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TECHNICAL INSTRUCTION S.4 Audio-frequency Test Apparatus BRITISH BROADCASTING , CORPORATION ENGINEERING DlVlSlON - ', : . iv- TECHNICAL INSTRUCTION S.4 Third Issue 1966 instruction S.4 Page reissued May. 1966 CONTENTS Page Section I . Amplifier Detector AD14 . 1.1 Section 2 . Variable Attenuator AT119 . Section 3 . Wheatstone Bridge BG/I . Section 4 . Calibration IJnit CALI1 . Section 5. Harmonic Routine Tester FHP/3 . Section 6 . 0.B. Testing Unit 0BT/2 . Section . 7 . Fixed-frequency Oscillators OS/9. OS/ 10. OS/ IOA . Section 8 . Variable-frequency Oscillators TS/5 .. TS/7 . 1' . TS/8 . TS/9 . TS/ 10. TS/ 1OP . Section 9 . Portable Oscillators PTS/9 . PTS/IO . ... PTS/12 . PTS/13 . PTS/l5 .... PTS/l6 .... Appendix . The Zero Phase-shift Oscillator with Wien-bridge Control Section 10. Transmission Measuring Set TM/I . Section 1 I . Peak Programme Meter Amplifiers PPM/2 ..... PPM/6 . TPM/3 . Section 12 Valve Test Panels VT/4. VT/5 "d . Section 13. Microphone Cable Tester MCT/I . Section 14 . Aural Sensitivity Networks ASN/3. ASN/4 Section 15 . Portable Amplifier Detector PAD19 . Section 16. Portable Intermodulation Tester PIT11 Section 17. A.C. Test Meters ATM/I. ATM/IP . Section 18 . Routine Line Testers RLT/I. RLT/IP . Section 19. Standard Level Panel SLP/3 . Section 20 . A.C. Test Bay AC/55 . Section 21 . Fixed-frequency Oscillators: OS2 Series Standard Level Meter ME1611 . INSTRUCTION S.4 Page reissued May 1966 ... CIRCUIT DIAGRAMS AT END Fig. 1. Amplifier Detector AD14 Fig. 2. Wheatstone Bridge BG/1 Fig. 3. Harmonic Routine Tester FHP/3 Fig. 4. Oscillator OS/9 Fig. 5. Oscillator OS/10 Fig. 6. Oscillator OS/lOA Fig. 7.' Peak Programme Meter Amplifier PPM/2 Fig. 8. Peak Programme Meter Amplifier PPM/6 Fig. 9. Oscillator PTS/9 Fig. 10. Transmission Measuring Set TM/1 Fig. 1I. Test Programme Meter Amplifiers TPM/3 and TPM/3A Fig. 12. Tone Source TS/5 : Amplifier Fig. 12~.Tone Source TS/5: Oscillator and Detector Fig. 13. Tone Source TS/7 Fig. 14. Tone Source TS/8 Fig. 15. Valve Test Panel VT/4: Circuit Fig. 16. Valve Test Panel VT/4: Valve-holder Panel Fig. 16~.Valve Test Panel VT/4 : Adaptor Panel Fig. 17. Valve Test Panel VT/5 Fig. 18. Portable Tone Source PTS/I 3 Fig. 19. Tone Source TS/9 Fig. 20. Portable Tone Source PTS/ 10 Fig. 21. Portable Tone Source PTS/I2 Fig. 22. Portable Amplifier Detector PAD19 Fig. 23. Portable Amplifier Detector PAD/9: Modified for use with P.P.M. Fig. 24. Portable Intermodulation Tester PIT11 . Fig. 25. A.C. Test Meters ATM/l and ATM/lP Fig. 36. Routine Line Tester RLT/1 Fig. 27. Routine Line Tester RLT/lP Fig. 28. Tone Source TS/10 and TS/lOP Fig. 29. Standard Level Panel SLP/3 Fig. 30. AC.. Test Bay AC/55 Fig. 31. Intermodulation Test Oscillator IT011 Fig. 32. Amplifier Test Panel ATPI1 Fig. 33. Telephone Panel TP/12 Fig. 34. Relay and Repeating-coil Panel RRC/1 Fig. 35. Oscillator OS2/4 SECTION 1 AMPLIFIER DETECTOR AD;4 The Amplifier Detector AL)/I' is essentially a anode voltage, a stabiliser, coiisisting of a Metrosil \.alve voltmeter designed to read levels of -+ 10 db disk working in conjunction with R19, is includrtl to - 55 db. Its input impedance is 30 kilohms in the h.t, supply circuit of V.3. which is sufficiently high to permit its connection across most circuits without altering the voltagc Negative Feedback or operating conditions of the sending circuit. 'fhr high gain available from \'1 and 1'2 permits Fig. I. I. Face Panel AD:4 with Simpson Meter Circuit Description (Fig. I) tlw use of a consideraldc ;mount oi feedback. The input to the unit is taken via a11 input \Yitli \'I, serirs feedback of 1"l) is ilcwloprtl transformer, TI, to a 10-kilohm potentiomrtcr, ;moss I<" to compvnsate for high-frequency loss, Pa65P, having 14 studs, calibrated in steps of thc ferdhack is rcdr~cedby abor~t0-1 db at 10 kc-s 5 tlb, with an off position. This is followcd bj. and by about 0.2 dh at 15 kc,s. This recluctior~ two resistance-capacitance coupled stages which is effected by shunting CH and R20 across R2. use high-gain pentodrs. \'arinl)lc series feedback is usrd over V2, V3 and Tl~eoutpr~t stage to the rectificbr AIKI metctr ~xovides;i ready means of ndjusting thc working circuits consists of a triode, workcd at low anodc :rain iinr.l for lining up the meter. Tl~cfecdback \.oltage. This res~iltsin the \xlvc working near \-oltngc is rlevelopetl in thc cathoilt- circr~i.tnf \.I! tlit 01-crload point : to minimisc. instabilit!. of th~~across R1.5 and R8 : 118 is variahlc to provides :LII Instruction S.4 Section 1 adjust-gain control ; its ~~ljustmentvaries the performed carefully ant1 cannot be hurried, sincc output current of V3 which flows throiigh the the mcter movemcnt is rclativcly slow. rectifier-meter circuit. i'C.leas/tri)~,qLevels Gain Controls It should be clearly untlcrstood that the AD/I The calibrated gain controls used for taking was designed primarily for the measurement of tone rneasurcments consist of the two potentiometers level as distinct from programme volume, for 1'/65P and P/64P. The P/65P is variablc in steps of which latter purpose a test programme meter is 5 db over a range of - 50 to + 10 db ; thc P/6?P more suitable. To check a given level, set the is variablc in stel)s of 0.5 dl, over a rangc of calibrated controls to correspond with this level, O to -- ,5 db. wherever possible setting the 0-5 dl) control to zero. Adiust thc fine control until the meter reads as near tb mid-scale deflection as possible. The Meter Circuits level is then obtained by the algebraic sum of the The anodc of the third stage fecds into a 1 mA rcadings of the two controls and the scale reading Westinghousi: bridge-connccted metal rectifier of of the meter. the meter type via a 20-kilohm rcsistor R14 and For cxample, if it be required to measure a level ;I I-microfarad capacitor C6. Thc output of this which slioultl normally be + 10 db, set the coarse recliticr is taken to thc terminals of an appro- control to + 10 tlb and the fine control to zero db. priate tylr of indicating mcter. If the meter ,reads well off mid-scale, adjust the Two typcs of indicating meter can be used, the fine control accordingly. If the nearest adiustmcnt !'limpson type, with normal veriical scale requiring is at - 2 db, on the fine control, and the meter ;L fectl of 1 mA for full scidc tlcflcclio:~, or the reads j--0.4 tlb, then the actual level is + 10 - 2 Elliott edgewise typc as usctl on the Trar~smission + 0.4 =:: -1- 8.4 dl). Measuring Set TM/l. Thc Simpson type meter is coniicctcd direct to thc rectifier output, but thc Elliott typc rcquircs to be shunted by a 30-ohm Supplies rcsistor. The ultcrnativc connections are shnun The unit is designetl to work from a 250-volt or i11 Fig. I. a 300-volt battery or a rcctitied h.t, supply. The Uoth meters arc calibrated for zero at mitl- 1.t. supply may be taken from batteries or from scnlc deflection, the scde being cxtencld to cover the mains, except in cases of iiistruments having a %ll, swing cither side of zcro, the calibration serial numbers below 136. Thcse carlicr models bcbin:y in stcps of 0.2 db. 1-Icnct. it is possiblc to have an unscreenetl input transformcr and arc obtain readings thc accuracy of which can be subject to a certain amount of hum pick-up. nio:lsured to within + 0.2 tlb, provitlcd that the Present practice is for ncw installations to be ii~ctcrreadings be correctly inttqolatcd betwecn provided with a mains unit, Typc MUIIG. thr rcatlings of thc calibrated potcntionctcrs. Valve Data Operation Anode Screen \1'hencvcr possible, the amplifier tlctector should Current Current FiL Fil. I)c switched on for at least ten minutes be for^ use mA . nzA 1,'olfs Amps. in order to ensurc stability. Stage 1, Calibmtion AC /SP3,1 1.2 0.35 4 1 Sct tlic Adj!jr(stGain potentiometcr to its extreme Stage 2, anti-clocl<wisc or minimum-gain position. Conncct ACjSP31i 145 0.4 4 I thc input of the AD/? to the output of a tone Stagc 3, source having a calibrated output level (e.g. AC>HI, 1.6 - 4 1 CBLj1). Sct the AD14 calibrated potentiometcrs Jletrosil Current 6 mA. to zero or +. 10 db, according to the sending level, Total Fccrl, 11 mA. 2nd turn ul) the Adjust Gain potcntiomcter until H.T. Supply, 300 1. or 250 \'. 11lc incter rcatls zero. This operation must be T,.'17. Supply, 4 1' a.c, or 6 1. d.c. Instruction S.4 Section 1 General Data Ampllfier Detectors AD/4A, AD/4B, AD/4C, l'otentinmslsrs AD/4D No. of Loss per All these models use thc samc basic circuit as Tybr' Rssistancs Sl~rds Stud the AD/4, but are moun ted on 9-inch panels instead Coarse of the nornial 64-inch panel. Adjustment P165P 10 kIl I4 .idb. AD[?A is a converted AD/2. Fin, AD/4B is a converted ADIS, with Muirhead Adjust-ment P/64P 100 kt2 I I 0-5dh, potentiometers. Adjust Gain AD/4C is a converted AD13 with fainton potentio- Type, Reliance TW.
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  • Ballastic Galvanometer This Is a Sophisticated Instrument. This

    Ballastic Galvanometer This Is a Sophisticated Instrument. This

    Ballastic galvanometer This is a sophisticated instrument. This works on the principle of PMMC meter. The only difference is the type of suspension is used for this meter. Lamp and glass scale method is used to obtain the deflection. A small mirror is attached to the moving system. Phosphorous bronze wire is used for suspension. When the D.C. voltage is applied to the terminals of moving coil, current flows through it. When a current carrying coil kept in the magnetic field, produced by permanent magnet, it experiences a force. The coil deflects and mirror deflects. The light spot on the glass scale also move. This deflection is proportional to the current through the coil. Q i = , Q = it = idt t Q , deflection Charge Fig 2.27 Ballastic galvanometer Measurements of flux and flux density (Method of reversal) D.C. voltage is applied to the electromagnet through a variable resistance R1 and a reversing switch. The voltage applied to the toroid can be reversed by changing the switch from position 2 to position ‘1’. Let the switch be in position ‘2’ initially. A constant current flows through the toroid and a constant flux is established in the core of the magnet. A search coil of few turns is provided on the toroid. The B.G. is connected to the search coil through a current limiting resistance. When it is required to measure the flux, the switch is changed from position ‘2’ to position ‘1’. Hence the flux reduced to zero and it starts increasing in the reverse direction. The flux goes from + to - , in time ‘t’ second.
  • Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science

    Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science

    Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6.002 - Circuits and Electronics Fall 2004 Lab Equipment Handout (Handout F04-009) Prepared by Iahn Cajigas González (EECS '02) Updated by Ben Walker (EECS ’03) in September, 2003 This handout is intended to provide a brief technical overview of the lab instruments which we will be using in 6.002: the oscilloscope, multimeter, function generator, and the protoboard. It incorporates much of the material found in the individual instrument manuals, while including some background information as to how each of the instruments work. The goal of this handout is to serve as a reference of common lab procedures and terminology, while trying to build technical intuition about each instrument's functionality and familiarizing students with their use. Students with previous lab experience might find it helpful to simply skim over the handout and focus only on unfamiliar sections and terminology. THE OSCILLOSCOPE The oscilloscope is an electronic instrument based on the cathode ray tube (CRT) – not unlike the picture tube of a television set – which is capable of generating a graph of an input signal versus a second variable. In most applications the vertical (Y) axis represents voltage and the horizontal (X) axis represents time (although other configurations are possible). Essentially, the oscilloscope consists of four main parts: an electron gun, a time-base generator (that serves as a clock), two sets of deflection plates used to steer the electron beam, and a phosphorescent screen which lights up when struck by electrons. The electron gun, deflection plates, and the phosphorescent screen are all enclosed by a glass envelope which has been sealed and evacuated.