MODEL 1491 Precision Decade Indicutor User and Service Manual
Contents
1. Before returning an instrument to QuadTech for service please call our Service Department at 800 528 8885 for return material authorization It will be necessary to include a Purchase Order Number to insure expedient processing although units found to be in warranty will be repaired at no charge For any questions on repair costs or shipment instructions please contact our Service Department at the above number Return material should be sent freight prepaid to QuadTech Inc Attn Service Dept 100 Nickerson Road Marlborough MA 01752 3 3 MINIMUM PERFORMANCE STANDARDS Total inductance values throughout the range of the 1491 can be checked for accuracy using any pre cision inductance or impedance bridge The GR 1608 Impedance Bridge or the GR 1632 Inductance Bridge or equivalent are recommended for this purpose 3 4 SERVICE AND MAINTENANCE NOTES 3 4 1 GENERAL The 1491 Decade Inductor will need little ser vice over the years Should one of the decades become faulty it is recommended that the complete decade assembly be replaced This can be done by competent user personnel or the instrument can be returned to General Radio for service Use the parts lists as a guide in determining which parts may be replaced 3 4 2 1491 DISASSEMBLY Access to the interior of the 1491 is obtained by the following procedure a Carefully place the instrument on a flat sur face with the back of the cabinet facing upward If the ins2. CHANGES WITH CURRENT Percentage changes in inductance with ac cur rent are shown in the NORMAL curves see Figure 2 6 in terms of the ratio of the operating current lac to the current Ij given in Table 2 4 Note that Table 2 4 RMS mA Switch Setting 0 25 Increase for the dashed lines that represent the changes in the 940 DD decade 1 is the current that gives a 0 1 change and for the other 940 decades I gives a 0 25 change Values of I1 Table 2 4 are approximate and based on the largest inductor in the circuit for each setting Percentage changes in inductance due to dc bias current are shown in the INCREMENTAL curves see Figure 2 6 in terms of the ratio of the dc current Ige to the current I given in Table 2 4 The ac current must be less than I for these curves to be valid 2 5 3 STORAGE FACTOR Q The 1491 inductors have maximum values of low frequency storage factor Q of 200 and above See Figure 2 7 for variations of Q with frequency for the individual 940 units 1000 aA 2 5 2 5 10 20 50 FREQUENCY KILOHERTZ Figure 2 7 Variation of Q for the maximum inductance of each 940 Decade Inductor Unit at low excitation levels Dashed curves correspond to use with chassis floating CAUTION The maximum voltage is 500 volts rms The switches will break the cir cuit at this voltage if turned rapidly but voltages above 500 volts can cause destructive arcing when the switc
3. it in place with the four 9 16 inch screws N Tighten these screws by inserting a screwdriver through the holes in the handles To reconvert the instrument for bench use proceed as follows a Remove the entire assembly from the relay rack Remove the instrument from the cabinet b Remove the blank panel E the support bracket H and both Rack Adaptor Assemblies Q from the cabinet c Reinstall the instrument in the cabinet e 1491 D F G To install one of these decade in ductors in a standard 19 inch relay rack use the Rack Adaptor Set parts listed in Table 2 2 refer to Figure 2 2 and proceed as follows a Remove the cabinet refer to paragraph 3 4 2 b Pierce and push out the plugs from the four bosses C on the inner sides of the cabinet near the front Be careful not to damage the threads c Attach one Rack Adaptor Assembly Q to the left side of the cabinet using two5 16 inch screws L as shown in Figure 2 2 Note that the screws enter the holes in opposite directions d Attach the other Rack Adaptor Assembly Q to the right side of the cabinet as described in step c Table 2 3 NOTE Parts E H and D as shownin Figure 2 2 are not used with 1491 D F and G Rack Adaptor Assembly Q is attached directly to the side of the cabinet e Install the instrument in the cabinet refer to paragraph 3 4 2 f Slide the assembly into the relay rack and lock it in place with the fo
4. terminals The banana plug patch cords listed in Table 2 3 are GR catalog items that are readily available for use with the 1491 and associated instruments equipped with 3 4 inch spaced binding posts 2 3 1 FRONT PANEL CONNECTIONS Standard 3 4 inch spaced binding posts are available on the front panel for general use The high H and low L binding posts are insulated from the panel and used for regular two terminal applications For grounded operation connect the ground link be tween the ground G terminal and the low L terminal 2 3 2 REAR CONNECTIONS A terminal board with high H and low L ter minals is provided onthe rear panel of the instrument If grounded operation is desired connect the ground link between the ground G terminal and the low L terminal on the front panel 2 4 READOUT All 1491 decades haveclear easy to read dials with numbered steps from 0 to X X 10 When set tion the decade switches observe the decimal refer ence point on the panel and remember that X equals ten units For example using a 1491 G to obtain a value of 1 492 H set the decade switches as follows 1 4920 1 492H or 1 491X 1 492 H see Figure 1 1 Note in the above example that X is equal toa value of ten 0 0001 H units in that decade or one 0 001 H unit in the next decade to the left The following example illustrates the result of setting all decades in the 1491 G to X Dial Settings X XXXX Le
5. 40 G 0 1 H steps 940 H 1H steps 940 E 0 001 H steps 940 G 0 1 H steps 940 F 0 01 H steps 940 G 0 1 H steps 940 F 0 01 H steps 940 G 0 1 H steps 1491 A 1491 B 1491 C 1491 D 1491 F 1491 G L903 940 DD 100 HH steps 940 F 0 01 H steps 940 E 0 001 H steps 940 F 0 01 H steps 940 E 0 001 H steps 940 F 0 01 H steps 940 E 0 001 H steps 940 DD 100 HH steps 940 E 0 001 H steps 940 DD 100 HH steps Ref No J901 O H J901 J902 J903 L901 thru L905 PARTS LIST Description JACK Binding post assembly JACK Binding post assembly JACK Binding post assembly INDUCTOR ASSEMBLY 940 DD 100 HH steps INDUCTOR ASSEMBLY 940 E 0 001 H steps INDUCTOR ASSEMBLY 940 F 0 01 H steps INDUCTOR ASSEMBLY 940 G 0 1 H steps INDUCTOR ASSEMBLY 940 H 1 H steps Mechanical Replacement Parts DIAL Marked 0 to X KNOB Bar WIRE LINK Connector ground strap FOOT SCREWS Cabinet No 10 32 3 8 O RING Cabinet assembly 5 32 Part No 0938 3000 0938 3000 0938 3022 0940 3390 0940 3350 0940 3360 0940 3370 0940 3380 5120 2122 5500 5420 5080 4800 5260 2060 7098 0200 5855 0156 Direct replacement units for 1491 refer to 940 specifications for individual units complete with dials and knobs Refer to Table 3 1 for list of 940 induc tors used with specific 1491 models 902 O L J90 L9OI tH STEPS 3 L904 l mH STEPS
6. 490 A 15 pounds Tyre 1490 B 19 pounds Other specifications are identical with those for the Type 940 Decade Inductor Units Type Inductance 1490 A 1 h total in steps of 0 001 h 1490 B 10 h total in steps of 0 001 h
7. C Bench Rack 12 x 8 4 x 61 2 in 19 x 8 4 x 47 in 325 x 225 x 170 mm 485 x 225 x 125mm 1491 D F G Bench Rack 435 x 225 x 170 mm 485 x 225 x 125 mm 17 x BY x 614 in 19 x 8 x 4 in Weight bench models add 1 Ib 0 8 kg for rack models Shipping est 1491 A B C 18 Ib 8 5 kg 25 Ib 11 7 kg 1491 D F 23 Ib 10 5 kg 30 Ib 13 7 kg 1491 G 26 2 Ib 12 5 kg 34 Ib 15 5 kg Inductance 940 s Total Steps Included 0 0001 H OD E F 0 0001 H DD E F G 0 001 H E F G 0 0001 H DD E F G H 0 001 H E F G 0 01 H F G H Max Safe Current Approx 200 times the pertinent I value 30 times for the 940 DD Max current engraved on dial Inductance Description Decade Inductor 9 40 DD 100 nH 940 E 0 001 H 940 F 0 01 H 940 G 0 1 H 940 H 1H Refer to parts list for 940 replacement units for 1491 Decade Inductors INTRODUCTION 1 1 PURPOSE The 1491 Decade Inductor is an assembly of several 940 Decade Inductor units in a single metal cabinet These inductance decades are convenient elements for use in wave filters equalizers and tuned circuits throughout the range of audio and low radio frequencies As components in oscillators analyzers and similar equipment they are especially useful during the preliminary design period when the ability to vary circuit elements over relatively wide ranges is necess
8. Figure 3 1 Wiring diagram for 1491 G Decade Inductor Wiring for all other 1491 models is the same except for the number of decades used 1491 2X TYPE 940 DECADE INDUCTOR UNIT USES The Tyre 940 Decade Inductor Units are convenient elements for use in wave filters and tuned circuits throughout the audio and low radio frequency range As components in oscillators analyzers and similar equipment they are especially useful during the preliminary design period when the ability to vary circuit elements over rela tively wide ranges is necessary to determine optimum operating values As moderately precise standards of inductance they have storage factor Q values which are much larger than can be obtained with air cored coils DESCRIPTION Each unit is an assembly of four toroids wound on molybdenum perm alloy dust cores All four coils relative values 1 2 2 5 are connected in series and the switch a modified Typr 920 short circuits combinations of the coils to give the eleven successive values from 0 to 10 The switch blades are phosphor bronze with silver over lay to decrease both contact and volume resistance FEATURES gt High values of storage factor Q are obtained in all models with maximum values over 200 gt Toroidal construction practically eliminates any external magnetic field and makes it possible to stack the coils closely without trouble from mutual inductances The toroids are nearly astatic to ext
9. I amp 940 A 1 mh 15 1 T2 940 A 2 mh 10 7 5 2 940 A 5mh 6 8 3 0 940 B 10 mh 4 8 2 3 940 B 20 mh 3 4 1 7 940 B 50 mh 2 1 1 0 940 C 100 mh 1 61 0 72 940 C 200 mh 1 07 0 52 940 C 500 mh 0 68 0 30 940 D lh 0 48 0 23 940 D 2h 0 34 0 17 940 D 5h 0 21 0 10 Currents of about 6 J will produce 0 5 increase in inductance 25 J gives 1 increase about 45 J gives a maximum increase of 2 while still larger currents produce a drop in inductance the error being zero at about 100 J The I values may reduce L to about 70 of its initial value Dissipation Factor The accompanying plot shows the variation of the dissipation factor D 1 Q with fre quency for the full value of each inductor see page 43 It will be seen that maximum storage factor Q val ues between 200 and 330 are obtained at frequencies between 2 and 5 ke Temperature Coefficient The temperature coefficient of inductance is about 50 parts per million per degree Centigrade Maximum Voltage The maximum r m s voltage for which the units are insulated is 500 volts The switch will break the circuit at 500 volts if turned rapidly to the new setting but voltages above 150 may cause destruc tive arcing if the switch is set between detent positions Terminals Soldering lugs are provided Mounting Each decade is complete with dial plate knob and mounting screws Type Inductance 940 A 0 01 h in 0 001 h steps 940 B 0 1 hin0O O1 hsteps 940 C 1 hin 0 1
10. MODEL 1491 Precision Decade Indicutor User and Service Manual INSTRUCTIONS Figure 1 1 Type 1491 G Decade Inductor 1491 Decade Inductor SPECIFICATIONS 1491 DECADE INDUCTOR see also specifications for 940 decade units Frequency Characteristics Refer to section 2 Zero Inductance Approx 1 uH Max Voltage 500 V rms Switch will break circuit at 500 V if turned rapidly but voltages above 150 V may cause destructive arcing with switch between detent positions Terminals Binding posts on in centers separate ground ter minal provided Terminal board for rear connection Mounting Lab Bench Cabinet Catalog Number Bench Rack 1491 9701 1491 9711 1491 4 1491 9706 1491 9716 1491 F 1491 9703 1491 9713 1491 0 1491 9707 1491 9717 1491 G 1491 9704 1491 9714 1491 0 1491 9702 1491 9712 1491 B Discontinued 940 DECADE INDUCTOR UNIT Accuracy Each unit is adjusted so that its inductance at zero fre quency and initial permeability will be the nominal value within the accuracy tolerance given in the following table Inductance per step Accuracy Frequency Characteristics and other operating characteristics Refer to section 2 Dc Resistance Approx 45 0 per henry Temperature Coefficient Approx 80 ppm per degree C between 16 and 32 C 1491 0100 00 Description Decade Inductor Dimensions width x height x depth 1491 A B
11. ary to determine optimum operating values 1 2 DESCRIPTION All 1491 models are available for either bench use or installation in a relay rack The panel binding posts are for general use and connection may also be made at the rear as is often preferred for rack mounted decade boxes The individual decade units have no electrical connection to the panel but a separate ground termi nal is provided which can be connected tothe adjacent low terminal leading to the smallest decade Each decade unit is an assembly of four inductors relative values 1 2 2 5 wound on molybdenum permalloy dust cores that are combined by switching to give the eleven successive values from 0 to X X 10 The decade switch has high quality ceramic stator and rotor members and well defined ball and socket detents All contacts are made of a silver alloy and have positive wiping action Shielded toroidal cores are used for small mutual inductance and minimum effect from external fields 1 3 ACCESSORIES AVAILABLE Rack Adaptor Sets are normally supplied with the relay rack models These adaptor sets listed in Table 1 2 are also available for mounting 1491 bench models in a standard 19 inch relay rack Table 1 1 RACK ADAPTOR SETS FOR 1491 DECADE INDUCTORS Catalog Number 0480 9715 0480 9705 Type 1491 A B C 1491 D F G INSTALLATION AND OPERATION 2 1 DIMENSIONS See Figure 2 1 for approximate dimensions of a
12. ernal magnetic fields gt Electrostatic shielding and mechanical pro tection are furnished by the aluminum frame and covers gt Moisture is kept from the windings by wax impregnation SPECIFICATIONS Accuracy Each unit is adjusted so that its inductance at zero frequency and initial permeability will be the nominal value within the accuracy tolerance given in the following table Inductance per step lmh 10 mh 100 mh lh Accuracy 2 1 0 5 0 25 Frequency Characteristics The equivalent inductance of these units in terms of the nominal inductance L is given by the following equation L L equivalent Ico Typical values for the distributed capacitance Co of the Typp 940 A Decade Inductor Unit are as follows Step 1121314 5 6 7 81 9 110 Co upf Chassis tied to Low Terminal 90 60 50 50 50 45 40 37 35 35 Co uut Chassis Floating 45 45 85 35 50 40 35 32 30 25 For the Tyres 940 B C and D the above values should be multiplied by the factors 1 1 1 25 and 1 5 respectively Current Characteristics and Maximum Current Ratings The core permeability and the inductance value of each toroid are raised 0 1 by the application of 1 20 ampere turns The corresponding r m s current values J for each of the toroids are listed below together with the r m s current values J corresponding to a safe heat dissipation of two watts per toroid I ma Inductor Torotd for 0 1 increase
13. h is between detent positions SERVICE AND 3 1 WARRANTY QuadTech warrants that Products are free from defects in material and workmanship and when properly used will perform in accordance with QuadTech s applicable published specifications If within one 1 year after original shipment it is found not to meet this standard it will be repaired or at the option of QuadTech replaced at no charge when returned to a QuadTech service facility Changes in the Product not approved by QuadTech shall void this warranty QuadTech shall not be liable for any indirect special or consequential damages even if notice has been given of the possibility of such damages This warranty is in lieu of all other warranties MAINTENANCE expressed or implied including but not limited to any implied warranty or merchantability or fitness for a particular purpose THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE 3 2 SERVICE Our warranty attests the quality of materials and workmanship in our products If malfunction should be suspected or other information be desired applications engineers are available for technical assistance Application assistance is available in the U S by calling 508 485 3500 and asking for Applications Support For support outside of the United States please contact your local QuadTech distributor
14. hsteps 940 D 10 hinl h steps a 2 S E z a 6 FREQUENCY MILOCYCLES Variation of dissipation factor for the full value of each inductor Dashed curves correspond to use with chassis floating Dimensions Width 744 x height 314 x depth behind panel 314 inches over all Net Weight 3 pounds Code Word Price P E EN AN INDUCTOANT Price E Braa A AAAS INDUCTOBOY on E EAT INDUCTOCAT Be Ai INDUCTODOG Request TYPE 1490 DECADE INDUCTOR USES Where an adjustable inductance cover ing a very wide range is required these boxes will be extremely useful DESCRIPTION The Tyre 1490 Decade Induc tor is an assembly of three or four Typr 940 Decade Inductor Units in a single metal cabinet The units have no electrical connec tion to the panel but a separate ground terminal is provided which may be connected to the low terminal of the smallest unit SPECIFICATIONS Frequency Characteristics In determining the correc tion factor w CoL use the Co value corresponding to the largest decade unit actually in circuit For each larger decade unit not in circuit add 100 uuf if the inductor is grounded to the panel or add 20 uf if the inductor is not grounded to the panel Terminals Jack top binding posts Mounting The decades are mounted on an aluminum panel in a metal cabinet Dimensions 1490 A 1234 x 734 x 5 inches over all height 1490 B 1614 x 7384 x 5 inches over all height Net Weight Tyre 1
15. le b Inductance Values 1 H 2 5 OPERATING CHARACTERISTICS The following paragraphs give a brief resume of the operating characteristics of the 1491 decade box and the 940 decade units 2 5 1 FREQUENCY CHARACTERISTICS 1491 The percentage increase in effective series inductance above the zero frequency value Lo can be obtained by interpolation in the accompanying CALETA ela F ooh PT VTA YI AT FRACTIONAL INCREASE AL Le IN PERCENT 2 5 10 FREQUENCY IN kHz Figure 2 4 Variation of inductance with frequency for the 1491 Decade Inductors chassis grounded graph see Figure 2 4 for any setting of the highest value decade used when the low L terminal is grounded to the cabinet e940 Figure 2 5 shows the percentage increase in effective series inductance above the zero frequency value Lo with extreme settings X 10 of the indi vidual decade inductor units when the chassis is float ing Interpolate for intermediate settings HU 10 FRACTIONAL INCREASE AL Le IN PERCENT sO WO 200 500 2 5 0 20 FREQUENCY KILOHERTZ tr Figure 2 5 Change in effective inductance with frequency for the 940 Decade Inductor Units chassis floating 4L Lo IN PERCENT 20 50 100 200 Sy os 5 10 Lacy or Io Figure 2 6 Percentage change in normal and incremental inductance with ac and bias current Incremental curve is limited to an ac excitation less than 1j 2 5 2 INDUCTANCE
16. ll 1491 Decade Inductors 2 2 RELAY RACK INSTALLATION e 1491 A B C To install one of these decade inductors in a standard 19 inch relay rack use the Rack Adaptor Set parts listed in Table 2 1 refer to Figure 2 2 and proceed as follows a Remove the cabinet refer to paragraph 3 4 2 b Pierce and push out the plugs from the four bosses c on the inner sides of the cabinet near the front Be careful not to damage the threads c Press the sub panel D into the blank panel E d Attach the short flange of the blank panel E to the side of the cabinet using two screws F Table 2 1 as indicated in Figure 2 2 The blank panel may be attached to either side of the cabinet Note that the screws F enter in opposite directions one from the inside of the cabinet and one from the outside e Pierce and push out the plug in the lower rear boss G on the side of the cabinet where the support bracket H is to be attached f Attach one end of the support bracket H to the lower rear boss G using a 5 16 inch screw J Use the end of the support bracket with the elongated hole g Attach the other end of the support bracket H to the lower rear hole in the sub panel D using a 5 16 inch screw K h Attach one Rack Adaptor Assembly Q to the other side left side in Figure 2 2 of the cabinet using two 5 16 inch screws L Note that the screws enter the holes in opposite directions i Attach the re
17. maining Rack Adaptor Assembly Q to end of the blank panel E using two 5 16 inch screws M Note that these screws enter in opposite directions and passthrough the holes in sub panel D as shown j Install the instrument in the cabinet refer to paragraph 3 4 2 k Place a straight edge across the instrument panel and the blank panel E Loosen the screw J in the support bracket H adjust the alignment of the blank panel E so that it forms a straight line with Table 2 1 RACK ADAPTOR SET P N 0480 9715 Quantity Description Fig Ref Blank Panel Sub Panel Rack Adaptor Assembly Support Bracket Hardware Set includes the following parts Screw BH No 10 32 5 16 Screw BH No 10 32 9 16 with nylon cup washers k i 325 mm Figure 2 1 Approximate dimensions of 1491 bench and rack mount decade c HIODEN E Figure 2 2 Assembly of the 1491 for installation in a relay rack Part Number 0480 8925 0480 8945 0480 4905 0480 8522 0480 3080 225 mm inductors 80 45 Table 2 2 RACK ADAPTOR SET P N 0480 9705 Quantity Rack Adaptor Assembly Hardward Set includes the following parts Screw BH No 10 32 5 16 Description Fig Ref Part Number 0480 4905 0480 3080 Screw BH No 10 32 9 16 with nylon cup washers the instrument panel and tighten the support bracket screw J securely l Slide the entire assembly into the relay rack and lock
18. trument is equipped for rack mounting the handles must first be removed Table b Remove the four No 10 32 screws on the back of the cabinet c Slide the cabinet upand off the instrument To reassemble the instrument reyerse the above procedure and tighten the four No 10 32 screws securely 3 4 3 KNOB REPLACEMENT Knob Removal To remove a knoband dial assem bly a Set the decade to the X position b Grasp the knob firmly with the fingers and pull it straight away from the panel CAUTION To avoid damage to the knob and dial assembly do not pry the knob loose with a screwdriver or similar flat tool and do not attempt to twist the knob from the shaft c Release the No 3 32 set screw in the dial assembly hub and pull the assembly from the shaft Knob Installation To installa knoband dial assem bly a Mount the dial assembly in the correct pos ition on the shaft see step a under Knob Removal b Make certain the dial clears the panel and lock the No 3 32 set screw NOTE With the dial assembly properly in stalled the end of the shaft should not protrude through the dial assembly hub so that it interferes with proper seating of the knob c Place the knob on the dial assembly hub and Push it in until it snaps into the groove 3 1 INDUCTANCE PER DECADE ALL 1491 MODELS Refer to Figure 3 1 940 F 0 01 H steps 940 H 1H steps 940 G 0 1 H steps 940 H 1H steps 9
19. ur 9 16 inch screws N Tighten these screws by inserting a screwdriver through the holes in the handles To reconvert the instrument for bench use proceed as follows a Remove the entire assembly from the relay rack Remove the instrument from the cabinet b Remove both Rack Adaptor Assemblies Q from the cabinet c Reinstall the instrument in the cabinet 2 3 CONNECTIONS GENERAL The terminals on the 1491 are standard 3 4 inch spaced binding posts that accept banana plugs standard telephone tips alligator clips crocodile clips spade terminals and wire sizes up to No 11 See Figure 2 3 PATCH CORD ACCESSORIES Type I Gr e 274 NL oi amet E dib l 274 LLB 274 LLR sata Catalog Description Nasaber Double plug patch cord in line cord 36 long 0274 9860 Double plug patch cord right angle cord 36 long 0274 9880 Shielded double plug patch cord 36 long 0274 9883 0274 9408 Single plug patch cord black 36 lon igle plug p g 0274 9492 Single plug patch cord red 36 long Banana plug stabilized by se shoulder when fully inserted For metal top tan binding post only 3 famine ip foy enters Slender enpe Spe ing post body i all wire sizes assuring contact even p will clamp up to No when nut is loose under nut without cutting alligator clip Hl fits inside jacktop i of all binding posts Figure 2 3 Methods of connection to binding post
Download Pdf Manuals
Related Search