GR 1538A_Stroboscope Manual
Contents
1. Ses cam 20 4 5 Minimum Perforimatice ieee 20 cec oc 20 2 52 e Ue UIT CC EU 20 euentu C 20 4 5 4 Plashing Rate Accuracy Check siete tert tette tee a terea arenas 21 4 xe Bie M 21 2 5 60 Output Checle sues a tM te 21 BARN OL LSA GY 0 te Reg ne OT 21 44 1 Case Will NOP LOCK Proper N 0 TN 21 242 Clednme tie Bebe UE cad sta ete Pa delete cate 21 4 4 5 Removing the Instrument froni its IM 2 pud LM MM MINE E 21 4 4 5 Replacing the Strobotron 7 21 44 7 Repositioning the RPM Dial and Knob o e E 22 4 4 8 Converting to the other Power Line Voltage 222000000010100 3 22 23 4 5 stobotron Lamp does dol PlasDi TE HR HER dup ttn 23 45 2 Sttobotron Lamp lashes Erratigally ase Pom be ont 24 1 5 2 Improper Operation with External Input o HERRERA IER NER ENT 25 4 5 4 Improper Operation with Battery Power 8 25 4 5 5 1538 P2 External Lamp does not Flash Front Panel Strobotron Lamp Flashes2. 18 Figure 3 3 Block diagram of the Type 1538 Strobotac electronic stroboscope 222 18 Figure 3 4 The voltage buildup on the charging capacitor is in small steps 19 Figure 4 1 The power supply etched circuit board is pivoted to swing out when screws A and B are removed eit eco 22 Figure 4 2 The power supply board swung out to expose the under side the fuse and the dial lamp 22 Figure 4 3 Right side interior view of the Stroboscope 23 Figure 4 4 Voltage waveform at the panel OUTPUT jack 24 000 RPM 24 Iaeure 4 5 Voltage waveform atA LOS 24 000 RPM ic Pea hn dO dee a eto ouo auto 24 Figure 4 6 Voltage waveform at pin 3 of the panel EXT LAMP socket 50901 24 000 RPM 25 4 7 Voltage wavetotm at 23 24000 co EE uUo REGES 25 Figure 4 8 Voltage waveform at A T 63 24 000 2 0 4 1 1 66000000000000 25 Figure 420 Miscellaneous part boim died N 26 Figure 4 10 Interior view showing mounting of the swivel support assembly pivot blocks and connections 26 Figure 4 11 Name and location of parts included the IET Flip Tilt Case refer to table 4 1 27 Figur
3. 25 4 6 Replacement of Mechamcal 26 26 26 4 6 3 Swivel Support Assembly Pivot Blocks and Washers 26 5 k ASSCHIDIS oiii ec bo on boe te se 27 Ao 27 1538 P4 High Intensity Flash Capacitor See Figure 2 14 33 Type 15535 P2 Extension Mami 33 Figures Figure 1 1 The stroboscope can be mounted on a standard camera tripod 2 Figure 1 2 The front panel of the stroboscope showing the controls and connectors 2 Figure 1 3 The Type 1538 powered by the Type 1538 P3 Battery pack offers a precise bright stroboscope capability completely independent of the ac power line A unique advantage in use with large machine complexes such as found in textile and printing industries The battery pack can power the Strobo for up toG hours OF intermittent DENIM de E CD NEED i Dus 5 Figure 2 1 The transformer terminals on the stroboscope are numbered as shown 7 Figure 2 2 Typical charge retention characteristics of the battery 8 Figure 2 3 Stroboscopic i
4. Eq 6 2 5 6 Zl Power ine Pera 9 6 2 35 2 Battery 7 2525 ype 1538 P5 A Battery source and cce es I 2 4 Turnine heus tumen Osea ete idee eite aa 8 2 the SITODOSCODS A 8 2 Adj stine the Flashing Rate eris 8 DC EAE EE 8 INIGASUT CICS aean tudeke esu a ae a a 9 2 5 1 Fundamental Speed 220 9 2 6 2 Submultple Speed Measurements E 10 2 8 5 Measurement of Speeds above 150 000 RDPND dades 10 2 5 A LOWSSDCEO ODGELaLIOB lt fer M E 2 0 5 MOHOBSS BOITE S oct estote 2 9 06 72 Extension toDr2abloft 12 Input JAC Ras he e pee ode ids 12 2 10 2 Type 1531 P2 Flash Delay and type 1536 Photoelectric Pick off 000000nnnnnneeessesssssesen 12 2 10 5 Type 1557 Photoelectric PICGK O IT aoo aea ed
5. 750 if 50 Hz line is used OPERATION 1538 A Strobotac 2 8 Speed Measurements 2 8 1 Fundamental Speed Measurement If the speed of the object being viewed is not known at least approximately start at a high flashing rate where multiple images result and reduce the flashing rate until a single image is obtained The first single image occurs when the flashing rate is equal to the rotational speed of the object and the speed can then be read directly from the RPM dial IMPORTANT To determine that a single image has been obtained the object being viewed must have some identifying mark to provide non symmetry For instance a four bladed fan must have a mark on one blade only or a piece of tape can be applied to one tooth of a gear to produce the images shown in Figure 2 3 On the three lower speed ranges a quick check on whether or not the stroboscope is flashing at the fun damental speed of the device being measured can be made by simply switching to the next range without moving the RPM dial Since the ratio between ranges is approximately 6 1 six images will appear at the next higher range when the stroboscope has been set to the fundamental speed If only three images ap pear for example the stroboscope has been set to one half the correct frequency On the high speed range double the speed setting of the RPM dial to check for fundamental speed operation A double image will occur when the frequency setting 15 doubl
6. CAP CER DISC 390PF SPCT 500V CAP CER DISC 2200PF 500V CAP CER DISC 022 UF 80 20PCT 500V CAP TANT 1 0 UF 20PCT 35V DIODE 4154 1 25PIV IR 1UA SI DIODE 4154 1 25PIV IR SI DIODE RECTIFIER IN645 DIODE 1K455 30PIV IR 30UA GE TRANSISTOR 2N3414 TRANSISTOR 2N3414 TRANSISTOR 2N3414 TRANSISTOR 2N3414 TRANSISTOR 2N1303 TRANSISTOR 2N1303 TRANSISTOR 2N3414 TRANSISTOR 2N3414 RES COMP 100 5PCT 1 2W RES COMP 470 K 5PCT 1 2W RES FLM 6 98K 1 PCT 1 2W POT WW 2K CHM 10 PCT IOT ELECTRICAL PARTS LIST P N 1538 3000 PART NO 1538 0440 5330 0700 4260 1030 4260 1030 560 1000 4220 4400 8210 1172 6100 2435 7910 1500 7910 1300 1536 3070 1536 8090 1538 2000 8390 0310 1538 9601 FMC 24655 75915 82389 82389 24455 71785 04713 81349 04009 04009 24655 24655 24655 24455 24655 P N 1538 2710 4860 8250 4406 2228 4406 3109 4404 1395 4406 2228 4407 3229 4450 4300 6082 1012 6082 1012 6082 1016 6092 1010 8210 1290 8210 1290 8210 1290 8210 1290 8210 1019 8210 1019 8210 1290 8210 1290 6100 4105 6100 4475 6450 1698 6059 2209 56289 72982 72982 72982 72962 72982 56289 14433 14433 14433 14433 56289 56289 56289 56289 01295 01295 56289 56289 81349 81349 81349 80294 1538 A Strobotac MFGR PART NO 1538 0440 313 250 111 111 1819 004 254906 RCR20G432J 83054 83053 1538 3070 1538 8090 1538 2000 3AD 1538 9601 410P 0 1 UF
7. PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT 1538 A Strobotac Electronic Stroboscope User and Service Manual Copyright O 2001 IET Labs Inc 1538 A im March 2002 9 IET LABS INC Standards Decades Strobes Sound Level Meters Bridges Formerly manufactured by 534 Main Street Westbury NY 11590 TEL 516 334 5959 800 899 8438 FAX 516 334 5988 Ge n 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 N WARNING N 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 H
8. 81349 MFGR PART NO 410P 1 09 UF IPCT 410P 0 182 UF IPCT 410P 0 0301 UF IPCT DM20FC4320PF1PCT4CR 1531 4020 1531 0470 1538 0441 3068 1 503 RCR20G243J 3068P 1 503 3068P 1 503 RCR20G103J RCR20G472J RN65D4643F MAINTENANCE CR CR CR CaO Ee CT 201 301 301 302 303 304 305 306 301 302 301 302 303 304 501 502 503 504 505 506 509 511 REFDES CR CR CR CR CR CR CR CR CR CR CR 501 502 503 504 505 507 508 509 510 511 516 517 501 MAINTENANCE ELECTRICAL PARTS LIST cont SWITCH CIRCUIT PC BOARD SWITCH ROTARY ASM PC BOARD ASM CAP ALUM 200 200 UF 50V DIODE RECTIFIER 1N4003 DIODE RECTIFIER IN4003 DIODE RECTIFIER IN4003 DIODE RECTIFIER IN4003 DIODE RECTIFIER IN4003 DIODE RECTIFIER 1N645 TRANSISTOR 2N1540 TRANSISTOR 2N1303 RES COMP 1 0 K 5PCT 1 2W RES COMP 1 8 K 5PCT 1 2W RES COMP 47 5PCT 1 2W RES WW MOLDED 3 0 OHM 10 PCT 2W POWER SUPPLY PC BOARD CAP MYLAR 1 30UF 1 PCT 100V CAP PAPER 022UF 5PCT 600V U CAP CER DISC 2200PF 500V CAP PAPER 022UF 600V CAP CER DISC 220PF 5 500V CAP CER DISC 1000PF SPCT 500V CAP ALUM 600 300 300 UF 75V CAP CER SQ 0 01UF 80 20PCT 100 POWER SUPPLY PC BOARD DESCRIPTION DIODE RECTIFIER 1N645 DIODE 1N4154 25P1V IR IUA SI DIODE RECTIFIER 1N4003 ZENER DIODE 37V IPCT IW DIODE RECTIFIER 1N645 RECT MV16A 1600PI V 50 SI DIODE RECTIFIER 1N4003 DIODE RE
9. 942 526 529 AAA AA AAA AA ADA AA AAAAA FAR A 501 502 32 ELECTRICAL PARTS LIST cont POWER SUPPLY PC BOARD DESCRIPTION TRANSISTOR 2N1305 TRANSISTOR 2N3414 TRANSISTOR 2N3414 TRANSISTOR 2N3414 TRANSISTOR 2N697 TRANSISTOR 2N3414 TRANSISTOR 2N697 TRANSISTOR 2N1305 TRANSISTOR 2N1546 RES COMP 47 5PCT 1 2W RES COMP 3 3K 5PCT 1 2W RES COMP 91 OHM 1 2W RES WW AX LEAD 82 OHM 5 PCT 3W RES COMP 47 OHM 5PCT 1 21 W RES COMP 1 0 K 5PCT 1 2W RES COMP 2 2 K 5PCT 1 2W RES FLM 34 K 1 PCT 1 2W RES COMP 2 2 K 5PCT 1 2W RES COMP 1 0 K 5PCT 1 2W RES COMP 47 K 5PCT 1 2W RES COMP 10 K 5PCT 1 2W RES COMP 47 5PCT 1 2k RES COMP 22 K 5PCT 1 2W RES COMP 18 K 5PCT 1 2W RES COMP 18 K 5PCT 1 2W RES COMP 1 0 K 5PCT 1 2W RES COMP 27 OHM 5PCT 1 2W RES COMP 620 OHM 5PCT 1 2W RES COMP 10 5PCT 1 2W RES COMP 27 5PCT 1 2W RES COMP 3 3 K 5PCT 1 2W RES COMP 270 OHM 5PCT 1 2W TRANSFORMER POWER TRANSFORMER INDUCTOR P N 1538 2751 PART NO 8210 1305 8210 1290 8210 1290 8210 1290 8210 1040 8210 1290 8210 1040 8210 1305 8210 1073 6100 3475 6100 2335 6100 0915 6680 0825 6100 0475 6100 2105 6100 2225 6450 2340 6100 2225 6100 2105 6100 3475 6100 3105 6100 3475 6100 3225 6100 3185 6100 3185 6120 2105 6100 0275 6100 4625 6100 3105 6100 3275 6100 2335 6100 1275 0345 4130 0746 4450 FMC 01295 56289 56289 56289 04713 56289 04713 01295 04713 81349 81349 81
10. IOPCT 0871082Z5D00222J 0811082Z5U00103Z 083 1082Z5D00391J 0871082Z5D00222J 0841087Z5U00223Z 150D105X0035A2 IN4154 IN4154 IN645 IN455 2N3414 2N3414 2N3414 2N3414 2N1303 2N1303 2N3414 2N3414 RCR20G104J RCR20G474J RNO65D60981F 3067P 1 202 NOTE Composition resistors may be replaced by the same value and power rating in 5 carbon film or 1 metal film MAINTENANCE 29 1538 A Strobotac 30 AAA lt lt 9 lt 7 2 lt 79 lt 105 106 107 108 109 110 111 112 113 114 115 116 117 118 120 121 122 123 124 125 126 129 130 131 133 134 201 202 203 204 205 206 207 ELECTRICAL PARTS LIST cont OSCILLATOR PC BOARD RES COMP 24 K OHM 5PCT 1 4W RES COMP 20 K OHM 5PCT 1 2W RES COMP 2 4 K OHM 5PCT 1 2W RES FLM 14 K 1 PCT 12W RES COMP 2 2 K 5PCT 1 2W RES COMP 4 7 5PCT 12W RES FLM 5 9 K 1 PCT 1 2W RES COMP 620 OHM 5PCT 1 2W RES FLM 5 49 K 1 PCT 1 2W POT WW OHM 10 PCT 10T RES COMP 2 0 K OHM 5PCT 1 2W RES COMP 10 K 5PCT 1 2W RES COMP 1 0 5PCT 1 2W RES COMP 1 0 K 5PCT 1 4W RES COMP 43 K OHM 5PCT 1 2W RES COMP 10 K 5PCT 1 2W RES COMP 4 7 K 5PCT 1 2W RES COMP 4 7 K 5PCT 1 4W RES COMP 22 K 5PCT 1 4W RES COMP 2 2 K 5PCT 1 4W RES COMP 10 K 5PCT 1 2W RES COMP 4 7 K 5PCT 1 2W RES COMP 100 5 1 2W RES COMP 100 5 1 2W RES COMP 4 7 5PCT 1 2W RES COMP 22 K 5PCT 1 2W SWI
11. P2 1531 2 1536 1937 1539 1538 4 1 3 4 Accessories Available The accessories listed Table 1 2 are available for use with the stroboscope They are described else where in this book as noted in the table Figure 1 4 shows a typical setup using the strobo scope with the pick off the flash delay and the Stroboslave Table 1 2 Available Accessories for the Type 1538 Stroboscope Name Battery and Charger Extension Lamp Flash Delay Photoelectric Pick off Photoelectric Pick off Stroboslave High Intensity Flash Capacitor Function Offers rechargeable 24 Volt dc battery power option paragraph 2 3 3 Operates up to 6 feet from stroboscope paragraph 2 9 Longer cords available on special order Provides continuously adjustable time delay between external trigger pulse and stroboscope flash paragraph 2 10 2 With the Type 1532 P2 Flash Delay and the stroboscope permits analysis of motion of objects rotating at relatively steady speeds paragraph 2 10 2 Similar to Type 1536 Pick off but with no light source paragraph 2 10 3 A small stroboscope without internal os cillator paragraph 2 10 6 Increases light output 10 times for single flash photographic applications paragraph ZANT INTRODUCTION 1538 A Strobotac vr 22 E cM P E agi eo E m ZO ty Figure 1 3 The 1538 powered by the Type 1538 P3 B
12. Screwdriver control through panel 2 position toggle switch Neon lamp Phone jack Phone jack 1 2 inch pin 3 16 inch diameter 1538 A Strobotac Function Can be rotated to aim the light beam Provides a panel connection for the Type 1538 P2 Extension Lamp or the Type 1538 P4 High Intensity Flash Capacitor Accepts the power cable from the power line or from the Type 1538 P3 Battery and Charger Turns instrument ON or OFF Selects any of the four RPM ranges or the CAL range Calibrates the low end of Sets the frequency of the in ternal oscillator It is cali brated directly in revolutions per minute Calibrates the high end of the RPM dial Selects a signal from either the internal generator or one applied externally at the IN PUT jack Its flashing indicates the correct setting of the CAL potentiometers for calibration of the RPM dial Connects the stroboscope to an external synchronizing signal from either an electrical device or a mechanical contactor to paragraph 2 10 1 Trigger pulse 15 available at this jack for triggering accessory instruments refer to paragraph 2 10 8 Serves as a holding device for the ac power cable plug when the instrument 15 not in use refer to paragraph 2 2 1538 Strobotac 1 3 3 Accessories Supplied Supplied with the stroboscope are 42770 1100 Phone plug for INPUT or OUTPUT jack 1538 0420 Ac power cable No 1538 P3 1538
13. 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 c s 16 W Accessories Supplied Phone plug for input Accessories Available Type 1537 A Photoelectric Pickoff Type 1531 P2 Flash Delay with a Type 1536 A Photoelectric Pickoff Mechanical Data Shipping Weight in mm n mm in mm b kg lb kg PL owls ow fabs Dr 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 can be used for visual ob servation and analysis of repetitive motion whose period is not constant The flash delay also provides means for precise synchronization of camera shutter stroboscopic flash and objects moving at irregular speeds for high speed photography or other purposes Appendix SPECIFICATIONS Time Delay Range Approximately 100 ms to 0 8 ms in three ranges Output Pulse gt 13 V available for triggering the Type 1531 A and 1538 A Strobotac electronic strobo scopes and the Type 1539 A Stroboslave Sensitivity As little as 0 3V input will produce suf ficient output to trigger the stroboscope Input Phone jack for triggering jack for camera synchronization Accessories Available Type 1536 A Pho
14. instru ment proceed as follows a Set the range switch knob to the 4000 25000 RPM position b Turn the reflector down against the panel facing up c Push the 4 prong socket at one end of the ac power cable onto the panel power plug and wind the cable in a counterclockwise direction around the range switch bar knob and the reflector d To secure the cable end slide the 3 wire plug onto the 1 2 inch pin on the panel e To complete the closing of the case push down slightly on the handle of the case with one hand and with the Other swing the instrument so that the panel is facing down Lower the instrument onto the rubber gasket by slowly releasing the handle Apply light pres sure on the top of the case and slide the two gray latch blocks toward the handle to lock the case 2 3 Power Requirements 2 3 1 Power Line Operation The Type 1538 Strobotac electronic stroboscope can be operated from a 115 or 230 Volt 50 to 60 Hz or 400 Hz line as well as from a 24 Volt de supply For line operation one end of the ac power cable P N 1538 0420 mates with the 4 prong plug labelled 115 V 50 60 Hz 24 VDC on the panel and is locked place by the two attached clips To unlock the clips squeeze them toward each other with thumb and fore finger The input line voltage for which the instrument 15 wired is noted on the panel directly above the power plug To change from 115 Volt to 230 Volt operation re move the two ju
15. not large If this beam width is not adequate to light the subject the reflec tor can be easily removed and the bare lamp used to illuminate the area 2 11 4 Spectral Characteristics The spectral distribution of the flash of the Strobotac shown in Figure 2 8 15 excellent for photography with both orthochromatic and panchromatic films Equivalent color temperature ofthe flash is about 6500 to 7000 degrees Kelvin 1 5 HE al _ RELATIVE LIGHT OUTPUT SPECTRAL IRRADIANCE 6 LAMP Energy Allah 0 25 Joule Dis o ETT alit width 20 mis I m 0 500 400 500 600 TOO imp Figure 2 8 Spectral distribution of the Strobotron s light output OPERATION 2 11 5 Exposure Data Figure 2 9 can be used to determine the guide num ber for a given film speed when the Type 1538 Strobotac or Type 1539 Stroboslave is used To determine the effective lens aperture f setting divide the guide number by the stroboscope to sub ject distance in feet plus 1 5 refer to para graph 2 11 3 The guide numbers are given rather than the watt second ratings because the latter cannot be used to determine the subject illumination without a full knowl edge of the reflector characteristics and the tube ef ficiency Tes 1538 1839 P 10 690 RANGE TYPES 1538 1539 670 4 70 RANGE E 112 ani 7771 TYPES 153 1539 4000 25 00
16. of the dial The flashes of a neon light on the panel serve as an indicator for calibration ES n9 Figure 1 1 The stroboscope can be mounted on a standard camera tripod The strobotron lamp is mounted on a swivel arm and the reflector can be rotated about the lamp which makes it possible to aim the light beam in almost any direction The high intensity lamp provides adequate illumination for most objects even in normal ambient light When not in use the detachable ac power cable 15 wound around the reflector and the range switch knob refer to paragraph 2 2 1 3 2 Controls and Connectors controls and connectors are located on the front panel of the instrument see Figure 1 3 The type and function of each are given in Table 1 1 a Figure 1 2 The front panel of the stroboscope showing the controls and connectors INTRODUCTION Figure 1 3 Reference 1 10 12 refer 13 14 INTRODUCTION Name None EXT LAMP 115 V 50 60 Hz 24 VDC POWER ON OFF RPM range switch LOW CAL control through panel RPM dial HIGH CAL FLASH CONTROL EXTERNAL INTERNAL CALIBRATE INPUT OUTPUT None Table 1 1 Controls Connectors and Indicators Type Reflector and swivel arm of Strobotron lamp assembly 4 prong socket 4 prong plug 2 position toggle switch 5 position rotary switch Screwdriver the RPM dial 4 inch dial with fluted rim
17. ofa an 13 DMO SUODOSIdVC htt gh an DE 13 2 10 5 Uso Multiples StroDOSCODES eile be 13 2 10 6 Connecting the Accessory Instruments xis e n t Pec tends 13 Photography uui ia Seca iter LAM 14 PN EG HH IA T 14 a 4 2 2 ne etwas ners ioe TTE 14 2 LL Speciral Charactetisues oco a pU 14 ordi ALA T TH 15 2 06 51016 Photography uitio tie te tin d 15 Contents 2 11 7 Type 1538 P4 High Intensity Flash Capacitor 2 2 200 00 2 000000000000000000505550554 15 Section 3 PRINCIPLES OF 17 DM E E AE 17 So MS SURO WOR OM WO doses 17 MET X 17 Sd ME E Ud oS eio desean 19 Section 4 SERVICE AND MAINTENANCHE 20 ud 20 A Instrument
18. predetermined internal pressure This pressure buildup causes distortion of the O ring and creates a path to the atmosphere When pres sure within the cell returns to atmospheric pressure the O ring returns to its original shape and position and reseals the opening THE CHARGER The charger included in the Type 1538 P3 A Battery Source and Charger is a constant current type with microprocessor controller charging and supervision One end of the power line cable 15 permanently at tached to the charger When the battery is fully charged the charger will switch automatically to trickle charge which will con tinue until it is unplugged from the ac line When first received the battery should be charged for about 10 hours completely discharged battery can be charged to 70 of full capacity 10 hours A fully charged battery will power the Type 1538 for about 8 1538 A Strobotac hours of normal intermittent operation after which a 10 hour overnight charge should be adequate to re turn the battery to 100 capacity If the maximum operating time has been approached a full 14 16 hours will be required to recharge the battery to full capac ity With no warm up time required by the Type 1538 the POWER switch should always be turned OFF when the instrument is not in use to conserve the charge Although the life of the battery cells may be some what shortened by continual overcharging in the con stant current mode they can be
19. revolu tion 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 a rate of 1200 times each minute Thus the dot will appear to freeze or stand still Now if the flashing rate of the strobo scope is slowed to 1199 flashes per minute the dot will be illuminated at a slightly different position each time the disc revolves and the dot will appear to move slowly in the direction of ro tation through 360 and arrive back at its original position 3 O clock one minute later A similar movement but in a direction opposite to the rotation of the dot will be observed if the flashing rate of the stroboscope is increased to 1201 rpm If desired the rate of apparent move ment of the dot can be speeded up by further increasing or decreasing the stroboscope flashing rate 1538 Strobotac If the flashing rate of the stroboscope is known this is also the speed of a moving device made to stop under the stroboscope s light Thus the stroboscope has the dual purpose of measuring speed and of ap parently slowing down or stopping rapid motion for observation The practical significance of the slow motion effect 1s that since it 1s a true copy of the high speed motion all irregularities vibration torsion chatter whip present in the high speed motion can be viewed and studied refer to paragraph 2 8 5 1 3 The Type 1538 Strobotac Electronic S
20. the dial hub under the instrument panel d Mount the new dial at the approximate setting noted in step c Tighten one setscrew in the dial hub CAUTION The dial should not rub against the panel when ro tated allow a minimum clearance of 1 16 inch e Rotate the dial from the limit stop in one direction to the limit stop in the other direction Note the dis tance between the red marker and each end of the 4000 25000 RPM scale The ends ofthe scale should travel approximately 1 4 inch beyond the red marker Adjust the dial until the red marker is equidistant from each end of the scale f Tighten both setscrews in the dial hub g Mount the Scale Mask Assembly paragraph 4 6 4 steps c and d and remount the instrument in the case h Calibrate the stroboscope before making speed measurements MAINTENANCE 1538 A Strobotac COVER ASSEMBLY CABINET Figure 4 11 Name and location of parts included in the IET Flip Tilt Case refer to table 4 1 Table 4 1 Part numbers for the flip tilt case IET Name Part No Cabinet 1538 1080 Spacer 4170 0900 Pivot Stud 4170 1267 Screw 7080 0800 Handle Assembly 1538 2040 Cover Assembly 1538 2049 Screw 7080 0800 Washer 8050 1500 Mounting Plate 7860 1880 Inst Plate Stud 4170 1200 Slide 4170 1271 Handle 5360 5881 Mounting Plate 7864 8010 Nameplate Washer 8140 0102 Slide Washer 4170 7030 NOTE Tighten 10 32 screws to 20 25 in lbs torque Bend mounting plate to give 1 3
21. the neon CALIBRATE lamp stops or nearly stops The lamp may remain on off or barely on but it should not be changing The longer the time required for the lamp to complete one cycle from on to off then on again the closer the setting of the potentiometer is to an exact calibra tion For example if the CALIBRATE lamp takes two seconds to complete one full cycle with the RPM dial set at 3600 the error the dial calibration 15 3600 rpm 60 cycles sec x 2 sec cycle rpm NOTE Do not confuse the characteristic flicker on low ranges with the on off action referred to here When the CAL setting 15 very close to the power line frequency the CAL lamp will vary in inten sity very slowly e Set the RPM dial to 900 and repeat step d using the LOW CAL screwdriver adjustment on the front panel On this range for example a two second flash ing period of the CALIBRATE lamp represents an error of 900 rpm 60 cycles sec x 2 sec cycle IIR f Return the RPM dial to 3600 and repeat the pro cedure of step d until the CALIBRATE lamp is flash ing very slowly or not at all This step 1s not neces sary unless the LOW CAL adjustment was changed significantly In general it is not necessary to return to the 900 RPM point to repeat the procedure unless a very pre cise calibration 15 required The RPM dial is now cali brated to within 1 percent on all ranges 3000 if 50 Hz line is used
22. 0 108 000 90 000 72 000 60 000 45 000 36 000 30 000 Submultiples of Number of Fundamental Speed Images 180 000 rpm Assumed Produced 1 5 4 3 2 3 1 2 1 1 1 1 2 8 3 Measurement of Speeds above 150 000 RPM By means of submultiple synchronization speeds up to about 1 million rpm can be measured accurately with the stroboscope The procedure is as follows a Starting at 150 000 rpm decrease the flashing rate OPERATION of the stroboscope by turning the RPM dial clock wise until a single image 15 obtained Record the reading of the RPM dial and call it X b Observe the stroboscopic images as the reading of the RPM dial is slowly decreased Stop when the next single image appears Record the new reading of the RPM dial and call it Y c Calculate the harmonic number n by n XV Round off the value of n to the nearest whole number d Calculate the fundamental speed S by S nX For example if the first single image occurs at X 77 200 rpm and the second single image occurs at Y 58 000 rpm then 58 000 77 200 58 000 Pus n Rounded off to the nearest whole number 3 The fundamental speed is then S 3x 77 200 231 600 rpm There is a nomogram at the end of this section that may be used for this purpose 2 8 4 Low Speed Operation The measurement of speeds on the low range of the instrument below about 600 rpm is complicated by the flicker resulting from the inabi
23. 0 RANGE GUIDE NUMBER gra d ttt 95 Pd Figure 2 9 Guide number vs film speed when either the Type 1538 Strobotoc or the Type 1539 Strobo slave is used 00 000 FILM SPEED ASA 2 11 6 Single Flash Photography With single flash photography the camera shutter is opened the stroboscope 15 flashed once to expose the film and the shutter 1s closed again Single flash pictures taken in this manner have solved many puzzling industrial problems The subject 15 photo graphed in the position it occupies at the instant the stroboscope lamp flashes NOTE Because the first trigger pulse from the oscillator is used to charge the flash capacitor always trigger the stroboscope once or twice before actually taking a single flash photograph The capacitor will then be charged ready to flash the lamp on all subsequent trigger pulses OPERATION 1538 A Strobotac 2 11 7 Type 1538 P4 High Intensity Flash Capacitor An optional accessory for the Type 1538 Strobotac is the Type 1538 P4 High Intensity Flash Capacitor Figure 2 10 With this accessory connected a single 8 microsecond flash of 44 million candelas can be obtained Figure 2 10 The Type 1538 P4 High Intensity Flash Capacitor can be used with the Strobotac for short single flashes This is used when a brighter flash 15 needed to photo graph an object moving at an extremely high speed or one in high ambient light The circuit for the Type 1538
24. 2 to 1 16 spacing both sides 27 1538 A Strobotac 28 Figure 4 12 Power supply etched board assembly Complete assembly is P N 1538 2751 NOTE The number appearing on the foil side 15 not the part number The dot on the foil at the transistor socket indicates the collector lead Figure 4 13 Oscillator etched board assembly Complete assembly in P N 1538 2710 Figure 4 14 Switch circuit etched board assembly Complete assembly is P N 1538 2721 NOTE The number appearing on the foil side 1s not the part number The dot on the foil at the transistor socket indicates the collector lead MAINTENANCE REFDES 901 901 901 902 901 901 901 902 901 902 903 901 901 901 902 uuu 101 102 103 104 105 106 107 6 Fe 101 102 103 105 101 102 103 104 105 106 107 108 101 102 103 104 CHASSIS MOUNTED PARTS DESCRIPTION CAPACITOR FUSE SLC BLCK 1 4A 250V PHONE GNC 281L 2 CK T PHONE GNC 281L 2 CK T LAMP BAYONET BASE 28V 04A RECPT JCNES 4 CCNT MALE TRANSISTOR 2N4906 RES COMP 4 3 K OHM 5PCT I 2W SWITCH TOGGLE 2 5 DPCT STEADY SWITCH TOGGLE 2PCS DPST STEADY SWITCH ASM SOCKET MULTIPLE TRANSFORMER ASM LAMP NEON 1539 REPLACEMENT FLASH LAMP OSCILLATOR PC BOARD CAP MYLAR 1UF 10 PCT 100 V CAP CER DISC 2200PF 500 CAP CER DISC 01UF 80 20PCT 500V
25. 349 75042 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 61349 81349 81349 81349 81349 81349 81349 24655 24655 MFGR PART NO 2N1305 2N3414 2N3414 2N3414 2N697 2N3414 2N697 2N1305 2N1546 RCR20G473J RCR20G332J RCR20G910J AS 2 82 OHM 5PCT RCR20G470J RCR20G102J RCR20G222J RN6503402F RCR20G222J RCR20G102J RCR20G473J RCR20G103J RCR20G473J RCR20G223J RCR20G183J RCR20G183J RCR42G102J RCR20G270J RCR20G024J RCR20G103J RCR206273J RCR20G332J RCR20G271J 0345 4130 0746 4450 MAINTENANCE 1538 A Strobotac NOTE The number appearing on the foil side is not Type 1538 P4 High Intensity Flash Capacitor the part number The dot on the foil at the transistor See Figure 2 14 socket indicates the collector lead With the Type 1538 P4 High Intensity Flash Capaci tor connected to the Type 1538 refer to paragraph BATTERY AND 2 11 7 itis possible to produce a single brilliant flash CHARGER of 44 million beam candles with an 8 ms duration This accessory should be used when the object being PHOTOELECTRIC photographed is operating at extremely high speed or PICKOFF uem in unavoidably high ambient light FLASH DEL AY Some of the many accessory instruments available Type 1538 P2 Extension Lamp for use with the stroboscopes The Type 1538 P2 Extension Lamp consists of a lamp and reflector assembly identical to that on the Strobotac with a six foot co
26. 800 times a minute 1 e a stroboscope Since the time between flashes is the time it takes the fan to make one revolution every time the light flashes the fan blades are exactly where they were the pre vious time The blades are never seen in any other position thus it appears that the fan isn t moving at all The retina of the eye holds one image until the next flash so there is little if any flicker Ifthe light is switched on and off 1801 times a minute with the fan still turning at 1800 rpm it is flashing faster than the fan is turning Therefore each time the light comes on the fan blades have not quite reached the position they were in the previous time the light was on The fan is seen at progressively earlier parts of its cycle and therefore it appears to be turning very slowly back ward In like manner if the light flashes 1799 times a minute it shows the fan blade at successively later parts of its cycle so that the fan appears to be mov ing very slowly forward INTRODUCTION 1538 A Strobotac The following example illustrates this principle A white disc with a single black dot 15 mounted on the shaft of a 1200 rpm motor When the disc is rotating at 1200 rpm it is impossible for the human eye to distinguish a single image and the dot appears to be a blurred continuous circle When the disc is illuminated by the flashing Strobotac light which is syn chronized to flash once every
27. CTIFIER 1N4003 DIODE RECTIFIER 1N4003 DIODE RECTIFIER 1N4003 ZENER IN965B 15 ZENER IN748A 3 9V SPCT 4W CHOKE MOLDED 1 8 UH 10PCT P N 1538 2721 7890 3940 24655 P N 1538 2731 4450 5591 6081 1001 6081 1001 6081 1001 6081 1001 6081 1001 6082 1016 8210 1540 8210 1019 6100 2105 6100 2165 6100 3475 6760 9309 24655 14433 14433 14433 14433 14433 14433 04713 01295 81349 81349 81349 75042 P N 1538 2751 4860 8285 4510 4001 4406 2228 4510 4000 4404 1225 4405 2105 4450 5606 4403 4100 56289 56289 72982 56289 72982 72982 56289 72982 P N 1538 2751 PART NO 6082 1016 6082 1012 6081 1001 6083 1110 6082 1016 6081 1015 6081 1001 6081 1001 6081 1001 6081 1001 6083 1015 6083 1002 4300 1100 FMC 14433 14433 14433 24655 14433 13327 14433 14433 14433 14433 14433 14433 99800 1538 A Strobotac 7890 3940 4450 5591 IN4003 IN4003 IN4003 IN4003 IN4003 IN645 2N1540 2N1303 RCR20G102J RCR20G182J RCR20G473J SWH OHM IOPCT 410P 1 30 UF IPCT 416P22356 0871082Z5000222J 416P22396 083 1082Z5D00221J 0801082Z5D00102J 60D 75V 8131M100651104Z MFGR PART NO IN645 IN4154 14003 6083 1110 14645 MVILA IN4003 134003 14003 134003 139658 IN748A 1537 18 31 1538 A Strobotac REFDES 501 502 503 504 506 507 508 509 510 501 502 503 504 505 506 507 508 509 510 512 513 514 515 518 519 520 521 522 523
28. IGH VOLTAGES MAY BE PRESENT AT THE TERMINALS OF THIS INSTRUMENT WHENEVER HAZARDOUS VOLTAGES 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 N CAUTION N 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 Section 1 INTRODUCTION eec Ec 1 General DescripHomot Stl DOSCODe 2 ocio caches ate aC Mate Ue 1 1 1 1 3 The Type 1538 5000018069 Electronic Stroboscope 200001 2550 2 1 94 General ON dicto ntu ca de 2 3 2 Controls and CONMCC LOTS ar E SF Morgen z ACCESSES SUC wa 4 3 4 Aecessories AVallable ac ab es 4 Section 2 OPERATING PROCEDURE tni iit nti Eee iE ot Lai 6 2 FOpenino EE m 6 ehe aged
29. P4 Capacitor 15 given in Figure 2 11 To attach the Capacitor to the stroboscope open the Flip Tilt cabinet fully as shown in the lower right hand view of Figure 1 1 Place the Type 1538 on its side Attach the Capacitor to the base section ofthe Flip Tilt cabi net To do this line up the screw in the center of the capacitor with the tripod mounting hole in the bottom ofthe Flip Tilt cabinet Tighten the screw locking the capacitor in place Set the stroboscope upright and plug the cable into the 4 prong socket marked EXT LAMB on the panel of the stroboscope as in Figure 2 12 The assembly is now ready for single flash opera tion The maximum flashing rate with the combina tion 15 60 flashes per minute The Capacitor is auto matically discharged when the 4 prong plug in the EXT LAMP socket is removed The Capacitor can also be discharged by changing the setting of the RPM range switch Guide numbers for various film speeds when the Capacitor is used with the strobo scope are given in Figure 2 9 The reader should note the instructions paragraph 2 11 6 for single flash photography The Type 1538 P4 High intensity Flash Capacitor and the Type 1538 P2 Extension Lamp cannot be used simultaneously with the stroboscope 15 1538 A Strobotac 16 SHIELD Figure 2 11 Circuit of type 1538 P4 High Intensity Flash Capacitor NOMOGRAM FOR USE IN MEASURING SPEEDS BEYOND THE FLASHING RATE OF THE TYPE 1538 STROBOTAC The nomogra
30. TCH CIRCUIT PC BOARD DESCRIPTION CAP MYLAR 1 09 UF PCT 100V CAP MYLAR 0 182 UF PCT 100V CAP MYLAR 0 0301UF 1 PCT 100V CAP MICA 4320 PF IPCT 300V CAPACITOR CAPACITOR CAPACITOR POT COMP TRM 50 K OHM 20 PCT IST RES COMP 24 K OHM 5PCT 1 2W D POT COMP TRM 50K OHM 20 PCT IST POT COMP TRM 50K OHM 20 PCT IST RES COMP 10 5PCT 1 2W RES COMP 4 7 K 5PCT 1 2W RES FLM 464 K 1 PCT 1 2W P N 1538 2710 6099 3245 6100 3205 6100 2245 6450 2140 6100 2225 6100 2475 6450 1590 6100 1625 6450 1549 6059 2105 6100 2205 6100 3105 6100 2105 6099 2105 6100 3435 6130 3105 6100 2475 6099 2475 6099 3225 6099 2225 6100 3105 6100 2475 6100 4105 6100 4105 6100 2475 6100 3225 81349 61349 81349 61349 81349 81349 81349 81349 81349 80294 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 81349 RCR07G243J RCR20G203J RCR20G242J RN6501402F RCR20G222J RCR20G472J RN65D5901F RCR20G021J RN65D5491F 3067P 1 102 RCR20G202J RCR20G103J RCR20C102J RCRO7G102J RCR20G433J RCR20G103J RCR20G472J RCR07G472J RCR07G223J RCR07G222J RCR20G103J RCR20G472J RCR20G104J RCR20G104J RCP20G472J RCP20G223J P N 1538 2721 PART NO 4860 8010 4860 7905 4860 7842 4600 1350 1531 4020 1531 0470 1538 0441 6001 3509 6100 3245 6001 3509 6001 3509 6100 3105 6100 2475 6450 3464 562069 56289 56289 72136 24655 24655 24655 80294 81349 80294 80294 81349 81349
31. at an integral sub multiple of the speed of the rotating object under ob servation such as 1 2 1 3 1 4 1 n the motion of the object will be stopped showing a single image just as it will at the fundamental speed If speed mea surements are being made it is necessary to deter mine whether the stroboscope is flashing at a sub multiple rate or at the fundamental rate as described in paragraph 2 8 1 Where convenient switching to a lower range with its submultiple flashing rate approximately 1 6 of the fundamental frequency will often prove helpful be cause of the brighter image obtainable Submultiple flashing 15 necessary to observe or mea sure the speed of objects moving at rates above 150 000 rpm Refer to paragraph 2 8 3 for the method of determining the fundamental speed when submul tiple operation is necessary At flashing rates between integral submultiples mul tiple images will be observed Table 2 1 gives some examples of submultiple speeds and the correspond ing number of images produced for a fundamental speed of 180 000 rpm Note the numerical relation ship between the numerator of the submultiple frac tion and the number of images This relationship is true for all submultiple speeds Table 2 1 Relationship between submultiple speed settings and number of images produced for a fundamental speed of 180 000 rpm Reading of Range Switch RPM Dial T80 000 150 000 144 000 135 000 120 00
32. attery pack offers a precise bright stroboscope capability completely independent of the ac power line A unique advantage in use with large machine complexes such as found in textile and printing industries The battery pack can power the Strobe for up to 8 hours of intermittent use INTRODUCTION 5 1538 A Strobotac Section 2 OPERATING PROCEDURE 2 1 Opening the Case To open the Flip Tilt case a Set the instrument on a flat surface so that it rests on its rubber feet b Unlock the case by sliding the two gray latch blocks one on each side of the case away from the handle It may be necessary to push down on the top of the instrument to release the latch blocks 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 at any angle from vertical to about 30 by its friction against the gasket However the case 15 not locked in place and it may not stay in a tilted position under severe vibra tion If the instrument is to be hand held nestle the case into the cover and lock it in by sliding the latch blocks toward the handle d Disengage the 3 terminal ac power cable plug and unwind the cable from around the range switch bar knob and the reflector 2 2 Closing the Case To close the case for storage or transit of the
33. con light activated switch The output from this transducer will directly trigger the Type 1538 Strobotac or the Type 1539 Stroboslave SPECIFICATIONS Operating Rate Greater than 2500 pulses s Power Required 3 to 25 V dc 0 to 100 mA de pending on operating rate Power 1s 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 in magnet both supplied Net Weight 1 Ib 0 7 kg Shipping Weight 4 lb 2 1 kg 35
34. d 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 mode 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 a few examples of the many slow motion studies that are possible with the Type 1538 2 9 Type 1538 P2 Extension Lamp For use in spaces too small for the complete strobo scope the Type 1538 P2 Extension Lamp Figure 2 4 is aconvenient accessory The lamp and reflec tor in this assembly are identical to those on the Strobotac The assembly is supplied with a six foot cord and a plug that mates with the panel socket marked EXT LAMP When plugged in the Exten sion Lamp flashes instead of the lamp on the strobo scope This accessory makes it possible to mount the lamp in small out of the way places such as test cham bers and to control it from a safe distance Additional cable up to 50 feet long can be used with the Extension Lamp The cable and connectors are available from Labs Inc However when addi tional cable is used the peak intensity of the flash decreases For instance with a 25 foot cable the peak light output is reduced to one fourth of its o
35. dingly longer time 1s avail able in which to recharge the capacitor BO VOLTS ISO 5 TIME gt Figure 3 4 The voltage buildup on the charging capacitor is in small steps Principle of Operation 1538 A Strobotac 3 4 The Calibration Circuit To calibrate the RPM dial against the power line fre quency voltages at both the power line and the flash ing rate frequencies are superimposed across a neon lamp V901 When the flashing rate equals the power line frequency or a submultiple of it the volt age across the lamp remains constant and the lamp is in a condition of steady intensity Depending upon the phase relationship between the strobotron flashing rate and the power line frequency the steady intensity condition of the neon lamp may be maximum inten sity or zero intensity If the flashing rate of the stro botron differs from the power line frequency the av erage voltage across the neon lamp will vary and the intensity will change at the difference frequency 19 1538 A Strobotac 4 6 Replacement of Mechanical Parts 4 6 1 General Although the stroboscope 15 designed especially for use in manufacturing testing and other areas where the working environment is often unsuitable for pre cision electronic instruments certain mechanical parts mounted on the outside of the instrument case may eventually become contaminated or damaged To re place these parts see Figure 4 9 refer to
36. e 4 12 Power supply etched board assembly Complete assembly is P N 1538 2751 28 Figure 4 13 Oscillator etched board assembly Complete assembly in P N 1538 2710 28 Figure 4 14 Switch circuit etched board assembly Complete assembly is P N 1538 2721 28 Some of the many accessory instruments available for use with the stroboscopes 33 153927 5troboslaye ald DUO quii D 34 Type 1531 P2 Flash Delay and SpeclHaLIOTS order te veg apap esse nip 34 Type 1536 A Photoelectric Pickoff and Specifications 021 040 0 0 060000000000000000000000002200000 0 35 Type 1537 A Photoelectric Pickoff and Specifications 35 Section 1 INTRODUCTION NOTE The IET Handbook of Stroboscopy describes in detail many stroboscopic techniques and applications 1 General Description of a Stroboscope 1 1 Whatitis A stroboscope 15 a source of flashing light that can be synchronized with any fast repeating motion so that arapidly moving device seems to stand still or to move slowly 1 2 How it works To understand how the stroboscope stops or slows down motion consider a fan rotating at 1800 revolu tions per minute and a light that is switched on and off 1
37. e standard phone plug supplied Starting at the fully clockwise position adjust the RPM dial until satisfactory synchronization is obtained For large amplitude inputs there will be a wide range of settings for the RPM dial at which the instrument will operate satisfactorily For small amplitude inputs the range will be correspondingly smaller 2 10 2 Type 1531 P2 Flash Delay and type 1536 Photoelectric Pick off Two very useful accessories for the stroboscope are the Type 1531 P2 Flash Delay and the Type 1536 Photoelectric Pick off The combination of these three instruments Figure 2 5 makes it possible to synchro nize the flash of the Type 1538 with the moving ob ject at any desired point in the cycle of operation of the object These synchronizing devices can operate at very high speeds and do not load the machine un der observation The Type 1531 P2 Flash Delay is a small portable time delay unit used to insert a controlled delay pe riod between an externally generated trigger pulse and the resulting light flash from the stroboscope The flash delay also provides a convenient method of ob taining single flash photographs at any desired point in the cycle of the moving object The Type 1536 Photoelectric Pick off is used to con vert the motion of an object to electrical impulses that can be applied to the stroboscope It consists of a light source a simple cylindrical optical system and a photocell Variations in reflectivit
38. ed If the fundamental speed of the device be ing measured is above 75 000 rpm it is not possible to check for the correct speed setting by this method In this case refer to paragraph 2 8 3 1538 A Strobotac 10 Gear not marked for speed measure ment Simple observation is possible but observer cannot be certain if im age is single or multiple single image observed with tape ap plied to one tooth of gear Multiple double image observed with tape applied to one tooth of gear Im ages are 180 apart Stroboscope is flashing twice in one revolution of the gear Multiple triple image observed with tape applied to one tooth of gear Im ages are 120 apart Stroboscope 15 flashing three times one revolution of the gear Figure 2 3 Stroboscopic images produced by a rotating gear NOTE Multiple images will always be observed when the flashing rate of the stroboscope 15 set to a multiple of the fundamental speed of the object As the flashing rate is reduced from a rate higher than the funda mental speed of the object the first single image will appear when the flashing rate is equal to the funda mental speed Make the quick check described above to be sure that the first single image has not been missed 2 8 2 Submultiple Speed Measurements When the flashing rate is below the fundamental speed of the object single and multiple images will be ob served If the stroboscope flashes
39. et and leads X Y Z are as shown in the figure f Insert leads X Y Z through the slot between screws B and hold the swivel support assembly in position between the two pivot blocks Slide the pivot blocks together and tighten nuts A The pivot action ofthe swivel support assembly may need readjustment 1f so loosen either nut A adjust the corresponding pivot block and retighten the unit g Solder leads X Y Z to the terminals as shown Figure 4 10 Interior view showing mounting of the swivel support assembly pivot blocks and connections MAINTENANCE 4 6 4 Scale Mask Assembly To replace the Scale Mask Assembly a Set the range switch to the 4000 25000 RPM position b Loosen the two setscrews in the Scale Mask As sembly hub and remove the assembly from the range switch shaft c Mount the new Scale Mask Assembly on the shaft and center the 4000 25000 RPM window in the dial over the white panel segment beneath the dial d Tighten both setscrews securely 4 6 5 Dial To replace the Dial a Remove the instrument from the case Heed the warning of paragraph 4 4 3 to prevent contact with 800 volts b Setthe range switch to the 4000 25000 RPM posi tion and remove the Scale Mask Assembly refer to paragraph 4 6 4 steps a and b c Note the approximate dial setting and remove the dial from the potentiometer shaft without turning the shaft To remove the dial loosen the two setscrews in
40. he circuit for dc operation but protection 15 maintained by the 1 fuse mounted on the bat tery case The Type 1538 cannot be calibrated when operating on dc power Calibration on ac refer to paragraph 2 7 1s valid for both ac and dc operation and will hold for a long period of time OPERATION 1538 A Strobotac 2 3 3 Type 1538 P3 A Battery Source and Charger The Type 1538 P3 A Battery and Charger is avail able as an optional accessory for the Type 1538 stro boscope It includes a rechargeable nickel cadmium battery and an automatic battery charger mounted together in a carrying case The battery cable 15 per manently attached to the unit For battery operation simply mate the four contact connector on the end of the output cable with the 4 prong plug labelled 115 V 50 60 Hz 24 Vdc on the panel of the stroboscope The cable 15 locked to the panel by the two clips on the connector to remove the cable press the clips toward each other with thumb and forefinger To charge the battery plug the unit s power cord into the AC line The 1538 P3 can be ordered or modified for 220 V operation in the same manner as the 1538 THE BATTERY The battery consists of 20 sealed cylindrical Ni Cd cells which supply 24 volts at 2 3 ampere hours The cells incorporate a resealing safety vent mechanism that will not open during normal battery usage but should excessive gas pressure build up within the cell the vent opens at a
41. igh speed photography applications and motion studies other than tachometry The Stroboslave will flash upon closure of external contacts or upon reception of a 2 volt positive pulse at its panel INPUT jack It will operate directly from the OUTPUT jack of the Type 1538 Strobotac The lamp and reflector of the Stroboslave are connected to the unit by a five foot flexible cable to permit posi tioning the lamp close to the moving object Operat ing over a range of 0 to 25 000 flashes per minute the Type 1539 produces a peak light intensity of up to 11 million beam candles on the HIGH intensity range and OPERATION 1538 A Strobotac up to 18 million beam candles when used for single flash applications The reader should refer to the In struction Manual for the Type 1539 Stroboslave Com plete specifications are included in the Appendix of this book 2 10 5 Use of Multiples Stroboscopes When a multiple source of flashing light 1s needed several Type 1538 stroboscopes can be connected together A cable from the OUTPUT jack of the first instrument connects to the INPUT jack of another and so on Connected in this manner the stroboscopes will flash at the same time Types 1531 and 1546 Strobotac electronic strobo scopes can be substituted for any of the Type 1538 instruments for this multiple use However a Type 1531 4 Trigger Cable with built in transformer must be used at the OUTPUT of each Type 1531 to prevent overload and p
42. left on trickle charge for an indefinite period The cell life of the battery 1s reduced by repeated complete or nearly complete dis charging of the battery or by severe overcharging Under average operating conditions the number of charge discharge cycles may exceed 5000 before replacement of the battery becomes necessary How ever if the battery 1s deeply discharged a cycle life as low as 300 may result If the state of charge of the battery is unknown recharge it for ten hours Con tinuous trickle charging will maintain 100 capacity of the battery during prolonged storage periods The battery will discharge with time if trickle charging 1s not used the rate of discharge depends on the stor age temperature as shown in Figure 2 2 20 40 50 60 TO 90 100 10 20 Figure 2 2 Typical charge retention characteristics of the battery 2 4 Turning the Instrument On After connecting the power cable to the power line or connecting the 1538 P3 to the instrument pivot the reflector assembly to an upright position and turn the POWER switch ON The stroboscope is ready for use immediately 2 5 Positioning the Stroboscope The light beam can be aimed in almost any direction by means of the swivel arm and the rotating reflector 1 Figure 1 2 The intensity of the light pulse 15 so high and the beam angle 1s so small that it 1s usually not necessary to place the unit close to the object being viewed If the ins
43. lity of the eye to carry over the image from one flash to the next Such measurements should be made in a darkened envi ronment to reduce the disconcerting effect of high ambient room lighting on the observed pattern Dark glasses worn by the operator may prove helpful Speeds below 110 rpm can be measured by means of multiple images For example 11 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 etc This multiple image technique can also be used for higher speeds within the range of the stroboscope where flicker makes it difficult to tell when the cor rect flashing rate is obtained for example between 110 and 600 rpm OPERATION 1538 A Strobotac 2 8 5 Slow Motion Studies High speed motion can be reproduced by the strobo scope at an apparently much lower speed if the cy clic or reciprocating motion occurs at a constant rate If the flashing rate of the stroboscope 15 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 as noted paragraph 1 2 at a speed equal to the difference be tween the actual speed of the object and the flashing rate of the stroboscope If the flashing rate 1s set slightly higher than the speed of the object being ob serve
44. lustrates the problem The curves labeled R C and L C show the effects of charging the capacitor through a resis tor and an inductor respectively The slopes required to keep the voltage below the 80 volt deionization level would impose delays in reaching the firing level which in turn would restrict the maximum flashing rates to 24 000 and 54 000 flashes per minute respectively for the particular tube and voltages used in the Type 1538 The answer to this problem is to hold the volt age at zero for the deionization period and then to raise it quickly to the firing level The new circuit shown in Figure 3 2 provides an al most ideal charging curve labeled 1538 in Figure 3 1 During the 150 microsecond deioniza tion time after the strobotron has flashed the transis tor which acts as a switch 15 saturated and the trans former primary current increases storing energy in the transformer core The voltage induced in the sec ondary winding during this buildup is blocked by the diode rectifier and no voltage appears across the ca pacitor and strobotron tube At the end of this 150 microsecond interval the transistor 1s switched off and the primary current goes to zero The collapsing magnetic field generates a reverse polarity voltage in the secondary causing the diode to conduct and the stored energy to be transferred to the capacitor 17 1538 A Strobotac 18 When the energy in the transformer 15 zero the cu
45. m below can be used to determine quickly the fundamental speed of an object from two succes sive submultiple images X Y 130 120 110 80 To use the nomogram 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 determine the fundamental speed Example Suppose that the first time stopped motion image is obtained at 150 000 rpm the next lower one at 120 000 rpm A line drawn through 150 on the X scale and 120 on the Y scale intersects the n scale at 4 There fore the fundamental speed is 4 x 150 000 or 600 000 rpm 1538 19 OPERATION 1538 A Strobotac Section 3 PRINCIPLES OF OPERATION 3 1 General Ifa cyclically moving object is viewed by a light that is flashing at or near the cyclic rate of the object the latter will appear stationary or in slow motion The optical illusion thus produced depends on the periodic observation of the object If the flashing rate of the light 1s adjusted to produce a stationary image the flashing rate equals the cyclic speed of the moving object The stroboscope 15 essentially a source of flashing light with an adjustable calibrated con
46. mages produced by a rotating gear sse 10 Pigure 2 4 1538 P2 Extension Eambp s ente em sas ete ta vtae 12 Figure 2 5 A widely used combination consists of the stroboscope with the Type 1531 P2 Flash Delay and the Type 15936 PBotoelecttie Prek Oi sexo e Meo Rede dos Ste pi aa 13 Figure 2 6 Some of the many possible combinations of the Type 1538 Strobotac electronic Stroboscope and its accessory ooo PX EM RR MM M EM 13 Figure 2 8 Spectral distribution of the Strobotron s light output 2 40 2 042 02 000000000005000 5055244 14 Figure 2 7 Plot of light intensity vs time of the 1538 400 00022200000 0000098 14 Figure 2 10 The 1538 4 High Intensity Flash Capacitor can be used with the Strobotac for short single PNAS NCS 15 Figure 2 11 Circuit of type 1538 4 High Intensity Flash 2 1 11 1000000040000 0 16 Figure 3 1 Voltage vs time characteristics of various charging circuits 18 Figure 3 2 Charging circuit of the Type 1538 Strobotac electronic stroboscope
47. mpers on transformer T501 between terminals 1 and 3 and terminals 2 and 4 and add a jumper between terminals 2 and 3 see Figure 2 1 Replace the AC Power Plug with the correct plug for your location A 0 25 ampere fuse is used for either line voltage To indicate a change to 230 volt opera tion order an input power plate P N 1538 8110 from IET Labs This plate marked 230 V 50 60 Hz 24 VDC can be cemented onto the panel over the 115 V marking OPERATION change the instrument from 230 to 115 volt op eration remove the jumper on transformer T501 be tween terminals 2 and 3 and add jumpers between terminals 1 and 3 and terminals 2 and 4 see Figure 2 1 Always be sure the power to be applied corresponds with the panel marking above the panel power plug The male end of the power cable has three terminals The third pin ground on the power plug has been added for the safety of the operator it should not be disconnected If a 2 way adaptor must be used be sure the instrument 15 properly grounded Figure 2 1 The transformer terminals on the stroboscope are numbered as shown 2 3 2 Battery Operation The stroboscope will also operate on 24 volts dc The Type 1538 P3 Battery and Charger 15 recommended for this type of operation see paragraph 2 3 3 The dc power also is applied at the 4 prong plug on the panel and is controlled by the ON OFF POWER switch The 0 25 ampere fuse in the stroboscope 15 not in t
48. ossible damage to the input circuitry ofthe 1538 and 1546 units 2 10 6 Connecting the Accessory Instruments Figure 2 6 shows the Type 1538 Strobotac electronic stroboscope and the connections for some ofthe many possible combinations of accessory instruments EXTENSION LAMP 4 EE TYPE 1539 A DJ STROBOSLAVE 0 5 2 VOLTS 1537 PHOTOELECTRIC TYPE 1538 P4 CKOFF TYPE 1536 A PHOTOELECTRIC 153i P4 Wr TYPE 1531 2 FLASH DELAY 15 OR 1538 0 Tu ELECTRONIC SCOPE 115 OR 230 VOLTS 1531 m STROBOTAC ELECTRONIC 1538 P3 T BATTERY AND CHARGER Figure 2 6 Some of the many possible combinations of the Type 1538 Strobotac electronic Stroboscope and its accessory instruments 13 1538 A Strobotac 14 2 11 High Speed Photography 2 11 1 General The short duration of the flash of light from a strobo scope makes it ideal for high speed photography ap plications To control the exposure time the camera shutter can be left open and the light turned on and off very quickly With the use of convenient controls for triggering such as a photocell or microphone the Type 1538 can be used for single flash or can be set to flash at a given rate for multiple exposures The peak flash intensity of the Strobotac varies with the flashing rate from about 200 000 candela at the high est flash rate to several million candela at low speed
49. r rent again reverses and the diode appears as an open circuit leaving all the stored energy in the capacitor This transfer can be made as fast as one wishes and the flashing rate can therefore be made to approach the theoretical maximum 800 IDEAL TYPE L C R C 538 0 ju gt 80 0 0 150 us 1000 us 2000 5 Figure 3 1 Voltage vs time characteristics of various charging circuits Figure 3 2 Charging circuit of the Type 1538 Strobotac electronic stroboscope The transfer of energy from the power supply to the intermediate storage inductor and then resonantly to the discharge capacitor can be made with an effi ciency approaching 100 In the conventional RC charging circuit however half of the available en ergy 15 dissipated in the charging resistor regardless ofthe value ofthe resistor including zero ohms The use of inductive charging saves the power ordinarily dissipated in the charging resistor and reduces power requirements so that battery operation 1s practical Moreover the use of a transformer as the inductive element permits the use of a low voltage transistor circuit to generate the high voltage required by the strobotron tube A block diagram of the complete cir cuit is shown in Figure 3 3 A transistorized RC oscil lator sets the flashing rate of the stroboscope Once each cycle a transistor trigger circuit generates a 5 kilovolt 5 us pulse to trigger the strobotron tube In
50. rd and plug This light weight lamp assembly makes a convenient accessory for observing the motion of object in those hard to reach places The reflector is identical to that of the 1538 Strobotac The entire assembly excluding the connecting cable is 7 inches 180 mm long its weight including the cord is 8 ounces 0 3 kg Custom cables of any length can be ordered MAINTENANCE 33 1538 A Strobotac 34 APPENDIX Type 1539 A Stroboslave The Type 1539 Stroboslave 15 an auxiliary light source that will produce a flashing light with output charac teristics that are similar to the Type 1531 Strobotac This compact stroboscope will flash on command when triggered from a contact closure or from a va riety of equipment including the Type 1531 orthe Type 1538 Strobotacs X S gt SPECIFICATIONS Flashing Rate Ranges 0 to 700 0 to 400 0 to 25 000 flashes per min on high medium and low intensity ranges respectively Flash Duration Approx 0 8 1 2 and 3ms 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 million beam candles 0 6 3 5 and 11 X 10 lux mea 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
51. riginal value the flash duration is doubled and the total light output is reduced to one half 11 1538 A Strobotac 12 NOTE The Type 1538 P2 Extension Lamp and the Type 1538 P4 High Intensity Flash Capacitor cannot be used simultaneously Figure 2 4 Type 1538 P2 Extension Lamp 2 10 External Synchronization 2 10 1 Use of the Input Jack The instrument can be triggered by any electrical sig nal of at least 1 volt peak to peak to a maximum of 10 volts rms applied at the INPUT jack For sine wave inputs the unit will operate with a 0 35 volt rms signal down to 100 Hz Below this frequency the re quired amplitude increases to 3 5 volts at 5 Hz For pulse inputs 1 e step wavefront signals the repeti tion rate can have any minimum value The instru ment can be synchronized with external signals at fre quencies up to at least 150 000 rpm 2 5 kHz Be cause a positive going signal is required at the input to flash the stroboscope positive pulses are required to synchronize on the leading edge Negative pulses will result in a delay depending on the trailing edge characteristics of the input pulse To operate the stroboscope from an external electri cal signal set the RPM range switch so that the fre quency ofthe driving signal d does not exceed the maximum frequency indicated on the range mask Set the FLASH CONTROL switch to EXTERNAL Connect the external signal to the INPUT jack on the panel use th
52. s When it is desirable even greater single flash light intensity to 44 million candela can be obtained by addition of the Type 1538 P4 High Intensity Flash Capacitor an optional accessory that plugs directly into the Type 1538 Strobotac referto paragraph 2 11 7 2 11 2 Flash Duration The duration of the stroboscope flash can vary from 0 5 to 8 microseconds depending on the flash rate range setting refer to Table 2 2 Table 2 2 Flash duration at 1 3 peak intensity for each range of the Type 1538 Strobotac Flash Duration RPM Range Switch Microseconds Settin 110 690 3 670 4 170 1 2 4 000 25 000 0 8 24 000 150 000 0 5 Figure 2 7 shows a plot of light intensity versus dura tion time When the Type 1538 P4 High Intensity Flash Capacitor is used to produce extra bright single flashes duration 1s increased to 8 microseconds Figure 2 7 Plot of light intensity vs time of the Type 1538 Stroboscope 1 PEAK INTENSITY FLASH DURATION 1538 0 5 4 1538w 1538 P4 8 0 0 OUTPUT LIGHT INTENSIT Y PER CENT OF PEAK VALUE 2 11 3 Beam With the standard reflector in position on the Strobotac the light output 1s concentrated 1n a 10 degree beam measured at 1 2 peak intensity points whose apparent source is 18 inches behind the front of the reflector Outside this 10 degree cone the light intensity falls off sharply so that the area of reason ably constant illumination is
53. the fol lowing instructions 4 6 2 Reflector and Cover Remove the old reflector by pulling it off the swivel support assembly Mount the new reflector by sliding it onto the assembly until the spring loaded detent button snaps into the groove inside the reflector base To replace the reflector cover remove the old cover by pushing on the edge at each of the molded in clips that clamp over the rim of the reflector housing the cover will snap off Then mount the new cover by pulling its edge toward the rim of the reflector hous ing until the three clips snap securely into place PIVOT BLOCKS 1531 7110 COVER 2 1531 7120 SPRING 53 CONDE REFLECTOR rv 1 1531 7002 SCALE MASK ASSEMBLY SUPPORT ASSEMBLY 1531 2020 Figure 4 9 Miscellaneous part numbers 26 4 6 3 Swivel Support Assembly Pivot Blocks and Washers To replace the swivel support assembly see Figure 4 10 a Remove the reflector and the strobotron lamp then remove the instrument from its case b Loosen do not remove two nuts A Figure 4 10 and slide the two pivot blocks apart The heads of the two screws B clamp the pivot blocks in position when nuts are tightened c Unsolder the three swivel support assembly leads X Y Z and remove the assembly d The pivot blocks and washers can now be replaced e Position the new swivel support assembly so that the strobotron tube sock
54. the time between these pulses the main discharge capacitor which varies from 0 007 the high range to 1 5 uF on the low range must be recharged to 800 volts The monostable circuit trig gered by the oscillator generates a 200 us pulse that saturates the transistor switch stores energy in the transformer and allows the strobotron to deionize At the end of the 200 us pulse sufficient energy has been stored to resonantly charge the capacitor to 800 volts in an additional 200 us Thus a maximum flashing rate of us or 2500 flashes per second is possible 400 STROBOTRON kV OSCILLATOR GO Figure 3 3 Block diagram of the Type 1538 Strobotac electronic stroboscope The average light output of a stroboscope varies di rectly with flashing rate and discharge capacitance The exceptionally wide flashing rate range of the Type 1538 1500 to 1 would mean a drastic variation in light output if only one discharge capaci tor were used On the other hand a continuously ad justable discharge capacitor with a 1500 to 1 range was obviously impractical The compromise solution was to switch in a different capacitor for each of the four 6 1 speed ranges The resulting capacitance varia tion is 216 to 1 and this raises another design problem Principle of Operation If the discharge capacitor varies in value over a 216 0 1 range then in the resonant charging circuit dis cussed earlier either the ind
55. toelectric Pickoff Power Required 105 to 125 or 210 to 250 V 50 to 400 c s 5 W with Type 1536 A connected Mechanical Data Shipping Weight Ib kg 5 2 3 Type 1536 Photoelectric Pickoff The Type 1536 Photoelectric Pickoff contains a light source an optical system and a photocell that pro duces a pulse when light from a moving object is re flected 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 in struments the motion of objects rotating at irregular speeds can be analyzed visually or by photographic means Appendix 1538 A Strobotac f e SPECIFICATIONS Maximum Pulse Rate Approximately 2500 pulses s as limited by the 200 us time constant of the photo cell and cable combination Power Required 20 to 28 V dc 40 mA Power 15 supplied by the Type 1531 P2 Flash Delay or the Type 1150 B or Type 1151 A Digital Frequency Meter Accessories Supplied 10 ft roll of 3 8 1n 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 1 magnet both supplied Net Weight 1 Ib 0 6 kg Shipping Weight 4 Ib 1 9 kg 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 sili
56. troboscope 1 3 1 General Description Supplementing the basic 1531 Strobotac elec tronic stroboscope 15 the Type 1538 Figure 1 1 In addition to providing a much higher flashing rate than its predecessor the Type 1538 can be operated from an accessory battery pack or from the power line It can be used with the Type 1538 P2 Extension Lamp to illuminate hard to reach areas With the plug in High Intensity Flash Capacitor Type 1538 P4 very short flashes of light of 44 million beam candles can be produced for single flash photography applications The Type 1538 15 a small portable stroboscope housed in a General Radio flip tilt case This case serves as a tilting base when the stroboscope 15 in use and pro tects the instrument during storage and in transit The cover of the case 15 permanently attached to the in strument and the base contains a tripod mounting socket The stroboscope can be held in the hand placed on a convenient flat surface or mounted on a tripod as in Figure 1 1 In the stroboscope the flashing rate of the tube 15 governed by the frequency of an internal generator which is adjusted by means of the RPM controls a bar knob and a large diameter dial The knob selects any of four direct reading RPM ranges the dial 1s concentric with the bar knob and provides precise setting of the flashing rate The screwdriver adjust potentiometers on the panel are used to set the cali bration at the low and high ends
57. trol of flash frequency In most modern stroboscopes the actual flash occurs inside a xenon filled tube The gas is ionized by the rapid discharge of a capacitor The gas must then deionize before the next flash can oc cur This deionizing time sets a limit on the maximum flashing rate If voltage 1s applied across the tube before the gas is deionized continuous conduction known as holdover occurs 3 2 The Strobotron Tube As used in a stroboscope the strobotron tube con tains two main electrodes a cathode and an anode separated by 3 8 inch in an envelope filled with xe non gas at a pressure of one half atmosphere A spe cially designed capacitor acts as a low impedance source to supply 800 to 1000 volts across these elec trodes The gas however remains nonconducting until a 5000 volt pulse is applied to trigger wires inter spersed between these main electrodes This trigger pulse ionizes the gas and causes up to 1000 amperes to flow through it This peak flow of almost one mil lion watts generates an intense flash of white light of 15 million beam candles Principle of Operation After this tremendous pulse of light the tube requires about 150 microseconds to deionize The voltage across the tube must remain less than 80 volts during this deionization time or holdover will result 3 3 The Charging Circuit The necessary deionization time limits the maximum flashing rate of the stroboscope Figure 3 1 il
58. trument is to be held in a fixed position for a long period of time a tripod or other support should be used 2 6 Adjusting the Flashing Rate The flashing rate of the strobotron lamp is adjusted by means of the RPM range switch knob and the RPM dial 5 and 7 Figure 1 2 The total range of the stroboscope 1s divided into four overlapping ranges selected by the range switch knob The limits for each range are marked near the appropriate window in the range mask The windows on the mask reveal only the range in use To operate the RPM dial turn the fluted transparent rim that surrounds the range switch mask The red indicator line over the dial scale gives the speed set ting in flashes per minute corresponding to rpm for speed measurements 2 7 Calibration To use the stroboscope for the most accurate mea surements of speed the RPM dial can be calibrated using the frequency of the ac power line The cali bration 1s then valid for either ac or battery operation There is no provision for calibrating the instrument on battery power OPERATION To calibrate the Type 1538 proceed as follows a Allow the instrument to warm up for at least ten minutes b Turn the RPM range switch to the CAL position c Set the RPM dial to 3600 60 cycles second x 60 seconds minute by rotating it until the mark at 3600 is exactly under the red indicator line d Adjust the panel screwdriver control marked HIGH CAL until the flashing of
59. uctance must also vary by a factor of 216 or the current must vary by a fac tor of 216to supply sufficient energy per cycle Large coils and 30 A current were both unappealing so an other approach was found On lower speed ranges however where the dis charge capacitance 16 higher the energy stored in the transformer is insufficient to produce the desired 800 volt firing potential On these ranges the 200 us de lay following the monostable circuit generates a trig ger pulse occurring 200 us after the end of the monostable pulse to retrigger the monostable circuit Thus a single pulse from the oscillator starts a train of 200 Ls pulses in the monostable circuit and its delay loop Each of these pulses stores energy in the induc tor that 15 repeatedly transferred to the capacitor dur ing the time between pulses Each pulse raises the capacitor voltage in a small step as shown in Figure 3 4 This process continues until the capacitor is charged to 800 volts At each step a voltage pulse equal to the capacitor voltage divided by the trans former turns ratio appears across the Zener diode on the transformer primary When the capacitor reaches 800 volts the diode voltage is exceeded and the flip flop closes the gate This breaks the feedback loop and ends the pulse train started by the oscillator While this multiple cycle resonant charging technique used on the lower ranges requires more time than the single cycle charge a correspon
60. y produced by the motion of the object being observed produce electri cal signals that are amplified delayed and shaped by the Flash Delay and are 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 Appendix of this book and to the Operating Instructions for the Type 1531 P2 Flash Delay and the Type 1536 Photoelectric Pick off for further information concerning these instru ments and their use with the Type 1538 Stroboscope OPERATION Figure 2 5 A widely used combination consists of the stroboscope with the Type 1531 P2 Flash Delay and the Type 1536 Photoelectric Pick off 2 10 3 Type 1537 Photoelectric Pick off The Type 1537 Photoelectric Pick off differs from the Type 1536 in that no light source 1s included The photosensitive element is a silicon light activated switch This pick off will trigger the type 1538 Stro boscope directly Refer to the Instruction Manual for the Type 1537 for further details on the operation of this accessory its specifications are given in the Ap pendix of this manual 2 10 4 Type 1539 Stroboslave The Type 1539 Stroboslave is an inexpensive minia ture electronic stroboscope It has no internal oscil lator for setting the flashing rate and so it must be triggered by an external device It cannot be used for direct measurement of rotational speed This small stroboscope is suitable for h
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