High-Speed Transient Recording System

François Martzloff

General Electric Company

Schenectady NY 12345

Reprinted, with permission, from General Electric TIS Report 68-C-019, January 1968

Significance:

Part 5 – Monitoring instruments, laboratory measurements, and test methods

The recording system described in this report was developed at a time when there were no available commercial

probes combining high-frequency response, high-voltage capability, and long connecting cable (to allow removing

the oscilloscope from close proximity to the source of the transients to be measured). 

The need for such a system arose at the time when pre-strikes and restrikes in high-voltage vacuum switches were

emerging as a potential problem for transformer and motor winding insulation, and in some cases arrester failure. 

Thirty years later, the problem seems to have abated and the vanishing need for such a custom-built system (even

if assembled from components that were commercially available at the time, including a “standard modification” of

a Tektronix oscilloscope – no longer available) relegates this system to the museum category and is included in this

Anthology only to provide some historical perspective on measurement methods.
I AUTHOR 1 SUBJECT I NO. 

GENERAL @I ELECTRIC 

SCHENECTADY, NEW YORK 

Ihilartzloff, FD I transient measurement 

 

TECHNICAL INFORMATION 

SERIES 

I ADDITIONAL COPIES AVAILABLE AT I NO. PAGES 

I 

TITLE 

High Speed Transient Recording 

System 

January 1968 

C.E. CLASS 

COW, CLASS - 

Switching transients have been responsible for equipment 

failures; however, their accurate measurement is difficult with 

currently available oscilloscopes and attenuators. 

The major difficulties in recording single fast transients are 

- twofold: photographic limitations for a single sweep at high 

speed, and spurious signals entering the measuring system. 

A system based on differentiation-integration of the signal 

has been developed at the Research and Development Center. 

This system is used with a Tektronix 544 oscilloscope featuring 

24 kV acceleration. The passive differentiator-integrator was 

assembled from commercially available components. In addition to transient recording, the oscilloscope can also be used as 

a general purpose laboratory oscilloscope at normal accelerating 

potential. Thus, a new system, which can easily be duplicated in 

operating components of the Company, is available for making 

reliable transient measurements and for making comparisons of 

results from different laboratories. This system offers excellent recording capabilities, with a response that is flat within 

& 10% from 0.3 to 30 MHz. 

Distribution Unit, Bldg. 5, Room 345 

Research and Development Center 

P. 0. Box 8, Schenectady, New York 12301 

KEY WORDS 

transients, oscilloscopes, probes, shielding 

25 

l NFORMATI ON PREPARED FOR: 

SUMMARY 
High Speed Transient Recording System 

1.. Introduction 

It is known that switching transients in power circuits have been responsible for equipment failure; however, accurate measurement of these transients is 

difficult with currently available oscilloscopes and voltage attenuatorsl' 2. Accurate detection and measurement are necessary for an understanding of the problem before appropriate corrective action is taken. 

The major difficulties in recording single fast transients (i.e., rise times 

of less than 0.2 ps) are twofold: the first is the limitation of photographic 

recording(brightness of the trace vs. film and lens speed) for a single sweep at 

high speed; the second is caused by spurious responses of the system to signals 

radiated by the test circuit. 

Both problems were solved in 1962 by H. W. Lord, through the use of a special traveling wave Edgerton, Germeshausen & Grier (EGG) oscilloscope with high 

writing speed, and a special differentiator-integrating amplifier voltage atten3 uator . However, both the oscilloscope and the differentiator-integrator system 

are highly specialized, custom made equipment and the active amplifier requires 

a large power supply. Furthermore, EGG has discontinued the manufacture of the 

traveling wave oscilloscopes. 

A system based on the same differentiation-integration techniques used by 

Mr. Lord has been developed at the Research and Development Center. This system 

is used with a modified Tektronix 544 oscilloscope and a 1Al preamplifier. The 

change in the oscilloscope is a "standard modification" featuring a 24 kV acceleration anode. The passive differentiator-integrator was assembled from commercially available components. In addition to transient recording, the oscilloscope can also be used as a general purpose laboratory oscilloscope at normal 

accelerating potential. Thus, a new system, which can easily be duplicated in 

operating components of the Company, is available for making reliable transient 

measurements and for making comparisons of results from different laboratories. 

This system offers excellent recording capabilities, with a response that is flat 

within f 10% from 0.3 to 30 MHz. 
This report presents a discussion of the differentiator-integrator approach 

and of the problems associated with high speed CRT photography. The development of the integrator is discussed in the report. The evaluation of the 

system is also described, based on single frequency analysis and on high 

voltage step function methods. 

2. The Differentiator-Integrator Attenuator 

2.1 Principle 

Figure 1 shows the basic circuit, where the signal occurring across the 

test piece Z is differentiated by the C1-R1 circuit and integrated by the 

R2-C2 circuit before being applied to the oscilloscope input. 

FIGURE I 

'I pcA* INSERT CABLE FILTERS 

CRO 

FIGURE 2 

Figure 2 shows the circuit as applied to measurement of high frequency, 

high voltage signals where direct radiation of spurious signals into the 

oscilloscope becomes a problem. 

The differentiator consists of a high voltage capacitor C1 and an arbitrary length of 50-ohm cable terminated into a 50 ohm load. The fact that 

this cable length can be arbitrary, makes possible two desirable features: 

the oscilloscope can be placed at the end of the long cable, far away from 

the strong radiation caused by the circuit under test, and a cable filter, 

requiring additional cable length, can be inserted to block circulation of 

ground currents. In contrast, most commercial high voltage probes are 
4 limited to 10 to 12 feet and have limited built-in cable filters . The 

spurious effects of this limited filtering capability are illustrated in 

the appendix . 

2.2 Practical Limitations 

The basic design of the ~1-~1/~2-C2 circuit must be refined to compensate for the capacitance of the cable (considered as a pure resistance 

in the basic circuit), for the stray capacitances of the resistors, and 

for inductances of the wiring that the basic circuit theory neglects. 

It must be recognized that resonances will also occur; they can be 

eliminated by suitable selection of the component values and careful 

construct ion. 

The design of an actual integrator will be restricted by theoretical 

limits such as the frequency roll-off points of the RC's, by practical 

limitations such as resonances and by the specifications on the gain. 

Frequency Limits and System Gain 

P Ji 

The attenuation of the R1~1/R2~2 system is: out - - R1 C1 

Ein R2 C2 

The -3 dB 

The -3 dB 

high frequency point is defined by: UQ = 1 

C1 R1 

low frequency point is defined by: u - 1 

2 C2 R2 

Thus, with a fixed value of R1 and C1, extending the low frequency 

response of the system can only be done at the expense of the system gain. 

The desired system gain is determined by the magnitude of the signals to 

be recorded and by the input requirements of the oscilloscope. For the 

5441181 combination, performance is slightly degraded for attenuator 

settings below 0.050 volts/cm, so that optimum performance will be 

obtained with integrator outputs above 0.1 volts. 
Numerical Example 

Let us choose R1 = 50 ohms (a typical surge impedance 

for a cable likely to be used) 

C1 = 5 pF (for minimum circuit loading) 

then, RlCl = 250 lo-'* 

= 640 MHz 

For a desired attenuation of 5000:l 

R2C2 = RlCl x 5000 

then 

Thus, in this example, the high upper frequency limit resulted from the desire to have minimum loading of the test circuit, while the relatively high 

low frequency limit resulted from the desire to produce the mild attenuation. 

A lower value for the low frequency limit could be obtained by more attenuation or by a larger coupling capacitor C1, if the resultant circuit loading 

is acceptable. 

Resonances 

Precautions must be taken to keep the input connection inductance low 

(capacitor C1 and leads) so that these will not resonate at frequencies 
within the pass-band. For instance, assuming C1 = 5 pF, resonance occurs for an input inductance L1 at w such that: lr 

6 For a system with an upper frequency limit in the order of 100 MHz, or 628 10 radlsec, 

6 

Wlr should be in the order of 1000 10 radlsec or higher. Thus, 

hence L1 = 1 

5 10-l2 x 10 18 

This points out tkle need for close coupling of the probe to the circuit as 1 foot 

of wire has an inductance in the order of 0.1pH. 

3. Oscilloscope Photography 

High speed recording of single transients is limited by a number of parameters: 

a. Cathode ray tube (CRT) - phosphor emission 

- beam accelerating potential 

- spot diameter 

b. Camera design - lens opening 

- reproduction ratio 

c. Film - speed at phosphor emission 

- contrast 

Very small spot di.ameter is useful in producing a brilliant trace if the 

film contrast is adequate; a poorly focussed beam produces a smeared trace which 

would be poorly recorded on a soft emulsion. 

Polaroid 410 (ASA 10,000) film has the highest available speed at this time. 

The P-11 CRT phosphor has the highest available writing speed, and is matched 

with Polaroid 410 characteristics. 

Thus, the only parameters which may be improved are the accelerating potential of the CRT, the capability of fine focusing of the CRT, and the camera design. 
The EGG oscilloscope mentioned earlier has an extremely sharp beam, and produces a brilliant trace. However, this trace is only 1.5 cm long. Most Tektronix 

oscilloscopes have a sweep 10 cm long, in contrast to the 1.5 cm of the EGG. 

Therefore, comparison of photographic records obtained with the two oscilloscopes 

should be made for the same sweep length, in the same time. 

Further ambiguity in recording ability is introduced by the camera design. 

High speed lenses (f:1.3 or less) are generally associated with an image ratio of 

1:0.5, producing a smaller image on the film. This results in more light concentrated on the film and produces a shorter, brighter trace than a conventional 

camera with a 1:O.g ratio. 

These differences are illustrated (within the limitation of half-tcne process) in Figure 3 showing full size reproductions of the original photographs of 

three oscilloscope-camera systems and reproductions of the same traces enlarged 

to a comparable trace length for a single transient recording. The transient recorded for this example is the breakdown at about 12 kV of an oil gap with capacitor discharge current in the gap. The differences of picture quality in the 

original photographs and in the enlargement to equivalent trace size are quite 

apparent. 

'The first "trace" (a) was produced by a Tektronix 545 oscilloscope with accelerating potential boosted to 12 kV (a readily available modification kit), and 

a standard Tektronix C12 camera (f:1.9 lens, 1:O.g ratio). At this 0.02 ps/cm 

speed even the original Polaroid picture does not show the faint change in gloss 

which can sometimes be seen, but not reproduced in print. 

The second trace (b) was recorded by the same system, but at a speed 5 times 

slower, 0.1 ps/cm. This is the fastest single sweep that can be recorded. The 

original Polaroid picture does show the front as the faint gloss change mentioned 

above. 

The third traces (c) were recorded with the EGG oscilloscope and Mark I attenuator. A zero line has been added since the EGG oscilloscope has no graticule. 

The fourth traces (d) were recorded with the new Tektronix 544 oscilloscope 

and high speed camera (f:1.3, 1:0.5 ratio). An enlargement has been made to the 

same scale as traces c and a, with complete resolution of the trace. 

The difference on traces c and d, as far as the high frequency oscillation 

seen on trace c is concerned, will be discussed in Section 4.2. 
b. Tektronix 545, 12 kV acceleration 

0.1 ps/division - P6015 probe 

recorded 1:O.g ratio, f:l.9 lens 

(original Polaroid allows reading 

of the front) 

Total sweep time: 1 ys 

EGG oscilloscope, Mark I 

0.1 p/cm on CRT 

below: recorded 1: 1 ratio, f: 1.4 lens 

right: enlargement from original below 

Total sweep time: 0.15 ps 

Tektronix 544, 24 kV acceleration 

0.02 ps /d ivis ion - Mark IV 

below: recorded 1 : 0.5 ratio, f : 1.3 lens 

right: enlargement from original below 

Total sweep time: 0.2 ps 
4. An improved Recording System 

4.1 Approach 

Oscilloscope-Camera 

With the objective of using readily available components, the choice of 

oscilloscopes was narrowed to Tektronix,Fairchild, and Hewlett-Packard. Admittedly, there may have been a slight bias in favor of Tektronix since most 

oscilloscopes in use at the Research and Development Center and in the Departments tend to be Tektronix. The Tektronix 519 oscilloscope (traveling wave 

tube) has excellent single transient writing speed, and is a catalog item, but 

it has a fixed single input (10 V/cm, 125 ohm), making it a highly specialized 

instrument. On the other hand, the Tektronix 544 oscilloscope is available on 

special order in a "standard modification" for high writing rate at 24 kV 

accelerating potential. 

The meaning of "standard modification" on a special order is that Tektronix - 

will readily accept orders for this model, since the demand has been sufficient to prepare instruction books, etc. While special order means a delay in delivery, it seems at present that most catalog-listed oscilloscopes, 

in particular the 519, are in back-order state; consequently, the special 

order delay does not result in much longer delivery time than that required 

for catalog items. 

The real advantages of the 544 oscilloscope are that it accepts the normal 

letter-series preamplifiers, and that setting of a switch converts it back to 

the normal operation of a 544 oscilloscope (i.e., a general purpose oscilloscope 

suitable for a large number of laboratory applications). This is in contrast to 

the specialized use of the 519 oscilloscope. Cost of the oscilloscope with modi 

fication (without preamplifier) is also lower than that of the 519. Therefore, 

a Tektronix 544 Mod. 108G with C12 camera was selected and purchased for this 

system. 

The frequency response of the oscilloscope with 1Al preamplifier is flat 

within -3dB to 50 MHz for preamplifier settings of 0.05 to 20 v/cm, where the 

system is expected to operate. For calibration purposes, different attenuator 

settings must be used. Appropriate corrections are discussed in Section 4.2. 
The 6 x 10 cm viewing area under the normal 12 kV acceleration is reduced 

to 4 cm vertical x 5 cm horizontal at 24 kV. With the sweep magnifier on, the 

sweep is again 10 cm long on the face of the CRT and is linear, except for the 

first and last cm of the entire trace. Thus, the useful viewing area is effectively 4 x 10 cm, which is equivalent to that of a conventional Tektronix 

545 oscilloscope. 

Mark IV Different iator - Integrator 

Earlier approaches to the measurement of high speed transients used the 

differentiator integrator with an active circuit. These approaches have been 

described in Reference 5 as Mark I and Mark 11. A Mark I11 designation is reserved for a system built for the Specialty Transformer Department. The new 

system described here has been designated as Mark IV in order to acknowledge 

the continuity of the development. 

- In order to minimize loading of the test piece and to move away the resonant frequency of the probe input circuit, we selected a 5pF vacuum capacitor 

(Jennings Cat. JCD-5) rated 60 kV for the coupling capacitor, and 50-ohm RG8 

or RG 58 as the cable. 

The capacitor is actually shielded by a guard at the potential of the low 

side, which is generally the single ground point of the system. 

The complete circuit is enclosed in a copper box, starting with the filter 

consisting of 20 turns of coaxial cable around a ferrite core. The basic R2/C2 

integrator has been refined as shown in Figure 4 in order to provide flat response over the widest possible band. The major integration is performed by the 

resistor R2 and capacitor C2. Addi- FILTER 

tional compensation is obtained by the 

~3/~3 integrator, and the output is 

fed through the R4/50 ohm divider, where 

the 50 ohm resistance also acts as ter- FIGURE 4- WIDE BAND ATTENUATOR 

minating impedance for the output cable at the oscilloscope panel input. 

This terminating resistance was added so that the box could be connected 

to any oscilloscope through a short cable. As this produced an additional at- 
tenuation (the R3 + R4/50 divider) it became necessary to increase the gain 

of the integrator so that R2 C2 was made smaller. The corresponding increase 

of the low frequency limit was then compensated by introducing the R1/C4 instead of a single resistance R1. Proper matching of these elements was achieved 

by actual response curve plotting of circuits until the flat response described 

in Section 4.2 was obtained. 

Camera 

The Tektronix C27 camera is available with a f: 1.3 lens; it has no mirrors 

to decrease the amount of light reaching the film and produces a sharp trace with 

a 1:0.5 reproduction ratio. Although advertized as recording two graticules per 

frame of film, this is really not the point of the 1:0.5 ratio; few operators 

will actually take two exposures of a test without wanting to see the results of 

the first test. 

Shielding Requirements 

The perennial pitfalls of transient measurements are ground loops and radiated noise entering the oscilloscope circuits. 

The most common type of ground loop is Ir 

that shown in Figure 5, involving the sheath 

of the coaxial cable which brings the signal 

to the oscilloscope. 

This effect is substantially reduced by 

inserting in the cable a filter, consisting FIGURE 5 

of a number of turns of coaxial cable on a ferrite core. The signal, 

traveling in the coax is not affected by the filter, while ground currents 

circulating along the coax sheath are impeded by the inductance of the coil 

of cable. 

Noise radiated to the oscilloscope can be abated by barriers (shielding) 

or merely by distance. Shielding means an enclosure either for the test circuit or the oscilloscope; depending upon the size of the test circuit, it may 

be necessary to enclose the oscilloscope rather than the circuit. For the two 

to he physically close (i.g., in the same area of a laboratory bay), it will 

be necessary to provide very good attenuation by the enclosure, such as 90 dB 

at 100 MHz, that is, an "RFI" type design, not just a safety type enclosure. 
Since an enclosure may not always be available, considerable attenuation 

can be obtained merely by removing the oscilloscope from the test circuit, 

around a metal building corner, etc. Here, the availability of a long cable between the differentiator and integrator becomes a very significant asset. 

4.2 System Performance 

The performance of the system was evaluated in two ways: by single frequency response and by step function response. The single frequency method 

allows a separate evaluation of the components and, provided that suitable 

generators, calibrated attenuators, and receivers are available, it yields an 

answer in absolute terms. Step function response involves the total system at 

once, including shielding, and can be performed at high voltage so that it gives 

a pictorial evaluation of the response; however, since it requires a true step 

function, which is rather difficult to produce, it really yields an answer in 

relative terms. 

Single Frequency Evaluation 

The method consists merely in applying a variable frequency sinusoidal voltage of known amplitude at the input and measuring the output, in this case the 

deflection on the face of the CRT, as a function of frequency. 

However, since the sinusoidal signal generator has a limited output voltage, 

such as 10v p-to-p compared to the voltages in the range of 1 to 50 kV which may 

be involved in the actual measurement, the oscilloscope preamplifier must be 

operated at high gain. This introduces the response of the oscilloscope/preamplifier at this high gain setting, which at high frequency is poorer than the 

response at medium gain where the preamplifier will be operating for actual 

use. 

lo1 0.05 lo 20 v/cm 1. Plot response of the oscilloscope 

and preamplifier at high gain + -- -- --- . - - - 

(0.005 v/cm - see Figure 6. -4 01 0005 v/cm 

2. Plot response of the oscilloscope -6 

and preamplifier at gain for I 5 10 20 50 

actual use (0.05 v/cm and above) FREQUENCY MHz 

- see Figure 6. RESPONSE OF TEKTRONIX 544 OSCILLOSCOPE 

WITH IAl PREAMPLIFIER SETTING AS SHOWN 

Thus, four steps are required to obtain a quantitative description of 

the system performance: I 

FIGURE 6 

11 

-- - 

I 1 
3. Plot response of the complete differentiator-integrator oscilloscope 

with low level input signal and high gain setting of the preamplifier - 

see Figure 7. 

4. From 1 and 2, correct 3 to compensate for the difference in response 

between the high gain and normal gain settings, and then plot the corrected response point-by-point at high frequency - see Figure 7. 

From 1 and 3, calculate the response of the differentiator-integrator 

alone and make a point-by-point plot at high frequency - see Figure 8. 

0 ------- - 

-2 / 

-4 

db-6 

-8 

-I0 

/ 

The system attenuation is shown ZE 

in Figure 8. This attenuation is 10~0al 

+ 20% 5 

equal to 5,000:l - 0% from 300 kHz ~5000;l 

to 30 MHz, and produces usable ' 0.02 0.05 0.1 0 2 0.5 1 2 5 10 20 50 

FREOUENCY MHz 

in£ ormation below and above this ATTENUATION OF COMPLETE SYSTEM 

flat range. DIFFERENTIATOR-INTEGRATOR-IAI PREAMP AT 0.05 V/cm-544 OSCILLOSCOPE 

FIGURE 8 

For reference, a similar evaluation was made of the earlier Mark I system (5) 

using the 544 oscilloscope and 1Al preamplifier. The corresponding curve is 

shown in Figure 9a. The Mark I has been previously used with the EGG oscilloscope 

which does not show any drop in response at 50 MHz, so that the response of the 

complete system, Mark I + EGG oscilloscope would exhibit the rise shown in dotted 

line in Figure 9a. The attenuation of the Mark I and EGG oscilloscope is shown 

in Figure 9b. 

0.01 0.02 0.05 0 1 0.2 0.5 I 2 5 10 20 50 

FREOUENCY, MHz 

RESPONSE OF COMPLETE SYSTEM- DIFFERENTIATOR, INTEGRATOR, 

IAl PREAMPLIFIER WITH SETTINGS AS SHOWN, 544 OSCILLOSCOPE 

FIGURE 7 

I 

1 

I 

at 0.005 - v/cm+\ 
002 0050.1 02 0.5 1 2 5 10 20 50 

FREOUENCY MHz 

A MARK I WlTH TEKTRONIX IAl AT 0.005 vkm AND 544 OSCILLOSCOPE FREOUENCY MHz 

B ATTENUATION WlTH EGG. OSCILLOSCOPE DERIVED FROM A 

FIGURE 9 

PERFORMANCE OF MARK I ATTENUATOR 

UNMR SAME TEST CONDITIONS AS MARK CII EVALUATION 

At this point, we can discuss the difference in Figures 3c and 3d which were men- :\ *.- --I 

tioned earlier, and are reproduced on this f ., . -.?A / 1 F' 

page as negatives. " ."$'.I 

3c MK I 

It is possible that the high frequency 

(about 200 MHz) shown in the Mark I trace 

is present in the circuit. However, the 

increasing gain of Mark I beyond 50 MHz 

which turns into a resonance towards 250 

MHZ(~) will show this 200 MHz oscillation 

with a magnification in the order of 3 to 1 

On the other hand, the Mark IV trace 

does not show any of these, since its response begins to drop at 30 MHz. Were 

any of these frequencies actually present in the circuit, Mark IV has "edited 

out" the ambiguity existing in the Mark I recording. Thus, Figure 3d represents 

more useful and less confusing information with, of course, the understanding 

that one should not expect frequencies beyond 50 MHz to be recorded. 
Step Function Evaluation 

Breakdown of an oil gap at 10-12 kV was used as the high voltage step function 

generator. A .001 pF capacitor was slowly charged from a DC supply until the gap 

would break down. The complete circuit (DC supply, capacitor, gap) was contained 

in the shielded enclosure, and only the coaxial 

cable after the differentiator was brought out. 

An additional filter on the signal cable, identical to that contained in the integrator box, 

was installed at the point of exit from the 

shielded enclosure - see Figure 10. This may 

or may not be necessary in actual use of the 

system. Figure 11 shows the recording obtained with this system, where a rise time of 

25 ns is completely resolved, even in a negative line type print. The photograph in 

Figure 13 shows the installation at the Research and Development Center. 

SHIELDED 

ENCLOSURE 

OIL GAP 

FILTER 

FIGURE 10 

CIRCUIT FOR FAST RISE TRANSIENT RECORDING 

Sweep: 10 ns/div. 

Figure 11 

5. Precautions 

The clean and credible recording shown in Figure 11 will be obtained only 

if the necessary shielding precautions are taken. In order to illustrate what 

happens when these precautions are not observed, the series of oscillograms in 

Figures 12a, 12b, 12c were recorded under various conditions of inadequate shielding, using the step function evaluation setup described in Figure 10. Half tone 

process was used to show the effect of oscillations on trace brightness. 

Sweep: 20 ns/div. Sweep: 20 ns/div. 

a - test piece in enclosure, b - door ajar 

door tight 

Figure 12 

Sweep: 20 ns/div. 

c - door open 

Furthermore, care is required in the construction of the integrator circuit, by selecting components with low inductance as well as by correct layout 

of the components and bonding of the integrator housing. Figure 14a shows the 

inside of the integrator circuit that was built with the utmost care, while 

Figure 14b shows the same circuit built with less care. The response of the 

two integrators to the same signal is illustrated in Figures 14a and 14b. 

Sweep: 20 ns/div. 

Figure 14a 

Sweep: 20 ns/div. 

Figure 14b 
6. Detailed S~ecifications 

6.1 Oscilloscope (Reprinted from Tektronix 544 Mod. 108G instruction book) 

Introduction 

The Type 544 Oscilloscope is a versatile laboratory instrument designed for 

use with all Tektronix lettered or 1 Series plug-in units. 

Vertical Deflection System 

The plug-in unit and probe used with the Type 544 determine the overall 

characteristics of the vertical deflection system. Refer to Table 1-1 for the 

characteristics. 

Sweep Generation 

Sweep Rates 

(at 1X magnification) 

Sweep Magnification 

Trigger Source Selection 

Trigger Couplicg Selection 

Trigger Signal Requirements 

O.l~sec/cm to 5sec/cm in 24 calibrated steps. 

Sweep-rate accuracy is 22% of the indicated rate. 

Any sweep rate can be increased by expanding the 

center portion of the display horizontally in 

fixed steps of 2X, 5X, lox, 20X, 50X, and 100X. 

Sweep-rate accuracy is within 5% in the magnified positions at effective sweep rates up to 

10 nseclcm. 

Internal normal, internal plug-in, external, 

and line. 

Dc, ac, and ac low-frequency rejection. 

Internal (ac): Minimum deflection is 2mm 

with signals at about 150 cps, rising to 1 

cm at about 50 n~c. 

Internal (dc): Minimum deflection is 5mm 

at dc. 

Internal (ac low-frequency rejection) : Minimum deflection is 2mm with signals at about 

2 kc, rising to 1 cm at about 50 mc. 

External: Frequency ranges are the same as 

internal. Minimum amplitude is 200 mvolts 

peak-to-peak (ac), 200 mvolts change in dc 

level (dc) , and 200 mvolts peak-to-peak (ac 

low-frequency rejection). A MAXIMUM INPUT 

OF 2 30 VOLTS must not be exceeded in the 

EXTERNAL trigger position. Minimum trigger 

level range is greater than f 2 volts with the 

TRIGGER LEVEL control pushed in and f 20 volts 

with the control pulled out. 
Horizontal Deflection Svstem 

The following characteristics apply when the HORIZONTAL DISPLAY switch is 

set to the EXT position. 

Deflection Factor Variable in fixed steps of .l, 1, and 10 volts/cm. Accuracy 

+ is - 5% when VARIABLE control is set to CALIBRATED. 

Frequency Response 

Input Characteristics 

Amplitude Calibrator 

Output Voltages 

Frequency 

Output Current 

Output Impedance 

Amplitude Accuracy 

Dc to 400 kc (3-dB down at maximum sensitivity). 

(approximately) 1 megohm paralleled by 55 pf. 

0.2 mvolts to 100 volts peak-to-peak in 18 steps. 

In addition, a 100-volt dc output is available. 

Approximately 1 kc square wave. 

5 ma squarewave available at the front panel 

current loop. 

50 in .2 to 200 mVOLTS positions. Progressively higher output impedances in the .5 to 

100 VOLTS positions. 

Peak-to-peak amplitude accuracy is 2 3% of indicated value when working into an impedance of 

1 megohm or higher in the .5 to 100 VOLTS position. When working into a 50 ohm load, in the 

.2 to 200 mVOLTS positions, output amplitude is 

one-half of the indicated voltage. (Nominal 

accuracy in this case, is f 3% assuming the - 

external load impedance is an accurate 50 ohms). 

The 5 ma current accuracy is + 3%. 

Front-Panel Output Signals 

+ GATE OUT 

SWEEP OUT 

VERT SIG OUT 

At least a 20 volt peak-to-peak squarewave 

pulse having the same duration as the sweep. 

Minimum dc load resistance is 5 k. 

Approximately a 100 volt peak-to-peak sawtooth 

voltage having the same duration as the sweep. 

Minimum load impedance is 100 k. 

Vertical signal output connector. Output amplitude is approximately 0.4 volt per centimeter of 

deflection on the crt. Rise time is 20 nsec or 

faster. Output is ac coupled. 

External Single-Sweep Input Requires a positive-going step or pulse of at 

Signal Requirements least + 20 volts with a risetime of 0.5 ysec 

or faster. 
Horizontal Deflection Svstem 

The following characteristics apply when the HORIZONTAL DISPLAY switch is 

set to the EXT position. 

Deflection Factor Variable in fixed steps of .l, 1, and 10 volts/cm. Accuracy 

+ is - 5% when VARIABLE control is set to CALIBRATED. 

Frequency Response 

Input Characteristics 

Amplitude Calibrator 

Output Voltages 

Frequency 

Output Current 

Output Impedance 

Amplitude Accuracy 

Front -Panel Output Signals 

+ GATE OUT 

SWEEP OUT 

VERT SIG OUT 

External Single-Sweep Input 

Signal Requirements 

Dc to 400 kc (3-dB down at maximum sensitivity). 

(approximately) 1 megohm paralleled by 55 pf. 

0.2 molts to 100 volts peak-to-peak in 18 steps. 

In addition, a 100-volt dc output is available. 

Approximately 1 kc square wave. 

5 ma squarewave available at the front panel 

current loop. 

50 R in .2 to 200 mVOLTS positions. Progressively higher output impedances in the .5 to 

100 VOLTS positions. 

Peak-to-peak amplitude accuracy is f 3% of indicated value when working into an impedance of 

1 megohm or higher in the .5 to 100 VOLTS position. When working into a 50 ohm load, in the 

.2 to 200 mVOLTS positions, output amplitude is 

one-half of the indicated voltage. (Nominal 

accuracy in this case, is f 3% assuming the - 

external load impedance is an accurate 50 ohms). 

The 5 ma current accuracy is f 3%. 

At least a 20 volt peak-to-peak squarewave 

pulse having the same duration as the sweep. 

Minimum dc load resistance is 5 k. 

Approximately a 100 volt peak-to-peak sawtooth 

voltage having the same duration as the sweep. 

Minimum load impedance is 100 k. 

Vertical signal output connector. Output amplitude is approximately 0.4 volt per centimeter of 

deflection on the crt. Rise time is 20 nsec or 

faster. Output is ac coupled. 

Requires a positive-going step or pulse of at 

least + 20 volts with a risetime of 0.5 psec 

or faster. 
Power Supplies 

Line Voltage 

Line Frequency 

Power Consumption 

Protect ion 

Cathode -Ray Tube 

Type 

Unblanking 

Accelerating Potential 

Useable Viewing Area 

Focus 

Construct ion 

Gra t icule 

Mechanical - 

C~nstruction 

+ 

- 10% of nominal line voltage. (See Operating 

Instructions) . 

50-60 and 400 cps. 

400 watts typical. 

Primary of power transformer is fused and a 

thermal relay is installed that interrupts 

power in the event of overheating. 

Dc coupled. 

6 cm high by 10 cm wide 

Vertical: 2 horizontal lineslmm distinguishable over the center 4 cm. 1.5 horizontal 

lines/mm distinguishable in the top and bottom 1 cm. 

Horizontal: 2 time markers/mrn distinguishable 

over the middle 8 cm. 1.5 time markers/mm distinguishable in the first and tenth cm. 

All glass 5 inch, flat-faced crt. 

Internal, adjustable edge lighting, 6 x 10 

cm with vertical and horizontal 1 cm divisions with 2 mm markings on the center 

lines. 

Three piece, blue-vinyl covered textured 

aluminum. Front panel is photo-etched and 

anodized. Chassis is aluminum alloy. 

Net Weight 80 pounds 7 ounces 
Mod 108G Features 

A special high-voltage power supply, which can be switched for either 12 kV or 

24 kV operation, has been installed. 

A high-voltage slow-up circuit has been installed. When the instrument'is turned 

on, in the 24 kV position, it will take 1-112 to 2 minutes to reach proper voltage. 

Also, this circuit turns the high-voltage off in the event of any power line interruptions of 15 milliseconds or longer. 

The auto stability circuit is disabled during 24 kV operation. 

For CRT phosphor protection, a circuit has been added to prevent triggering on 

a repetitive signal during 24 kV operation. 

The unblanking circuit provides normal 60 volts unblanking at 12 kV in all sweep 

speeds. At 24 kV, unblanking has been increased to 110 volts in the .2 pSEC 

through 20 pSEC positions of the TIME/CM switch. At 40 pSEC through 10 SEC, unblanking is reduced to of burning the CRT 

phosphor. 

The, linear scan area w 

40 volts to remove the 

then in 24 kV operation 

probability 

is 4 cm vert 

tally. With the MAG on, the linear display area is 4 x 8 

ically by 5 cm horizonem. 

6.2 Camera 

Tektronix C12, f:1.3 lens, roll-film back, electric shutter actuator 

order #C-27-662-RS. 
6.3 Differentiator-Integrator 

Differentiator 

The differentiating capacitor Jennings Cat. JCD-5. 

A brass tube serves as electrical shield and mechanical 

protection. 

RG 213/U is a 50-ohm cable 

with non-contaminating 

jacket (RG 8/U is 52 ohms). 

Filter 

20 turns of RG 58 on Ferroxcube 

1F10-3C5 "U" core (Elmira Ferrite 

Laboratories, Inc.) or equivalent. 

Construction of the integrator 

as seen earlier, requires care. 

The components are identified in 

Figure 4 and in the photograph. 

Exact specifications are: 

R1: 4 series parallel 50 R IRC-HFR 

R2: 4 series parallel 300 R IRC-HFR 

R3: 1 150 IRC-HFR 

R4: 1 150 Q IRC-HFR 

C2: 2 parallel Erie 654-017 251 K 

250 pF each 

Complete Mark IV Attenuator 

Integrator and Filter 

FILTER 

C3: 1 single TCZ-33 Centralab 33p~ 

C4: 2 parallel one Erie 654-017 251 K 

one Cornell-Dubilier 5RST-J 

500 pF 
Substitute Component List for the Integrator 

R1: 2 series 24.9 Q 1RC-DCC 

R2: 2 series 150 0 1RC-DCC 

R3: 1 single 150 R 1RC-DCC 

R4: 1 single 150 R 1RC-DCC 

C2: 1 single Erie 662-003 501 K 500 pF 

C4: 2 parallel one Erie 662-003 501 K 500 pF 

one Erie 662-003 251 K 250 pF 

7. Conclusions 

1. The new Mark IV system provides a 5,000:l attenuation, flat within 

10% from 300 kHz to 30 MHz. 

2. Photographic recording of single transients is possible at sweep 

speeds up to 10 nanoseconds per centimeter. 

3. Further development work is required to extend the response of Mark IV 

towards lower frequencies. 

8. Acknowledgements 

The basic differentiator-integrator approach was suggested by Mr. H. W. Lord, 

formerly on the R&D Center Staff, now retired. 

The design and development of the integrator, evaluation tests and photography 

were contributed by H. S. Lasher. 

9. References 

1. Electrical Transients in Power Systems - General Electric Course, by 

A. N. Greenwood 

2. On Potential Dividers for Cathode Ray Oscilloscopes, by F. P. Burch, 

Phil. Mag. S.7 Vol 13, N. 86 (1932) p. 760. 

High Speed Transient Voltage Measuring Techniques by H. W. Lord 

Voltage Probes for Measurement of Transients 

at Remote Points, by P. Chowdhuri 

Instrumentation for Wide Band Observation of 

High Voltage Transients by W. N. Coffey 
Appendix 

Limitations of the Tektronix P6015 Probe 

Comparisons with Mark I and Mark IV 

A voltage transient has two characteristics which are significant: the initial rate of rise and the total transient. The instrumentation discussed in 

the present report is mostly concerned with the recording of the initial rise, 

as being the most difficult, and does not provide for total transient recording 

since the attenuation of the probe increases rapidly for frequencies below 300 kHz. 

However, it i s s t i l l desirable to record both characteristics so that one 

method of obtaining such recording might be a combination utilizing the Mark IV 

attenuator and the modified 544 oscilloscope at 0.02 ps/cm for the initial rate 

of rise, and a "slower" oscilloscope such as the 545 with the ~6015" high voltage 

probe for the total transient, at a sweep speed such as 0.2 ps/cm or slower. 

However, in the presence of fast rise time transients, unexpected problems 

arise in the use of the P6015 probe and 545 oscilloscope, as demonstrated below. 

The oscilloscope response appears to suffer from saturation of the preamplifier and/or amplifier, which lasts long enough to interfere with the desired 

reliable measurements. 

The saturation of the preamplifier is attributed to insufficient filtering 

of the probe ground sheath, allowing large currents associated with the fast rise 

time to flow in the probe cable sheath. These currents cause a voltage drop in 

the ground sheath of the probe and preamplifier ground connections; this spurious 

voltage is added to the true signal and has such a large magnitude that the preamplifier is saturated and does not recover in time. The following three oscillograms illustrate this measurement problem, which has not yet been solved, and 

adds to the incentive of extending the response of Mark IV towards lower frequencies to produce complete reading with a single attenuator. 

-- 

The high voltage probe Tektronix P6015 is rated 1:1000 attenuation, 40 kV peak, 

bandpass Dc to 50 MHz (flat within 2%) and has a limited built-in filter in the 

12 ft. cable to reduce the effect of ground currents. 
which shows a peak of only 13 kV, when the same gap breakdown is recorded with 

Mark IV and the 544 oscilloscope, at the same sweep speed and 1 ~/cm (5,000 ~/div). 

intensity was set lower, producing a 

trace that would not cause any "bloom". However, the fast oscillations at the 

front almost caused the trace to disappear. 

we obtained the trace shown at right only 

after having reduced the oscilloscope sensitivity to 10 V/cm (10,000 V/div) 

and still the trace goes off screen, indicating severe disturbance of the preamplifier. 
The improvement in lower frequency response, as well as the "editing" 

of questionable high frequencies which was discussed earlier are illustrated 

in the four oscillograms below, recorded with Mark I and with Mark IV. 

This trace, recorded with the 

Mark IV, shows 2 ps of sweep 

with appreciable droop, but at 

1 ks, there is still a useable 

signal recorded, compared to the 

ideal flat step function which 

the P6015 would deliver, if it 

were not subject to the difficulties mentioned above. 

In contrast, the Mark I recording, 

showing almost 2 ps in this trace, 

already suffers from considerable 

droop at 1 bs. 

1% 4 

I 

While the capability of Mark I and - 1 

the EGG oscilloscope for recording 

fast rising fronts are outstanding: t 

! 

as shown in this single sweep trace 

of only 45 ns, there is some doubt 

on the existence of the fast front 

shown here, as the frequency involved approaches the resonance of 

Mark I. 

This trace, also single sweep, made 

with Mark IV and the 544 oscilloscope 

leaves little to be desired in resolution. While admittedly frequencies 

above 50 MHz will be recorded with 

appreciable attenuation, it is a substantial improvement over presently 

available systems.