GR 1531AB_Stroboscope Manual
Contents
1. 3 Figure 2 1 Synchronization of Type 1531 Strobotac with rotating cam using Type 1531 P2 Flash Delay and MDe1536Pfot6eleetmle BtcKO Eo 10 Figure 2 2 Vibration test using a stroboscope and a Type 1539 Stroboslave 12 Figure 2 3 Stroboscope Flash Delay and Photoelectric Pickoff used for high speed photography 12 Figure 2 4 Guide number versus film speed for Type 1531 AB intensity settings Data for single flash opera tion see Figure 2 6 for correction required for repetitive flashing cccccscesseesscescceeeeeseeeseeeseeeseeeseeesees 13 Figure 2 5 Guide number correction for repetitive ec eeeeeeseesecseceseeseeseceeeeeeseesececeaeeaecseceeeesesseeeeeeeeseeaeeate 13 flashing with a Type 1531 AB Stroboscope ceccecseessessseeecesecesecesecesecseeesseceeceeceseceeeceesesesaeceeeseseseseenseeags 13 Figure 4 1 Side internal view of Type 1531 AB stroboscope with etched board swung open 20 Figure 4 2 Top internal view of Type 1531 AB Strobotac ee 21 Figure 4 3 Location and part numbers of mechanical parts for the Type 1531 AB Strobotac 23 Figure 4 4 Internal view of Swivel Support Assembly lead connections terminals and mounting 24 Figure 4 5a Etched board layout of Type 1531 AB Oscillator Trigger Circuit2. COMP 1 1 M OHM 5PCT 12W COMP 10 K 5PCT1W COMP 8 2 K 5PCT1W COMP 240 K OHM 5PCT 1 2W COMP 100 K 5PCT 12W COMP 510 K OHM 5PCT 1 2W COMP 24 K OHM 5PCT 1 2W COMP 1 0 K 5PCT 12W COMP 100 K 5PCT 2W 27K 5PCT 25W COMP 100 K 5PCT 12W COMP 150 K 5PCT 12W COMP 560 K 5PCT 12W COMP 51 OHM 5PCT 2W COMP 6 8 K SPCT 1W WW MOLDED 2 7 OHM 10PCT 2W COMP 10 K SPCT 2W COMP 150 K 5PCT 12W WW MOLDED 6 8 OHM 10 PCT 2W COMP 3 3 LAMP NEON M 5PCT 1 4W TRANSFORMER POWER NE2H PART NO 4860 7400 4400 1100 4404 1105 4860 7400 4450 0800 4450 6175 6081 1002 6081 1002 6081 1002 6081 1002 5330 1000 6110 3155 6100 4245 6100 5115 6110 3105 6110 2825 6100 4245 6100 4105 6100 4515 6100 3245 6100 2105 6120 4105 1531 0410 6100 4105 6100 4155 6100 4565 6120 0515 6110 2685 6760 9279 6120 3105 6100 4155 6760 9689 6099 5335 1531 2005 8390 0300 MER PART NO 663UW 0047 UF10PCT QC 10PF 10PCT 500V 0831082Z5D00101J 663UW 0047 UF10PCT 60D 450V TCG 10UF 1N4004 1N4004 1N4004 1N4004 313 500 RCR32G153J RCR20G244J RCR20G115J RCR32G103J RCR32G822J RCR20G244J RCR20G104J RCR20G514J RCR20G243J RCR20G102J RCR42G104J 1531 0410 RCR20G104J RCR20G154J RCR20G564J RCR42G510J RCR32G682J BWH 2 7 OHM 10PCT RCR42G103J RCR20G154J BWH 6 8 OHM 10PCT RCRO7G335J 1531 2005 C2A 27 1531 AB STROBOTAC 28 SWITCH CIRCUIT BOARD P N 1531 2710 PART NO MER PART NUMBER 4406 3109 08110
3. PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT 4 1531 AB SERIES Strobotac Electronic Stroboscope User and Service Manual Copyright 2001 IET Labs Inc 1531 AB im March 2002 ET LABS NC 534 Main Street Westbury NY 11590 Formerly made by TEL 516 334 5959 800 899 8438 FAX 516 334 5988 Gen Rad www ietlabs com WARRANTY We warrant that this product is free from defects in material and workmanship and when properly used will perform in accordance with applicable IET specifications If within one year after original shipment it is found not to meet this standard it will be repaired or at the option of IET replaced at no charge when returned to IET Changes in this product not approved by IET or application of voltages or currents greater than those allowed by the specifications shall void this warranty IET shall not be liable for any indirect special or consequential damages even if notice has been given to the possibility of such damages THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUD ING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF MERCHANTIBILITY OR FITNESS FOR ANY PARTICULAR PURPOSE Contents WARRANTY oaee ae uate woh alone sya vata a ace vh a ween von yews ea cac a A a er e o e eS 1 WARNING Nai e oa v CAUTION data a a taaan AA i v Chapter 1 INTRODUCTION siccssvetscpsccduisvsstdsacesacioustavesosseuaconsietnxadsnivasdussasunseavanebsBwesdosscas tes saba
4. part number for complete asseimblyit53132700J LO 25 Figure 4 6 Elementary schematic diagram for Type 1531 AB Strobotac 00 ceceeceeceeseeseeeeceeeeeeeeeeeeeseeaeenee 26 Figure 4 5b Etched board layout of Type 1531 AB Switch Circuit part number for complete assembly 1531 A O itl a heal TEE Geddes eles ala E ers peat 26 Switch wafers in the schematic are shown with dial in this position 29 AN WARNING AN OBSERVE ALL SAFETY RULES WHEN WORKING WITH HIGH VOLTAGES OR LINE VOLTAGES Dangerous voltages may be present inside this instrument Do not open the case Refer servicing to qulified personnel HIGH VOLTAGES MAY BE PRESENT AT THE TERMINALS OF THIS INSTRUMENT WHENEVER HAZARDOUS VOLTAGES gt 45 V ARE USED TAKE ALL MEASURES TO AVOID ACCIDENTAL CONTACT WITH ANY LIVE COMPONENTS USE MAXIMUM INSULATION AND MINIMIZE THE USE OF BARE CONDUCTORS WHEN USING THIS INSTRUMENT Use extreme caution when working with bare conductors or bus bars WHEN WORKING WITH HIGH VOLTAGES POST WARNING SIGNS AND KEEP UNREQUIRED PERSONNEL SAFELY AWAY CAUTION A DO NOT APPLY ANY VOLTAGES OR CURRENTS TO THE TERMINALS OF THIS INSTRUMENT IN EXCESS OF THE MAXIMUM LIMITS INDICATED ON THE FRONT PANEL OR THE OPERATING GUIDE LABEL vii 1531 AB STROBOTAC Chapter 1 INTRODUCTION 1 1 Purpose The Type 1531 AB Strobotac is a versatile flashing light sour
5. put jacks spare fuses Accessories Available TYPE 1538 P2 Extension Lamp TYPE 1538 P3 Battery and Charger TYPE 1538 P4 High Intensity Flash Capacitor TYPE 1531 P2 Flash Delay TYPES 1536 A Photoelectric Pick off for use with Flash Delay TYPE 1537 A Photo electric Pickoff and TYPE 1539 A Stroboslave Mounting Flip Tilt Case Dimensions Width 10 5 8 height 6 5 8 depth 6 1 8 270 x 170 x 160 mm including handle Net Weight 7 1 4 lb 3 3 kg Shipping Weight 10 lb 4 6 kg APPENDIX
6. Type 1536 A connected Mounting Aluminum case with bracket which clips directly onto the Strobotac electronic stroboscope TYPE 1536 PHOTOELECTRIC PICKOFF 31 1531 AB STROBOTAC 32 Type 1536 A Photoelectric Pickoff The Type 1536 Photoelectric Pickoffcontains a light source an optical system and a photocell which produces a pulse when light from a moving object is reflected back to the photocell This output pulse is fed through a Type 1531 P2 Flash Delay and then used to trigger a stroboscope With this combination of instruments the motion of objects rotat ing at irregular speeds can be analyzed visually or by photo graphic means Specifications Maximum Pulse Rate Approximately 2500 pulses s as limited by the 200 ps time constant of the photo cell and cable combination Power Required 20 to 28 V dc 40 mA Power is supplied by the TYPE 1531 P2 Flash Delay Accessories Supplied 10 ft roll of 3 8 in black tape 10 ft roll of 3 8 in silver tape carrying case Mounting C clamp capacity 1 5 16 in flat or round or 1 2 in magnet both supplied 2 Type 1537 A PHOTOELECTRIC PICKOFF In appearance the Type 1537 Photoelectric Pickoff is similar to the Type 1536 The Type 1537 however has no light source the photosensitive element is a silicon light activated switch The output from this transducer will trigger the Type 1538 A Strobotac or the Type 1539 Stroboslave directly It
7. cannot be used with the Type 1531 AB SPECIFICATIONS Operating Rate Greater than 2500 pulses s Power Required 3 to 25 V dc up to 100 OA de pending on operating rate power is supplied by in strument with which it is used Accessories Supplied 10 ft roll of 3 8 in black tape 10 ft roll of 3 8 in silver tape carrying case Mounting C clamp capacity 1 5 16 in flat or round or 1 2 in magnet both supplied PART NUMBERS FOR THE FLIP TILT CASE 1531 8130 4170 0900 4170 1267 7080 0800 Cabinet Spacer Pivot Pin Screw Mounting Plate 7860 1880 Inst Plate Pin Handle Slide 4170 1200 4170 1271 5360 5881 Handle Mounting Plate 7864 8000 Nameplate Washer Slide Washer 8050 1500 4170 8010 Tighten 10 32 screws to 20 25 in lbs torque Bend to give 1 32 to 1 16 spacing both sides APPENDIX 1531 AB STROBOTAC CABINET ASSEMBLY COVER ASSEMBLY GASKET src ae mae FOOT SPACER ll S A NUT PLATE SCREW AND WASHER HANDLE ASSEMBLY J mL HANDLE ASSEMBLY I Type 1539 A Stroboslave The Type 1539 Stroboslave is an auxiliary light source that will produce a flashing light with output charac teristics that are similar to the Type 1531 AB Strobotac This compact stroboscope will flash on command when triggered from a contact closure in a textile machine printing press etc or from a variety of IET strobos
8. feet to the measured distance between the stroboscope and subject For example if this distance is 2 feet use 3 5 as the number to be divided into the guide number to obtain your aperture setting 1000 9 HIGH INTENSITY LOW GUIDE NUMBER Liitil LALLI 3 4 56789I00 2 3 4567891000 2 FILM SPEED ASA BIS 10 2 3 45678910000 Figure 2 4 Guide number versus film speed for Type 1531 AB intensity settings Data for single flash operation see Figure 2 6 for correction required for repetitive flashing OPERATION 1531 AB STROBOTAC The guide numbers shown in Figure 2 4 should be regarded as only a starting point for obtaining correct exposure Contrast between subject and background type of film development techniques and many other variables should also be taken into consideration s LOW INTENSITY 1 MEDIUM INTENSITY HIGH INTENSITY a e 1 0 0 9 0 8 0 7 0 6 05 GUIDE NUMBER MULTIPLIER K Figure 2 5 Guide number correction for repetitive flashing with a Type 1531 AB Stroboscope Trial photographs are most helpful in determining op tim
9. fully clockwise the flash will occur at a de layed time after the contacts open and the unit will not operate properly at high speeds 2 9 4 Use of Electrical Signal Triggers The instrument can be triggered by any electrical sig nal of at least 6 volts peak to peak amplitude maxi mum of 500 volts For sine wave inputs the unit will operate with a 2 volt rms signal down to 5 Hz For pulse inputs i e step wavefront signals the rep etition rate has no minimum value The instrument can be synchronized with external signal frequencies up to at least 24 000 rpm 400 Hz Refer to paragraph3 2 7 Since a positive going sig nal is required at the input to trigger the stroboscope positive pulses are required to synchronize on the lead ing edge Negative pulses will result in a delay de pending on the width and trailing edge characteristics of the input pulse To operate the unit from an external electrical signal turn the range switch to one of the EXT INPUT po sitions depending on the frequency of the driving sig nal Connect the external signal source to the IN PUT jack Observe the precaution given in NOTE paragraph 2 9 3 In the LINE EXT INPUT position the power line excitation is automatically removed when a plug is inserted in the INPUT jack In the EXT INPUT po sitions the RPM control adjusts the sensitivity of the input circuit Starting at the fully clockwise position adjust the RPM control until satisfactory
10. just the HIGH CAL control on the panel to obtain a stationary pattern of 12 images e Set the RPM dial to 5400 RPM and adjust the LOW CAL control on the panel to obtain a stationary pattern of 3 images f Repeat steps d and e until no further adjustment is necessary g Set the range switch to the 670 4170 position and set the RPM dial to 3600 RPM h Adjust potentiometer R7 so that a stationary pat tern of 2 images is obtained Check operation at 900 RPM by adjusting the RPM control until the image is stationary The correct setting should be less than one half division from the 900 RPM mark If the set ting is not correct repeat steps d e f and check set ting again i Set the range switch to the 110 690 RPM position and set the RPM control to 600 RPM j Adjust potentiometer R8 so that a single stationary image is obtained Check operation at 150 rpm The stationary image setting should be within one quarter of a division of the 150 RPM mark If not repeat steps d e and f before checking this setting again k If the above procedure does not correct the diffi culty try replacing tube V1 5965 and check values of C4 C5 and C6 PIVOT PA 00 BLOCKS 1531 7H0 WASHER BO20 O6O 1531 AB STROBOTAC 4 5 Test Voltages Test voltages from tube pins to ground are shown on the schematic diagram Figure 4 7 Voltages are dc unless otherwise indicated Deviations of up to 20 from the stated dc volta
11. low speed applications below 1000 rpm where significant speed variations are encountered it may be desirable to use a mechanical contactor or contact closure such as a microswitch for synchronization and phasing The phase adjustment is generally inde pendent of the speed of rotation The Type 1531 AB stroboscope will flash on the opening of a mechanical contact refer to paragraph 3 2 7 NOTE Before connecting the contactor to the stroboscope make sure the range switch is not in any one of the EXT INPUT positions This precaution will prevent holdover of the thyra tron when the plug is inserted After the plug is connected the range switch can be set to any desired position If the stroboscope fails to flash because of holdover turn the in strument off for ten seconds and then on again refer to paragraph 3 2 2 After making sure the range switch is not in an EXT INPUT position connect the contactor to the INPUT OPERATION 1531 AB STROBOTAC jack using the standard phone plug supplied Then the synchronization procedure is as follows a Set the range switch to one of the EXT INPUT positions depending on the speed of the object being observed The maximum speeds indicated can be exceeded up to the point where the lamp flashes er ratically Generally the highest intensity position that allows satisfactory flashing of the instrument should be used b Set the RPM control fully clockwise If this control is not
12. speeds below 600 rpm on the low range of the Type 1531 AB may be difficult be cause of flicker resulting from lack of persistence of vision It is recommended that these measurements be made in a darkened environment or that the op erator wear dark glasses in order to reduce the con fusing effect of high ambient room lighting on the pattern observed OPERATION 1531 AB STROBOTAC Speeds below 110 rpm can be measured by means of multiple images For example if the flashing rate of the stroboscope is twice the fundamental speed of the device two images 180 degrees apart will ap pear At three times the fundamental speed three images 120 degrees apart will appear Refer to para graph 3 1 2 for illustrations This multiple image tech nique can also be used for higher speeds within the range of the Type 1531 AB when flicker makes it difficult to tell when the correct flashing rate is set for example between 110 and 600 rpm N 1531 AB STROBOTAC 10 2 8 5 Slow Motion Studies High speed motion can be reproduced by the strobo scope at an apparently much lower speed if the rotat ing or reciprocating motion occurs at a constant rate If the flashing rate of the instrument is set at a speed slightly lower than the fundamental speed of the ob served object the object will appear to move slowly in the same direction as the actual motion at a speed equal to the difference between the actual speed of the object and t
13. stroboscope is increased to 1801 rpm If desired the rate of appar ent movement can be speeded up by further increases or decreases in the flashing rate This is especially helpful in viewing cyclic motion When the image is stopped the flashing rate of the stroboscope equals the speed of the moving object and since the flashing rate is known the speed of the object is also known Thus the stroboscope has the PRINCIPLES OF OPERATION dual purpose of measuring speed and of effectively slowing down or stopping rapid motion for observa tion The practical significance of the slow motion ef fect is that since it is a true copy of the high speed motion all irregularities vibration torsion chattering whip present in the high speed motion can be stud ied 3 1 2 Single and Multiple Images Single images will occur at the fundamental speed of the object under observation and at predictable sub multiples of the fundamental speed Multiple images will be observed at various speeds above and below the fundamental speed Refer to paragraphs 2 7 1 and 2 7 2 When the Type 1531 AB Strobotac is used for ob servation purposes only the ability to distinguish be tween single and multiple images is usually not nec essary When making speed measurements however the operator must be able to make this distinction Generally odd shaped not symmetrical objects cause little difficulty Assume for example a fan with only one blade t
14. 82Z5U00103Z 4860 7900 4410P 0 182 UF 1PCT 4860 7600 410P 0301 UF 1PCT 4360 0160 4560 0160 1531 4000 1531 4000 1531 0470 1531 0470 1531 4020 1531 4020 6100 4105 RCR20G104J 6100 5335 RCR20G335J 6010 2200 JA1G032S504UZ 6010 2200 JA1G032S504UZ 6100 5105 RCR20G105J 6100 5105 RCR20G105J 7890 1830 7890 1830 4428 3109 4407 2478 6081 1003 1531 0490 4260 1030 4300 4600 5600 0700 6010 0800 6110 3125 0975 4030 6010 2450 6100 1105 7910 1300 1531 2000 8380 5965 8380 5727 1538 9601 2KV 01UF 80 20 25U 0811087Z5F00472K 1N4005 1531 0409 111 3500 28 4A JA1G0328502UZ RCR32G123J 0975 4030 JA1G0328255UZ RCR20G101J 83053 1531 2000 5727 2D21W 1538 9601 REF DES DESCRIPTION C 1 CAP CER DISC 01UF 80 20PCT 500V C 4 CAP MYLAR 182UF 1 PCT 400V C 5 CAP MYLAR 0301UF 1 PCT 400V C 6 CAP MICA 5230PF 1 PCT 500V C 10 CAPACITOR PAPER 047UF 10PCT C 11 CAPACITOR C 14 CAPACITOR R 4 RES COMP 100K 5PCT 1 2W R 6 RES COMP3 3M SPCT 1 2W R 7 POT COMP SCDR 500KOHM 10PCT LIN R 8 POT COMP SCDR 500KOHM 10PCT LIN R 32 RES COMP1 0M 5PCT 1 2W R 33 RES COMP1 0M 5PCT 1 2W S 2 SWITCH ROTARY ASM CHASSIS MOUNTED PARTS 1531 3100 C 15 CAP CER DISC 01UF 80 20PCT 2000V C 16 CAP CER DISC 4700PF 10PCT 500V CR 5 RECT 1N4005 600PIV 75A SI A50A J 1 JACK J PHONE GND 281L 2 CKT L 1 CHOKE MOLDED 680 UH 10PCT P 1 LAMP BAYONET BASE 6 3V R 1 POT COMP SCDR 5K OHM 10PCT LIN R 2 RES COMP 12 K 5PCT 1W R 3 POTENTIOMETER R 5 POT COMP SCD
15. Chapter 2 OPERATING PROCEDURE 2 1 Power Requirements The Type 1531 AB Strobotac operates from a line frequency of 50 to 400 Hz and from either a 105 to 125 volt 195 to 235 volt or 210 to 250 volt line input as noted just above the power cord The instrument is normally supplied for either 105 to 125 volt or 195 to 235 volt operation but can be modified for 210 to 250 volt operation refer to paragraph 4 4 3 and Fig ure 4 7 2 2 Opening the Case To open the case for operation a Set the instrument on a flat surface so that it is resting on its rubber feet b Unlock the case by sliding the two slide pins one on each side away from the handle It may be nec essary to push down on the top of the instrument to release these pins c Using the palm of the hand push the handle down as far as possible With the other hand swing the instrument to the desired angle Lower the instrument onto the rubber gasket by slowly releasing the handle The instrument will be held in position by its friction against the gasket at any angle from vertical to about 30 However since the case is not locked in position it may not stay in a tilted position under severe vibration If the instrument is to be hand held lower the case into the cover and lock it in position by sliding the locking buttons toward the handle OPERATION 2 3 Closing the Case Before closing the instrument push the reflector down against the panel with t
16. R 2 5MOHM 20PCT LIN R 35 RES COMP 100 OHM 5PCT 1 2W S 1 SWITCH TOGGLE 2POS DPST T 2 TRANSFORMER PULSE V 1 TUBE VACUUM 5965 V 2 TUBE VACUUM 5727 2D21W V 3 1338 P1 REPLACEMENT FLASH LAMP V 5 NEON LAMP NE 2H Note 8390 0300 C2A Replace all carbon composition resistors with 5 carbon film or 1 metal film preferred equivalents MAINTENANCE 1531 AB STROBOTAC REFERENCE DESIGNATOR ABBREVIATIONS C Capacitor P Plug VOLTAGE MEASUREMENTS CR Diode R Resistor Measured with unit operating on 115 volt line and DS Lamp S Switch Range switch on Ext Input High Intensity Where a F Fuse T Transformer voltage range is given first voltage is with R3 Flash J Jack X Socket ing Rate Control fully clockwise second voltage with L Inductor Y Crystal R3 fully counterclockwise Voltage may deviate 20 References ASA Y32 16 and MIL STD 16C Rotary switch sections are shown as viewed from the panel end of the shaft The first digit of the con tact number refers to the section The section near est the panel is 1 the next section back is 2 etc The next two digits refer to the contact Contact 01 is the first position clockwise from a strut screw usu ally the screw above the locating key and the other contacts are numbered sequentially 02 03 04 etc proceeding clockwise around the section A suffix F or R indicates that the contact is on the front or rear of the section respectively Switch wafers
17. bd 21 4 4 7 Strobotron does not Flash ccccecccsscesssesseesseescecsseceseceseeeseceseceeeceecesecesesseeseeessseceeeseseenseeags 22 4 4 8 Strobotron Flashes Erratically ccccsccsssessseesseeseceeeeseceseceseeesecesecesecesecesecsseceseseeeeneeeneeeaes 22 4 4 9 No Indication from Calibration Lamp ccccccccssesssesseeeeeeseeeseeeseenseceseceseeeseenseceseenseenseeags 22 4 4 10 Instrument cannot be Calibrated c cc ccceccesscesseceseeeeeeseeesecesecnsecesecnseceseenseenseseseenseeaes 22 4 4 11 Incorrect Ratio between Ranges cccccesscesseesseessceseeeecesecesceesecesecnseeeseenseeeseenseenseenseeaes 22 A S Fest Voltages merae a O 23 4 6 Replacement of Mechanical Parts cccccesscesseessesseceeceseeeseeesecseceseeeseceseeeseeeseceseseaeeeseenseeeaees 23 4 6 1 Reflector and Coveri arein a a iaia e a E aan 24 4 6 2 Swivel Support Assembly Pivot Blocks and Washers ooooonocnnoconoconocononononcnnnonanonnncnn conos 24 4 6 3 Scale Mask Assembly iaa 24 AS A TIA ancora tgs EN 24 vi Speci IT211 S11 0 31 Type 1536gAPhotoelectmeP16kOE ae 32 Specifications id a diene ad aii 32 DO 32 PHOTOELECTRIC RIKO SS 32 1 5160 M OUIN ya ASA A di it E 32 Type 1939 A StroDoslave iii AS eae UA Sealants 33 SA ANO 33 WDe 538 AESUEODO ACE 34 SDeC1HIC8HOTSSL AS 34 Figures Figure 1 1 Type 1531 Strobotac Electronic Stroboscope showing controls and connectors
18. ce that is used to measure the speed of fast moving objects or to produce the optical effect of stop ping or slowing down high speed motion for purposes of observation analysis or high speed photography 1 2 Description 1 2 1 General The Type 1531 AB is a portable electronic strobo scope that emits a high intensity short duration flash of light The instrument includes a strobotron lamp and reflector an electronic pulse generator that con trols the flashing rate and a line operated power sup ply A built in calibration system utilizes the power line frequency for checking and adjusting the flash ing rate calibration INTRODUCTION The strobotron lamp and reflector assembly is mounted on a swivel arm which can be pivoted 180 the reflector can be turned 360 Thus the operator can conveniently aim the light beam in almost any direction while the instrument is hand held or mounted in a stationary position The high intensity light will adequately illuminate most moving objects even in relatively high ambient light and it permits obser vation of distant and difficult to illuminate objects in otherwise inaccessible areas The Type 1531 AB Strobotac is housed in the classic General Radio Flip Tilt case which protects the in strument when it is not in use and also serves as a convenient support during operation see Figure 1 1 When in use the instrument can be held in the operator s hands placed on any conveni
19. cope equipment including the Type 1531 AB or the Type 1538 A Strobotacs Specifications Flashing Rate Ranges 0 to 700 0 to 4200 0 to 25 000 flashes per min on high medium and low intensity ranges respectively Flash Duration Approx 0 8 1 2 and 3 Us measured at 1 3 peak intensity for the low medium and high intensity ranges respectively Peak Light Intensity Typically 0 6 3 5 and 11 mil lion beam candles 0 6 3 5 and 11 X 10 lux mea APPENDIX 33 1531 AB STROBOTAC sured at 1 m distance at the beam center for low medium and high intensity ranges respectively For single flash 18 million beam candles at 1 meter Reflector Beam Angle 10 at half intensity points External Triggering Either a switch closure across the input jack terminals or a 2 V peak positive pulse Power Required 100 to 125 or 195 to 250 V 50 to 400 Hz 16 W Accessories Supplied Phone plug for input Accessories Available TYPE 1537 A Photoelec tric Pickoff TYPE 1531 P2 Flash Delay with a TYPE 1536 A Photoelectric Pickoff Type 1538 A Strobotac The Type 1538 A Strobotac is functionally similar to the type 1531 AB but the instrument has additional fea tures which include Fourth flashing rate range for higher speeds Greater light intensity 6 foot extension lamp Battery pack rechargeable plus conventional power line operation Either instrument can be used to trigger the other
20. d aims flashing light Permanently attached six foot power cord For storage cord is wound clockwise around range switch knob and reflector plug is secured by any of several types of fitting Flashes at 3600 rpm until external signal is plugged in INTRODUCTION 1531 AB STROBOTAC Figure 1 1 Type 1531 Strobotac Electronic Stroboscope showing controls and connectors See Table 1 1 for description INTRODUCTION 3 1531 AB STROBOTAC 1 3 Accessories Table 1 2 lists the accessories supplied with the Type 1531 Strobotac Table 1 2 ACCESSORIES SUPPLIED Part Number Description Quantity 4270 1100 Plug for input and output jacks 1 4 Auxiliary Equipment Table 1 3 lists accessory equipment and auxiliary light sources available for use with the Type 1531 AB Stro botac Table 1 3 AVAILABLE ACCESSORY EQUIPMENT AND LIGHT SOURCES Type Description ACCESSORIES 1531 P2 Flash Delay used with Type1536 Photoelectric Pick off 1536 1537 Photoelectric Pick offs used with Type 1531 P2 Flash Delay 1538 9601 Replacement Strobotron Lamp LIGHT SOURCES 1531 AB Strobotac electronic stroboscope 1538 A Strobotac electronic stroboscope 1539 A Stroboslave stroboscopic light source 1540 Strobolume electronic stroboscope Refer to Section 2 OPERATING PROCEDURE and APPENDIX for details describing the use of this equipment with the Type 1531 AB Strobotac INTRODUCTION 1531 AB STROBOTAC
21. e moved from the circuit when a plug is inserted into the INPUT jack Enough voltage is available to per mit synchronization at all bias RPM control settings PRINCIPLES OF OPERATION 1531 AB STROBOTAC 3 2 8 Calibration Circuit To calibrate the frequency dial vs power line fre quency voltages at both the power line and the flash ing rate frequencies are superimposed across a neon bulb V5 When the flashing rate of the strobotron equals the power line frequency or a multiple or sub multiple of it the voltage across V5 will remain con stant and the bulb will not vary in intensity Depend ing upon the phase relation between the strobotron oscillator and the power line voltage the steady state condition of the neon bulb may be maximum intensity partial intensity or zero intensity If the flashing rate of the strobotron differs from the power line frequency the voltage across the neon bulb will vary and the intensity will change at the differ ence frequency The above calibration can easily be made at many flashing rates between 600 and 7200 rpm Below 600 rpm the flashing rate will produce the appearance of flicker The flicker frequency will be superimposed on the difference or beat frequency described above when the flicker is pronounced it may be difficult to distinguish between the flicker and the beat frequency Above 7200 rpm the variation in intensity may be so slight that calibration is difficult 17
22. ect These synchronizing devices can operate at very high speeds and do not load the machine under observa tion See Figure 2 1 TYPE 1531 STROBOTAC FLASH DELAY Figure 2 1 Synchronization of Type 1531 Strobotac with rotating cam using Type 1531 P2 Flash Delay and Type 1536 Photoelectric Pickoff OPERATION The Type 1531 P2 Flash Delay is a small portable time delay unit that is used to insert a controlled de lay period between an externally generated trigger pulse and the resulting light flash from the strobo scope The flash delay also provides a convenient method of obtaining single flash photographs at any desired point in the cycle of the moving object The Type 1536 Photoelectric Pickoff is used to con vert the motion of a moving object to electrical im pulses that can be applied to the stroboscope It con sists of a light source a simple optical system and a photocell Variations in reflectivity caused by the motion of the object being observed produce electri cal signals which are amplified delayed and shaped by the Flash Delay and then fed to the stroboscope Power for both the photocell and the lamp are sup plied by the Type 1531 P2 Flash Delay The reader should refer to the Operating Instructions for the Type 1531 P2 Flash Delay and the Type 1536 Photoelectric Pickoff for further information concern ing these instruments and their use with the Type 1531 AB Stroboscope 2 9 3 Use with a Contactor For
23. ee baat E E ea 15 32 2 Strobotron TUD vid aaa 16 3 2 3 Strobotron Circuit esines e iris 16 9 OS 16 3 23 Trigger Circulo o A A EG 16 EA A RN 16 3 27 External Synchronization ii A ia e 16 3 28 Calibration Circuit ti id di A o dit 17 Chapter 4 SERVICE AND MAINTENANCE seciicantiaoir miii inci ii 18 Ail Field Service tada 18 4 2 Minimum Performance Standards cccccescsescesscesseesceeseeeseeceecseeeseeeeeeseesseeseeceeeeeeneeeseeeseensees 18 ADV E RN 18 4 2 2 Preliminary Testi a a tidad 18 4 23 Flashing Rate Testi lat da 18 4 3 Maite anne cita A idos 19 E NN 19 4 3 2 Cleaning the Reflector and Cover ccccccccsccsssessscesseeseeeeceseceseeeseeesecnsecsseensecneeeseeneeneenaes 19 4 3 3 Loose Erequency Dial atorrante a IA oe dt 19 4 3 4 Case will not Lock Properties E 20 4 3 5 Replacement of Strobotron Lamp cccccescesseesseeeseeeeeseeeseecseecseeceseesseeseeeseecesecseeeneeenseeags 20 4 3 6 Removal of the Instrument from it Case cceccecsessseeseeeseeeeceseceseceseeeseensecnseceseenseeeaeeaes 20 4 3 7 Replacement Of FUSE aa 20 A A Trouble Arlt 20 RE TNA 20 442 Preliminary Chess A as 21 4 4 3 Conversion for a Different Input Voltage oocoonnconoconocnoononononononononononononnnonnnon nono nonononnnonnss 21 4 4 4 No Flash and no Dial Light 20 0 ce eccesseessceseeeseeeeeceseeeseeeeeeseeeseeeeeeseeseeeseeeeseesseeeseeeneeeaes 21 4 4 5 Instrument Blows Fusesiiia il indias 21 4 4 6 No Dial TUNA A AAA A A tt
24. eeeseeeseeeeseeeeees 9 2 33 Slow Motion Udine 10 2 9 External Synchronization A task 10 2 9 1 Synchronizing to Power Line Frequency ccccesceessesseesseeeseeeceeeneceeeeeseeseecnseceeeceeeeeseenseeags 10 2 9 2 Use with flash Delay and Pickoff 0 0 0 cc cccceccceesscesseeseeeeeeseeeseceseeeseesseceseenseenseeeseenseenseesaes 10 293 USE with a COMA A aee a ra 11 2 9 4 Use of Electrical Signal Triggers ccccccccsscssscsseeetseeeceseceseesseceseceseenseenseesseesseeeeseeenseenaes 11 2 10 Operation with auxiliary light source cceeceesseeseeeseeeseesseeseeeseceseeeseeseceeceeseeeaeenseeesesnseenseeaes 12 2 10 1 Use with Type 1539 Stroboslave cccecccesesssssseestesseeseecssecseecsseesseceeecseecesecneecseeenseeseeeaees 12 2 10 2 Multiple Stroboscope uses ee 12 2 11 Use in High Speed Photography lt 12 Chapter 3 PRINCIPLES OF OPERATION scsscssedssssssssusensincesossevncesinrgasessoesessecssvenavinvnsiesb used suvesbevancisekcededessadentnieens 14 3 1 Basic Stroboscope Operation cccccccscesseesseesseessecssecseecseeenseeseecseecsaecaeceeesesecssecseecnaesnseseseeneeaaes 14 3 1 1 Whats a StrobOscO pe srei ire a Medusv ee a e at desis nese 14 3 1 2 Single and Multiple Images nnna n e a a a N h 15 3 2 CATCUIL Details A e Bun ee eaae ee ae oe steal A aT 15 3 2A General oasa aes E E E E E oe
25. ent flat sur face or mounted on a conventional tripod 1531 AB STROBOTAC 1 2 2 Controls and Connectors CHASSIS MOUNTED PARIS 1331 3106 All controls and connectors are conveniently located on the panel of the instrument See Figure 1 1 for location of controls and connectors referred to in Table 1 1 POWER Switch RPM Control Range Switch CALibration Indicator Lamp HIGH CAL LOW CAL OUTPUT TRIGGER Jack INPUT Jack Reflector Lamp Assembly Power Cord Table 1 1 CONTROLS AND CONNECTORS see Figure 1 1 Use Turns power on and off Controls flashing rate of light by rotating fluted rim Dial is calibrated directly in RPM revolutions per minute Selects any of three RPM ranges using internal oscil lator plus three External Input positions Internal Ranges External Input 110 690 RPM High Intensity 700 FPM max 670 4170 RPM Med Intensity 4000 FPM max 4000 25 000 Low Intensity 25 000 FPM max Indicates correct setting of CALibration adjustments for calibrating RPM dial to power line frequency Calibration adjustments used for calibrating RPM dial Trigger pulse available at this jack for triggering Types 1531 and 1538 Strobotacs and Type 1539 Stroboslave Refer to paragraph 2 9 and 2 10 for connection cables required Used for connecting Stroboscope to external synchronizing signal from electrical device or mechanical contactor Refer to paragraph 2 9 Produces an
26. g ranges selected by the Range Switch Windows on the range mask reveal only the range in use A red line inscribed below the RPM dial indicates the frequency setting in flashes per minute corresponding to rpm for speed mea surements The frequency limits for each range are marked near the appropriate window The range switch has no limit stops and can therefore be ro tated continuously The rotation of the RPM control however is limited to 300 degrees by stops 2 7 Calibration 2 7 1 General If the instrument is to be used for speed measure ments the RPM dial should be calibrated with re spect to the power line frequency The Type 1531 AB Strobotac will normally remain calibrated for a considerable period of time unless significant changes occur in ambient temperature or in the power line volt age To calibrate the stroboscope proceed as follows a Allow the instrument to warm up for about 10 minutes b Refer to the calibration table in the instrument cover or to Table 2 1 for the HIGH CAL and LOW CAL RPM dial settings indicated for the power line fre quency being used Turn the range switch to the cor responding range required to make these settings c Set the RPM dial to the exact HIGH CAL RPM dial setting called for in the calibration table d Adjust the HIGH CAL screwdriver control until the on off cycling of the CAL neon indicator lamp stops or nearly stops refer to paragraph 2 7 2 e Set the RPM dial at t
27. ge are normal Voltage ranges given for V1 are to be measured with R3 the RPM control either fully clockwise or fully counter clock wise refer to VOLTAGE MEASUREMENTS on schematic diagram 4 6 Replacement of Mechanical Parts Although the stroboscope is designed for use in manu facturing test and other areas where the working environment is often unsuitable for precision electronic instruments certain mechanical parts mounted on the outside of the instrument case may eventually become contaminated or damaged To replace these parts see Figure 4 3 refer to the following instruc tions Figure 4 3 Location and part numbers of mechanical parts for the Type 1531 AB Strobotac MAINTENANCE 23 REF DES RECT RECT RECT RECT FUSE 9 RES 10 RES 11 RES 12 RES 13 RES 14 RES 15 RES 16 RES 17 RES 18 RES RES ELECTRICAL PARTS LIST 1531 AB STROBOTAC OSCILLATOR TRIGGER CIRCUIT BOARD P N 1531 2700 DESCRIPTION 20 RESISTOR 22 RES 23 RES 24 RES 25 RES 26 RES 27 RES 28 RES 29 RES 31 RES 34 RES ARABIA ADD DABA AAA DADA DADA a MAINTENANCE 3 CAP MYLAR 0047UF 10PCT 600V 7 CAP CER TUB 10 PF10PCT 500V 8 CAP CER DISC 100FF 5PCT 500V 9 CAP MYLAR 0047UF 10PCT 600V 12 CAP ALUM 50 25 25 UF 450V 13 CAP ALUM 10UF 450V 1N4004 400PIV 75A SI ASOA 1N4004 400PIV 75A SI ASOA 1N4004 400PIV 75A SI ASOA 1N4004 400PIV 75A SI ASOA SLO BLOW 1 2A 250V COMP 15 K SPCT 1W COMP 240 K OHM 5PCT 12W
28. he approximate speed of the object can be estimated an operator can accurately measure the speed of rotating objects quickly and with confidence It is necessary how ever to thoroughly understand the following basic prin ciples involved in making speed measurements with a stroboscope OPERATION 1531 AB STROBOTAC e The operator must distinguish between single and multiple images Odd shaped objects usually cause little difficulty but objects which are symmetrical in shape gears discs fan blades etc must be marked to provide a visible reference refer to PRINCIPLES OF OPERATION paragraph 3 1 2 e Multiple images will always be observed when the stroboscope flashing rate is set to a multiple of the fundamental speed of the object e When reducing the flashing rate from a rate higher than the fundamental speed of the object the first single image will be seen when the flashing rate is equal to the fundamental speed When the flashing rate is below the fundamental speed of the object single and multiple images will be observed The single images will always occur at in tegral submultiples of the fundamental speed of the object refer to paragraph 2 8 2 2 8 2 Submultiple Speed Measurements If the Type 1531 AB Strobotac is set to flash at an integral submultiple of the fundamental speed of a rotating object a single image will be observed just as at the fundamental speed At flashing rates be tween these submulti
29. he exact LOW CAL RPM dial setting indicated in the calibration table and ad just the LOW CAL screwdriver control until the on off pattern of the CAL neon indicator lamp stops or nearly stops f Return the RPM dial to the HIGH CAL RPM set ting If the CAL indicator lamp blinks on and off too rapidly repeat steps d e and f This step is usually not necessary unless the LOW CAL adjustment was changed substantially g After calibration on the middle range dial accu racy is as follows to within 1 170 690 RPM 1020 4170 RPM 6100 25000 RPM to within 2 110 170 RPM 670 1020 RPM 4000 6100 RPM Table 2 1 CALIBRATION DATA RPM Dial Settings HIGH CAL LOW CAL Power Line Frequency Hz 3000 60 3600 900 400 24 000 6000 2 7 2 Calibration Error The CAL indicator lamp is used to determine when either the HIGH CAL or LOW CAL adjustments are properly set Extremely slow on off action of the lamp indicates the calibration setting is very close to the line frequency and generally accurate enough for most speed measurements If desired the calibration error can be calculated as follows a First observe the period in seconds required for the CAL indicator lamp to complete one full cycle on to off to on again for example Then calculate the calibration error by RPM rpm error line frequency Hz x T OPERATION where T time in seconds for one cycle of CAL indica
30. he flashing rate of the stroboscope If the flashing rate is set slightly higher than the speed of the object being observed the same slow motion will result but in the opposite direction This stroboscopic technique of slowing down motion can be extremely useful in investigating the operation of a device under normal operating conditions Ex cessive vibration misalignment of parts modes of vi bration of equipment on a shake table operation of vibrating reeds actual relation between traveler and thread during a complete revolution of the traveler on a textile spinning frame these are only a few ex amples of slow motion studies that are possible with the Type 1531 AB PHOTOELECTRIC PICKOFF CAM 2 9 External Synchronization 2 9 1 Synchronizing to Power Line Frequency Synchronization of the flashing rate to the 50 or 60 Hz power line frequency is obtained automatically by setting the range switch to the LINE EXT INPUT position For 400 Hz operation set the range switch to the EXT INPUT LOW INTENSITY position and inject a 400 Hz signal at the INPUT jack refer to paragraph 2 9 5 2 9 2 Use with flash Delay and Pickoff Two very useful accessories for the stroboscope are the Type 1531 P2 Flash Delay and the Type 1536 Photoelectric Pickoff The combination of these three instruments makes it possible to synchronize the flash of the Type 1531 AB with a moving object at any desired point in the cycle of operation of the obj
31. he single blade will be seen when a single image occurs two blades 180 apart will be seen when a double image occurs three blades 120 apart will be seen when a triple image occurs etc But when the object is symmetrical in shape fan with 4 blades for example multiple images cannot always be distinguished from a single image This difficulty is easily overcome simply upset the symmetry of the object by applying a reference mark with pencil paint chalk tape etc Make sure your mark does not unbalance the rotating object O Gear not marked for speed measurement Simple observation is possible but observer cannot be cer tain if image is single or multiple PRINCIPLES OF OPERATION 1531 AB STROBOTAC se Single image observed with tape applied to one tooth of gear a Multiple double image observed with tape applied to one tooth of gear Images are 180 apart Y 3 o Multiple triple image observed with tape applied to one tooth of gear Images are 120 apart 3 2 Circuit Details 3 2 1 General The Type 1531 AB Strobotac consists basically of a strobotron an oscillator to set the flashing rate of the strobotron and a power supply Component designa tions in the following paragraphs refer to the sche matic diagram Figure 4 7 15 1531 AB STROBOTAC 16 3 2 2 Strobotron Tube In most modern stroboscopes the flash occurs inside a xenon filled tube The gas in the tube is ioni
32. he transparent reflector cover facing up Turn the range switch bar knob to the 4000 25 000 RPM position and wrap the power cord clock wise around the knob and reflector Secure the power cord plug using the fitting provided Lift the instru ment until it is free to pivot on the handle and lower it into the case 2 4 Turning the Instrument ON The following precautions should be observed before turning the stroboscope on a Before plugging the power connector into a power receptacle make certain the power corresponds to the data above the power cord on the panel b The power plug has three terminals For operator safety the third pin on the power plug must be prop erly grounded Pivot the reflector assembly to an upright position and turn the power switch on The stroboscope will be ready for use in about 10 seconds 2 5 Positioning the Stroboscope The light beam can be aimed in almost any direction by means of the swivel arm and the rotating reflec tor The intensity of the light pulse is so high that it is usually not necessary to place the unit very close to the object being viewed 1531 AB STROBOTAC 2 6 Adjusting the Flashing Rate The flashing rate of the strobotron lamp is adjusted by means of the Range Switch and the RPM control To operate the RPM control grasp and rotate the fluted transparent rim which surrounds the range mask The overall frequency range of the Stroboscope is divided into three overlappin
33. in the schematic are shown with dial in this position MAINTENANCE 29 1531 AB STROBOTAC APPENDIX Note Certain of the items described below may not be available They are shown as application refer ences only Check with IET for availability or possible substitutes Type 1531 P2 Flash Delay The Type 1531 P2 Flash Delay provides a continu ously adjustable time delay between an external trig gering device and a stroboscope The triggering de vice can be an oscillator photocell or other type of transducer A typical combination of flash delay photoelectric pickoff and stroboscope shown below can be used for visual observation and analysis of repetitive mo tion whose period is not constant The flash delay also provides means for precise synchronization of camera shutter stroboscopic flash and objects mov ing at irregular speeds for high speed photography TYPE 1531 STROBOTAC APPENDIX Specifications Time Delay Range Approximately 100 Us to 0 8 s in three ranges Output Pulse Better than 13 V available for trig gering the TYPES 1531 AB and 1538 A Strobotac electronic stroboscopes and the TYPE 1539 A Stroboslave Sensitivity As little as 0 3 V input will produce suf ficient output to trigger the stroboscope Inputs Phone jack for triggering jack for camera synchronization Accessories Available TYPE 1536 A Photoelec tric Pickoff Power Required 105 to 125 or 210 to 250 V 50 to 400 Hz 5 W with
34. led by an internal oscillator The two sections of the oscillator tube V1 constitute a bistable circuit in such a cir cuit one section conducts while the other section is shut off Then very rapidly the two sections reverse states Each section is alternately turned on and off at a rate determined by the values of resistors and capacitors in the circuit and the voltage setting of R3 RPM control Several of these components are ad Justable by panel controls The RPM control is R3 RI and RS are the calibration screwdriver adjustments The range switch S2 introduces the proper timing capacitor into the circuit to step the flashing rate up or down by a factor of 6 3 2 5 Trigger Circuit The output of the oscillator V1 is applied to the thyra tron tube V2 through C8 The thyratron together with C9 and the pulse transformer T2 is used to pro duce the high voltage pulse necessary to trigger the strobotron 3 2 6 Power Supply A voltage doubler power supply furnishes 400 and 400 volts dc to operate the strobotron The 400 volt supply is filtered by a two stage R C filter to ob tain the 250 volt supply The power transformer is capable of operating on line frequencies ranging from 50 to 400 Hz and is normally wired for either 115 or 230 volt operation see Figure 4 7 3 2 7 External Synchronization For operating with an external synchronizing signal the oscillator circuit is converted to a conventional ampli
35. necesad enana abaesasicbseatel 1 TT PURPOSE ut tn e ade SRA 1 1 2 DOSCripth Ott ti A A A cea Tees 1 1 2 F Generalene EE E oun denky eave tice Tees bag a ia e E EEEE NSE 1 1 2 2 Controls and Connectors a ea a E E a das 2 33 ACCESSOTICS N AE E TE sta dee tastes AE EN E TENEN E AE EAE AE EETA 4 LACA EU MN AE 4 Chapter 2 OPERATING PROCEDURE sisscosscosisssncosetscasestconessvnceseayteseavdpossissevanssnstnsossesensixogestolievsnebessuesusenseaeessonenys 5 2 1 Power Requirements ii uia n n e a a a a a nat 5 2 2 Opening the Ca emore sretna A a e 5 23 Closing the CaSe igasse A A A Aa EEO aS 5 2 4 Turning the Instrument ON cooconncccoccconaconoconcconnconoconononocanncon n as a Ee o E a E AE 5 2 5 Positioning th StrobOsCope siii do id ER E E E 5 2 06 Adjusting the Flashing Rate seia kerer id td a e e dida bd iia 6 2 Calibra aaa 6 A A RS CN 6 Df 2 CAMION E oes Seb dyxe ois ogeaes so ches Sates spas gana pa acess Gea geen dd Baa des Ds tees 6 2 8 Speed Measurement cccccccescessscsssceseeeeceseceseeesecesecsseceseesseceseeeseceaeceseceseeeseeeseeeseceseseeeeaeesseeeeees 7 2 8 1 Fundamental perdi do 7 2 8 2 Submultiple Speed Measurement cccceccccssesscesseeseeeseceeeeseceeceeeseeeseeeseeeeeeseeeteesseeneees sf 2 8 3 Measurement of Speeds above 25 000 RPM ccccccscesssessseeseeeneeeeeeseceseeeseeeseceeeeeenseenseens 8 2 8 4 Low Speed Operation cccccsccssscesscesscessceseceseceseeeseceeeeseeeseceseceseceeeseeseeeee
36. ples multiple images will be ob served Table 2 2 shows as an example the number of images that will be obtained at various stroboscope flashing rates below the fundamental speed of a de vice rotating at exactly 1800 rpm Note the numerical relationship between the numerator of the submul tiple fraction and the corresponding number of im ages seen This relationship will always hold true re gardless of the speeds involved Table 2 2 lists only a few of the more useful submul tiple speeds and corresponding images many other multiple images are possible for example five im ages will be seen at 5 7 5 8 etc Submultiple flash ing is necessary in order to observe or measure the speed of objects moving at rates above 25 000 rpm Refer to paragraph 2 8 3 for the method of determin ing the fundamental speed when submultiple opera tion is necessary 1531 AB STROBOTAC Table 2 2 SUBMULTIPLE SPEED IMAGE RELATIONSHIP Submultiples of Number of Fundamental RPM Dial Speed Setting 5 4 3 2 3 1 2 1 1 1 1 At dial settings above fundamental speed multiple images al ways occur Refer to table 4 1 2 8 3 Measurement of Speeds above 25 000 RPM Speeds up to about 250 000 rpm can be accurately determined by calculations based on submultiple mea surements The procedure is as follows a Starting at 25 000 rpm decrease the flashing rate of the stroboscope until a single image is obtained Record the RPM dial
37. setting and call it X b Continue to decrease the RPM dial setting slowly Watch the changing images carefully and stop when the next single image occurs Record the RPM dial setting as Y c Calculate the harmonic number n by n _Y X Y and round off the value of n to the nearest whole number d Calculate the fundamental speed S by Example If X is 22 500 and Y is 16 800 then 16 800 n 295 3 22 500 16 800 and the fundamental speed is Sp 3 x 22 500 67 500 rpm The nomograph below can also be used to quickly determine the fundamental speed of an object from two successive submultiple images To use the nomograph find the point on the X scale corresponding to the highest flashing rate at which a true stopped motion image occurs Then find the point on the Y scale where the next lower true stopped image occurs Hold a straightedge so that it inter sects the X and Y scales at the points plotted The straightedge should intersect the n scale at an inte ger Multiply the X scale value by this Integer to de termine the fundamental speed Example Suppose that the first true stopped motion image is obtained at 20 000 rpm the next lower one at 15 000 rpm A line drawn through 20 on the X scale and 15 on the Y scale intersects the n scale at 3 Therefore the fundamental speed is 3 x 20 000 rpm or 60 000 rpm OPERATION 2 8 4 Low Speed Operation The measurement of
38. slave 2 11 Use in High Speed Photography The short duration of the light flash from a Type 1531 AB Strobotac when triggered by a controlled time delay pulse from the Type 1531 P2 Flash Delay al lows the photographer to capture on film a sharp im age of very fast moving objects see Figure 2 3 FLASH DELAY TYPE 1531 STROBOTAC y la PHOTOELECTRIC PICKOFF X Figure 2 3 Stroboscope Flash Delay and Photoelectric Pickoff used for high speed photography The instrument can be triggered by an external signal e g from a photocell or microphone for synchroni zation of a single flash or can be set to flash at a given rate for multiple exposures The entire system should be checked for proper synchronization before making the final exposure Determining correct film exposure is simplified by the use of a guide number GN that relates the lamp to subject distance d to the camera aperture setting f f GN d The guide number as determined from Figure 2 4 is used for single flash applications When repetitive flashing of the stroboscope is required the guide number must be multiplied by a correction factor Guide Number Multiplier K taken from Figure 2 5 OPERATION When computing aperture setting you must adjust the distance measured between the stroboscope and the subject Since the light effectively originates from a point 1 5 feet behind the reflector cover you must add 1 5
39. synchroni zation is obtained For large amplitude inputs there will be a wide range of settings of the RPM control at which the instrument will operate satisfactorily For small amplitude inputs the range will be correspond ingly smaller 11 1531 AB STROBOTAC 12 2 10 Operation with auxiliary light source 2 10 1 Use with Type 1539 Stroboslave The Type 1539 Stroboslave is used with the strobo scope when a second light source is needed or when a difficult to illuminate object requires the use of a compact light source mounted at the end of a flexible cord see Figure 2 2 Since the Stroboslave has no internal oscillator the trigger signal is supplied by the Type 1531 AB stroboscope through a Type 1531 P4 Trigger Cable Plug the large end of this cable into the OUTPUT TRIGGER jack on the panel of the stroboscope and plug the other end into the INPUT jack on the panel of the Type 1539 Stroboslave 2 10 2 Multiple Stroboscope uses A second Type 1531 AB or a Type 1538 A strobo scope can be used in conjunction with the Type 1531 AB when a second source of light is needed A Type 1531 P4 Trigger Cable is required to connect the two instruments Plug the large end of the cable into the OUTPUT TRIGGER jack of the master Type 1531 Then plug the small end into the INPUT jack of the slave stroboscope either a Type 1531 AB or a Type 1538 A Figure 2 2 Vibration test using a stroboscope and a Type 1539 Strobo
40. tor lamp Example if the CAL lamp period equals 2 seconds the line frequency is 60 c s and the RPM dial is set at 900 the calibration error is 900_ 7 5 rpm 60 x 2 2 8 Speed Measurement 2 8 1 Fundamental Speed When measuring the rotational speed of an object set the RPM dial initially to a higher flashing rate than the speed of the object Then slowly reduce the flashing rate until the first single image is observed At this point the flashing rate of the stroboscope will be equal to the rotational speed of the object and the speed can be read directly from the RPM dial When using the middle or low speed ranges simply switch to the next higher range without changing the RPM dial setting to check whether the stroboscope is flashing at the fundamental speed of the object Since the ratio between ranges is exactly 6 1 six im ages will appear at the next higher range if the stro boscope has been set to the fundamental speed If only three images appear for example then the stro boscope has been set to one half the correct speed On the high speed range double the speed setting to check for fundamental speed operation A double im age should occur when the frequency setting is doubled If the fundamental speed of the device be ing measured is above 12 500 rpm it is not possible to check for correct speed setting by the method out lined above In this case refer to paragraph 2 8 3 With practice and especially when t
41. tude sensitive bistable circuit The RPM con trol varies the bias on V1 so that optimum sensitivity for sine wave or pulse input signals can be obtained The greater the amplitude of the input signal the greater will be the range of bias values that will allow proper flashing of the stroboscope The input circuit can also be driven by an external contactor In such operation half of the dc voltage divider R32 and R33 is short circuited by the closing of the external contactor The positive pulse required to operate the thyratron is generated by the input circuit when the external contactor opens so the flashing is synchro nized with the opening of the switch not with the clos ing PRINCIPLES OF OPERATION The input impedance at the panel input jack is about 500 kohms Because of the dc voltage divider about 50 volts dc is present at the input terminals There are three frequency ranges for external input LOW INTENSITY MED INTENSITY and HIGH INTENSITY Operation above the maximum frequen cies indicated will not damage the strobotron but op eration may become erratic On the LOW INTEN SITY range the instrument can often be synchro nized at frequencies up to 600 Hz 36 000 rpm or higher before the strobotron begins to misfire In the LINE EXT INPUT position the Type 1531 AB Strobotac is synchronized with the power line fre quency by applying an ac voltage from the power transformer to the input circuit This voltage is r
42. um exposure Follow the film manufacturer s rec ommendations when processing the film 13 1531 AB STROBOTAC 14 Chapter 3 PRINCIPLES OF OPERATION 3 1 Basic Stroboscope Operation 3 1 1 What is a Stroboscope A stroboscope is a source of flashing light that can be synchronized with any fast repetitive motion so that arapidly moving object seems to stand still or to move slowly To illustrate this principle consider the following ex ample Assume a white disc with a single black dot mounted on the shaft of an 1800 rpm motor When the disc is rotating at 1800 rpm it is impossible for the human eye to distinguish a single image and the dot will appear to be a blurred continuous circle When illuminated by the flashing stroboscope light syn chronized to flash once every revolution of the disc when the dot is at 3 o clock for example the dot will be seen at this position and only at this position at arate of 1800 times each minute Thus the dot will appear to freeze or stand still Now if the flashing rate of the stroboscope is slowed to 1799 flashes per minute the dot will be illumi nated at a slightly different position each time the disc revolves and the dot will appear to move slowly in the direction of rotation through 360 and arrive back at its original position 3 o clock one minute later A similar movement but in the opposite direction will be observed if the flashing rate of the
43. when a second flashing light source is required Type 1538 A Strobotac Extension ca y Lamp Specifications Flashing Rate Range 110 to 150 000 flashes per minute in four direct reading ranges 110 to 690 670 to 4170 4000 to 25 000 and 24 000 to 150 000 rpm Speeds to over 1 million rpm can be measured Accuracy 1 of reading on all ranges after cali bration against line frequency Flash Duration Approximately 0 5 0 8 1 2 and 3 s for high to low speed ranges respectively mea sured at 1 3 peak intensity for single flashes with Type 1538 P4 High Intensity Flash Capacitor 8 Us Peak Light Intensity Typically 0 16 1 5 and 15 million beam candlepower 0 16 1 5 and 15 X 10 High Intensity 4 Flash Capacitor 34 APPENDIX 35 lux measured at 1 meter distance at the beam center for high to low speed ranges respectively 44 mil lion beam candlepower for single flash with Type 1538 P4 High Intensity Flash Capacitor Reflector Beam Angle 10 at half intensity points Output Trigger Greater than 6 V positive pulse be hind 400 ohms External Triggering Either a switch closure across the input jack terminals a 1 V peak positive pulse or a 0 35 Vrms sine wave down to 100 Hz increasing to 3 5 Vrms at 5 Hz Power Required 100 to 125 or 195 to 250 V 50 to 400 Hz 15 W or 20 to 30 V de 12 W 1531 AB STROBOTAC Accessories Supplied Phone plug for input and out
44. zed by the rapid discharge of a capacitor The gas must then deionize before the next flash can occur This deionization time sets the limit on the maximum flashing rate of the instrument If too high a voltage is applied across the tube before it is deion ized an erratic condition continuous conduction known as holdover will result The strobotron tube contains two main elements a cathode and an anode A discharge capacitor acts as a low impedance source of voltage across these elec trodes The gas remains nonconducting deionized until a high voltage pulse is applied to trigger wires interspersed between the two electrodes This trig ger pulse ionizes the gas and causes current to flow through the tube generating an intense flash of white light 3 2 3 Strobotron Circuit The high voltage output from the trigger circuit is ca pacitively coupled from T2 to the strobotron The coupling capacitors are built into the ceramic insula tor in the swivel neck The energy to flash the stro botron is stored in the discharge capacitors C10 C11 and C14 The correct capacitance for each RPM range is connected across the strobotron by the range switch After the strobotron flashes the active ca pacitors are recharged to 800 volts dc The unused capacitors are kept charged to 800 volts to reduce arcing at the switch contacts when the range switch setting is changed 3 2 4 Oscillator The flashing rate of the instrument is control
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