Fluke 9116A, User Manual

Page 1: ...9116A Furnace User s Guide Rev 842101 Hart Scientific ...

Page 2: ...ty period To obtain warranty service contact your nearest Hart authorized service center or send the product with a description of the difficulty postage and insurance prepaid FOB Destination to the nearest Hart au thorized service center Hart assumes no risk for damage in transit Following warranty repair the prod uct will be returned to Buyer transportation prepaid FOB Destination If Hart determ...

Page 3: ...llation 9 3 1 Unpacking 9 3 2 Location 9 3 3 Power 9 3 4 Plumbing 11 3 5 Heat Pipe Installation 11 4 Parts and Controls 17 4 1 Control Panel 17 4 1 1 Controller 17 4 2 Furnace Core 18 4 3 Access Well 20 4 4 Back Panel 20 5 General 21 5 1 Sodium Heat Pipe Information 21 5 1 1 Minimum Temperature and Heat Up Rate 21 5 1 2 Safety Precautions 21 6 Controller Operation 23 6 1 Well Temperature 23 6 2 Re...

Page 4: ...TA 33 6 12 Operating Parameters 33 6 12 1 Temperature Scale Units 34 6 12 2 Cut out Reset Mode 34 6 12 3 Approach 34 6 12 4 Soak Stability 35 6 13 Serial Interface Parameters 35 6 13 1 Baud Rate 35 6 13 2 Sample Period 35 6 13 3 Duplex Mode 36 6 13 4 Linefeed 36 6 14 IEEE 488 Parameters 37 6 14 1 IEEE 488 Address 37 6 14 2 Termination 37 6 15 Calibration Parameters 38 6 15 1 CTO 38 6 15 2 CO and C...

Page 5: ...stalling the Metal Freeze Point Cell 47 8 2 Purpose 47 8 3 Procedure 49 9 Freeze Point Realization 69 9 1 General 69 9 2 How to Realize the Freezing Point of Copper 69 10 Calibration Procedure 71 10 1 Two Point Calibration Procedure 71 10 1 1 Compute R0 ALPHA 71 10 1 2 Accuracy Repeatability 72 11 Maintenance 73 12 Troubleshooting 77 12 1 Troubleshooting 77 iii ...

Page 6: ...g paper towel with reagent grade alcohol 51 Figure 13 Clean cell completely 52 Figure 14 Place insulation in re entrant well 53 Figure 15 Push insulation to bottom of re entrant well 54 Figure 16 Clean the basket thoroughly 55 Figure 17 Place insulation in cell basket 56 Figure 18 Insure the insulation is flat at the bottom of the cell basket 57 Figure 19 21 6 x 14 cm 5 5 x 8 5 in paper 58 Figure ...

Page 7: ...u control The temperature control and uniformity of the furnace allows the user to achieve plateaus ranging many hours in length NOTE Many of the illustrations and examples used in this manual as sume the use of the copper point cell Any of the three cells indicated may be used with the appropriate set points 1 2 Symbols Used Table 1 lists the International Electrical Symbols Some or all of these ...

Page 8: ...IC Australian EMC Mark The European Waste Electrical and Electronic Equipment WEEE Directive 2002 96 EC mark 1 3 Safety Information Use this instrument only as specified in this manual Otherwise the protection provided by the instrument may be impaired The following definitions apply to the terms Warning and Caution WARNING identifies conditions and actions that may pose hazards to the user CAUTIO...

Page 9: ...iratory tract May be harmful if inhaled May contain or form cristobalite crystalline silica with use at high tem peratures above 1600 F which can cause severe respiratory disease Possible cancer hazard based on tests with laboratory animals Animal studies to date are inconclusive No human exposure studies with this product have been reported Service personnel coming into contact with these materia...

Page 10: ...Allow sufficient air circulation by leaving at least 6 inches of space between the furnace and nearby objects Nothing should be placed over the top of the furnace The furnace should not be placed under cabinets or tables Extreme temperatures can be generated out the top of the well The furnace is equipped with cooling coils use cold water circulation when the furnace is used above 600 C For specif...

Page 11: ...letely 1 4 Authorized Service Centers Please contact one of the following authorized Service Centers to coordinate service on your Hart product Fluke Corporation Hart Scientific Division 799 E Utah Valley Drive American Fork UT 84003 9775 USA Phone 1 801 763 1600 Telefax 1 801 763 1010 E mail support hartscientific com Fluke Nederland B V Customer Support Services Science Park Eindhoven 5108 5692 ...

Page 12: ...Service Center 60 Alexandra Terrace 03 16 The Comtech Lobby D 118502 SINGAPORE Phone 65 6799 5588 Telefax 65 6799 5588 E mail antng singa fluke com When contacting these Service Centers for support please have the following information available Model Number Serial Number Voltage Complete description of the problem 9116A Furnace User s Guide 6 ...

Page 13: ...ting Exterior Dimension 838 mm H x 610 mm W x 406 mm D 33 x 24 x 16 in Weight 82 kg 180 lb Safety EN 601010 1 CAN CSA C22 2 No 601010 1 04 2 2 Environmental Conditions Although the instrument has been designed for optimum durability and trou ble free operation it must be handled with care The instrument should not be operated in an excessively dusty or dirty environment Maintenance and clean ing r...

Page 14: ... altitude less than 2 000 meters indoor use only If the unit is operating at temperatures above 600 C cooling coils are accessi ble on the rear of the chassis to prevent the furnace heat from loading down the room air conditioning system See Section 3 4 Plumbing 8 ...

Page 15: ... shipment Small parts may be packed in a separate box inside the crate Check carefully for all parts If there is any damage due to shipment notify your carrier immediately 3 2 Location A furnace of this type is typically installed in a calibration laboratory where temperature conditions are generally well controlled Best results will be ob tained from this type of environment Avoid the presence of...

Page 16: ...lement Top Thermal Shunt Disk Control Probe Metal Freeze Point Cell Basket and Cover Metal Freeze Point Cell Heat Pipe Ceramic Fiber Insulation Air Gap Circulating Air Bottom Support Block Bottom Thermal Shunt Disk Retaining Plate 2 7 1 Top Support Block 3 6 5 4 1 27 cm Fiber Ceramic Board Figure 1 Furnace Core Diagram ...

Page 17: ...e sump 3 5 Heat Pipe Installation NOTE The first heat of the furnace should be done without the heat pipe to verify operation and to become familiar with the furnace Re move any packing material before operating The heat pipe is shipped separately in order to prevent damage to the heater and delicate fiber ceramic insulation Re installation of the control HTPRT and cutout thermocouple is also requ...

Page 18: ...ere is a grounding wire attached to the top flange of the heat pipe BE CAREFUL that it does not damage the ceramic heaters as the heat pipe is lowered into the furnace 3 Attach the installation tool to the heat pipe and lower it very carefully into the furnace Maintain the heat pipe in the center of the well so as to allow the bottom support block to slide into the cavity at the bottom of the heat...

Page 19: ... two star washers and a screw Make sure that the ground wire is securely attached to the fur nace chassis Check the ground continuity to ensure that the ground wire is intact and the heat pipe 5 is grounded Insure that the wire routing for the Control 6 and Cutout 7 probe is as shown in Figure 2 13 Figure 2 HTPRT control probe and cutout thermocouple wire routing and heat pipe ground wire placemen...

Page 20: ...ont right of the furnace when facing the furnace and down to the access hole into the electronics com partment at the center left when facing the electronics panel Connect the probe wires to the controller The labels on the probes and the con troller must be used to correctly complete the wiring The thermocouple wires should be firmly attached using the screw down terminals on the controller print...

Page 21: ...metal freeze point cell 15 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 MH1 MH6 CUTOUT CONTROL J10 BLACK CUTOUT RED CUTOUT White J2 1 2 3 4 5 Green Red Black NC Figure 3 Attachment of thermocouples ...

Page 22: ...el is located on the upper right portion of the furnace see Fig ure 4 The controller itself is a hybrid ana log digital device utilizing the high stability of analog circuitry with the flexibility of a micro processor interface and digital controls The following controls and indicators are present on the primary controller panel 1 the digital LED display 2 the control but tons and 3 control indica...

Page 23: ...es which reduces the lifetime Refer to the Section 5 for more information CAUTION In the unlikely event that the heat pipe should leak do not at tempt to put out the fire with water or chemical fire extinguishers Smother the fire with dry soda ash in accordance with the MSDS sheets at the end of this manual The heat pipe is centered in the heating element and supported by means of fi ber ceramic b...

Page 24: ...19 Figure 5 Back Panel ...

Page 25: ...sists of an exhaust fan a serial communications connector a power cord and cooling water ports See Figure 5 on page 19 1 The exhaust fan allows air circulation around the electrical components Be sure to keep this fan free of foreign objects that could hinder air flow 2 The serial communication connector is a DB 9 connector for interfacing the furnace to a computer or terminal with serial RS 232 c...

Page 26: ...t the factory and in the furnace In the event of an accident which results in a rupture of the heat pipe the small quantity of sodium may burn DO NOT use water or standard fire extinguishers on sodium fires Refer to MSDS Standard commercially available materials for extinguishing sodium fires are dry soda ash Na2CO3 or powdered graph ite A container of one of these products should be kept in the l...

Page 27: ...ture This temperature value is what is normally shown on the dis play The units C or F of the temperature value are displayed at the right For example 100 00 C Well temperature in degrees Celsius The temperature display function may be accessed from any other function by pressing the EXIT button 6 2 Reset Cut out If the over temperature cut out has been triggered the temperature display al ternate...

Page 28: ...9116A Furnace User s Guide 24 Figure 6 Controller Flow Chart ...

Page 29: ...d to help prevent this occurrence Setting the temperature involves two steps 1 select the set point memory and 2 adjust the set point value 6 3 1 Programmable Set points The controller stores 8 set point temperatures in memory The set points can be quickly recalled to conveniently set the calibrator to a previously programmed temperature set point To set the temperature one must first select the s...

Page 30: ...and enabled so that when the set point is changed the furnace heats or cools at a specified rate degrees per minute until it reaches the new set point With the scan disabled the furnace heats or cools at the maxi mum possible rate 6 4 1 Scan Control The scan is controlled with the scan on off function that appears in the main menu after the set point function ScAn OFF Scan function off Press UP or...

Page 31: ...r a determined length of time The user can select one of four different cycle functions The program parameter menu is accessed by pressing SET and then UP 100 00 C Well temperature S U Access program menu ProG Program menu Press SET to enter the program menu S Enter program menu 6 5 1 Number of Program Set points The first parameter in the program menu is the number of set points to cycle through ...

Page 32: ...ed as desired press EXIT to continue E Continue to next menu function 6 5 3 Program Soak Time The next parameter in the program menu is the soak time The soak time is the time in minutes that the furnace maintains each of the program set points after settling before proceeding to the next set point The duration is counted from the time the temperature settles to within a specified stability The st...

Page 33: ... SET to continue S Save new setting 6 5 5 Program Control The final parameter in the program menu is the control parameter There are three choices to choose from 1 start the program from the beginning 2 con tinue the program from where it was when it was stopped or 3 stop the program Pr off Program presently off Use the UP or DOWN buttons to change the status Pr StArt Start cycle from beginning Pr...

Page 34: ...econdary menu Press SET and EXIT simultaneously and release The heater power is displayed as a percent age of full power 100 00 C Well temperature S E Access heater power in secondary menu 12 Pct Heater power in percent To exit out of the secondary menu press EXIT To continue on to the propor tional band setting function press SET 6 8 Proportional Band In a proportional controller such as this the...

Page 35: ...usted from the front panel The width may be set to discrete values in degrees C or F depending on the selected units The proportional band adjustment is accessed within the secondary menu Press SET and EXIT to enter the secondary menu and show the heater power Then press SET to access the proportional band S E Access heater power in secondary menu 12 Pct Heater power in percent S Access proportion...

Page 36: ...t has two modes automatic reset or manual reset If the mode is set to auto matic the cut out automatically resets itself when the temperature falls below the reset temperature allowing the well to heat up again If the mode is set to manual the heater remains disabled until the user manually resets the cut out The cut out set point may be accessed within the secondary menu Press SET and EXIT to ent...

Page 37: ...brator This procedure is ex plained in detail in Section The probe parameters are accessed by pressing SET after the name of the parameter is displayed The value of the parameter may be changed using the UP and DOWN buttons After the desired value is reached press SET to set the parameter to the new value Pressing EXIT causes the parameter to be skipped ignoring any changes that may have been made...

Page 38: ... selection and resume displaying the well temperature 6 12 2 Cut out Reset Mode The cut out reset mode determines whether the cut out resets automatically when the well temperature drops to a safe value or whether the operator must manually reset the cut out The parameter is indicated by CtorSt Cut out reset mode parameter Press SET to access the parameter setting Normally the cut out is set for m...

Page 39: ...Serial baud rate parameter Press SET to choose to set the baud rate The current baud rate value is displayed 1200 b Current baud rate The baud rate of the serial communications may be programmed to 300 600 1200 or 2400 baud Use UP or DOWN to change the baud rate value 2400 b New baud rate Press SET to set the baud rate to the new value or EXIT to abort the opera tion and skip to the next parameter...

Page 40: ... executed but not echoed The du plex mode parameter is indicated by DUPL Serial duplex mode parameter Press SET to access the mode setting DUP FULL Current duplex mode setting The mode may be changed using UP or DOWN and pressing SET DUP HALF New duplex mode setting 6 13 4 Linefeed The final parameter in the serial interface menu is the linefeed mode This pa rameter enables on or disables off tran...

Page 41: ...address setting Add 22 Current IEEE 488 interface address Adjust the value with UP or DOWN and then use SET to set the address to the displayed value Add 15 New IEEE 488 interface address 6 14 2 Termination The transmission termination character can be set to carriage return only line feed only or carriage return and linefeed Regardless of the option selected the instrument will interpret either a...

Page 42: ...ation parameters menu is indicated by CAL Calibration parameters menu Press SET five times to enter the menu 6 15 1 CTO Parameter CTO sets the calibration of the over temperature cut out This is not adjustable by software but is adjusted with an internal potentiometer 6 15 2 CO and CG These parameters calibrate the accuracy of the temperature set point These are programmed at the factory when the ...

Page 43: ...e serial interface the user may access any of the functions parameters and settings discussed in Section 6 with the exception of the baud rate setting 7 1 1 Wiring The serial communications ca ble attaches to the calibrator through the DB 9 connector at the back of the instrument Fig ure 8 shows the pin out of this connector and suggested cable wiring To eliminate noise the serial cable should be ...

Page 44: ...sampling is dis abled with a sample period of 0 Press SET to choose to set the sample period Adjust the period with UP or DOWN and then use SET to set the sample rate to the displayed value 7 1 2 3 Duplex Mode The next parameter is the duplex mode indicated with dUPL The duplex mode may be set to half duplex HALF or full duplex FULL With full duplex any commands received by the thermometer via the...

Page 45: ...device address of the calibra tor if necessary to match the address used by the communication equipment by pressing UP or DOWN and then SET IEEE 488 Operation Commands may now be sent via the IEEE 488 interface to read or set the temperature or access other controller functions All com mands are ASCII character strings and are terminated with a carriage return CR ASCII 13 Interface commands are li...

Page 46: ...otation Characters are shown in lower case although upper case may be used Spaces may be added within command strings and are ignored Backspace BS ASCII 8 may be used to erase the previous character A terminating CR is im plied with all commands 9116A Furnace User s Guide 42 ...

Page 47: ...Read proportional band setting pr op band pr pb 999 9 pr 15 9 Set proportional band to n pr op band n pr 8 83 Depends on Configuration Read cutout setting c utout c c 9999 C or F c 620 C in Set cutout setting c utout n r eset Set cutout to n degrees c utout n c 500 Temperature Range Reset cutout now c utout r eset c r Read heater power duty cycle po wer po p 9999 po 1 Ramp and Soak Menu Read numbe...

Page 48: ...0 0038433 00370 to 00399 Read DELTA calibration parameter de lta de de 9 99999 de 1 46126 Set DELTA calibration parameter to n de lta n de 1 45 0 0 to 2 9 Operating Parameters Menu Set temperature units u nits c f C or F Set temperature units to Celsius u nits c u c Set temperature units to Fahrenheit u nits f u f Read cutout mode cm ode cm cm xxxx cm AUTO Set cutout mode cm ode r eset a uto RESET...

Page 49: ...rameter cg cg cg 999 99 cg 406 25 Set CG calibration parameter to n cg n cg 406 25 999 9 to 999 9 These commands are only used for factory testing Read software cutout mode sco sco sco ON or OFF sco ON Set software cutout mode sco ON OF F ON or OFF Set software cutout mode on sco ON sco on Set software cutout mode off sco OF F sco off Miscellaneous not on menus Read firmware version number ver sio...

Page 50: ...use devitrification or physical break down of the quartz shell Handle the cell with cotton gloves Discard the gloves before they become appreciably soiled Any foreign material should be carefully removed with high purity alcohol Refer to Figure 9 on page 48 Sealed cells for freezing points are delicate devices and the quartz shell is prone to be broken THE CELL MUST BE HANDLED WITH EXTREME CARE Ma...

Page 51: ...Point Cell cell interior construction shown Quartz Shell Graphite Crucible Quartz Reentrant Tube High Purity Metal Sample Fiber Ceramic Cushion 25 4 mm 1 in Insulation Top Thermal Shunt Disk Insulation Insulated Reflector Assy Insulation Fiber Ceramic Board Bottom Thermal Shunt Disk Figure 9 Metal Freeze Point Cell installed in canister ...

Page 52: ...paper for cushioning around cell 0 64 cm 0 25 in diameter piece to be placed in the re entrant well of the cell Quartz rod Cotton gloves Paper towels Stand to support cell Cell installation removal tool 8 3 Procedure 1 Remove cell from packaging and place in stand or support it in a vertical position 49 8 Fixed Point Cell Installation Instructions Procedure Figure 10 Cell supported by stand ...

Page 53: ...2 Put on cotton gloves to avoid contaminating cell with body oils 9116A Furnace User s Guide 50 Figure 11 Cotton gloves MUST be used ...

Page 54: ...Clean cell with reagent grade alcohol to remove any dust or oil that may be on the cell 51 8 Fixed Point Cell Installation Instructions Procedure Figure 12 Preparing paper towel with reagent grade alcohol ...

Page 55: ...4 Return cell to stand see Figure 10 5 Place the 0 64 cm 0 025 in diameter piece of insulation in the re entrant well of the cell 9116A Furnace User s Guide 52 Figure 13 Clean cell completely ...

Page 56: ...53 8 Fixed Point Cell Installation Instructions Procedure Figure 14 Place insulation in re entrant well ...

Page 57: ...6 Using quartz rod move insulation to the bottom of the cell 9116A Furnace User s Guide 54 Figure 15 Push insulation to bottom of re entrant well ...

Page 58: ...7 Clean cell basket with reagent grade alcohol 55 8 Fixed Point Cell Installation Instructions Procedure Figure 16 Clean the basket thoroughly ...

Page 59: ...8 Place 2 54 cm 1 in thick piece of insulation in the cell basket 9116A Furnace User s Guide 56 Figure 17 Place insulation in cell basket ...

Page 60: ...quartz rod to verify that insulation is at the bottom of the basket and flat 57 8 Fixed Point Cell Installation Instructions Procedure Figure 18 Insure the insulation is flat at the bottom of the cell basket ...

Page 61: ...5 x 5 5 in piece of paper from standard printer paper This paper is used to protect the cell from being scratched while installing the cell into the basket 9116A Furnace User s Guide 58 Figure 19 21 6 x 14 cm 8 5 x 5 5 in paper ...

Page 62: ...11 Roll the paper lengthwise and place it in the opening of the basket 59 8 Fixed Point Cell Installation Instructions Procedure Figure 20 Paper placement ...

Page 63: ...and slide cell into basket Push with your fin ger until cell reaches bottom of the basket 13 Remove paper and return cell and basket to stand in the vertical position 9116A Furnace User s Guide 60 Figure 21 Insert cell into basket ...

Page 64: ... 04 cm 5 x 2 25 x 0 016 in piece of fiber ceramic paper width wise and place it in the cell basket 61 8 Fixed Point Cell Installation Instructions Procedure Figure 22 Place fiber ceramic paper to center the cell in cell basket ...

Page 65: ...m 0 25 in thick piece of insulation on top of the cell and use rod to verify the alignment of the hole in the insulation 9116A Furnace User s Guide 62 Figure 23 Fiber ceramic insulation installed on top of cell Figure 24 Fiber ceramic paper pushed below cell basket top ...

Page 66: ...he lid installed otherwise the cell and the basket may be broken The Alumina basket needs to be installed before the basket lid is placed on the basket 17 Place the cell removal installation tool into the holes on the basket Us ing both hands one on the removal installation tool lift and move basket assembly into the furnace 63 8 Fixed Point Cell Installation Instructions Procedure Figure 25 Prepa...

Page 67: ...18 Slowly insert cell into furnace 9116A Furnace User s Guide 64 Figure 26 Installing basket assembly in furnace ...

Page 68: ... the furnace 20 Place one circular 2 54 cm 1 in thick piece of insulation on top of bas ket 21 Place the top thermal shunt disk in the furnace 22 Place one circular 2 54 cm 1 in thick piece of insulation on top of the thermal shunt disk 65 8 Fixed Point Cell Installation Instructions Procedure Figure 27 Width of insulation placed on top of basket assembly ...

Page 69: ...23 Install the furnace lid Figure 28 9116A Furnace User s Guide 66 Figure 28 Basket insulation and furnace lid installed ...

Page 70: ...24 Install the heat radiation guard Figure 29 67 8 Fixed Point Cell Installation Instructions Procedure Figure 29 Heat radiation guard installed ...

Page 71: ...ing high temper ature platinum resistance thermometer or a Type S Type R thermocou ple to monitor the temperature in the cell When the copper sample begins to melt the temperature stops rising and remains almost constant during the melting process Write down the resistance or EMF indicated by the working thermometer at the melting point for future reference 2 As soon as the copper sample is melted...

Page 72: ...g is that the equilibrium time in the cell may be shortened by nearly one half i e from about 20 minutes to 10 minutes Preheat the thermometers for 20 minutes or so near the freezing point Preheating the thermometers for too long is unnecessary and should not be done The thermometer sensors could possibly be contaminated if they remain in metal wells for a long period of time 4 SPRT Annealing The ...

Page 73: ...t point accuracy Calibration is done by adjusting the controller probe calibration constants R0 and ALPHA so that the process temperature as measured with a standard thermometer agrees more closely with the set point The thermometer used must be able to measure the temperature with higher ac curacy than the desired accuracy of the system 1 The two set points that should be used for the calibration...

Page 74: ...emperature and resistance at 800 0 C T2 and R2 are the measured temperature and resistance at 1060 0 C 5 Program the new values for R0 rzero and ALPHA alpha into the instrument 10 1 2 Accuracy Repeatability 1 Check the accuracy of the calibrator at various points over the calibrated range 2 If calibrator does not pass specification at all set points repeat the Calibra tion Procedure 9116A Furnace ...

Page 75: ...nner not in accordance with the equip ment design the operation of the furnace may be impaired or safety haz ards may arise The over temperature cut out should be checked every 6 months to see that it is working properly In order to check the user selected cut out fol low the controller directions Section 6 for setting the cut out Adjustment of Temperature Uniformity Vertical uniformity should be ...

Page 76: ...74 Thermocouple Melted Cell 10 2 cm 4 in Insulation Adjust amount of insulation to adjust uniformity 1 2 cm 0 5 in Fiber Ceramic board Figure 30 Testing Uniformity ...

Page 77: ...abilize as would be done in preparation for a freeze Measure the EMF of a ther mocouple inserted into the cell Compare the measured EMF to one taken at the M P or F P The actual temperature t in the cell can be calculated by using the following equation t E E 961 78 0 0114 1 0 C mV C where E1 is the measurement EMF and E0 is the EMF at the M P 961 78 C is the M P temperature of copper for this exa...

Page 78: ...e process temperature displayed seems grossly in error consult the following problem The display flashes Cut out and an incorrect pro cess temperature Normally the cutout disconnects power to the heater when the instrument temperature exceeds the cutout set point causing the temperature to drop back down to a safe value If the cutout mode is set to AUTO the heater switches back on when the tempera...

Page 79: ...ng the Factory Reset Sequence sets all controller parameters to default Factory Reset Sequence Hold the SET and EXIT buttons down at the same time while powering up the instrument The instrument display shows init the model number and the firmware version Each of the controller parameters and calibration constants must be reprogrammed The values can be found on the Report of Test that was shipped ...

Page 80: ...oo narrow typically causes this oscillation Increase the width of the proportional band until the temperature stabi lizes as discussed in Section 6 8 Proportional Band The controller erratically heats then cools control is unstable If both the instrument temperature and output power do not vary periodi cally but in a very erratic manner the problem may be excess noise in the system Noise due to th...