TEGAM Inc. Model 1806 Dual Type IV Power Meter MODEL 1806
Contents
1. eese nennen neon non rennen enne nennen 2 2 Comparison of Voltmeter Errors When Reference Voltage Generator Is and Is Not Used 4 8 Required Test and Calibration Equipment ss 5 1 Power Supply Line Regulation Testing ss 5 8 111 1v Instruction Manual Section I Dual Type IV Power Meter Model 1806 General Information SECTION GENERAL INFORMATION SCOPE OF MANUAL This manual contains operation and maintenance information for the TEGAM Model 1806 Dual Type IV Power Meter shown in Figure 1 1 This information is in five sections that outline general information installation operation principles of operation and maintenance Discussions throughout this manual concerning use of the Model 1806 treat it as a stand alone item The TEGAM System IIA Automatic Power Meter Calibration System manual contains information for use operational role and cabling of the Model 1806 within a power sensor calibration system Figure 1 1 Model 1806 Dual Type IV Power Meter PURPOSE AND USE OF EQUIPMENT The TEGAM Model 1806 in conjunction with an external thermistor mount and a digital voltmeter DVM forms a precision power measurement system that measures microwave power within the frequency bandwidth of the thermistor mount The primary application of this system is for power sensor calibration The Model 1806 contains two Type IV Bridge circuits and two thermistor mount temperature control2. z 4 1806 I gt ZZ 2 CL 1009 1000 C i I 15V 15V I EE A r o Lo RF iN Figure 4 2 Simplified Schematic of Precision Power Measurement System POWER MEASUREMENTS The precision measurement system measures RF power in terms of a voltage change across the precision resistance leg The digital voltmeter measures voltage across the precision resistance leg before the application of RF power V and after the application of RF power V5 The difference V2 V1 indicates the change in voltage across the precision resistance leg due to the application of RF power The RF power introduced to the thermistor is directly proportional to the change in dc power across the precision resistor The change in dc power is calculated by the formula AV Pac R Where Pic the change in de power across the precision resistor AV2 change in voltage across the precision resistor Vi V2 R resistance value of precision resistor 4 3 Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation RF Power Level Calculation The Model 1806 measures high frequency or microwave power in terms of a dc voltage change The system does not measure the RF power level directly Instead it measures dc voltages before and after the application of RF power using a DVM or a DVM and an RVG The difference between these voltages
3. 2V1 Vp Vp x Vp V pj Qv Vp Vp X Vos Vp Pac Ro Where AV Change in voltage across the precision resistance leg of the Model 1806 bridge Vi Model 1806 bridge output reading with no RF power applied Vo 1 Difference between Model 1806 output with no RF power applied and reference voltage generator Vp Difference between Model 1806 output with RF power applied and reference voltage generator Ro Mount operating resistance and Pic Proportional amount of dc substituted power PRECISION MEASUREMENT SYSTEM ERRORS Precision measurement system errors are due largely to the inaccuracy of the external voltage measuring equipment However servo errors dependent on power level such as those caused by amplifier offset and finite gain amplifier input bias currents and the nominal resistance of the precision resistor do occur Figure 4 5 depicts typical bridge errors over a 30 mW RF power range with and without a reference voltage generator Figure 4 5 shows values obtained when using a typical coaxial dual element thermistor with an ohms per watt coefficient of 1300 and a bias current of 12 8 mA Because this type of mount experiences a dual element substitution error the normal maximum RF power level is 10 mW However the graph in Figure 4 5 extends beyond this level to illustrate better the nature of errors Table 4 1 offers a comparison of voltmeter errors when a reference voltage source is used and not
4. PRF the RF power incident on the terminating mount Pdc the dc substituted power as measured at the Model 1806 Ki the measured or known calibration factor for the terminating mount RF power measurements are traceable to a primary laboratory standard in cases where the terminating thermistor mount has been calibrated by NIST PRECISION POWER MEASUREMENT SYSTEM The Model 1806 Dual Type IV Power Meter the NIST calibrated TEGAM Model 1110 Terminating Mount a reference voltage generator and a digital voltmeter with a 6 5 digit resolution combine to provide the precision power measurement system shown in the functional block diagram in Figure 4 1 This system features one of the two Model 1806 closed loop self balancing Type IV Bridge circuits consisting of two legs a precision resistance leg 100 or 200 ohms and a leg linked to a thermistor element in the Model 1110 A thermistor is a type of bolometer whose resistance decreases as a function of increasing heat associated with ambient temperature or applied power This system also features the Model 1806 temperature control circuitry that temperature stabilizes the thermistor mount This eliminates changes in the thermistor element s resistance due to ambient temperature changes and thus isolates the causes of thermistor variation to the application of RF and dc power only An IEEE 488 bus compatible controller controls DVM measurements across the precision resistance leg of the Model 1
5. and date of original purchase Also write the company name your name and phone number on an index card Then attach the card to the instrument to be returned and send to TEGAM INC 800 666 1010 toll free TEN TEGAM WAY 440 466 6100 phone GENEVA OH 44041 USA 440 466 6110 fax 5 10 Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance Warranty TEGAM Inc warrants this product to be free from defects in material and workmanship for a period of one year from date of shipment During the warranty period we will at our option either repair or replace any product that proves to be defective TEGAM Inc warrants the calibration of this product for a period of one year from date of shipment During this period we will recalibrate any product that does not conform to the published accuracy specification To exercise the warranty contact TEGAM Inc Ten TEGAM Way Geneva Ohio 44041 phone 440 466 6100 fax 440 466 6110 M F 8 a m 5 p m ET You will be given prompt assistance and return instructions Send the instrument transportation prepaid to the indicated service facility Repairs will be made and the instrument returned transportation prepaid Repaired products are warranted for the balance of the original warranty or at least 90 days whichever is longer Limitation of Warranty TEGAM Inc warranty does not apply to defects resulting from unauthorized modification or misuse of any product or p
6. and the Model 1806 blue positive SENSE Connector TP1 B Install a shorting link P N 138 495 between the Model 1806 black negative BOLOMETER Mount Bias Connector TP4 and the Model 1806 white negative SENSE Connector TP2 C Connect the anode of the 1N914 diode to the Model 1806 red positive BOLOMETER Mount Bias Terminal TP3 and connect the cathode to the black negative BOLOMETER Mount Bias Terminal TP4 D Setthe Bridge OPERATING RESISTANCE Switch S2 to 100 ohms the in position E Setthe Variac for 117 volts and connect it to the Model 1806 rear panel Power Input Connector and Voltage Selector Fuse Assembly XF1 F Set the Model 1806 rear panel FLOAT GROUND Switch S3 to the FLOAT position This switch should remain in this position throughout the entire alignment G Connect the bolometer mount s temperature control connector to the Model 1806 TEMPERATURE CONTROL Connector J5 via the temperature control cable P N 138 477 and H Remove the top dust cover of the Model 1806 and ensure that all boards are properly and securely installed in their respective slots POWER SUPPLY ASSEMBLY TEST AND RECALIBRATION This procedure recalibrates the power supply assembly within the Model 1806 and tests its line regulation In order to test and recalibrate the power supply assembly perform the following A B Set the Model 1806 front panel POWER Switch S1 to the STANDBY position and ensure that the yellow fron
7. operational indicator will be illuminated When using a 100 ohm thermistor mount set S2 to the in position for 100 ohm operation and to illuminate operational indicator DS4 When using a 200 ohm thermistor mount set S2 to the out position for 200 ohm operation and to illuminate operational indicator DS5 Float Ground Switch S3 FLOAT GROUND Switch S3 is a two position toggle switch located on the rear panel directly above the Power Input Connector and Voltage Selector Fuse Assembly XF1 refer to Figure 2 1 S3 grounds or ungrounds floats the Model 1806 depending on whether or not the thermistor and DVM are grounded The up position of S3 grounds the Model 1806 The down position of S3 floats the Model 1806 If either the thermistor mount or DVM or both are grounded place the FLOAT GROUND Switch in the FLOAT position When both bridges are used if any external voltage measuring instrument is grounded place the FLOAT GROUND Switch in the FLOAT position RF POWER LEVEL MEASUREMENT The Model 1806 is one component in a precision measurement system that measures RF power in terms of a dc voltage change across the Model 1806 bridge circuit This system measures the voltage change with a digital voltmeter DVM with a 6 5 digit resolution or the same DVM and reference voltage generator RVG when the applied RF power level is small a few milliwatts The following paragraphs describe these two methods of measurement 3 4 Instruction Manu
8. Figure 3 1 depicts the location of front panel switches The rear panel of the Model 1806 contains one switch S3 for grounding or ungrounding the Model 1806 depending on the ground state of the thermistor and DVM used with the Model 1806 Power Switch S1 The Model 1806 POWER Switch S1 controls operational power S1 is in the lower left hand corner of the front panel next to the ON Indicator DS1 S1 is a three position toggle switch that completes extends or terminates power to the Model 1806 In the uppermost position S1 extends power to the entire circuitry within the Model 1806 that enables all unit operations In the middle position S1 places the Model 1806 in a STANDBY mode for warm up STANDBY mode applies only necessary power to heat the Model 1806 and associated thermistor mounts When switched to the lowest position S1 terminates power to the Model 1806 Ensure that input connector and voltage selector fuse assembly are set for the proper voltage before switching the POWER Switch S1 to ON or STANDBY otherwise damage may result to internal circuitry 100 200 Ohm Operating Resistance Switch S2 Each bridge on the Model 1806 contains a two position push button OPERATING RESISTANCE Switch S2 The location of this switch is in the center of each bridge control panel The position of S2 configures individual bridge circuitry for either 100 or 200 ohm operation Depending on the position of this switch either the 100 ohm or 200 ohm
9. M1 is in the upper left hand corner of Bridge A M1 measures with a resolution of 1 mA the thermistor bias current level applied through the Model 1806 Bolometer Mount Bias Connectors Temperature Control Meter M2 Temperature Control Meter M2 is in the upper right hand corner of Bridge A M2 indicates a dc voltage level that is proportional to the current applied through Temperature Control Connector J5 to a heater bridge in the thermistor mount The green area on M2 indicates that the thermistor mount is in the correct temperature range FRONT PANEL INDICATORS The Model 1806 contains eight front panel LED indicators Each bridge control on the Model 1806 contains three indicators and the overall unit control contains two indicators This assortment of LEDs varies in color from yellow to green to red Each indicates either an ON or OFF condition Figure 3 1 also shows the location of front panel indicators ON Indicator DS1 The location of DS is in the lower left hand corner just to the right of the POWER Switch S1 This green indicator illuminates when the Model 1806 POWER Switch is in the ON position indicating supply of operational power to the unit and availability of all operations Standby Indicator DS2 The DS2 indicator location is just below indicator DS1 in the lower left hand corner of the front panel This yellow indicator illuminates when the Model 1806 POWER Switch is in the STANDBY position and power is being applied to the
10. ea it RE e Ru 4 2 Power Meas rements As Sech nn Re Pn e IF RR RF 4 3 RP Power Level Calculation s Seet refe etie iio 4 4 Controlling Thermistor Mount Internal Temperature 4 4 Temperature Control Board 3 e e a rH PUO DRE e EP oE V ee ted 4 5 Model 1806 Power Supply 5 2 enne e emt rd P e e ERR RE RR OPE e NEES 4 5 Power Supply Electrical Configuration ss 4 5 Power Supply Application Transformation and Isolation seseseesesesesieeesreesrstseerrereresrsrsrrereree 4 5 Motherboard EE 4 6 Front Panel SE EE 4 6 Measurements Using a Reference Voltage Source ss 4 6 Precision Measurement System Errors sense 4 7 Calculating Model 1806 Aecur cies ei indt oe erre EO Ete Peer D e Ree aper a 4 8 SECTION V MAINTENANCE Tntrodtiction M H 5 1 Preventive Maintenance con 5 1 Troubleshooting Procedures 5e eser it ele Eae Het dert iia 5 1 Specification Testi E 5 1 Power Up Operational Test ss 5 2 Bolometer Current Meter Test 5 3 Bridge Noise Test d enisi teet ee de eee ee EE ce veio eo ZER 5 4 Bridge Balance T tanos ii 5 4 Temperature Controla cosa 5 5 Corrective Maintenance and Recalibration siennes 5 6 A ONO 5 6 Power Supply Assembly Test and Recalibration esee ener 5 7 Bridge Board Circuitry Test and Recalbraon sess 5 8 Bolometer Current Meter Calibration ss 5 8 Calibration of Internal Resistance 5 9 Bridge
11. is proportional to the RF effect on the thermistor s resistance and is calculated in terms of dc substituted bias required to rebalance the bridge as follows v v d C Ro Where V DVM reading across the precision resistance leg in the absence of RF power V DVM reading across the precision resistance leg with RF power applied Il Mount operating resistance 100 or 200 ohms and DC power across precision resistance which is proportional to the applied RF power Pa C The dc effect is translated into an RF power level using the mount calibration factor according to this equation Pa 4 Fer K Where Pap Level of RF power applied to the thermistor Pic Level of proportional de substituted power from previous equation and K Terminating Mount calibration factor which is directly traceable to NIST CONTROLLING THERMISTOR MOUNT INTERNAL TEMPERATURE When the Model 1806 operates in conjunction with a thermistor mount a temperature sensitive device it must eliminate or minimize the effects of changes in the ambient temperature upon the thermistor in order to provide precise measurements The Model 1806 temperature control board accomplishes this by raising the mount s internal temperature to a level higher than the ambient temperature and maintaining that level by controlling the current applied to the mount s internal heater element This prevents any thermistor imbalance due to ambient temper
12. negative terminals to the Model 1806 VOLTMETER terminals TPS and TP6 respectively C Select the appropriate bridge operating resistance for the bolometer mount being used 100 or 2000 D Turn the Model 1806 POWER Switch S1 to the ON position and ensure that the operational Resistance Indicator DS4 or DS5 illuminates and that the ERROR Indicator DS3 is dark E Connect the null detector to the bridge board at TP2 and TPS The null detector should indicate less than 10 microvolts if the amplifier offset adjustment was performed properly Record this reading as V F Record the dc voltmeter reading across TPS and TP6 as V1 G Apply the necessary RF power to the mount to reduce the dc voltmeter reading to about 0 2 volts H Record the readings of both the null detector V 45 and the dc voltmeter V5 I Connect the null detector to the bridge board at TP9 and TP7 and repeat steps G and H J Calculate the gain of each amplifier from the following relationship V4 Vi gain and Vio Vai K Ensure that the gain is equal to approximately 125 000 FACTORY MAINTENANCE If the procedures above do not correct Model 1806 malfunctions and the Model 1110 is in proper working order contact TEGAM DO NOT send the instrument to TEGAM without prior authorization When it is necessary to return an item state the symptoms or problems catalog and type number of the instrument serial number of the item
13. or 240 volts 5 10 to the Model 1806 This ac power source supplies the Model 1806 with all operational power required The Model 1806 requires no other external power The Model 1806 operates within its specifications at an ambient temperature of 12 C to 32 C Operating beyond these limits could affect the accuracy of this unit and damage internal circuitry TEGAM ships the Model 1806 with four plastic feet and a tilt stand mounted on the bottom of the unit for bench use however the Model 1806 is also rack mountable To rack mount the unit first remove the four plastic feet and the tilt stand on the bottom of the unit Next remove the rear panel trim and slide the side panels out Then remove the side trim and install rack adapters on the left and right sides of the Model 1806 Re attach the rear panel trim to the unit while leaving the side panels off When rack mounting the unit ensure access to the rear panel so that rear panel connections can be made The unit may now be mounted into a standard rack INSTALLATION Installation of the Model 1806 consists of rack mounting or bench configuring the unit selecting the proper line voltage fuse and circuit board and connecting the unit to the desired ac power source that matches the fuse and circuit board POWER INPUT CONNECTOR AND VOLTAGE SELECTOR FUSE ASSEMBLY XF1 Assembly XFl is in the lower right hand corner of the rear panel of the Model 1806 This assembly contains a three
14. output across the precision resistance by a known amount so that the measurement can be made on a scale with better resolution This change takes place because the RVG output and the Model 1806 output are in opposition when measuring with the double pole double throw switch in the Measure Vp position refer to Figure 4 4 For example when the RVG switch is in the Measure Vj position the connection poles between the DVM and the Model 1806 are aligned and a direct bridge output reading by the DVM occurs When the double pole double throw switch is in the Measure Vp position the connection is re aligned so that the RVG output voltage opposes the Model 1806 output voltage This allows only the voltage difference caused by the introduction of RF power to the Model 1806 bridge to remain The small reduction of bridge outputs with and without the application of RF power by the opposition of the reference voltage generator enables DVM readings on a smaller scale with a wider resolution This provides readings of greater accuracy Since the output difference between the RVG and Model 1806 with no RF power applied is known Vp it can be subtracted from the difference between the two devices when RF power is applied VD This process leaves the RF generated voltage difference AV which is used to calculate Pg in the following equations 4 6 Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation AV
15. reshipping an instrument or component NOTE e DO NOT return any instrument or component to TEGAM without receiving prior factory authorization RMA Number e Use the best available packing materials to protect the instrument during reshipment When possible use original shipping container and packing materials a Wrap the instrument in sturdy paper or plastic Place the wrapped instrument in a strong shipping container and place a layer of shock absorbing material 3 4 inch minimum thickness around all sides of the unit to provide a firm cushion and to prevent movement inside the container c If shipping the unit for service attach a tag to indicate Model and serial numbers Service required Description of malfunction Return address Authorization to conduct repairs and UPON Thoroughly seal the shipping container and mark it FRAGILE STORAGE Storage of the unit is possible for extended periods without incurring damage to internal circuitry if the instrument is packaged according to the instructions above The safe limits for storage environment are Temperature 67 to 167 F 55 to 75 C Humidity 95 Altitude 40 000 12 192M 2 1 Instruction Manual Section II Dual Type IV Power Meter Model 1806 Installation POWER ENVIRONMENTAL AND MOUNTING REQUIREMENTS TEGAM supplies a detachable three conductor power cord for connecting an ac power source of 48 to 62 Hz at line voltages of 100 120 220
16. shorting link P N 138 495 between the Model 1806 black negative Bolometer Mount Bias Connector TP4 and the Model 1806 white negative SENSE Connector TP2 3 Set the Bridge OPERATING RESISTANCE Switch S2 to 200 ohms the out position and 4 Set the Model 1806 rear panel FLOAT GROUND Switch S3 to the FLOAT position B Turn the Model 1806 POWER Switch S1 to the ON and STANDBY positions and ensure that 1 The ON green and STANDBY yellow Power Indicators DS1 and DS2 respectively illuminate while the switch is in the ON or STANDBY positions 2 The ERROR Indicators DS3 are lit red for both bridges and 3 Depression of the OPERATING RESISTANCE Switch S2 triggers the operational Resistance Indicators DS4 and DS5 to indicate the corresponding bridge impedance 100 or 200 ohms and C Turn the Model 1806 POWER Switch S1 to the OFF position SHORTING LINKS MODEL 1806 Figure 5 1 Power up Operational Test Configuration Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance Bolometer Current Meter Test This test ensures that the BOLOMETER CURRENT Meter M1 indicates the correct dc bias level applied by the Model 1806 to the bolometer mount Perform this test for both bridges Figure 5 2 illustrates the cabling arrangement of the BOLOMETER CURRENT Meter test A 1 Configure the test arrangement according to Figure 5 2 and the following steps Install a shortin
17. signal from a cold thermal bridge that forces the series pass transistor Q3 to pass a current proportional to the imbalance signal This current drives the mount heater to restore thermal bridge balance As the thermal bridge nears the steady state condition Q3 causes DS1 to illuminate If the mount is cold DS1 does not illuminate since the Darlington pair configuration made up by U2 2 and Q4 is not in a conducting state U1 U2 responds to an imbalance signal from an overheated mount by turning off Q3 so that it passes no current to the heater or DS1 Transistor Q2 and Resistor R16 combine to provide circuit protection by limiting current in the event of an output short circuit Throughout this process the TEMPERATURE CONTROL Meter M2 senses the balance state of the thermistor heater element This control meter contains a marked green operating range that indicates the operating point for thermistor mount temperature stabilization MODEL 1806 POWER SUPPLY The power supply assembly transforms the ac power input into six different power sources for the varying operations of the Model 1806 while completely isolating those supplies for bridge circuitry biasing These power supplies consist of 5 volt and 20 volt operational power supplies and four completely isolated 15 volt bridge board biasing power supplies The 5 volt control signal enables front panel controls and is applied only when the Model 1806 is in the ON mode The 20 volt potenti
18. unit Illumination of DS2 indicates that partial power is supplied to the unit and test functions such as changing the bridge operating resistance or monitoring bridge bias are not available 100 Ohm Operational Indicator DS4 Each bridge circuit on the Model 1806 contains indicator DS4 in the center of the bridge control panel shown in Figure 3 1 on Bridge B This green indicator illuminates when the OPERATING RESISTANCE Switch S2 sets the bridge circuitry for 100 Ohm operation 200 Ohm Operational Indicator DS5 Each bridge circuit on the Model 1806 also contains indicator DS5 below DS4 on the front panel shown in Figure 3 1 on Bridge B This green indicator illuminates when the OPERATING RESISTANCE Switch S2 sets the bridge circuitry for 200 Ohm operation 3 3 Instruction Manual Section III Dual Type IV Power Meter Model 1806 Operation Error Indicator DS3 Each bridge on the Model 1806 contains one red DS3 indicator between meters M1 and M2 at the top of the bridge control panel ERROR indicator DS3 illuminates for any condition preventing the Type IV Bridge circuit from balancing MODEL 1806 SWITCHES The Model 1806 uses two front panel switches and one rear panel switch during individual bridge operation Switch S1 located on the front panel selects ON OFF STANDBY power requirements for the entire Model 1806 Each bridge control panel on the Model 1806 employs one switch S2 for selecting the bridge circuit operating resistance
19. used over a 0 1 to 10 mW power range p 0 05 e Without Reference r 0 04 eee Generator c e n 0 03 With Reference Generator 0 02 E T 001 o Total Servo Errors r 0 Power in mW Figure 4 5 Graph of Typical Bridge Errors With and Without Reference Voltage Generator Neil T Larsen A New Self Balancing DC Substitution RF Power Meter IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT VOL IM 25 NO 4 December 1976 page 345 4 7 Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation Table 4 1 Comparison of Voltmeter Errors When Reference Voltage Generator Is and Is Not Used mW ECT EAE Use PI RVG Use Dese ama V Range 1000V Vp Range 1V CALCULATING MODEL 1806 ACCURACIES The specification for the Model 1806 Dual Type IV Bridge is given as Substituted DC Power Accuracy 0 03 2 W The actual Model 1806 bridge is accurate to better than 0 003 up to 25mW This means that the voltages measured across the 200 Ohm resistor in the self balancing bridge give the bias power in the thermistor mount to better than 0 003 Accuracy is lost when the specifications of the voltmeter used to measure this voltage are taken into account For example consider the Fluke Model 8506A digital voltmeter It has a 6 1 2 digit display with quoted specifications after 90 days of 0 001 8 counts in the 10 Volt range Consider the bias of the thermistor beads with no RF power prese
20. 0D pea7 Jojeoipu HOLIMS YHALSWLIOA If WUO 002 H111N07104 ebpua 3SN3S pnoy A8 GNVLS HaMOd SONVASISS f HIE ONTAVI3dO DRUI yo 9 aen 8 xxi AILIN AJADA AI 3dAL Ae GOBI gr 1012a8uu05 OBINOO psa ZN teen esa Zs yams LW 4919 tsa 3univuadWal Joje3ipu 7TOHINOO 10 e91puj AONVLSISSY 1NauHno Joyeaipu NO WYO 001 3univHadWat HOH Ges uaiawodos 10 29uuo pue SIYIJLAS s 0jeorpug SIIIN PULd JUOLH ASIA I1240d AT AAT ENG 9081 I9poIA Le 301A 3 2 Instruction Manual Section III Dual Type IV Power Meter Model 1806 Operation Voltmeter Connectors TP5 and TP6 VOLTMETER Connectors TP5 and TP6 are spade lug connecting posts Placement of these connectors is in the lower right hand corner of either bridge shown in Figure 3 1 on Bridge B TP5 and TP6 complete the dc path between the Model 1806 and a digital voltmeter with a 6 5 digit resolution DC voltage present at TP5 and TP6 is equivalent to the voltage across the thermistor element The red connector is for positive dc power and the black connector is for negative dc power FRONT PANEL METERS The front panel of the Model 1806 has four analog meters two for each bridge They are the TEMPERATURE CONTROL Meter and the BOLOMETER CURRENT Meter The following discussion of Bridge A meters applies equally to Bridge B meters Figure 3 1 shows the location of front panel meters Bolometer Current Meter M1 The Bolometer Current Meter
21. 130 Vac Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance Table 5 2 Power Supply Line Regulation Testing STEP TEST POINTS INITIAL ALLOWABLE VOLTAGE VOLTAGE RANGE READING M J1 pin 12 and pin 11 15V 0 6V 10 of the initial voltage reading 13 5V to 16 5V N J1 pin 7 and pin 8 15V 0 6V 10 of the initial voltage reading 13 5V to 16 5V O J1 pin 9 and pin 8 15V 0 6V 10 of the initial voltage reading 13 5V to 16 5V P J1 pin 4 and pin 5 15V 0 6V 10 of the initial voltage reading 13 5V to 16 5V Q J1 pin 6 and pin 5 15V 0 6V 10 of the initial voltage reading 13 5V to 16 5V R J1 pin 1 and pin 2 15V 0 6V 10 of the initial voltage reading 13 5V to 16 5V S J1 pin 3 and pin 2 15V 0 6V 10 of the initial voltage reading 13 5V to 16 5V BRIDGE BOARD CIRCUITRY TEST AND RECALIBRATION The bridge board circuitry test checks the Model 1806 bridge board for amplifier offset and provides a calibration of bridge board components For the bridge board circuitry test use the same configuration as the power supply test and perform the following for both Bridge A and B A Ensure that the unit has been on for a least five minutes and has attained a state of thermal equilibrium Ensure that it is not exposed to drafts strong light sources or any other causes of ambient temperature change Connect a null detector DVM with micro
22. 8 526 2 sets ea 4 Model 1806 Instruction Manual IM 140 1 ea 5 Shorting Link P N 138 495 4 ea installed on front panel OPTIONAL ACCESSORIES The following items can be purchased separately and are needed to perform calibration service on the 1806 1 Assembly Extender Board P N 138 439 1 ea 2 Printed Circuit Card Pullers P N 139 1141 2 ea Instruction Manual Section I Dual Type IV Power Meter Model 1806 General Information 17 65 448 3mm I TEGAM UNO e WAN a AANANANANANNNNNN BOLOMETER ERROR TEMPERATURE BOLOMETER ERROR TEMPERATURE CURRENT CONTROL CURRENT CONTROL 3 ma 5 100 E j BOLOMETER BOLOMETER OPERATING OPERATING RESISTANCE RESISTANCE Oma Oma POWER Cy o 7 x GN N IN FA N Cc o O gt fo o o o KE 9 LO 9 O K9 E 9 ser A s V y SENSE VOLTMETER SENSE VOLTMETER or o SY i Figure 1 2 Model 1806 Dimensions Top Front 1 3 Instruction Manual Section I Dual Type IV Power Meter Model 1806 General Information 1 4 Instruction Manual Section II Dual Type IV Power Meter Model 1806 Installation SECTION Il INSTALLATION UNPACKING AND INSPECTION TEGAM ships the Model 1806 cushioned between molded in place expanded plastic pads in a double walled carton Upon unpacking the equipment retain the shipping container and packing material until the equipment has been thoroughly inspected an
23. 806 bridge circuit A reference voltage generator RVG increases the accuracy of the DVM measurements when the RF power level is below a few milliwatts Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation HEATER THERMISTOR Pde V2 R MOUNT BIAS Figure 4 1 Functional Block Diagram of Precision Power Measurement System SELF BALANCING BRIDGE CIRCUITS The Model 1806 contains two identical bridge circuits on individual PC boards that perform dc substitution independently from each other Figure 4 2 shows a simplified schematic of one of the two bridge boards circuits depicting its interaction with system components internal and external to the Model 1806 Each self balancing bridge circuit in a closed loop configuration consists of two legs a precision resistance leg 100 ohm or 200 ohm and a leg containing a thermistor element The precision resistance leg maintains a constant effective resistance value of either 100 or 200 ohms depending on the bridge operating resistance selection When the thermistor mount is temperature stabilized by the Model 1806 temperature controller thermistor resistance varies solely due to the application of RF and dc power Each leg uses an operational amplifier U1 or U2 to sense voltage imbalances and to drive transistors Q1 and Q2 to correct them The power supply assembly provides isolated 15 volt biasing to each op amp Since the voltage differential a
24. C Allow the thermistor mount to temperature stabilize for one hour D Record the digital voltmeter reading V and perform the calculation below v 2000 E Ensure that Power P remains approximately equal to 30 mW 7 mW F Ensure that power measurements for Bridge A equal those for Bridge B 6 4 uW TEMPERATURE CONTROL To check the 1806 temperature control circuit monitor the TEMPERATURE CONTROL Meter M2 located in the upper right hand corner of the bridge control panel The meter should always remain in the green shaded area after a one hour warm up period MODEL 1110 DIGITAL VOLTMETER Figure 5 4 Bridge Balance Test Configuration Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance CORRECTIVE MAINTENANCE AND RECALIBRATION Corrective maintenance and recalibration for the Model 1806 involves a series of procedures that show the status of internal operating circuitry and include steps for adjusting or recalibrating specific components These alignment procedures include the calibration of the power supply assembly and four elements of either bridge the bridge circuitry the BOLOMETER CURRENT Meter and bridge precision resistance and bridge amplification To ensure complete recalibration follow all of the calibration procedures in the provided order If recalibration cannot be achieved return the Model 1806 to TEGAM according to the instructions at the end of Section V INITIAL SETUP Before
25. Circuit Amplifier Gain Test 5 9 Factory Mamternance it 5 10 List of Illustrations Model 1806 Dual Type IV Power Meter iii 1 1 Model 1806 Dimensions Top Front View 1 3 Model 1806 Dual Type IV Power Meter Rear Panel Voltage Selector Fuse Assembly 2 3 Model 1806 Operational Voltage Selection Process ss 2 4 Model 1806 Dual Type IV Power Meter Front Panel Meters Indicators Switches and Connectors 3 2 Location of Digital Voltmeter in Typical Test Configuration 3 5 Location of Reference Voltage Generator in Typical Test Configuration 3 6 Functional Block Diagram of Precision Power Measurement System sssseeeesesseeseereresrsrsrerrererrersrsreerere 4 2 Simplified Schematic of Precision Power Measurement System 4 3 Simplified Schematic of Model 1806 Temperature Control Board 4 4 Use of Reference Voltage Generator in Typical Test Configuration 4 6 Graph of Typical Bridge Errors With and Without Reference Voltage Generator 4 7 Power Up Operational Test Configuration ss 5 2 Bolometer Current Meter Test Configuration ss 5 3 Bridge Noise Test Configuration ses 5 4 Bridge Balance Test Confeuratpon conc crono nono e a nennen trennt tente i EE enne nein 5 5 Initial Test and Calibration Configuration ss 5 6 ii LIST OF TABLES Model 1806 Dual Type IV Power Meter Specifications 1 2 Model 1806 Line Voltage Fuse Requirement
26. Dual Type IV Power Meter including preventive maintenance troubleshooting procedures and corrective maintenance and recalibration PREVENTIVE MAINTENANCE While the Model 1806 requires little preventive maintenance it should not be subjected to physical abuse severe mechanical shock high humidity or operating temperatures outside the specification range refer to Table 1 1 The unit should be kept free of excessive dirt and dust as these can interfere with normal heat dissipation and connector functions Care should be taken to prevent physical strain on the interconnecting cables as damage here may not always be apparent To remove dirt or dust use a slightly dampened lint free cloth Avoid use of cleaning solvents Interior dust may be blown out using a low pressure air blower Occasionally check external cables and connectors for signs of cracked insulation and bent or worn pins TROUBLESHOOTING PROCEDURES Where the 1806 in question is a component of a System II Automatic Power Meter Calibration System troubleshooting procedures herein assume completion of system level diagnostics The System II manual contains these diagnostics When the System II manual refers further diagnostics to this manual follow the specification tests and then perform the appropriate calibration procedures Inability to resolve the problems using an accurate voltmeter with these procedures indicates that an uncalibrated thermistor mount or a burned out therm
27. Kj Terminating Mount calibration factor directly traceable to NIST VOLTMETER MODEL 1806 CONNECTORS FRONT PANEL H ACCURACY DCVOLTMETER Figure 3 2 Location of Digital Voltmeter in Typical Test Configuration RF POWER LEVEL MEASUREMENT WITH DVM AND REFERENCE VOLTAGE GENERATOR When the applied RF power level becomes small change of voltage across the bridge also becomes very small In this situation even a high accuracy voltmeter magnifies measurement 3 5 Instruction Manual Section III Dual Type IV Power Meter Model 1806 Operation uncertainties because the large DVM measurement scale has limited resolution Use of a reference voltage generator like the one in Figure 3 3 minimizes voltmeter uncertainties by enabling use of a measurement scale that has better resolution When a reference voltage generator is used with the DVM calculation of the RF power level requires a different process First adjust the reference voltage generator to an output power level approximately equal to the Model 1806 bridge output measured by a DVM when no RF power is applied Ensure stabilization of the RVG output throughout the entire measurement period Next record the DVM reading with no RF power applied to the bridge and the double pole double throw switch in the Measure V position This value is V1 Switch the DVM to a scale with improved resolution for smaller power levels Record the DVM reading with no RF power appl
28. TEGAM Inc Model 1806 Dual Type IV Power Meter BRIDGEA e Cm TEMPERATURE CONTROL e RESISTANCE MODEL 1806 Instruction Manual PN IM140 CD Publication Date June 2004 REV G 1999 TEGAM Inc All rights reserved NOTE This user s manual was as current as possible when this product was manufactured However products are constantly being updated and improved Because of this some differences may occur between the descriptions in this manual and the product received Please refer to www tegam com for future updates of this manual Table of Contents SECTION I GENERAL INFORMATION Scope of Maddalena 1 1 Purpose and Use of Equipment mn ia 1 1 Specifications 25 amoenitate io 1 1 Iteins Supplied a 1 2 SECTION II INSTALLATION Unpacking and InSpection 5er e EE tee abe De able oh cee ates 2 1 Preparation for Reshipment or Storage esse 2 1 Power Environmental and Mounting Requirements enne 2 1 nstall MN A AER 2 2 Power Input Connector and Voltage Selector Fuse Assembly GEI 2 2 AC Power Input Connector nite tpe eor re en ipee 2 2 Voltage Selector Fuse Subassembly ss 2 2 Selection of Proper Fuse Circuit Board for XF1 sese 2 2 SECTION III OPERATION General Operating Considerations ses 3 1 Front Panel Meters Indicators Switches and Connectors ooooocconoccnonocncononcnononnnncnononcnno
29. al Section III Dual Type IV Power Meter Model 1806 Operation RF POWER MEASUREMENT WITH DVM ONLY The Precision Measurement System does not measure the RF power level directly Instead a DVM measures dc voltages before and after the application of RF power to the Model 1806 bridge This necessitates calculation of the RF power level using data obtained from the DVM measurements To calculate the RF power level applied to the thermistor element configure the Model 1806 and the DVM according to Figure 3 2 and measure the voltage across the bridge with the DVM before the application of RF power V Then measure the voltage across the bridge after applying RF power and record that measurement as V5 Determine the RF power level using the following equations First calculate the level of proportional dc substituted power from the operating resistance and DVM readings with the equation a v v2 Pde Ro Where Vi DVM reading across the bridge in the absence of RF power V5 DVM reading across the bridge with RF power applied and Ro Mount operating resistance 100 or 200 ohms Pc dc substituted power which is proportional to the applied RF power Next calculate the applied RF power level using the mount calibration factor and the level of de substituted power Pac PRF 1 Where Pre Level of RF power applied to the terminating thermistor Puc Level of proportional dc substituted power from previous equation and
30. al powers the temperature control circuitry in both STANDBY and ON modes The four isolated 15 volt supplies bias bridge board circuitry in the STANDBY and ON modes of operation POWER SUPPLY ELECTRICAL CONFIGURATION The power supply electrical configuration uses transformers and a network of full wave rectifiers capacitive filters and three terminal voltage regulators to produce the six power sources needed for Model 1806 operation POWER SUPPLY APPLICATION TRANSFORMATION amp ISOLATION To produce the six required voltages the power supply assembly contains two transformers One transformer contains dual secondary windings that supply the voltages for the 5 volt and 20 volt supplies The other transformer has four center tapped secondaries that supply four 15 volt bridge biasing supplies The power supply assembly isolates the four 15 volt circuits by using a transformer with primary to secondary and secondary to secondary isolation The power supply circuitry applies these voltages to a network of full wave rectifiers and capacitive filters in order to smooth out ripple effects A series of three terminal regulators control the 15volt supplies while two individual variable regulators control the 5 volt and 20 volt supplies When in the STANDBY position the front panel Power Switch turns off the 5 volt supply thus disabling front panel switches When in the ON position the front panel Power Switch allows power to all front pane
31. art This warranty also does not apply to fuses batteries or damage from battery leakage This warranty is in lieu of all other warranties expressed or implied including any implied warranty of merchantability or fitness for a particular use TEGAM Inc shall not be liable for any indirect special or consequential damages Statement of Calibration This instrument has been inspected and tested in accordance with specifications published by TEGAM Inc The accuracy and calibration of this instrument are traceable to the National Institute of Standards and Technology through equipment that is calibrated at planned intervals by comparison to certified standards maintained in the Laboratories of TEGAM Inc How to Contact TEGAM TEGAM Inc Ten TEGAM Way Geneva OH 44041 Phone 440 466 6100 Fax 440 466 6110 email sales tegam com
32. ature change Therefore all temperature changes are due to the application of RF and dc power The temperature controller maintains the temperature of one or two external temperature stabilized thermistor mounts above the ambient temperature OUTPUT GROUND Figure 4 3 Simplified Schematic of Model 1806 Temperature Control Board 4 4 Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation TEMPERATURE CONTROL BOARD The temperature control board performs three basic functions the control of current applied to the mount heater indication of the mount temperature by a front panel meter and illumination of a balanced state indicator LED on the temperature control board window indicator Refer to Figure 4 3 for the following discussions concerning the temperature control circuit The temperature control board controls current to the thermistor mount heater element which is a thermal bridge configuration Ul a high gain amplifier with excellent offset drift characteristics senses imbalances across the thermal bridge located in the temperature stabilized feedthrough thermistor mount via inputs 2 and 3 This thermal bridge which is composed of two types of resistance with differing temperature coefficients balances at approximately 60 C U1 U2 interaction provides a varying response to thermal bridge imbalances according to the relationship between the voltage differential inputs U1 U2 amplifies an imbalance
33. bridge balance test checks the Model 1806 bridge circuitry balance at a 30 mW 1 mW operating bias Figure 5 4 shows this test configuration Perform this test for Bridge A and B Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance A Configure the test arrangement according to Figure 5 4 and the following steps 1 Connect the bolometer mount s positive mount bias connector to the Model 1806 red positive BOLOMETER Mount Bias Connector TP3 2 Connect the bolometer mount s negative mount bias connector to the Model 1806 black negative BOLOMETER Mount Bias Connector TP4 3 Connect the bolometer mount s positive mount bias connector to the Model 1806 blue positive SENSE Connector TP1 4 Connect the bolometer mount s negative mount bias connector to the Model 1806 white negative SENSE Connector TP2 5 Remove any shorting links from either bridge between the Model 1806 BOLOMETER Mount Bias Connectors TP3 and TP4 and the Model 1806 SENSE Connectors TP1 and TP2 6 Connect the digital voltmeter s positive and negative terminals to the Model 1806 VOLTMETER Terminals TP5 and TP6 respectively 7 Connect the bolometer mount s temperature control connector to the Model 1806 TEMPERATURE CONTROL Connector J5 via a temperature control cable P N 138 477 and 8 Set the Bridge OPERATING RESISTANCE Switch S2 to 200 ohms the in position B Turn the Model 1806 POWER Switch S1 to the ON position
34. cal physical and environmental specifications for the Model 1806 Figure 1 2 contains an outline drawing and design dimensions 1 1 Instruction Manual Dual Type IV Power Meter Model 1806 Section I General Information Table 1 1 Model 1806 Dual Type IV Power Meter Specifications RF Power Measurement Range 10 uW to 25 mW Substitution Bridge Accuracy 0 003 Power Measurement Accuracy 0 03 2uW when using an HP 3458A Voltmeter Bias Power Temperature Sensitivity 2 uW C hr Ambient Temperature Dynamic 12 C to 32 C Range 54 F to 90 F Mount Warm up Time 2 hrs to achieve 60 C 140 F nominal operating temperature Loop Gain 80 dB minimum Open Loop Frequency Response 0 1 Hz Thermistor Mount Temperature Control Indicator Operating Range Bolometer Mount Bias Current Indicator Resolution Temperature meter with marked operating point 0 1 mA Power Requirements 100 120 220 240 VAC 5 10 25W 48 62 Hz Dimensions 18 35 in 466 1 mm L x 17 05 in 433 1 mm W x 5 80 in 147 3 mm H Constructions Cabinet or standard rack mount Weight Net 16 lbs 7 26 kg Shipping 20 lbs 9 07 kg ITEMS SUPPLIED The following items are supplied with the TEGAM Model 1806 Dual Type IV Power Meter 1 Assembly AC Power Cable P N 068 21 1 ea 2 Assembly Temperature Control Cable P N 138 477 2 ea 3 Assembly Mount Bias Cables P N 13
35. ch S1 to the ON position and allow five minutes for stabilization Adjust potentiometer R32 for a OV 10uV reading on the null detector Turn the Model 1806 POWER Switch S1 to OFF position Use jumpers to connect the bridge board at TP8 to the junction of R30 and R33 Remove Shorting Plug JP4 from the bridge board and set the Bridge OPERATING RESISTANCE Switch to the 200 ohm position the out position Turn the Model 1806 POWER Switch S1 to the ON position and allow five minutes for restabilization Adjust potentiometer R28 for a OV 10uV reading on the null detector Turn the Model 1806 POWER Switch S1 to the OFF position Re insert Q7 and JP4 Remove jumpers from between TP8 and the junction of R30 and R33 and Remove jumpers from between TP1 and the junction of R21 and Q6 pin 1 Bridge Circuit Amplifier Gain Test This test measures bridge circuit amplifier gain that should equal approximately 102 dB Each bridge circuit deploys two amplifiers therefore the test should be performed for both amplifiers on each bridge A and B To measure bridge circuit amplifier gain perform the following Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance A With the Model 1806 POWER Switch S1 in the OFF position connect the bolometer mount s positive and negative mount bias terminals to the Model 1806 BOLOMETER Mount Bias Terminals TP3 and TP4 respectively B Connect the dc voltmeter s positive and
36. ctor PC board Replacement of the fuse and proper selection of the voltage selector PC board change the operational power requirement to ac voltages of either 100 120 220 or 240 volts at 48 to 62 Hz Refer to the following paragraph for the proper fuse PC board selection Selection of Proper Fuse Circuit Board for XF1 TEGAM ships the Model 1806 configured for 120 volt operation Table 2 1 lists fuse requirements for other available operational voltages Figure 2 2 depicts the procedure including outline steps for removal of the line voltage fuse selection of the proper line voltage PC board and replacement of the fuse Instruction Manual Section II Dual Type IV Power Meter Model 1806 Installation Operational Line Voltage Fuse Requirement 100 volts 5 10 at 48 to 62 Hz Y Amp Slo Blo 120 volts 5 10 at 48 to 62 Hz Y Amp Slo Blo 220 volts 5 10 at 48 to 62 Hz 14 Amp Slo Blo 240 volts 5 10 at 48 to 62 Hz Ya Amp Slo Blo 2 3 Section II Installation Dual Type IV Power Meter Model 1806 Instruction Manual K quisss y 2sn q 10329 9 S 938310 A PUB ABIY IIN JAMO AT IAAT PNA 908T PPO T C 910314 TAX A quiassy 9snJ 10329 9S ISBIO A pue 10399Uuu07 duj 19mog EE GZ EST f 4 d 4 ir H 4 ES ms ANAOAD LVOTA 2 4 Section II Instruction Manual Installation Dual Type IV Power Meter Model 1806 Rear Panel Power Input Connector and Voltage Selecto
37. d it is ensured that reshipment is not necessary Perform the following initial inspection a Carefully look at the outside of the shipping container for discoloration stains charring or other signs of exposure to excessive heat moisture or liquid chemicals Check for any physical damage to the shipping container such as dents snags rips crushed sections or areas or similar signs of excessive shock or careless handling b With the equipment and any accessory package removed from the shipping container check each item against the packing list or items supplied list If any items are missing contact the factory or the manufacturer s local representative c Carefully inspect the equipment looking for dents deep scratches damaged or loose pushbuttons or knobs or any other signs of physical abuse or careless handling If damage is found forward an immediate request to the delivering carrier to perform an inspection and prepare a concealed damage report Do NOT destroy any packing material until it has been examined by an agent of the carrier Concurrently report the nature and extent of damage to TEGAM giving equipment model and serial numbers so that necessary action can be taken Under U S Shipping regulations damage claims must be collected by the consignee do NOT return the equipment to TEGAM until a claim for damages has been established PREPARATION FOR RESHIPMENT OR STORAGE RESHIPMENT Perform the following procedures when
38. figuration 3 6 Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation SECTION IV PRINCIPLES OF OPERATION INTRODUCTION This section contains information that describes the basic circuitry and functions of the Model 1806 Dual Type IV Power Meter the major component in a precision power measurement system that measures high frequency or microwave power in the 01 to 18 GHz range The key role of the Model 1806 within this system is the realization of the principle of dc substitution It also provides temperature stabilization of up to two mounts each associated with one of the two bridges The Model 1806 contains a power supply assembly and five printed circuit PC boards The five PC boards are the temperature control board two bridge boards a front panel board and a motherboard The functions of each of these boards are detailed in this section PRINCIPLE OF DC SUBSTITUTION The Model 1806 uses the principle of dc substitution to provide a measure of RF power DC substitution refers to the measurement of RF power according to the amount of dc power that must be substituted for the RF power in a bolometer in order to cause equivalent thermal effects This principle extends to the determination of terminating thermistor mount calibration factors ratio of substituted dc power to the power incident on the thermistor mount by the following formulas Pdc PRE gt Ki Pdc Ki gt PRF Where
39. g link P N 138 495 between the Model 1806 red positive BOLOMETER Mount Bias Connector TP3 and the Model 1806 blue positive SENSE Connector TP1 Install a shorting link P N 138 495 between the Model 1806 black negative BOLOMETER Mount Bias Connector TP4 and the Model 1806 white negative SENSE Connector TP2 Connect the anode of the 1N914 diode to the Model 1806 red positive BOLOMETER Mount Bias Terminal TP3 Connect the cathode of the 1N914 diode to the 100 ohm adjustable resistor Connect the 100 ohm resistor s other terminal to the negative terminal of the dc milliammeter Connect the dc milliammeter s positive terminal to the Model 1806 black negative BOLOMETER Mount Bias Connector TP4 Set the Model 1806 OPERATING RESISTANCE Switch S2 to 100 ohms the in position and Turn the Model 1806 POWER Switch S1 to the ON position Adjust the external adjustable resistor to obtain 30 mA of current as indicated on the BOLOMETER CURRENT Meter M1 Ensure that the de milliammeter reading is 30 mA 1 mA and Ensure that the front panel ERROR Indicator DS3 remains dark throughout the entire test except for momentary flashes when changing the bridge operating resistance settings MODEL 1806 Dc 1N914 DIODE legen MILLIAMMETER ADJUSTABLE RESISTOR Figure 5 2 Bolometer Current Meter Test Configuration 5 3 Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance Bridge Noise Test T
40. he bridge noise test employs an oscilloscope to measure bridge noise The bridge noise test ensures that the Model 1806 bridge does not source noise that would disrupt measurements or bridge balance capability Perform this test for both Bridge A and Bridge B A Configure the test arrangement according to Figure 5 3 and the following steps 1 Install a shorting link P N 138 495 between the Model 1806 red positive BOLOMETER Mount Bias Connector TP3 and the Model 1806 blue positive SENSE Connector TP1 2 Install a shorting link P N 138 495 between the Model 1806 black negative BOLOMETER Mount Bias Connector TP4 and the Model 1806 white negative SENSE Connector TP2 3 Connect the anode of the 1N914 diode to the Model 1806 red positive BOLOMETER Mount Bias Connector TP3 4 Connect the cathode of the 1N914 diode to the to the Model 1806 black negative BOLOMETER Mount Bias Connector TP4 5 Connect the oscilloscope s positive and negative terminals to the Model 1806 VOLTMETER Terminals TP5 and TP6 respectively 6 Set the Model 1806 OPERATING RESISTANCE Switch S2 to 100 ohms the in position and B Turn the Model 1806 POWER Switch S1 to the ON position and C Ensure that the oscilloscope indicates approximately 1 mV peak to peak amplitude with no short term bursts or large peak transients 1N914 DIODE GENERAL PURPOSE OSCILLOSCOPE Figure 5 3 Bridge Noise Test Configuration Bridge Balance Test The
41. ied and the double pole double throw switch in the Measure Vp position This reading is the difference between the Model 1806 bridge output and the setting of the reference voltage source Vp Finally apply RF power to the bridge and record the voltmeter reading with the double pole double throw switch in the Measure Vp position This value is the difference between the Model 1806 output and RVG output including the proportional RF power effect on the bridge circuit Vp Use these values and the following method to calculate the applied level of RF power First determine the level of dc substituted power using the measurements taken above with the equation Qv Vp Vpj x Vp S Vpj Pac Ro Where Vi Model 1806 bridge output measured by DVM with no RF power applied V D Difference between 1806 bridge output with no RF applied and RVG output Vp Difference between 1806 bridge output with RF applied and RVG output Ro Mount operating resistance and Pac Proportional amount of dc substituted power Next apply the mount calibration factor to find the level of RF power using the second equation in the RF POWER MEASUREMENT WITH DVM ONLY section above VOLTMETER CONNECTORS MODEL 1806 FRONT PANEL DOUBLE POLE DOUBLE THROW SWITCH REFERENCE VOLTAGE GENERATOR HIGH ACCURACY DC VOLTMETER Figure 3 3 Location of Reference Voltage Generator in Typical Test Con
42. istor element may be the source of problems For further information on these situations refer to the repair manual for TEGAM Models F1109 and M1110 Temperature Stabilized Coaxial Thermistor Mounts This section provides a series of operational checks that ensure that the unit is working properly When out of specification conditions are found note the problem area and continue the audit procedures When all the audit procedures are completed perform all of the corrective maintenance and recalibration procedures indicated in Corrective Maintenance and Recalibration later in this section Testing and recalibrating the Model 1806 requires the use of several items not supplied with the unit Table 5 1 lists this equipment SPECIFICATION TESTS This section provides a series of operational tests that check the Model 1806 for possible out of specification conditions These operational tests are 1 a power up operational test 2 a bolometer current meter test 3 a bridge noise test and 4 a bridge balance test This process draws attention to specific circuits as probable sources of unit malfunctions When an out of specification condition is revealed refer to the calibration procedures to correct the problem Table 5 1 Required Test and Calibration Equipment EQUIPMENT EQUIPMENT SPECIFICATIONS Voltmeter DC Null Detector Range 30V Sensitivity of Smallest Scale 10 V Input Impedance 100 KQ or greater resistive Acc
43. l switches Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation MOTHERBOARD The motherboard within the Model 1806 routes power between the power supply assembly and temperature control board the bridge board and the front panel board The motherboard contains only simple conductor paths FRONT PANEL PC BOARD The front panel PC board extends the circuitry of the temperature control board the power supply assembly the bridge boards and the mother board to front panel meters indicators and switches The front panel PC board contains several electrical components MEASUREMENTS USING A REFERENCE VOLTAGE SOURCE When the applied RF power level becomes small the change in voltage across the precision resistance also becomes very small In this situation even a high accuracy digital voltmeter magnifies measurement uncertainties because the measured voltages differ only slightly and the DVM has a limited resolution Use of a reference voltage source like the one in Figure 4 4 minimizes voltmeter uncertainties by employing a measurement scale with improved resolution VOLTMETER CONNECTORS MODEL 1806 FRONT PANEL DOUBLE POLE DOUBLE THROW SWITCH REFERENCE VOLTAGE GENERATOR HIGH ACCURACY DC VOLTMETER ooh ee 1 YD Figure 4 4 Use of Reference Voltage Generator in Typical Test Configuration The RVG increases measurement accuracy by reducing the voltage
44. lers Each Type IV Bridge circuit operates at a dc resistance of either 100 or 200 ohms which is front panel selectable A complete power measurement system includes an accurate DVM and some means of offsetting the DVM to measure small voltage changes more accurately This offsetting voltage source or reference voltage generator RVG becomes increasingly important when measuring power levels below a few milliwatts The Model 1806 is designed for use with a temperature stabilized thermistor mount 100 or 200 ohms and a DVM with a 6 5 digit or higher resolution The Model 1806 contains two self balancing Type IV Bridge circuits that pass current through a bolometer mount while sensing the voltage across the mount which defines the resistance of the bolometer at its dc terminals This process eliminates lead errors associated with Wheatstone Bridges Therefore the Model 1806 suits applications such as power measurement and insertion loss measurement applications requiring high accuracy and computer control The role of the Model 1806 within the TEGAM System IIA Automatic Power Meter Calibration System is to measure precisely RF and microwave power applied to terminating standards in order to transfer the calibration factor of one standard to another The System IIA is an IEEE Bus compatible system designed to calibrate feedthrough and terminating power sensors in the 01 to 18 0 GHz frequency range SPECIFICATIONS Table 1 1 contains the electri
45. nnnnonoonnonconnnnnnronnnnnoos 3 1 Front Panel Connectors meierier ete pe eem eire epi etre tenet ee ree ee eoa 3 1 BOLOMETER Mount Bias Connectors TP3 and TP4 3 1 Mount SENSE Lead Connectors TP1 and TR 3 1 TEMPERATURE CONTROL Connector J5 esee enne 3 1 VOLTMETER Connectors TPS and 3 3 Front Panel EC 3 3 BOLOMETER Current Meter MI 3 3 TEMPERATURE CONTROL Meter MI 3 3 Front Panel IndiCators z oso tete eoe terret e re ee EO n non 3 3 ON Indicator DST EE 3 3 STANDBY Indicator DS Dinastia dade pO D t PR EET 3 3 100 Ohm Operational Indicator DS 3 3 200 Ohm Operational Indicator DS5 ss 3 3 ERROR Indicator DS3J eersten ster idle tubes egest hae mes 3 4 Model 1806 Switth s uei a eg erste diel itd hide 3 4 Power With Sly iaa Renee e RU erdt ae ad aieo teat i abe ie 3 4 100 200 Ohm OPERATING RESISTANCE Switch S2 eee 3 4 FLOAT GROUND Switch S3 iii enne eren 3 4 RF Power Level Measurement retten tenerte epe Herne deat ete codi ico inner Yee eerte thv ee Eege 3 4 RF Power Measurement With DVM Only nemen nennen nenne 3 5 RF Power Measurement With DVM and Reference Voltage Generator 3 5 SECTION IV PRINCIPLES OF OPERATION Introduction narnia cita e ero Bo eid AIR a ire Be a RR GR eden Gave RE te 4 1 Principle of DC Substitutlon 4 adt nne eb ees 4 1 Precision Power Measurement System ss 4 1 Self Balancing Bridge Circuits aiii aces eich Aiea ee ee ate
46. nt Vorr 0 030 200 Where Vorr is the voltage across the 200 Ohm resistor VorF 2 44949 V 4 8 Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation If the incident RF causes the bias to drop by 1 mW i e the dc Substitution power is 1 mW then V12 2 40832V The 0 001 figure in the voltmeter accuracy and the 0 003 for the 1806 are linear and always in the same direction The ability to correctly measure the 1 mW is thus directly affected by both The 8 counts part of the accuracy can be of any sign or value within these limits and is a function of the nonlinearity of the voltmeter Thus in the worst case the Vorr could be read as 2 44957 V i e 2 44949 0 00008 and V as 2 40824 V i e 2 40832 0 00008 The former gives an initial bias power of 30 002 mW and the latter a bias power after RF substitution of 28 998 mW The measurement answer would thus be 1 004 mW i e a 0 496 error A similar calculation for a 10 mW substituted power gives 0 04 from this alone This error is far greater than either the voltmeter reference accuracy or the 1806 bridge accuracy Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation 4 10 Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance SECTION V MAINTENANCE INTRODUCTION This section contains maintenance and troubleshooting information for the TEGAM Model 1806
47. proceeding with corrective maintenance and recalibration ensure that the initial setup outlined below and shown in Figure 5 5 is complete Each test and calibration procedure contains instructions for re arranging this basic setup After testing begins the red front panel ERROR Indicator DS3 should remain dark throughout the entire procedure except for momentary flashes when changing the bridge operating resistance setting If DS3 remains lit this indicates a malfunction that should be corrected before proceeding with the adjustment and recalibration An optional extender board is available for purchase TEGAM P N 138 439 to ease the following test and calibration procedures Use the extender board by removing the board to be tested from its motherboard connection inserting the extender board in this motherboard connection and inserting the replaced board into the extender board slots This facilitates access to the circuit boards for testing while maintaining the proper motherboard to circuit board connections To Power Input Connector and Voltage Selector Fuse Assembly XF1 VARIAC MODEL 1110 MODEL 1806 1N914 DIODE Figure 5 5 Initial Test and Calibration Configuration Arrange the initial test configuration as follows 5 6 Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance A Install a shorting link P N 138 495 between the Model 1806 red positive BOLOMETER Mount Bias Connector TP3
48. prong ac power input connector and a voltage selector circuit board fuse assembly The design of XF1 prevents use of the voltage selector fuse assembly while an ac power cord is connected to the ac power input connector Disconnect the power cord and slide the protective plastic window to the left to change the line fuse and printed circuit PC board This arrangement eliminates the possibility of electric shock to operating personnel Power source voltages of sufficient current to constitute a HAZARD to operating personnel exist at the voltage selection PC board and line fuse Ensure that the power cord is DISCONNECTED prior to changing line voltage selection or line fuse AC Power Input Connector This connector located on the left side of XF1 is a plug type prong insert connector with three conductors for connection of the 100 120 200 240 volt ac power cord P N 068 21 to the power supply assembly within the Model 1806 Arrangement of the conductors and keying of the insertion area prevent an incorrect connection This connector also passes the ground current of the Model 1806 when the ac power cord is plugged into a grounded wall outlet When the wall outlet contains two insertion slots use a three prong to two prong adaptor Voltage Selector Fuse Subassembly The voltage selector fuse subassembly on the right side of XF1 reconfigures the Model 1806 for different operational voltages This subassembly contains a line fuse and a voltage sele
49. r Fuse Assembly XF1 VOLTAGE SELECTION PROCESS PROCESS Pull to the back and left on the fuse pull lever to eject the fuse Remove the voltage selector circuit board from the module by pulling it out carefully Position the voltage selector circuit board so that the desired voltage appears readable right side up on the left hand side of the wafer as it faces you The X on the board in the diagram depicts this location Slide the board back into the module as shown in the diagram with the desired voltage still appearing as set in step 3 Replace the fuse with the proper fuse according to Table 2 1 Re insert the new fuse by placing it in the fuse brackets Figure 2 2 Model 1806 Operational Voltage Selection Process 2 5 Instruction Manual Section III Dual Type IV Power Meter Model 1806 Operation SECTION Ill OPERATION GENERAL OPERATING CONSIDERATIONS Operation of the Model 1806 consists of 1 cabling the unit to the device for testing 2 selecting the proper voltage fuse and circuit board 3 grounding or ungrounding the Model 1806 4 selecting the proper operating resistance 5 monitoring several indicators and meters located on the front panel of the unit 6 using a digital voltmeter DVM or a DVM and a reference voltage generator RVG to measure substituted dc bias and 7 calculating the amount of RF power The Model 1806 contains two identical Type IV Bridge circuits Bridge A and Bridge B with individual
50. sets of controls and indicators Two black outlined squares on the front panel separate each set of controls and indicators for each bridge Figure 3 1 depicts these bridge control panels Since both bridge circuits perform identical functions Section III discusses operation of Bridge A only Operation of Bridge B is exactly the same as Bridge A operation Operation of these bridges may occur individually or simultaneously Figure 3 1 also shows the front panel location of meters indicators switches and connectors that control the operations of the Model 1806 Refer to this figure throughout the discussion in Section III The TEGAM System II Automatic Power Meter Calibration System manual contains information about typical power meter calibration procedures FRONT PANEL METERS INDICATORS SWITCHES amp CONNECTORS The Model 1806 contains a Power Switch that controls power for the entire unit Two indicators located next to the switch show the Model 1806 power status As shown in Figure 3 1 each bridge control panel contains two meters three dual binding post connectors one temperature control connector three light emitting diode LED indicators and an operating resistance switch FRONT PANEL CONNECTORS The front panel of the Model 1806 contains fourteen connectors seven connectors for each bridge The following paragraphs discuss connectors contained in Bridge A only Bridge B connectors have functions identical to those in Bridge A Refer
51. t panel STANDBY Indicator DS2 lights Connect the de voltmeter s negative and positive terminals to the power supply board at TP2 and TP3 respectively Ensure that the dc voltmeter reads 20V 1 V and note this value Vary the Variac controls slowly from 105 Vac to 130 Vac and verify that the voltage reading at the dc voltmeter is within 10 of the value noted in step C 18V to 22V Turn the Model 1806 Power Switch S1 to the ON position Connect the dc voltmeter s positive and negative terminals to the power supply board at TP1 and TP2 respectively Ensure that the dc voltmeter reads 5V 0 25V and note this value Vary the Variac controls slowly from 105 Vac to 130 Vac and verify that the voltage reading at the dc voltmeter is within 10 of the value noted in step G 4 5V to 5 5V Connect the dc voltmeter s positive and negative terminals to the power supply board at connector J1 pin 10 and pin 11 respectively Ensure that the dc voltmeter reads 15V 0 6V and note this value Vary the Variac controls slowly from 105 Vac to 130 Vac and verify that the voltage reading at the dc voltmeter is within 10 of the value noted in step J 13 5V to 16 5V Repeat the general procedures outlined in steps I J and K according to Table 5 2 by making the indicated test point connections ensuring the appropriate initial voltage readings and ensuring the allowable voltage ranges upon varying the Variac controls from 105 Vac to
52. t the input stage of op amp U2 is negligibly small it provides a virtual common reference to op amp U1 Oe it acts as a virtual common ground since the voltage approaches zero with respect to either ground This forces the current through the thermistor to equal the current through the precision resistance leg The application of RF power to the thermistor element creates a decrease in the voltage drop across the thermistor element due to its negative temperature coefficient This decreased voltage drop in turn creates an unbalanced bridge condition When resistance in the thermistor element leg of the bridge changes due to the application of RF power op amp Ul senses a voltage difference between V and V and causes V to equal V4 When V equals V the voltage across the thermistor element leg equals the voltage across the precision resistance leg Also the closed loop circuit configuration maintains equal current throughout the bridge Since the voltage and current throughout the circuit is equal the resistance in both halves is also equal Therefore when the thermistor mount s temperature is stabilized and RF power is applied a change in voltage across the precision resistance leg is proportional to the amount of RF power applied to the themistor mount 4 2 Instruction Manual Section IV Dual Type IV Power Meter Model 1806 Principles of Operation EEE 433 BUS DNS Ny S S CONTROLLER S SESS
53. ternal 100 ohm adjustable resistor to obtain a 30 mA reading on the dc milliammeter and H Adjust potentiometer R41 to obtain a full scale deflection of the BOLOMETER CURRENT Meter M1 Calibration of Internal Resistance The Model 1806 internal resistance calibration procedure involves the alignment of several key resistors within the unit When performing this procedure ensure that the power is off while making connections Note that the amplifier offset adjustment must be accurately performed before the following calibrations can be made Perform this procedure for both Bridge A and B To complete the calibration procedure follow the steps below A B T A ron oO EE E Remove Q7 from the bridge board and on the same board use jumpers to connect TP1 to the junction of R21 and Q6 pin 1 refer to the component location drawing Set the Model 1806 OPERATING RESISTANCE Switch S2 to the 100 ohm position the in position Remove the shorting links from between the Model 1806 BOLOMETER Mount Bias Connectors TP3 and TP4 and the Model 1806 SENSE Terminals TP1 and TP2 from Bridge A B or both Connect the four terminal 100 ohm resistance standard between the Model 1806 BOLOMETER Mount Bias Connectors TP3 and TP4 and the Model 1806 SENSE Terminals TP1 and TP2 respectively Connect a DVM with microvolt sensitivity between the bridge board at TP2 and TPS to act as a null detector Turn the Model 1806 POWER Swit
54. to Figure 3 1 for locations of all connectors Bolometer Mount Bias Connectors TP3 and TP4 Bolometer Mount Bias Connectors TP3 and TP4 are spade lug connecting posts that pass de current applied by the Model 1806 to and from a thermistor mount typically Model 1110 The location of TP3 and TP4 is in the lower left hand corner of Bridge A above the Mount SENSE Lead Connectors The red connector is for positive dc bias current and the black connector is for de bias current return Mount SENSE Lead Connectors TP1 and TP2 Mount SENSE Lead Connectors TP1 and TP2 are spade lug type connecting posts located in the lower left hand corner of Bridge A Voltage present at TP1 and TP2 is proportional to the effective de current passing through the thermistor element Use of the voltage potential present at TP1 and TP2 reduces errors associated with lead resistance Temperature Control Connector J5 The location of TEMPERATURE CONTROL Connector J5 is in the center right of Bridge A This connector is a four pin threaded connector that links a temperature controller within the Model 1806 to a heater which stabilizes the internal temperature of the thermistor mount The TEMPERATURE CONTROL Meter M2 indicates current present at this connector 3 1 Section III Instruction Manual Operation Dual Type IV Power Meter Model 1806 bdl pue ed 941 pue Gd ssa 10 98UU09 sjoued zdL pue tdi zsa LS siooauu09 10789 pul seg Juno 1oHU09 10 98UU
55. uracy 2 of full scale General purpose oscilloscope Bandwidth 10 MHz 5 1 Instruction Manual Dual Type IV Power Meter Model 1806 Section V Maintenance Four terminal 100 ohm resistance standard 0 01 or better DC milliammeter Range Sensitivity Accuracy Temperature stabilized thermistor mount Resistance Bias Requirement 30 mA mA 2 200 ohms 30 mW Decade resistance box or multi turn potentiometer Adjustment Range 0 to 100 ohms Resolution 0 1 1N914 silicon diode or its equivalent Variac Line Voltage Requirement 117 Vac Adjustment Range 105 to 130 Vac PC Extender Board Tegam P N 138 439 PC Board Puller Tegam P N 139 1141 Power Up operational Test The power up operational test ensures that the Model 1806 power supply circuitry bridge meters and indicators are working properly Figure 5 1 shows the power up test configuration and cabling procedure The Model 1806 Dual Type IV Power Meter has two bridges Bridge A and Bridge B that have identical circuitry The following procedure should be repeated for both bridges To test the Model 1806 power supply perform the following A Cable the test configuration according to Figure 5 1 and the following steps 1 Install a shorting link P N 138 495 between the Model 1806 red positive Bolometer Mount Bias Connector TP3 and the Model 1806 blue positive SENSE Connector TP1 2 Install a
56. volt sensitivity which is preferably isolated from ground or battery operated to the bridge board at TP2 and TPS NOTE Ensure that this measurement is not made between TP3 and TP5 Current flow at TP3 will introduce error in this adjustment Adjust potentiometer R23 for a 0V 10uV reading on the null detector and Connect the same null detector to the bridge board at TP7 and TP9 and adjust potentiometer R24 for a null condition indicated by a OV 10uV reading on the null detector Bolometer Current Meter Calibration The BOLOMETER CURRENT Meter calibration procedure ensures that the BOLOMETER CURRENT Meter M1 indicates the actual amount of dc bias current applied to the bolometer mount Perform this procedure for both bridges To perform the calibration procedure follow the steps below A B e Connect the anode of the 1N914 diode to the Model 1806 red positive BOLOMETER Mount Bias Terminal TP3 Connect the cathode of the 1N914 diode to the 100 ohm adjustable resistor Connect the 100 ohm adjustable resistor to the dc milliammeter s negative terminal Connect the dc milliammeter s positive terminal to the Model 1806 black negative BOLOMETER Mount Bias Connector TP4 5 8 Instruction Manual Section V Dual Type IV Power Meter Model 1806 Maintenance E Set the Model 1806 Bridge OPERATING RESISTANCE Switch S2 to 100 ohms the in position F Turn the Model 1806 POWER Switch S1 to the ON position Adjust the ex
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