED SCALE SIZE DRAWING NO CHECKED 22219 A BEI 9 NT USAPROJECTION f gt Q ses o 22219 NTC DESCRIPTION DATE APPROVED A ITC BD REV M N 21FEB89 ECN
5. How does all this relate to stability improvement Well assuming that a stability problem exists it may be attributable to excessive heater power By this we mean that the heater is simply too powerful for the application The situation usually results from designing the system to heat quickly and operate over a broad temperature range The problem is characterized by the controlled temperature s tendency to spend most of the time above the bandwidth occasionally falling into its upper reaches The temperature will not stay within the bandwidth because 14 POWER APPLICATIONS 3 CONTROLLED TEMP aq pem ees i 1 EXCURSION POWER APPLICATIONS ra CONTROLLED TEMP 6 1 EXCURSION CONTROLLED TEMP ER EXCURSION TEMP Figure 9 power is increased too abruptly quickly driving the temperature up out of reach If the heater size cannot be reduced the bandwidth must be increased Doing so will decrease the rate of change in applied power hopefully increasing stability Always allow ten to fifteen minutes after making each adjustment before making another This will allow the system enough time to reveal whether or not further adjustment is required As a consequence of increasing the bandwidth the user should be aware that the controlled temperature is usually shifted upward as well This notion is most eas ily
6. we would again point out that the environment and maximum temperature must not be harmful to the solder It is important to note that considerations pertaining to junction integrity are also applicable to the insulation around each wire As stated earlier a new junction is formed each time the two thermocouple wires come into contact Obviously unplanned junctions are to be avoided In matters concerning the thermocouple measuring junction mass thermal conductivity of the controlled medium and placement can greatly affect controlled temperature stability In Section 1 326 an example was given illustrating tempera ture instability It was pointed out that stability is obtained by supplying heater power proportional to the need At this point it is important to recall that the thermocouple is responsible for telling the controller what the need is Most importantly any change in temperature must be reported without appreciable delay This causes instability regardless of how craftily the correction is carried out This notion of minimizing delay is carried to fact by observing two rules 12 1 The measuring junction should be of the lowest mass practicable for the appli cation Simply put the higher the mass the more time required for the junction to reach the temperature of its surroundings 2 The measuring junction should be placed as close as possible thermally to the heater Whenever there is doubt about proper location of a t
7. 1808 NEW DWG 15APR94 2050 SHOW NEW VER W R13 amp R14 8AUG94 ASSY 22218 SCH 22219 BD 22217 AW 160 REV N ADD JUMPER COMPONENT SIDE COMPONENT SIDE NOTE INSTALL R13 AND R14 ON BOARD FOR 220V VERSION 237K 1 1 4W 1 112373 THIS DOCUMENT AND THE INFORMATION WHICH IT CONTAINS SHALL NOT BE USED EXPLOITED OR SOLD AND SHALL NOT BE REVEALED OR DISCLOSED TO OTHERS WITHOUT THE EXPRESSED WRITTEN PERMISSION OF VALCO THIS DOCUMENT SHALL REMAIN THE PROPERTY OF VALCO AND SHALL BE RETURNED UPON DEMAND APPROVED DATE con ES MIE eem v FILE NAME DRAWN FRACTIONS DEC ANGLES 21647 R B D 5 SUB DIR DESIGNED d Do PCB CONVERSION ITC 3 SHEET or 21 647 110V TO 220V 24
8. 3 Technical Description A general knowledge of the ITC s organization and operation is helpful to its successful implementation To facilitate understanding three questions are posed 1 What position does the ITC occupy in a thermal system 2 How is the ITC organized to accomplish its task 3 What is the most important aspect of the ITC s organization These questions are answered by Sections 1 31 1 32 and 1 33 respectively 1 31 Thermal System Overview Figure 1 depicts a generalized closed loop control system The system is termed closed loop since the controller bases its corrective actions on the actual status of the controlled function In an open loop system corrective actions are based on anticipated status Closed loop systems are definitely preferable CONTROLLED FUNCTION SENSOR CORRECTION ELEMENT T CUM CONTROLLER Figure 1 The system is comprised of Controlled Function Water level air pressure etc Sensor Appropriate to the function level sensor pressure transducer etc Controller Determines when corrective action is necessary based on information supplied by the sensor Correction Element Means of adding water increasing pressure etc With slight modification the diagram becomes appropriate to a thermal system utilizing an ITC as shown in Figure 2 HEATED SO ZONE THERMOCOUPLE HEATER INSTRUMENTATI
9. CLIP PCB MOUNT 102080 HWFUSECLIP 1 4EA er FOR 110V MODELS WIRE BUSS UNINSULATED 025 DIA 22 AWG I W BUSS 1 78 EA FOR 220V MODLES RES 237 K 1 1 4W 1 112373 2 R6 R8A R8B MAY BE SUBSTITUTED BY TRIM POTS k INSTALL JUMPERS FOR R13 amp R14 110V MODELS INSTALL R13 amp R14 ON 220V MODELS REV P BOARDS ONLY DRILL FEEDTHRUS OUT AT THIS LOCATION JUMPER LAND ON BOTTOM OF BOARD TO BRIDGE HOLE REFER TO DWG 21647 THIS DOCUMENT AND THE INFORMATION WHICH IT CONTAINS SHALL NOT BE USED EXPLOITED OR SOLD AND SHALL NOT BE REVEALED OR DISCLOSED TO OTHERS WITHOUT THE EXPRESSED WRITTEN PERMISSION OF VALCO THIS DOCUMENT SHALL REMAIN THE PROPERTY OF VALCO AND SHALL BE RETURNED UPON DEMAND TOLERANCES UNLESS OTHERWISE SPECIFIED STEREO Ed Valco Instruments Co Inc LE XXX 005 LI veas ASSY ITC DRAWN M CHIU 1 11 89 REV M N P I 22218 DESIGNED DO NOT SCALE DRAWING 2 DRAWING NO SCALE 3 ii B 22218 NEXT ASSY FILE NAME SUB DIR 21866 22218 ITO USA PROJECTION f sheet c REVISIONS
10. deduce that this is a potentially disastrous situation However a separate circuit is employed specifically to detect a break condition Its output will cause the Heater Power Switch to be disabled and a front panel indicator to be illuminated whenever a break occurs 1 326 Proportional Power Control To this point power application to the heater has been described as simply applied or interrupted In reality this would be analogous to trying to maintain a dragsters speed at 30 mph using full throttle applications only Obviously power must be delivered according to the need For this reason the ITC employs pro portional power control where net power is delivered to the heater according to the difference between the setpoint and zone temperature The proportioning technique is discussed in Section 1 33 1 827 Power Attenuation Effective heater size can be tailored to the application by proper adjustment of the power attenuation control Excessive heater ratings are often the cause of system instability at near ambient temperatures Proportional control and power attenuation work hand in hand to produce excellent temperature stability Refer to Section 2 3 1 828 Zero Crossing Switch This allows the heater to come on only if the AC waveform is at zero to suppress noise on the powerline 1 33 Proportional Power Control Although the ITC s input amplifier and D A circuitry are accurate and predictable in their temperature representat
11. understood by noting the position of the 196 power point before and after adjust ment Remember that the system will still require the same average power to maintain a given temperature Therefore as the bandwidth is increased the given power point shifts upward carrying with it the controlled temperature Note that the controlled temperature shifts upward only if it was originally trying to stabilize above the setpoint 50 power point There usually is no stability problem when the temperature is settling below the setpoint However we will point out that in this situation the temperature will shift downward when bandwidth is increased The value of the bandwidth in C can be determined by the following method 1 Reduce the setpoint temperature until the HTR indicator is OFF continu ously Make note of this temperature 2 Increase the setpoint until the HTR indicator is ON continuously Make note of this temperature 3 Determine the difference between the two temperatures This value is the bandwidth 15 2 5 Installation The following discussion is intended to assist you in the initial installation of an ITC It is assumed that you have read the foregoing portions of this manual Check the instrument for shipping damages Open the instrument and check for loose components There shouldn t be any In the event that damage is noted notify the carrier immediately Valco assumes no responsibility for damage incurred in s
12. ET RUBBER STICK ON HW 1658 4 12 NUT HEX 4 40 UNC STAINLESS HWNUT HEX 4 1 18 RECEPTACLE POWER OUTLET BLACK HW OUTLET 1 14 WIRE 14 AWG TEFLON BLACK CSA SPEC FW 4 BLACK 593 4 15 WIRE 14 AWG TEFLON GREEN CSA SPEC LFW 4 GREEN 333 4 18 16 WIRE 14 AWG TEFLON WHITE CSA SPEC HFW 4 WHITE 333 4 SEE NOTE 2 17 TUBING HEAT SHRINK 1 4 ID STUBE 250 125 18 SCREW SMS 4 3 8 LG PL SS HWSC SM4 6 6 19 TAG SERIAL ALL ELEC DEVICES 1 21988 1 20 MANUAL OPERATION ITC MANUALITC 1 21 PLATE ADAPTER 220V ITC PLUG 1 21820 1 22 SCREW PLMS 6 32 X 3 8 LG HWSC PL6 6 2 23 NUT KEP 6 32 HWNUT KEP 6 2 24 PLUG 4 PIN CABLE 304 1 25 SOCKET MOUNT 4 PANEL 3045 1 REF POWER CORD SCHUKO PLUG I W 17800 1 NOTE FOR 220V MODEL REMOVE ITEM 13 AND DRILL MOUNTING HOLES USING DRILL TEMPLATE A 21819 INSTALL CINCH SOCKET S304 AB WITH COVER PLATE ITEM 20 A 21820 WIRE SCHEDULE POWER CORD 220V WIRE PCB TERMINAL SOCKET I W 17800 BLACK HOT 1 HOT BRN WHITE NEUT 2 NEUT BLU GREEN GND 3 GND YEL GRN MODIFY PCB PER DRAWING A 21647 NCLUDE I T304PCCT PLUG 23 22 ENCLOSURE 5 AND SHALL BE RETURNED UPON DEMAND THIS DOCUMENT AND THE INFORMATION WHICH IT CONTAINS SHALL NOT BE USED EXPLOITED OR SOLD AND SHALL NOT BE REVEALED OR DISCLOSED TO OTHERS WITHOUT THE EXPRESSED WRITTEN PERMISSION OF VALCO THIS DOCUMENT SHALL REMAIN THE PROPER
13. However at a point just below the setpoint say 70 the power is reduced to 95 As the temperature continues to rise power is linearly reduced such that power will be applied 5096 of the time when the temperature reaches the setpoint and only 596 when it reaches 80 When the temperature begins to settle the process is reversed Heater power is gradually increased as the temperature declines toward the setpoint As a result the temperature will tend to stabilize at a point where the power application is sufficient to maintain equilibrium In conclusion the system s tendency to oscillate is greatly reduced if some form of proportional control is employed Commonly two methods can be used to electronically control AC power phase proportioning and time proportioning With phase proportioning some percentage of each AC cycle is applied to the load While this method is just fine for power drills it is not acceptable for instrument use This is due to the fact that the power is not switched at zero crossings Therefore large amounts of RFI EMI can be generated If such electrical noise is generated it may upset the operation of other instruments in the vicinity With time proportioning the average power is controlled by dividing time into specified periods During each period the percent age of power ON versus OFF time is proportional to the difference between the setpoint and the controlled temperature Power is switched only at AC v
14. LECT 220uF 35V AXIAL LEAD I CE227 35AL 2EA C34 14 CAP TANTAL 4 7MF 35V 475 35 CAP CERAMIC 0220 50V 250 LEADS 1 223 50 CERAMIC 27 PF 50V I CC270 50 1EA 11 CAP MONO CERAMIC 22 uF 50 2 LEADS I CC224 50 1EA 12 13 TANTAL 1 35V 1 7105 35 2EA ANI RES NET 10K 16 PIN DIP DISCRETE I RN761 3 10K 1EA RN2 3 RES NET 100 K 16 PIN DIP DISCRETE 1 761 3 100 2 ai TRANSISTOR NPN T093 DARLINGTON QMPSA13 1EA 023 TRANSISTOR PNP TO93 DARLINGTON 5 65 2EA swi SWITCH TOGGLE DPDT RPC N P S I SW MTM206 1EA 11 2 LAMP NEON RED 9001 52 C 03 2RN HLAMP R 2EA 13 LED RED WITH MOUNT 9001 52 C 03 2RN I LED550 01 1EA BRI RECTIFIER BRIDGE I D VE28 1EA VRI IC VOLTAGE REGULATOR 12V T0220 1 107912 1EA VR2 IC VOLTAGE REGULATOR 12V T0220 1 107812 1EA D1 DIODE SILICON SIGNAL 01 914 1EA R1 RES 100 5 1 2W R521000 1EA R2 RES 1 27 K 1 1 4W 8111271 1EA R3 RES 2 2 MEG 5 1 4 R512204 1EA R4 RES 10 1 1 4W 111080 1EA R5 7 RES 10 K 5 1 4 1 R511002 2EA R6 RES 953 1 1 4W R119530 1EA R8A RES 10 0 1 1 4W R111002 1EA R8B RES 715 1 1 4W 1 R117150 1EA R9 R10 POT 10 K TRIM SHORT CT9W 103 2EA R11 RES 100 K 5 1 4 1 R511003 1EA 35 R12 RES 1 K 5 1 4W R511001 1EA 1 6 MALE TABS HW 607 6EA 501 6 SCREW PLMS 6 32 X 1 4 LG SS HWSC PL6 4 6EA KN1 6 NUT KEP 6 32 HWNUT KEP 6 6EA 4 FUSE
15. ON TEMPERATURE CONTROLLER ITC Figure 2 It is readily seen that the ITC is responsible for maintaining the temperature within the heated zone However proper selection and application of the thermocouple and heater are essential if the ITC is to perform its function Refer to Section 2 2 1 32 ITC Block Diagram by Function Almost any electronic device can be described by a block diagram of its circuit elements each element performing something essential to the function of the device Indeed such a diagram is typically the first state in its design Further devices of similar function will have similar block diagrams TCPL BREAK DE TECTION INPUT DIFFERENTIAL SENSOR AMP COMPARATOR lt SWITCH ATTENUATOR SWITCH D A mE ror CONVERTER PROPORTIONAL POWER CONTROL Figure 3 The function of the ITC is to control the temperature in a heated zone A brief discussion of what is required to perform the function reveals the elements contained in its block diagram Figure 3 1 321 Input Amplifier The signal supplied by the thermocouple is too small to be recognized by the other circuit elements approx 50 microvolts C Therefore the signal must be amplified to a useful level 1 822 Set Point Selectors and D A Converter The thumbwheel
16. TY OF VALCO TOLERANGEB UNLESS 63 7 OTHERWISE SPECIFIED FRACTIONS DEC ANGLES VIGI Valco Instruments Co Inc ver X1 ITC ASSY 10 AMP APPROVED DATE 10399 220 9 REV M N P ITC10399 DESIGNED SCALE SIZE DRAWING NO CHECKED G 21556 FINAL ASSY as iren USA PROJECTION 3 sneer NOTE INSTALL TR1 AS SHOWN 35 REVISIONS LTR DESCRIPTION DATE INTIATED A REPLACE R9A R9B FOR TRIM POT 10K R9 2 28 89 B ECN 1805 UPDATE PER REV P BOARDS 4 5 94 JDURR C ECN 2145 CHG R2 TO 1 27K WAS 2 2K 225 94 JDURR o E E e o ot T TP TP6 TPS TPO TPS coe lil a 4H d B OQO MT2 5 MTI 01925 c BS H SC3 sc2 SC1 a Gao te 02855 Co HB KN3 KN2 Nt gHZB o8 d B S7 os 2 Id I 022 RRR C Fi 9 g
17. cifications care should be taken to avoid exceeding the ITC s specifications for switched power The ITC10 will switch loads up to 1000 watts If you attempt to exceed this rating the instrument will probably sacri fice its fuses and or power triac The present ITC power circuitry is intended to switch resistive loads only This means that inductive loads such as electric motors solenoids and especially variacs cannot be switched successfully Damage may result if inductive loads are used Always use three wire power connections for the instrument as well as heater connection Ref Section 2 2 It is important that the heater block etc be 16 connected to AC ground Failure to do so may cause a shock hazard or controller malfunction or both Locate the ITC where it will not be subjected to abrupt changes in ambient temperature This will improve the controlled temperature stability When installing the thermocouple be sure to observe electrical restrictions noted in Section 2 2 Actual installation consists of first thinking about what must be done then connecting the heater and finally inserting the thermocouple After this is done turn it ON and play with the system Notice whether or not corrections need to be made in such areas as thermocouple location bandwidth adjustment etc Enjoy If you re not enjoying yourself call us We ll try to help in any way we can 2 6 Troubleshooting and Schematic Diagram Tr
18. d to this being the best choice of sensors Sensor junctions of very low mass can be easily fabricated Lower mass means quicker recognition of temperature changes Thermocouples are inherently rugged requiring little in the way of special handling precautions Thermocouple wire is inexpensive and readily available In keeping with this choice of sensors the instrument is appropriately equipped with Automatic reference junction compensation Circuitry automatically references to 0 C regardless of ambient temperature Thermocouple break detection Should the thermocouple break the heater power circuitry will be disabled and a front panel indicator illuminated High impedance differential input circuitry This circuitry allows the instrument to tolerate floating or grounded thermocouples with high common mode noise immunity The ease of fabrication for sensors compatible with the ITC is such that users can seriously consider making their own In many cases all that is needed is a small torch silver solder and a roll of thermocouple wire 1 12 Proportional Heater Power Control The ITC utilizes proportional power application to minimize temperature overshoot and improve temperature stability about the setpoint Controls are accessible to the user allowing the proportioning bandwidth in C to be adjusted to meet specific requirements 1 13 Power Attenuation Many temperature controllers are used in conjunc
19. dth adjustment 2 41 Bandwidth Defined Rigorously defined bandwidth is the peak to peak value of the proportioning wave form expressed in degrees centigrade The bandwidth pot controls the height of the waveform More importantly the height determines the slope of the diagonal In Figure 9 two waveforms are shown one with 3 bandwidth and the other with 6 bandwidth In each case the controlled temperature is depicted 1 below the peak height of the waveform Notice that the resulting power applications are different In fact power is applied twice as long in the 3 example as in the 6 example This is due to the slope of the diagonal and as we shall see is a very useful thing to remember The important thing to notice in Figure 9 is that as the controlled temperature changes within the bandwidth the resulting change in heater power is dependent on the slope of the diagonal More specifically the rate of change in applied power is controlled by the slope of the diagonal If in each case the temperature falls 1 1 excursion the resulting changes in applied power are dramatically different In the 3 example application changes from 33 1 396 to 66 2 3 The same 1 excursion in 6 bandwidth causes application to change from 16 2 396 to 33 1 396 per degree and 16 2 3 per degree respectively By observation increasing the bandwidth decreases the amount of change in average applied power for a given change in temperature
20. ere the thermocouple measuring junction contacts metal If this is not done the TCPL circuit can sometimes be fooled into believing there is a malfunction As a final consideration disconnect the thermo couple and check it for electrical continuity If the problem is not located consult the factory 17 2 63 Situation No power being applied to heater TCPL indicator OFF In this situation the HTR indicator remains OFF The power triac is protected against continuous current overload with a 10 amp fuse Refer to Figure 6 Item 11 If this fuse is blown no power is available to the heater circuitry In addition to replacing a blown fuse consider what may have caused the overload The heater and or power triac may have developed a short circuit This sort of occur rence is usually accompanied by burned wiring Be certain that the heater doesn t exceed the power rating for the ITC 1000 watts It is the case that the situation described above can occur without blowing the fuse If this occurs consider whether or not the load is inductive Remember that such loads cannot be switched with the ITC s present circuitry The appropriate schematic diagram is supplied in this section Should you require any explanation of the circuitry please contact the factory 18 3 WARRANTY This Limited Warranty gives the Buyer specific legal rights and a Buyer may also have other rights that vary form state to state For a period of 365 calenda
21. etc It is worthy of note that almost all electronic components are mounted on a single printed circuit board This feature directly translates to simple troubleshooting methods and minimal spare parts inventory 1 2 Product Numbers and Specifications Product Numbers ITC10X X corresponding to 399 for 0 C to 399 C range 999 for 0 to 999 C range Example ITC10399 ITC 1000 watts maximum heater power 0 C to 399 C range Sensor Requirement Thermocouple Type K Range 0 to 390 or 0 to 999 C as ordered Absolute Accuracy 5 of full scale Repeatability 5 at constant ambient Sensititivity to Ambient Changes 05 C per C change Operating Ambient 10 to 50 C Switched AC Power 1000 watts zero crossing error 5V AC max Proportioning Bandwidth 3 C Proportioning Frequency 2 Hz Setpoint 1 C increments push button selection Max Power Input Requirement 10 0 amps at 117 VAC Power Attenuation 0 to 90 in 10 increments Physical Dimensions 2 4 x 8 3 x 5 9 weight 1 14 4 oz Visual Indicators Power On PWR illuminated whenever the instrument is plugged into a source of 120V AC and the PWR switch is in the ON position Heater On HTR illuminated whenever the controller applies power to the heater Thermocouple Fault TCPL illuminates whenever thermocouple sensor opens lf a sensor failure is detected heater power is automatically interrupted and the HTR indicator will remain OFF 1
22. factory Buyer shall return the goods prepaid and bear all the risks of loss until delivered to the factory If Seller returns the goods they will be delivered prepaid and Seller will bear all risks of loss until delivery to Buyer Buyer and Seller agree that this Limited Warranty shall be governed by and construed in accordance with the laws of the State of Texas THE WARRANTIES CONTAINED IN THIS AGREEMENT ARE IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING THE WARRAN TIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE This Limited Warranty supercedes all prior proposals or representations oral or written and constitutes the entire understanding regarding the warranties made by the Seller to Buyer This Limited Warranty may not be expanded or modified except in writing signed by the parties hereto 19 4 TECHNICAL DRAWINGS Assembly Drawing 21556 Page 21 Assembly Broad Drawing 22218 Page 22 Schematic TG Board t v teet tede Drawing 22219 Page 23 Board Converslom ete eie ett Drawing 21647 Page 24 20 Le 220V VERSION ONLY 4 AN 12 FROM BOTTOM 110V VERSION eS n N T1 OF ENCLOSURE YELLOW RED e I al E
23. heater TCPL indicator OFF 3 0044 19 4 TECHNICAL DRAWINGS 2 4 2 20 1 INTRODUCTION AND GENERAL DESCRIPTION The Instrumentation Temperature Controller ITC is an isothermal temperature controller intended for broad spectrum usage in thermal systems common to modern analytical instrumentation The instrument is designed to be a flexible building block with which the user can configure a thermal system to suit particular requirements Although the controller is only a single element in such a system its flexibility and performance ultimately determine the stability reproducibility and accuracy of the entire system Inasmuch as we do not attempt to present a portfolio of specific applications this manual is more general than specific Instead we are attempting to strike a spark of intuitive understanding and interest for how the ITC functions The ITC s func tion and relationship to thermal systems are the most valuable notions transmitted by this manual Just as there is no application manual for vice grip pliers there is not an application manual for the ITC Both are basic extremely useful devices whose real worth is determined by the user 1 1 Standard Features 1 11 Thermocouple Sensors The ITC utilizes thermocouple sensors fabricated from ordinary thermocouple wire A variety of factors lea
24. hermocouple follow these suggestions a Place the junction directly between the heater and the object to be heated as close to the heater as possible b In a stirred air or liquid bath place the junction immediately downstream from the heater In addition to the more common considerations there are a few important specific notions regarding thermocouples to be used with the ITC Electrical contact If the measuring junction is in electrical contact with an object that object must be connected to AC ground For example this would require a heater block to be grounded unless the thermocouple is electrically insulated from it The junction must float or be grounded Thermocouple resistance The following data describes the thermocouples normally shipped with the ITC ITC K 10 ft 28 gauge 40 ohm ANSI Type K 2 3 Setpoint Set C Loosely defined the setpoint denotes the desired temperature within the heated zone However the user should be aware that the denoted setpoint is not neces sarily the temperature at which the zone will stabilize To be more precise the setpoint denotes the temperature at which power will be applied 50 of the time It is entirely possible that the zone will require more or less than 50 power to maintain stability As a consequence the zone tempera ture will settle above the setpoint if less than 50 power is required and below the setpoint if more than 50 power is needed Essential
25. hipment Assuming no damage is seen perform the following checkout You will need an ordinary incandescent light or other resistive load that provides indication of when power is applied 1 Connect the load to the ITC In 110V models a receptacle labeled P1 is provided which accepts ordinary three wire appliance plugs The 220V uses a cinch socket 2 Connect the instrument to a suitable source of 120V AC 3 Set the setpoint and attenuation switches to 0 Switch the instrument on The TCPL indicator should illuminate momentarily The instrument is determining whether or not its thermocouple is OK The HTR indicator should be OFF 4 After allowing the instrument to warm up for a few minutes increase the setpoint until the HTR indicator flashed with a 50 50 duty cycle The setpoint should approximate the ambient temperature 5 Hold the thermocouple s measuring junction firmly in one hand Since your skin temperature is usually 10 above ambient and subsequently the setpoint the HTR indicator should cease flashing 6 Increase the setpoint until the indicator is ON continuously Try 50 Change the power attenuation switch to 9 The HTR indicator should flicker faintly Progressively decrease the ATTN setting noting that the HTR indicator bright ness increases at each position When the ATTN switch is at zero the HTR indi cator should be ON continuously with no visible flickering Regarding the zone heater spe
26. ions they do not in themselves constitute a good temperature controller In a control system the essential factor is stability A temperature controller is not doing its job if the zone temperature is allowed to oscillate about the setpoint to a degree which upsets the process In short the aim is to reduce a thermal system s natural tendency to oscillate to a level where it is not significant If zone heater power is simply applied or interrupted according to the comparator s verdict correction required not required the result is wholly unacceptable To illustrate Assume that a zone is to be heated from room ambient to 75 C If 100 power is applied until the temperature reaches 75 and then interrupted the temperature will overshoot As the temperature settles back to 75 100 power will again be applied in an effort to prevent the temperature from falling below the setpoint As a result the temperature will overshoot again In this manner the temperature will continue to oscillate about the setpoint As can be seen on off stop go etc are corrective measures that would make the ITC unacceptable for all but the crudest applications The key to obtaining acceptable stability lies in applying heater power relative to the need Using the above example but employing proportional control more reasonable results are obtained While the temperature rises from ambient toward 75 C power is applied continuously just as before
27. ly this characteristic offset is brought about by the proportional power control method used in the ITC coupled with the thermal characteristics of the user configured heated zone Without prior knowledge of the zone s heat input vs heat loss properties the only certainty is that the zone temperature will stabilize somewhere within the proportioning bandwidth Exactly where the temperature settles can be optimized by adjustment of the proportioning bandwidth Refer to Section 2 4 13 2 4 Proportioning Bandwidth Note Current models of the ITC may have fixed valued resistors in the trim pot location for the bandwidth calibration If the ITC needs further calibration they may be replaced with 10K trim pot and the following text will explain the band width adjustments Given that the controlled temperature is reasonably accurate stability becomes a most important measure of system performance Perfect stability is obtained by applying the exact amount of power required to offset a system s demand addition the power must be applied instantaneously whenever a demand occurs Think about this Theoretical notions like exact and instantaneous soon reveal the meaning of the term optimum In attempting to achieve optimum stability we assume that the user will experiment with the proportioning bandwidth adjustment pot Refer to Section 2 1 item 7 In keeping with this assumption we offer the following explanation of bandwi
28. oltage zero crossings avoiding RFI EMI generation Figure 4 is a graphic representation of time proportioning as it is implemented in the ITC The heart of the process is the proportioning waveform This sawtooth shaped waveform defines three important parameters of operation lower tempera ture boundary setpoint and upper temperature boundary The setpoint will always be situated in the exact center of the waveform The lower temperature bound ary represents the point below which 10096 power will be applied The upper temperature boundary represents the point above which no power will be ap plied And as stated earlier the setpoint denotes the point at which power will be applied 5096 of the time Observe also that between the two boundary tempera tures the average applied power is linearly proportional to the difference between the setpoint and the actual temperature within the heated zone 102 PROPORTIONING WAVEFORM 98 APPLICATIONS 100001 0 D TIME 1 CONTROLLED TEMPERATURE RISING FROM AMBIENT NOTICE POWER APPLICATION IS PROGRESSIVELY REDUCED AS THE TEMPERATURE RISES 2 OVERSHOOT NO POWER APPLIED 3 EQUILIBRIUM CONTROLLED TEMPERATURE HAS SETTLED AT APPROX 40 POWER Figure 4 The number of degrees between the upper and lower temperature boundaries is referred to as the proportioning bandwidth Proper adjustment of the bandwidth will further enhance temperature s
29. oubleshooting the ITC is straightforward in most cases The device can be thought of as being divided into two sections instrumentation and power circuitry Problems with the power circuitry are the most easily identified and can be handled with a minimum of electronics experience Isolation and repair of mal functions in the instrumentation circuitry require sophisticated test equipment and extensive electronics expertise For this reason it is recommended that the factory be consulted when the following procedures are of no help 2 61 Situation PWR ON indicator fails to illuminate instrument does nothing A 1 2 amp fuse is employed to fuse the instrument s DC power supply If this fuse is blown the PWR ON indicator will not illuminate and the instrument will not perform any functions The fuse is located at the left rear corner of the enclosure Refer to Figure 6 Item 10 If the ITC persists in blowing this fuse consult the factory 2 62 Situation TCPL indicator ON continuously no power applied to heater When the TCPL indicator is ON continuously the instrument thinks an open circuit has developed in the thermocouple As a consequence the ITC will refuse to apply power to the heater The thermocouple is connected to the instrument by a barrier strip designated B1 Refer to Figure 6 Item 9 Be certain these connec tions are snug As a second consideration be certain that proper connection to AC ground is made in any case wh
30. r days from the date of shipment Valco Instruments Company Inc hereinafter Seller warrants the goods to be free from defect in material and workmanship to the original purchaser During the warranty period Seller agrees to repair of replace defective and or nonconforming goods or parts without charge for material or labor OR at seller s option demand return of the goods and tender repayment of the price Buyers exclusive remedy is repair or replacement of defective and nonconforming goods OR at Seller s option repay ment of the price SELLER EXCLUDES AND DISCLAIMS ANY LIABILITY FOR LOST PROFITS PERSONAL INJURY INTERRUPTION OF SERVICE OR FOR CONSEQUEN TIAL INCIDENTAL OR SPECIAL DAMAGES ARISING OUT OF RESULTING FROM OR RELATING IN ANY MANNER TO THESE GOODS The Limited Warranty dose not cover defects damage or nonconformity resulting from abuse misuse neglect lack of reasonable care modification or the attach ment of improper devices to the goods This Limited Warranty does not cover expendable items This warranty is VOID when repairs are performed by a non authorized service center or representative If you have any problem locating an authorized service center or representative please call or write Customer Repairs 713 688 9345 Valco Instruments Company Inc RO Box 55603 Houston Texas 77255 At Sellers option repairs or replacements will be made on site or at the factory If repairs or replacements are to be made at the
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32. supplied 13 Top Cover Retaining Screws Remove these screws to gain access to interior of ITC 2 2 Thermocouples Thermocouples when used properly are a very expedient and reliable means of sensing temperature In this section we will attempt to help the user avoid certain general and specific pitfalls in thermocouple usage with the ITC Thermocouple measuring junctions are fabricated by joining two dissimilar metals A type K thermocouple is formed from chromel and alumel In theory the thermo couple is functional so long as the two metals remain in contact This does imply that a measuring junction can be formed by twisting two wires together We would point out that the junction will not be suitable for any real application however Maintaining the integrity of the measuring junction is of prime importance This means that for a given application thought must be given the junction s maximum attainable temperature corrosion resistance to its environment and mechanical strength Commercially available thermocouples are usually joined by welding This produces a junction in which the maximum temperature and corrosion resistance properties are those of the metals themselves For applications below 400 C a quite serviceable junction can be formed by twisting the bare ends of the wire together and then securing with silver solder For applications above 400 C the junction should be welded In the case of silver soldered junctions
33. switches provide a means of representing the desired tempera ture within the heated zone This temperature is hereafter referred to as the setpoint The switches provide a digital representation of the setpoint which is then converted to a more useful signal by means of a ten bit D A converter The D A converter conforms to the same transfer function as the input amplifier i e a representation of 100 C by the input amplifier is identical to the D A converter s representation of 100 C 1 323 Differential Comparator A differential comparator is used to compare the output of the D A converter with that of the input amplifier Subsequently the comparator s output denotes whether the zone temperature is higher or lower than the setpoint 1 324 Heater Power Switch In accordance with the comparator s decision the power circuitry will apply power to the heater when the zone temperature is below the setpoint and interrupt power when it is above the setpoint In strictly theoretical terms the above four elements are all that would be required to implement the controller s function However practical application requires three additional elements 1 325 Thermocouple Break Detection The most common physical malfunction in thermocouples is a break or open circuit If a break occurs the input amplifier can no longer report the zone temperature and usually will report the ITC s temperature instead From the preceding discussion one can
34. tability within the heated zone Some guidelines for adjustment are found in Section 2 4 1 34 Power Attenuation In the preceding section proportional power control was described as the process by which the ITC applies a percentage of power proportional to the difference between the setpoint and the controlled temperature It is not unusual that this technique alone will not yield acceptable temperature stability Commonly this situation occurs when near ambient temperatures are desired of a thermal system originally designed for higher temperatures Consequently the heater size rated output is much too large for system demand In compensating for such difficulties laboratory personnel often employ variacs variable output step down transformers to attenuate the power delivered to the heater Power delivered to the heater can be attenuated in increments of 1096 by setting the ITC s front panel mounted ATTN pushbutton switch This control performs exactly the same function as the variac mentioned above However the method by which the ITC performs this function differs considerably from variac operation Here s how A variac provides a means of adjusting the voltage and consequently the power applied to the heater The ITC varies the number of half cycles avail able to be delivered by its power circuitry For example 10096 is available when the ATTN control is set to 0 If the attenuation is changed to 4 40 only six of every
35. ten half cycles are available for delivery to the heater As a result the heater output will be 60 of its full rating In summary the proportioning circuitry determines the percentage of time during which power will be applied while the attenuation circuitry determines what per centage of power is to be available for delivery during this time 2 OPERATION In this section practical considerations for the ITC s usage are discussed 2 1 Physical layout of the ITC Following are illustrations of the various models of the Instrumentation Temperature Controller Figure 5 shows the front panel and Figure 6 shows the top view of the ITC Figures 7 and 8 show the back panels of the 110V AC and 220V AC models The numbers on the illustrations relate to the numbered parts below 1 2 3 4 5 6 A T T N oom ON HTR Figure 5 Front panel model ITC 10 1 Power Switch PWR Front mounted toggle switch controlling power to heater and power supply circuits 2 Power On Indicator Front mounted neon indicator illuminated whenever the power switch is in the ON position and power supply fuse is intact 3 Heater Power On Front mounted neon indicator illuminated whenever instrument applies power to heater will not illuminate if heater is not connected or if broken thermocouple is detected 4 Thermocouple Fault Indicator Front mounted LED indicator lights whene
36. tion with variacs variable output transformers in order to improve temperature stability By reducing the maximum power available to the heater the user is adjusting the heater size to suit his particular thermal system This is a practical flexible solution to the problem but requires two devices to control the temperature one of which is heavy inefficient and expensive The ITC employs a pushbutton switch so the user can attenuate the total power available to the heater circuit Attenuation is selectable from 0 to 90 in incre ments of 10 1 14 Zero Crossing Power Application Power is applied to the load in increments of integral half cycles only This technique drastically reduces RFI EMI normally associated with high current AC switching 1 15 Digital Temperature Setting The ITC employs a bank of three digital thumbwheel switches for temperature setpoint selection The setpoint is selectable in 1 increments The most obvious advantage to this scheme is 100 setting repeatability 1 16 Compact Rugged Construction and Functional Layout The ITC s physical characteristics are strictly utilitarian In all cases rugged construction techniques are employed insuring that the assembled instrument is not delivered by a freight company in kit form The instrument is housed in an aluminum cycolac enclosure measuring 2 4 x 8 3 x 5 9 The top of the enclo sure can be quickly removed allowing access to all fuses electronics
37. ver thermocouple circuit is broken 5 Heater Power Attenuation Switch Front panel mounted bidirectional ATTN switch denotes heater power attenuation in increments of 10 percent 6 Setpoint Switches Front panel mounted switches denote controlled temperature setpoint in C 7 Calibration Adjustments Printed circuit board mounted pots DO NOT attempt adjustment 10 10 Figure 6 Top view model ITC10 8 Thermocouple Connector Printed circuit board mounted connector connect red lead of thermocouple to Terminal R 9 5 Amp Fuse Printed circuit board mounted fuses power supply primary circuitry 10 10 Amp Fuse Printed circuit board mounted fuses heater power circuitry 11 13 D THERMOCOUPLE YR UU 120V AC 10A MAX HEATER POWER THERMOCOUPLE YR 220 10 POWER Figure 8 Back panel model ITC10 220V AC 11 11 Heater Receptacle 120V AC only Rear panel mounted AC receptacle two wire plus ground connects heater via standard 16 or 18 gauge three wire power cord not supplied 12 Heater Receptacle 220V AC only Rear panel mounted AC receptacle two wire plus ground connects heater via power cord black and white to heater green to ground Power cord is not
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